A mold cavity curvature mutation section speed reduction distribution method and system

Abstract

The application relates to the technical field of numerical control precision machining, and discloses a mold cavity curvature mutation section speed reduction distribution method and system. The method comprises the following steps: acquiring a carving tool path of a mold cavity, determining a micro curvature mutation section; determining a micro texture width and a texture area; obtaining three threshold comparison results; querying a preset speed reduction distribution table according to the three threshold comparison results to obtain a local speed reduction distribution result comprising a speed reduction starting point, a speed reduction ending point and a target feed speed; and writing the local speed reduction distribution result into the carving tool path. The micro texture width, the tool diameter, the residual height and the minimum distance between adjacent tool paths are combined to perform local speed reduction distribution on the micro curvature mutation section in the carving tool path of the mold cavity, so that the profile retention and surface consistency of fine texture machining are improved.

Description

Technical Field

[0001] This application relates to the field of CNC precision machining technology, and more specifically, to a method and system for allocating deceleration in a mold cavity curvature abrupt change segment. Background Technology

[0002] Fine texture machining of mold cavities typically involves using CNC machine tools to perform small-mass machining on the cavity surface according to pre-generated engraving toolpaths. For molds used in consumer electronics housings, automotive interior parts, and precision exterior parts, the cavity surface often contains fine-lined corners, narrow groove boundaries, micro-texture edges, and localized folded textures. In these locations, the engraving toolpath easily forms short, concentrated micro-curvature abrupt changes in curvature. Current machining methods usually limit the feed rate based on the curvature of the engraving toolpath; the more concentrated the curvature change, the lower the feed rate, to reduce machining impact when the tool passes through turning points.

[0003] However, in the fine texture processing of mold cavities, the processing risk of small curvature abrupt changes is not solely determined by the curvature of the toolpath. For example, at a narrow groove corner, even if the curvature change of the engraving toolpath is similar to that of the corner of an open surface, if the tool diameter is already close to the width between the texture boundaries on both sides of the narrow groove, the tool is more likely to approach both texture boundaries simultaneously when passing through this position. Simply determining the feed rate based on the curvature magnitude is insufficient to reflect the risk of sidewall scratches.

[0004] For example, in the local convergence area of ​​leather texture or fish scale texture, the spacing between adjacent toolpaths may be lower than the spacing between toolpaths in the same texture area where no tool marks or joints appear. The preceding toolpath may also leave residual material near the corner. When the tool enters the small curvature change section, it will be affected by the residual material removal load and the repeated cutting of adjacent toolpaths at the same time. Existing curvature overall deceleration methods usually cannot distinguish such local material removal risks.

[0005] Therefore, existing methods that reduce speed based solely on curvature are often insufficient to determine the starting point, ending point, and target feed rate that match the actual machining risks, taking into account the relative occupancy of the tool diameter with respect to the width of the fine texture, the residual height of the preceding toolpath, and the spacing between adjacent toolpaths. Consequently, insufficient speed reduction at fine texture corners may lead to contour chipping; excessive lateral tool occupancy at narrow groove boundaries may cause sidewall scratches; and improper local speed distribution at close proximity of adjacent toolpaths may result in tool mark joints or local depressions, thus affecting the contour retention and surface consistency of the fine texture in the mold cavity. Summary of the Invention

[0006] This application aims to address the problem that in the current process of fine texturing of mold cavities, the speed reduction for locations of curvature abrupt changes in the engraving toolpath is usually based solely on the magnitude of curvature. This approach fails to reflect the impact of the tool diameter relative to the width of the fine texture within the small curvature abrupt change segment, the residual height of the preceding toolpath, and the spacing between adjacent toolpaths on the risk of local material removal. Consequently, the starting point, ending point, and target feed rate of the speed reduction do not match the actual processing risk, which can easily lead to problems such as contour trimming, sidewall scratches, tool mark joints, or local depressions.

[0007] This application identifies minute curvature abrupt change segments in the engraving toolpath, reads the corresponding texture boundaries on both sides based on the mold cavity model and determines the width of the minute texture, and then combines the ratio of the tool diameter to the width of the minute texture, the height difference, and the minimum distance between adjacent toolpaths to form three threshold comparison results. Based on the three threshold comparison results, a preset deceleration allocation table is queried to obtain local deceleration allocation results including the deceleration start point, deceleration end point, and target feed rate. This allows the deceleration process to be allocated according to the local machining risk of the minute curvature abrupt change segment.

[0008] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application discloses a method for deceleration allocation in a mold cavity curvature abrupt change segment, including: Obtain the engraving toolpath of the mold cavity, determine the curvature change between adjacent toolpath points according to the toolpath point sequence, and identify the continuous toolpath segment where the curvature change reaches the curvature change threshold and the continuous toolpath segment length is lower than the abrupt segment length threshold as a small curvature abrupt segment. Based on the position of the small curvature abrupt change segment in the mold cavity model, the texture boundaries on both sides are read, the minimum distance between the texture boundaries on both sides is determined as the small texture width, and the texture region is determined by the texture boundaries on both sides. The comparison results of three thresholds are obtained based on whether the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, whether the height difference between the toolpath envelope formed by the engraving toolpath in the processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent toolpaths in the micro-curvature abrupt segment and the texture area is lower than the toolpath distance threshold. Based on the comparison results of the three thresholds, the preset speed reduction allocation table is queried to obtain the local speed reduction allocation results, including the speed reduction start point, speed reduction end point, and target feed speed. The preset speed reduction allocation table records the speed reduction start point adjustment amount, speed reduction end point adjustment amount, and target feed speed corresponding to the comparison results of the three thresholds. Write the local speed reduction allocation results into the engraving toolpath.

[0009] Furthermore, the methods for establishing a preset speed reduction allocation table include: The query conditions are as follows: whether the ratio of tool diameter to micro-texture width reaches the width threshold, whether the height difference reaches the residual height threshold, and whether the minimum spacing is lower than the toolpath spacing threshold. For each query condition combination, the deceleration start adjustment amount, deceleration end adjustment amount, and target feed rate are configured.

[0010] Furthermore, methods for obtaining the local deceleration distribution results include: When the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, the corresponding target feed rate is lower than the target feed rate when the width threshold is not reached. When the height difference reaches the residual height threshold, the corresponding deceleration starting adjustment amount is greater than the corresponding deceleration starting adjustment amount when the residual height threshold is not reached, and the corresponding target feed rate is not higher than the original feed rate of the original engraving toolpath at the small curvature change section. When the minimum spacing is lower than the toolpath spacing threshold, the corresponding speed reduction endpoint adjustment amount is greater than the corresponding speed reduction endpoint adjustment amount when it is not lower than the toolpath spacing threshold, and the corresponding target feed rate is not higher than the original feed rate of the original engraving toolpath at the small curvature change section.

[0011] Furthermore, methods for generating the deceleration start point and deceleration end point include: The starting toolpath point of the small curvature change segment is shifted forward in the machining sequence according to the deceleration starting point adjustment amount to obtain the deceleration starting point; The end point of the small curvature change segment is shifted backward in the machining sequence according to the speed reduction endpoint adjustment amount to obtain the speed reduction endpoint.

[0012] Furthermore, methods for writing the local deceleration allocation results into the engraving toolpath include: When the local speed reduction distribution results of adjacent toolpaths in the texture area overlap in the projection range of the mold cavity model, and the target feed rate difference is greater than or equal to the speed difference threshold, the toolpath with the higher target feed rate value will be reduced until the target feed rate difference is lower than the speed difference threshold, while the toolpath with the lower target feed rate value will not be increased.

[0013] Furthermore, methods for determining height differences include: Based on the engraving toolpath and tool cutting edge shape that precede the processing sequence, a toolpath envelope surface is generated. The target surface of the mold cavity model is read at the corresponding position of the small curvature change segment. The maximum height difference between the toolpath envelope surface and the target surface along the outer normal direction of the target surface is used as the height difference compared with the residual height threshold.

[0014] Furthermore, methods for determining the minimum spacing between adjacent toolpaths include: The engraving toolpaths with adjacent processing order within the texture area and those whose projection distance in the mold cavity model is lower than the adjacency threshold are all selected as candidate toolpaths. Candidate toolpaths not located within the texture area are eliminated, and the engraving toolpath closest to the small curvature abrupt change segment among the remaining candidate toolpaths is selected as the adjacent toolpath.

[0015] Furthermore, methods for determining the width of minute textures include: Using multiple toolpath points on the small curvature abrupt change segment as ranging points, along the ranging direction perpendicular to the toolpath direction and pointing to the texture boundaries on both sides of the mold cavity model surface, read the distance between the texture boundaries on both sides, exclude the distances where the ranging path is not located in the texture area, and determine the minimum distance among the remaining distances as the small texture width.

[0016] Furthermore, methods for identifying minute curvature abrupt change segments include: Within a continuous toolpath segment where the curvature change reaches the curvature change threshold, identify at least one peak toolpath point with the largest curvature change value. With the peak toolpath point as the center, read the curvature change of adjacent toolpath points along the front direction and the back direction of the machining sequence, until the first toolpath point with a curvature change lower than the fallback threshold is read. The toolpath point where the machining sequence first falls below the fallback threshold in the forward direction is taken as the forward boundary point, and the toolpath point where the machining sequence first falls below the fallback threshold in the backward direction is taken as the backward boundary point. The toolpath segment between the forward and backward boundary points with a path length lower than the abrupt change segment length threshold is defined as the small curvature abrupt change segment after boundary correction.

[0017] Secondly, this application discloses a deceleration distribution system for a mold cavity curvature abrupt change segment, used to implement the deceleration distribution method for the mold cavity curvature abrupt change segment described in the first aspect, including: The micro curvature abrupt change segment determination module is used to obtain the engraving toolpath of the mold cavity, determine the curvature change between adjacent toolpath points according to the toolpath point sequence, and determine the continuous toolpath segment where the curvature change reaches the curvature change threshold and the length of the continuous toolpath segment is lower than the abrupt change segment length threshold as the micro curvature abrupt change segment. The texture region determination module is used to read the texture boundaries on both sides based on the position of the small curvature abrupt segment in the mold cavity model, determine the minimum distance between the two texture boundaries as the small texture width, and determine the texture region from the two texture boundaries; The threshold comparison module is used to obtain three threshold comparison results based on whether the ratio of the tool diameter to the width of the micro texture reaches the width threshold, whether the height difference between the tool path envelope formed by the engraving tool path with the processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent tool paths in the micro curvature abrupt segment and the texture area is lower than the tool path distance threshold. The deceleration allocation module is used to query a preset deceleration allocation table based on the comparison results of three thresholds to obtain local deceleration allocation results including deceleration start point, deceleration end point, and target feed speed. The preset deceleration allocation table records the deceleration start point adjustment amount, deceleration end point adjustment amount, and target feed speed corresponding to the comparison results of the three thresholds. The toolpath writing module is used to write the local deceleration allocation results into the engraving toolpath.

[0018] Compared with existing related technologies, this application has the following beneficial effects: This application identifies minute curvature abrupt change segments in the engraving toolpath of a mold cavity and generates local deceleration distribution results by combining the width of the minute texture, the tool diameter, the residual height, and the minimum spacing between adjacent toolpaths. This makes the deceleration control no longer solely dependent on the curvature magnitude, but can reflect lateral occupancy, residual material load, and the risk of overlapping cuts between adjacent toolpaths in the machining of minute textures. As a result, the deceleration start point, deceleration end point, and target feed rate can be better matched to the actual machining state of the minute curvature abrupt change segments. Without changing the spatial orientation of the engraving toolpath, it reduces the probability of fine texture corner contour trimming, narrow groove boundary sidewall scratches, adjacent toolpath joint marks, and local depressions, thereby improving the contour retention and surface consistency of the fine texture of the mold cavity.

[0019] This application establishes a preset speed reduction allocation table and sets query rules, so that the comparison results of the three thresholds—the ratio of tool diameter to micro-texture width, height difference, and minimum spacing—can correspond to the target feed rate, the speed reduction start adjustment amount, and the speed reduction end adjustment amount, respectively. This avoids simply superimposing different risk sources into a uniform speed reduction ratio, thereby ensuring that the risks of sidewall scratches, residual material load, and adjacent toolpath overlap are applied to the most relevant speed reduction parameters, improving the matching degree between the local speed reduction allocation results and the actual machining risks.

[0020] In this application, when the local speed reduction distribution results of adjacent toolpaths overlap in the projection range within the same texture area, and the target feed rate difference reaches the speed difference threshold, only the target feed rate with the higher value is reduced while the target feed rate with the lower value is kept unchanged. This constrains the speed difference between adjacent toolpaths and does not weaken the speed reduction protection of high-risk micro-curvature change segments. As a result, it reduces tool mark joints and local brightness inconsistencies caused by excessive speed differences within the same texture area. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the steps of the method for allocating speed reduction in the abrupt curvature segment of a mold cavity provided in this application embodiment; Figure 2 This is a schematic diagram of a small curvature abrupt change segment provided in the embodiments of this application; Figure 3 This is a schematic diagram of the combination of three threshold comparison results provided in the embodiments of this application; Figure 4 This is a schematic diagram of local deceleration distribution provided in the embodiments of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Example 1: Please see Figure 1 As shown, this embodiment provides a method for speed reduction allocation in the curvature abrupt change segment of a mold cavity, which is used for engraving toolpaths for fine texture processing of mold cavities. The mold cavity can be the cavity surface of an injection mold, a die-casting mold, or an appearance texture mold. The engraving toolpath is the tool center motion path generated by the processing software based on the mold cavity model.

[0024] Before the machining program is written into the CNC machine tool, this method performs a local analysis of the engraving toolpath. First, it identifies a small curvature abrupt change segment with concentrated curvature changes and limited length in the entire engraving toolpath. Subsequent readings of the micro-texture width, residual height, and minimum spacing between adjacent toolpaths are all based on this small curvature abrupt change segment. This allows the speed reduction allocation to be processed for fine texture corners, narrow groove boundaries, and local reversal positions, avoiding ordinary turning toolpaths from entering the local speed reduction allocation process. The following is a detailed explanation of each step of this scheme in conjunction with specific implementation methods.

[0025] Step 1: Obtain the engraving toolpath of the mold cavity. Determine the curvature change between adjacent toolpath points according to the toolpath point sequence. Identify the continuous toolpath segments where the curvature change reaches the curvature change threshold and the length of the continuous toolpath segment is lower than the abrupt change segment length threshold as small curvature abrupt change segments.

[0026] In practice, the engraving toolpath of the mold cavity is first read. The engraving toolpath can come from the tool position file output by the machining software or be obtained by the machining program. Each toolpath point contains at least the coordinates of the tool center point, the toolpath point sequence and the corresponding machining feed direction. After reading, adjacent toolpath points are processed in sequence according to the toolpath point sequence.

[0027] In actual machining files, some toolpath points may have uneven spacing due to the discrete rules of the machining software. In this case, while maintaining the original geometric direction of the engraving toolpath, the toolpath points can be made equidistant so that the subsequent judgment of curvature change is based on a uniform toolpath point density. It should be noted that the equidistant processing is only used to supplement the distribution of toolpath points, and does not change the position of the engraving toolpath in the mold cavity model, nor does it change the texture contour corresponding to the original machining program.

[0028] Subsequently, the curvature change between adjacent toolpath points is determined. As an optional implementation, three consecutive toolpath points can be fitted with a local arc, and the reciprocal of the radius of the local arc can be used as the curvature value of the middle toolpath point. When the three toolpath points are approximately collinear (the three toolpath points are collinear or cannot form an effective local arc), the curvature value of the middle toolpath point can be recorded as zero. After obtaining the curvature values ​​of each toolpath point, the absolute value of the difference between the curvature values ​​of adjacent toolpath points is used as the curvature change between adjacent toolpath points.

[0029] In another alternative implementation, the curvature change can also be determined based on the change in the machining feed direction corresponding to adjacent toolpath points. When the spacing between adjacent toolpath points is consistent, the more concentrated the change in the machining feed direction, the higher the corresponding curvature change. Both of the above methods are based on the order of toolpath points, and the final object obtained is the curvature change between adjacent toolpath points.

[0030] The curvature change threshold is used to identify the locations where curvature changes are concentrated in the engraving toolpath. The curvature change threshold can be predetermined through qualified machining records of similar mold cavities. Engraving toolpaths without contour trimming, sidewall scratches, or local depressions can be selected, and the curvature change at normal corner positions can be statistically analyzed. The quantile value closest to the upper limit in the statistical results can be used as the curvature change threshold. Alternatively, the curvature change threshold can be determined through trial cutting of samples. Under the same mold material, the same tool diameter, and the same toolpath point density, the curvature change before contour trimming begins can be recorded, and this curvature change can be used as the basis for setting the curvature change threshold. With this setting method, the curvature change threshold can match the current machining object and tool specifications, reducing the possibility of ordinary turning positions being identified as small curvature abrupt change segments.

[0031] After obtaining the curvature change, toolpath points whose curvature change reaches the curvature change threshold and are consecutive in the toolpath point sequence are grouped into continuous toolpath segments. Corners in fine textures are usually formed by multiple continuous toolpath points. If only a single toolpath point is used as the processing object, it is difficult to determine the deceleration start point and deceleration end point. Therefore, toolpath points that are adjacent in the toolpath point sequence and whose curvature change reaches the curvature change threshold are grouped into the same continuous toolpath segment.

[0032] If a toolpath point in a local corner does not reach the curvature change threshold, but the toolpath point is located between two toolpath points that have reached the curvature change threshold and is still within the same local corner, it is classified into the same continuous toolpath segment to avoid the same texture corner being discretized into multiple scattered objects.

[0033] Please see Figure 2 As shown, after the continuous toolpath segment is formed, the abrupt change segment length threshold can be used to determine whether the continuous toolpath segment belongs to a small curvature abrupt change segment. The abrupt change segment length threshold is used to limit the maximum toolpath length of the local abrupt change. In this embodiment, it can be measured according to the path length of the continuous toolpath segment in the engraving toolpath path direction, and can be preset according to the tool diameter, the micro-texture scale, and the minimum toolpath length that the CNC machine tool can perform speed adjustment. If the path length of the continuous toolpath segment is lower than the abrupt change segment length threshold, and there is a toolpath point or toolpath point interval within the continuous toolpath segment with a curvature change greater than or equal to the curvature change threshold, then the continuous toolpath segment is determined to be a small curvature abrupt change segment; if the length of the continuous toolpath segment reaches or exceeds the abrupt change segment length threshold, then the continuous toolpath segment is not determined to be a small curvature abrupt change segment.

[0034] To ensure that the small curvature change segment has a clear starting and ending toolpath point, the boundary can be corrected by combining the fallback threshold. Within the continuous toolpath segment, at least one toolpath point where the curvature change reaches the curvature change threshold and has the largest value can be determined first.

[0035] When there are multiple toolpath points with the largest values, each toolpath point with the largest value can be used as the center position for boundary search. Then, the curvature change is read in the forward direction along the machining sequence until the toolpath point where the curvature change is first lower than the fallback threshold is read in the backward direction along the machining sequence until the toolpath point where the curvature change is first lower than the fallback threshold is read in the backward direction. The toolpath segment between the two toolpath points where the curvature change is first lower than the fallback threshold is taken as the small curvature change segment after boundary correction.

[0036] In this embodiment, the fallback threshold is less than the curvature change threshold. It can be set proportionally according to the curvature change threshold, or it can be determined statistically by the curvature change fallback process at the corner position in the qualified engraving toolpath. This processing can allow the small curvature change segment to cover the complete local range of curvature change entry, peak and exit, providing a spatial basis for the subsequent generation of deceleration start and deceleration end points.

[0037] It is important to note that when multiple toolpath points with the largest values ​​exist within the same continuous toolpath segment, it is not advisable to retain only one toolpath point for boundary search. If the boundary search results corresponding to multiple toolpath points with the largest values ​​overlap, the overlapping results can be merged into the same small curvature change segment. If the boundary search results are separated by toolpath segments that have not reached the curvature change threshold, they can be identified as multiple small curvature change segments. This can adapt to the situation where adjacent small corners are densely distributed in leather texture, fish scale texture, and micro-text edges, and reduce the number of multiple local changes being mixed into an excessively long toolpath segment.

[0038] After the processing in step one above, one or more micro-curvature abrupt change segments can be obtained from the engraving toolpath of the mold cavity. Each micro-curvature abrupt change segment includes at least the starting toolpath point, the ending toolpath point, the corresponding toolpath length, and the corresponding curvature change amount. Subsequently, the textural boundaries on both sides are read, the micro-texture width is determined, the height difference is determined, and the minimum spacing between adjacent toolpaths is determined. All of these are carried out with this micro-curvature abrupt change segment as the unified object. Thus, the local deceleration allocation has a clear spatial range and toolpath range before entering the subsequent risk assessment. This helps to reduce the situation where ordinary turning toolpaths are included in the deceleration allocation and reduces the probability of micro-curvature abrupt change segments at fine texture corners and narrow groove boundaries being missed.

[0039] Step 2: Based on the position of the small curvature abrupt change segment in the mold cavity model, read the texture boundaries on both sides, determine the minimum distance between the texture boundaries on both sides as the small texture width, and determine the texture region from the texture boundaries on both sides.

[0040] After identifying the small curvature abrupt change segment, it is necessary to find the texture space range corresponding to the local toolpath segment in the mold cavity model. The small curvature abrupt change segment obtained in the previous stage only indicates that there is a curvature concentration change in the engraving toolpath within a certain short distance, but it cannot reflect the texture geometric constraints at that position.

[0041] For fine engraving of mold cavities, for toolpath segments of the same length and with the same curvature variation, if located on an open surface, the lateral allowance of the tool is provided by the width of the texture area; if located at a narrow groove boundary or fine texture corner, the relative occupancy of the tool diameter to the texture width will directly affect the risk of sidewall scratches and contour trimming. Therefore, before performing subsequent threshold comparison, it is necessary to first read the texture boundaries on both sides based on the position of the small curvature abrupt segment in the mold cavity model, determine the small texture width, and determine the texture area from the texture boundaries on both sides.

[0042] In practice, the starting point, ending point, and intermediate point of the micro-curvature abrupt change segment are first mapped to the mold cavity model. If the engraving toolpath itself is generated by the mold cavity model, each toolpath point usually corresponds to the tool contact position on the surface of the mold cavity model. If the engraving toolpath comes from the machining program analysis, the tool contact position can be calculated in reverse according to the coordinates of the tool center point and the shape of the tool cutting edge, and then the tool contact position is projected onto the surface of the mold cavity model. The mapping relationship here is only used to determine the position of the micro-curvature abrupt change segment in the mold cavity model, without changing the starting point and ending point of the micro-curvature abrupt change segment.

[0043] The texture boundaries on both sides can be derived from the texture outline, groove sidewall boundary, raised texture edge in the mold cavity model, or texture boundary data used by the processing software when generating the engraving toolpath. In this embodiment, the texture boundaries on both sides refer to the boundaries located on both sides of the small curvature abrupt change segment, used to define the lateral range of the same small texture.

[0044] For narrow groove textures, the two texture boundaries can be the intersection lines between the left and right sidewalls of the narrow groove and the bottom or adjacent surfaces; for fine ridge textures, the two texture boundaries can be the edge lines on both sides of the ridge; for micro-texture edges, the two texture boundaries can be the outline lines on both sides of the stroke. If the mold cavity model already contains texture boundary markers, these markers can be read directly; if the model only contains surface data, the two texture boundaries can be determined based on the intersection lines between adjacent surfaces, the location of texture depth changes, or the outline lines retained when the machining software generates the toolpath. It should be noted that the two texture boundaries should correspond to the same texture object, and the boundaries of adjacent different texture objects should not be mistakenly taken as the two boundaries of the same micro-texture.

[0045] After reading the texture boundaries on both sides, the texture region is determined by the texture boundaries on both sides. The texture region can be understood as the local range of the texture where the small curvature change segment is located. Its horizontal boundary is defined by the texture boundaries on both sides, and its vertical range at least covers the starting toolpath point and the ending toolpath point corresponding to the small curvature change segment.

[0046] For regular grooves, the strip-shaped area between the two texture boundaries can be used as the texture area; for curved fine lines, a local strip-shaped area covering the small curvature change segment can be intercepted along the direction of the two texture boundaries; for closed micro-text outlines, the area enclosed by the two texture boundaries and containing the projection position of the small curvature change segment can be used as the texture area. The determination of the texture area ensures that subsequent ranging will not cross the adjacent texture, thereby ensuring that the width of the micro-texture reflects the actual lateral constraint of the current small curvature change segment.

[0047] Subsequently, multiple toolpath points are selected as ranging points on the micro-curvature abrupt change segment. The ranging points can include the starting toolpath point, the ending toolpath point, and several toolpath points located between the two of the micro-curvature abrupt change segment. When there are many toolpath points in the micro-curvature abrupt change segment, they can be selected at equal intervals according to the order of the toolpath points, or all toolpath points can be used directly. The reason for selecting multiple ranging points is that the width of the fine texture corner and the narrow groove boundary may change along the toolpath direction. Reading the distance between the two texture boundaries at only one position is easy to miss the position with the most limited width. By measuring the distance through multiple ranging points, the final micro-texture width can be closer to the minimum lateral passage space in the micro-curvature abrupt change segment.

[0048] For each distance measurement point, along the distance measurement direction that is perpendicular to the toolpath and points to the texture boundaries on both sides of the mold cavity model surface, read the distance between the texture boundaries on both sides. Here, the distance measurement direction does not refer to the outward normal direction of the mold cavity model surface, but specifically to the transverse direction that intersects with the toolpath direction within the model surface.

[0049] Specifically, the toolpath direction at the measuring point can be determined first based on the adjacent toolpath points before and after the measuring point. Then, the measuring direction is taken as the direction perpendicular to the toolpath direction and pointing to the texture boundaries on both sides within the surface of the mold cavity model. The path length or projection distance is read from one texture boundary to the other texture boundary along the measuring direction to obtain the boundary distance corresponding to the measuring point. For curved surface textures, the path length read along the surface of the mold cavity model is preferred. For local areas with small curvature, the distance projected onto the local tangent plane can also be used as the boundary distance.

[0050] It is important to note that the distance measurement path must be located within the texture area. If the distance measurement direction corresponding to a certain distance measurement point extends beyond the texture area, or if the distance measurement path crosses an adjacent texture object before reaching the texture boundary on the other side, then the distance cannot be used to determine the width of the micro-texture. In practice, the positional relationship between the distance measurement path and the texture area can be determined to exclude distances where the distance measurement path is not located within the texture area. For mold cavities with dense boundaries such as leather texture and fish scale texture, the distance between adjacent textures is very close. If this exclusion process is not performed, the gap between adjacent textures may be mistakenly taken as the current micro-texture width, thus affecting the subsequent determination of the ratio of tool diameter to micro-texture width.

[0051] After obtaining multiple boundary distances within the textured region, the minimum distance among the remaining distances is determined as the micro-texture width. This is mainly because when the tool passes through a micro-curvature abrupt change segment, the narrowest position corresponds to the maximum risk of the tool simultaneously approaching the texture boundary on both sides. If the average distance is used as the micro-texture width, some local narrowing positions may be masked by the average value; if the maximum distance is used as the micro-texture width, it will be even less able to reflect the sensitive positions of sidewall scratches. Therefore, in this embodiment, the minimum distance among the remaining distances is used as the micro-texture width so that the ratio of the subsequent tool diameter to the micro-texture width can directly reflect the most restricted tool width situation within the micro-curvature abrupt change segment.

[0052] In another optional implementation, if the texture region width data has been pre-stored in the mold cavity model, the width data of the texture region corresponding to the micro curvature abrupt change segment can be directly read, and the minimum width covering the micro curvature abrupt change segment range can be taken as the micro texture width. This method is suitable for situations where the texture region is generated by the processing software parameterization, such as regular grooves, repeating array textures, or standard micro-text outlines. In this case, it is still necessary to ensure that the read width data comes from the texture region defined by the texture boundaries on both sides of the micro curvature abrupt change segment and cannot cross into the adjacent texture region. This implementation method is consistent with the aforementioned method of reading distance along the ranging direction in terms of processing results, and ultimately obtains the micro texture width for subsequent threshold comparison.

[0053] After the processing in step two above, each tiny curvature abrupt change segment corresponds to a texture region and a tiny texture width. The texture region is used to limit the search range of subsequent adjacent toolpaths, and the tiny texture width is used to form a ratio with the tool diameter and participate in the width threshold comparison. In this way, the tiny curvature abrupt change segment obtained in step one is no longer just a short abrupt change position in the geometry of the toolpath, but is further placed into the specific texture space in the mold cavity model, providing a reproducible data basis for subsequent judgment on whether the tool diameter occupies too much texture width.

[0054] Step 3: Based on whether the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, whether the height difference between the toolpath envelope formed by the engraving toolpath in the previous processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent toolpaths in the micro-curvature abrupt segment and the texture area is lower than the toolpath distance threshold, three threshold comparison results are obtained.

[0055] After obtaining the small curvature abrupt change segment, the small texture width, and the texture region, the next step is to transform the geometric constraints of this local location into a three-threshold comparison result that can be used for deceleration assignment. The texture region where the small curvature abrupt change segment is located, as well as the minimum lateral width of the texture region at the small curvature abrupt change segment, have already been determined.

[0056] This stage further determines whether the tool can easily approach the texture boundaries on both sides within this width, whether the previous machining left residual material that needs to be removed again, and whether adjacent toolpaths form a close, repetitive cutting relationship in the same texture area. These three judgments correspond to the ratio of the tool diameter to the width of the micro-texture, the height difference between the toolpath envelope and the target surface, and the minimum distance between adjacent toolpaths in the texture area from the micro-curvature abrupt change segment. Finally, three threshold comparison results are formed for subsequent use in querying the preset deceleration allocation table.

[0057] In this embodiment, the ratio of the tool diameter to the width of the micro-texture is first determined. The tool diameter can be read from the tool table of the machining program, the tool parameters of the machining software, or the process file. The object to be read should be the tool diameter for machining the micro-curvature change segment. For ball end mills, the tool diameter is the nominal diameter of the ball end mill. For tapered cutters, if the machining position is mainly participated in cutting near the tool tip, the effective tool diameter at the cutting depth corresponding to the micro-curvature change segment can be used.

[0058] For example, the three threshold comparison results can be formed as follows: Width ratio = Tool diameter involved in machining the small curvature abrupt change segment ÷ Small texture width; for a conical tool using an effective tool diameter, the tool diameter in this formula is the effective tool diameter; height difference is the maximum value of the toolpath envelope surface exceeding the target surface along the outer normal direction of the target surface; minimum spacing is the shortest distance from the small curvature abrupt change segment to the adjacent toolpath within the texture region. If the width ratio reaches the width threshold, the first threshold comparison result is recorded as 1; otherwise, it is recorded as 0. If the height difference reaches the residual height threshold, the second threshold comparison result is recorded as 1; otherwise, it is recorded as 0. If the minimum spacing is lower than the toolpath spacing threshold, the third threshold comparison result is recorded as 1; otherwise, it is recorded as 0. In this way, any small curvature abrupt change segment can obtain a query condition consisting of three binary results.

[0059] Since the width of the micro-texture has been determined in the previous stage by the minimum distance between the two texture boundaries, the tool diameter can be directly divided by the width of the micro-texture to obtain the ratio of the tool diameter to the width of the micro-texture. The closer this ratio is to 1, the closer the tool occupies the passable width of the texture area laterally, and the higher the probability that the two sides of the tool are close to the texture boundaries at the same time.

[0060] The width occupancy threshold is used to determine whether the occupancy of the tool diameter relative to the width of the small texture reaches a level that requires speed reduction and attention. The width occupancy threshold can be predetermined based on tool manufacturing deviation, machine tool positioning error, mold cavity model machining allowance, and allowable sidewall allowance.

[0061] As an optional implementation, the minimum lateral allowance allowed to be retained at the two side texture boundaries can be determined first. Then, the usable width after deducting the minimum lateral allowance on both sides from the width of the micro-texture can be converted to obtain the width threshold. Alternatively, it can be determined by trial cutting of similar textures. The sidewall scratch situation can be observed under different ratios of tool diameter to micro-texture width. The maximum ratio without sidewall scratch is used as the basis for setting the width threshold. If the ratio of tool diameter to micro-texture width reaches the width threshold, the first item in the comparison result of the three thresholds is recorded as reaching the width threshold; if the width threshold is not reached, the first item is recorded as not reaching the width threshold.

[0062] It is important to note that when machining narrow textures with a tapered cutter, directly using the nominal maximum diameter of the cutter may exaggerate the lateral occupancy of the cutter at the slight curvature abrupt change. In this case, the effective cutter diameter at the cutting position can be determined based on the shape of the cutter edge and the cutting depth corresponding to the slight curvature abrupt change. Then, the effective cutter diameter can be used to form a ratio with the width of the slight texture. This approach can adapt to situations where the cutter contact height is different at the edges of micro-textures, the bottom of narrow grooves, and in shallow relief textures, avoiding the impact of inconsistent cutter diameter readings on the width threshold comparison results.

[0063] The effective tool diameter can be determined based on the cone angle of the conical cutter, the radius of the tip arc, and the cutting depth corresponding to the small curvature change segment. The cutting depth can be determined by the height of the tool center point, the height of the target surface, and the machining allowance. When the same small curvature change segment corresponds to multiple measuring points, the maximum value of the cutting depth among the multiple measuring points can be taken to calculate the effective tool diameter, and the effective tool diameter should not be greater than the nominal maximum diameter of the conical cutter.

[0064] Subsequently, the height difference between the toolpath envelope and the target surface of the mold cavity model is determined. The toolpath envelope is used to represent the boundary of the machined surface formed by the tool cutting edge of the engraving toolpath that precedes the machining sequence. In specific implementation, the engraving toolpath that precedes the machining sequence and the shape of the cutting edge of the tool used for that engraving toolpath are read. The cutting edge of the tool is swept along the engraving toolpath that precedes the machining sequence to obtain the toolpath envelope. For ball end mills, the sweep envelope can be formed according to the radius of the ball end mill cutting edge. For tapered cutters, the sweep envelope can be formed according to the cone angle and the tip arc. If the machining software has already output the residual height map or machining allowance map of the preceding toolpath, the corresponding data can also be directly read and converted into the height difference between the toolpath envelope and the target surface.

[0065] The target surface of the mold cavity model is the cavity design surface that needs to be finally machined. At the position corresponding to the small curvature change segment, the maximum height difference between the toolpath envelope and the target surface is read along the outer normal direction of the target surface. This maximum height difference is used as the height difference compared with the residual height threshold. The reason for using the maximum height difference is that the local residual material in the small curvature change segment is often concentrated at the residual ridge position left by the previous toolpath. The material removal load when the tool enters this position is more significantly affected by the local highest residual. If the average height difference is used, the residual ridge may be diluted by the adjacent low residual position, which is not conducive to judging whether the small curvature change segment needs to be slowed down in advance.

[0066] The residual height threshold is used to determine whether the unremoved material left by the preceding toolpath will cause the cutting load of the small curvature abrupt segment to enter the range that requires speed reduction. The residual height threshold can be predetermined based on the target surface roughness requirements, subsequent polishing allowance, tool edge strength, and material removal requirements. In one optional embodiment, the upper limit of the single-cut residual height allowed by the process document can be used as the residual height threshold. Alternatively, the tool mark and contour retention at different residual heights can be determined by test cutting samples, and the maximum residual height without tool mark enlargement or contour trimming can be used as the residual height threshold. If the height difference reaches the residual height threshold, the second item in the comparison result of the three thresholds is recorded as reaching the residual height threshold; if the residual height threshold is not reached, the second item is recorded as not reaching the residual height threshold.

[0067] In actual implementation, there may be steep sidewalls or deep and narrow grooves in the mold cavity model, and the direction of the outer normal of the target surface changes rapidly. In such scenarios, the height difference reading should be limited to the local target surface corresponding to the small curvature change segment, and avoid crossing to adjacent sidewalls or other textured surfaces. If the same small curvature change segment covers multiple target surface pieces, the height difference can be read in each target surface piece separately, and then the maximum value of these height differences can be used for comparison of the residual height threshold. This processing can prevent the height difference reading deviation caused by the difference in normal between different surface pieces.

[0068] Next, determine the minimum spacing between adjacent toolpaths within the textured area from the small curvature abrupt change segment. The search range for adjacent toolpaths is limited to the textured area that has been determined earlier. This is because there may be multiple textured objects that are close to each other in the same mold cavity model. Spatial proximity does not necessarily mean that they form a repeated cutting relationship on the same textured surface.

[0069] In practice, the engraving toolpaths that are adjacent in processing order within the texture area, as well as the engraving toolpaths whose projection distance in the mold cavity model is lower than the adjacency threshold, can be selected as candidate toolpaths. Then, candidate toolpaths that are not located within the texture area are removed.

[0070] Specifically, when the projection of the candidate toolpath in the mold cavity model does not fall into the texture area, or when the shortest projection path between the candidate toolpath and the small curvature change segment passes through the texture boundaries on both sides, the candidate toolpath is determined to be outside the texture area. Then, the engraving toolpath closest to the small curvature change segment among the remaining candidate toolpaths is taken as the adjacent toolpath. The distance can be the shortest surface distance from the toolpath point on the small curvature change segment to the candidate toolpath, or the shortest projection distance after the two are projected onto the local cutting plane. For cavities with large surface changes, the shortest distance along the surface of the mold cavity model is preferred.

[0071] The adjacency threshold is used to exclude engraving toolpaths that are too far away from the small curvature abrupt change segment and will not cause repeated cutting effects in the same texture area when searching for candidate toolpaths. This threshold can be set according to the small texture width, tool diameter and step distance when the toolpath is generated. Since the adjacency threshold is only used for the initial screening of adjacent toolpaths, the adjacent toolpaths still need to be determined by texture area limitation and minimum distance. Therefore, this threshold does not need to participate in the subsequent deceleration allocation table. It only needs to ensure that engraving toolpaths that may cause overlapping cutting effects in the same texture area are not missed.

[0072] After determining the adjacent toolpaths, the minimum distance from the small curvature abrupt change segment to the adjacent toolpath is read, and this minimum distance is compared with the toolpath spacing threshold. The toolpath spacing threshold is used to determine whether the engraving toolpaths in the same texture area are close enough to cause local dwell time superposition or repeated cutting effects.

[0073] In one alternative implementation, the toolpath spacing threshold can be determined based on the conventional toolpath step distance corresponding to the tool diameter, micro-texture width, and residual height threshold; alternatively, it can be determined based on the minimum toolpath spacing in similar qualified machining records where no tool marks or joints appear. If the minimum spacing is lower than the toolpath spacing threshold, the third item in the comparison result of the three thresholds is recorded as being lower than the toolpath spacing threshold; if the minimum spacing is not lower than the toolpath spacing threshold, the third item is recorded as not being lower than the toolpath spacing threshold.

[0074] It is important to note that in the surface convergence region or texture reversal region, the engraving toolpaths with adjacent processing sequences are not necessarily the toolpaths spatially closest to the small curvature abrupt change segment. Conversely, some engraving toolpaths with far apart processing sequences may be close to the same texture region due to surface reversal. Therefore, this embodiment must consider both the adjacent relationship of processing sequence and the spatial projection distance relationship, and then eliminate irrelevant toolpaths through the texture region. This can take into account both the adjacent effects caused by sequential processing and the overlapping effects caused by spatial proximity, and avoid missing the real neighboring toolpaths at the surface convergence position when only looking for adjacent toolpaths according to the processing sequence.

[0075] After the processing in step three above, a small curvature abrupt change segment will yield three threshold comparison results: whether the ratio of tool diameter to micro-texture width reaches the width threshold, whether the height difference reaches the residual height threshold, and whether the minimum spacing is lower than the toolpath spacing threshold. These three threshold comparison results reflect the tool's lateral occupancy, the preceding residual load, and the overlapping relationship of adjacent toolpaths, respectively. When querying the preset speed reduction allocation table in the future, it is not necessary to recalculate the texture boundary, toolpath envelope, or adjacent toolpaths. It is only necessary to determine the speed reduction start adjustment amount, speed reduction end adjustment amount, and target feed rate based on these three threshold comparison results, so that the local speed reduction allocation can correspond to the actual machining risks within the small curvature abrupt change segment.

[0076] Step 4: Based on the comparison results of the three thresholds, query the preset deceleration allocation table to obtain the local deceleration allocation results, including the deceleration start point, deceleration end point, and target feed speed. The preset deceleration allocation table records the deceleration start point adjustment, deceleration end point adjustment, and target feed speed corresponding to the comparison results of the three thresholds.

[0077] Please see Figure 3 As shown, after completing the comparison of the three thresholds, the local deceleration allocation enters the speed parameter generation stage. The previous stage has transformed the machining risk in the small curvature change segment into three clear judgment results: whether the ratio of the tool diameter to the width of the small texture reaches the width threshold, whether the height difference reaches the residual height threshold, and whether the minimum spacing is lower than the toolpath spacing threshold.

[0078] The purpose of the preset speed reduction allocation table is to convert these three judgment results into the speed reduction start point, speed reduction end point and target feed speed that can be written into the engraving toolpath. This allows different sources of machining risks to be applied to different speed reduction parameters. After processing, the speed reduction results within the small curvature change segment have a traceable source, and the reason why each speed reduction parameter changes can be clearly determined during subsequent actual machine adjustment.

[0079] The preset speed reduction allocation table can be pre-established based on mold material, tool type, target surface quality, and machine tool execution capability before processing. The target feed rate can be obtained by multiplying the original feed rate (the original feed rate refers to the feed rate already set at the micro-curvature change section of the original engraving toolpath) by the speed reduction ratio. The speed reduction ratio is determined by the feed rate range in the test cut sample where no sidewall scratches are produced. The speed reduction start adjustment amount and speed reduction end adjustment amount can be determined by multiples of the length of the micro-curvature change section or the minimum toolpath length that the CNC machine tool can perform speed adjustment. The table uses three threshold comparison results as query conditions. The three threshold comparison results are whether the ratio of tool diameter to micro-texture width reaches the width threshold, whether the height difference reaches the residual height threshold, and whether the minimum spacing is lower than the toolpath spacing threshold. Each query condition combination corresponds to a set of speed reduction start adjustment amount, speed reduction end adjustment amount, and target feed rate. Since the three threshold comparison results are all binary judgments, the preset speed reduction allocation table can form eight basic query condition combinations.

[0080] For example, the preset deceleration allocation table can use three threshold comparison results as query conditions, where 1 indicates that the corresponding threshold comparison condition is met, and 0 indicates that the corresponding threshold comparison condition is not met. When the query conditions are 0, 0, 0, the deceleration start adjustment amount is 0, the deceleration end adjustment amount is 0, and the target feed speed adopts the feed speed of the original engraving toolpath. When the query conditions are 1, 0, 0, the target feed speed is lower than the feed speed of the original engraving toolpath. When the query conditions are 0, 1, 0, the deceleration start adjustment amount is greater than 0, and the target feed speed is not higher than the original feed speed of the original engraving toolpath at the small curvature change segment. When the query conditions are 0, 0, 1, the deceleration end adjustment amount is greater than 0, and the target feed speed is not higher than the original feed speed of the original engraving toolpath at the small curvature change segment.

[0081] For example, when the query conditions are 1, 1, 0, the target feed rate is the target feed rate corresponding to reaching the width threshold, and the deceleration start adjustment amount is the deceleration start adjustment amount corresponding to reaching the residual height threshold; when the query conditions are 1, 0, 1, the target feed rate is the target feed rate corresponding to reaching the width threshold, and the deceleration end adjustment amount is the deceleration end adjustment amount corresponding to being lower than the toolpath spacing threshold; when the query conditions are 0, 1, 1, the deceleration start adjustment amount is the deceleration start adjustment amount corresponding to reaching the residual height threshold, and the deceleration end adjustment amount is the deceleration end adjustment amount corresponding to being lower than the toolpath spacing threshold; when the query conditions are 1, 1, 1, the target feed rate corresponding to reaching the width threshold, the deceleration start adjustment amount corresponding to reaching the residual height threshold, and the deceleration end adjustment amount corresponding to being lower than the toolpath spacing threshold are all used.

[0082] When establishing a preset speed reduction allocation table, it is necessary to first determine the combination of query conditions that do not reach the width threshold, the height difference does not reach the residual height threshold, and the minimum spacing is not lower than the toolpath spacing threshold. This combination corresponds to the situation where there is no lateral occupancy restriction, residual load increase, or adjacent toolpaths approaching within the small curvature change segment. The feed rate in the original engraving toolpath can be used as the target feed rate. The speed reduction start adjustment amount and speed reduction end adjustment amount can be configured to zero, or configured to only cover the minimum adjustment amount of the small curvature change segment itself. This table entry is used as the comparison basis for other table entries, and also to avoid excessive speed reduction of small curvature change segments without local material removal risk.

[0083] When the ratio of the tool diameter to the width of the micro-texture reaches the width occupancy threshold, it means that the tool's lateral occupancy is close to the allowable passage width of the texture area. At this time, the target feed rate corresponding to the preset speed reduction allocation table should be lower than the target feed rate corresponding to the time when the width occupancy threshold is not reached. This setting reduces the risk of sidewall scratches when the tool approaches the texture boundaries on both sides at the same time by reducing the feed rate of the tool at the fine texture corners and narrow groove boundaries.

[0084] When actually setting up the table, the target feed rate can be set according to the allowable sidewall margin, the shape of the cutting edge, and the results of similar trial cuts. If sidewall scratches are the main risk of the mold cavity, the table that reaches the width threshold can prioritize reducing the target feed rate without having to expand the speed reduction range of the entire engraving toolpath.

[0085] When the height difference reaches the residual height threshold, it indicates that the unremoved material left by the earlier engraving toolpaths has reached a level requiring attention. Since this type of risk mainly occurs when the tool enters the small curvature abrupt change section and begins to cut into the residual material, the corresponding reduction starting point adjustment in the preset reduction allocation table should be greater than the corresponding reduction starting point adjustment when the residual height threshold is not reached. In other words, the reduction in the target feed rate not only occurs within the small curvature abrupt change section but can also occur earlier on a section of the engraving toolpath before the small curvature abrupt change section, ensuring that the tool has already reduced its speed before entering a position with more residual material. This setting helps mitigate contour trimming and tool mark amplification caused by the tool suddenly cutting into the residual ridge.

[0086] When the minimum spacing is lower than the toolpath spacing threshold, it indicates that the distance between adjacent toolpaths in the same texture area has become so close that it may lead to repeated cutting or overlapping of local dwell times. This type of risk may still affect the surface consistency in the same texture area after the tool leaves the small curvature change section. Therefore, the corresponding speed reduction endpoint adjustment amount in the preset speed reduction allocation table should be greater than the corresponding speed reduction endpoint adjustment amount when it is not lower than the toolpath spacing threshold. By delaying the speed reduction endpoint, the tool can maintain the target feed rate when it leaves the small curvature change section and passes the adjacent toolpath close position, reducing the probability of tool marks, joints and local depressions.

[0087] For query condition combinations that simultaneously meet multiple threshold comparison conditions, the preset speed reduction allocation table configures speed reduction parameters according to the risk source. However, it is necessary to avoid simply adding up the various adjustment amounts mechanically, which would result in an excessively long speed reduction range. As an optional implementation method, the basic table entries corresponding to the width threshold, residual height threshold, and toolpath spacing threshold are determined separately. Then, based on the combination of the three threshold comparison results, the target feed rate with the lowest value, the speed reduction starting adjustment amount that makes the speed reduction start point the earliest, and the speed reduction ending adjustment amount that makes the speed reduction ending point the latest are selected.

[0088] If the same combination of query conditions reaches both the width threshold and the residual height threshold, the target feed rate is reduced according to the table entry corresponding to the width threshold, and the starting adjustment amount of the deceleration is moved forward according to the table entry corresponding to the residual height threshold. If both are below the toolpath spacing threshold, the corresponding ending adjustment amount of the deceleration is further adopted. This allows each risk to correspond to the most relevant deceleration parameter, reducing over-conservatism caused by multiple risks being superimposed on the same parameter.

[0089] It is important to note that the target feed rate in the preset speed reduction distribution table should not be lower than the minimum feed rate that the machine tool can execute smoothly, nor should it be higher than the original feed rate of the original engraving toolpath at that position. If the target feed rate obtained from the table is lower than the minimum stable feed rate of the machine tool, the minimum stable feed rate of the machine tool can be used as the target feed rate. If the target feed rate obtained from the table is higher than the original feed rate, the original feed rate should be retained, and the adjustment amount at the starting point and the ending point of the speed reduction should also be limited to a range that will not be included by adjacent ordinary toolpaths. In specific implementation, the adjusted spatial range can be determined by combining the starting and ending toolpath points of the small curvature change segment to ensure that the local speed reduction distribution still revolves around the small curvature change segment.

[0090] When querying the preset speed reduction allocation table, the comparison results of the three thresholds obtained in the previous stage are used as query conditions. The corresponding speed reduction start adjustment amount, speed reduction end adjustment amount, and target feed speed are read. Then, based on the starting toolpath point of the small curvature change segment, the speed reduction start adjustment amount is shifted forward in the machining sequence to obtain the speed reduction start point.

[0091] Then, based on the end point of the small curvature change segment, the deceleration endpoint is offset in the backward direction of the processing sequence according to the adjustment amount of the deceleration endpoint to obtain the deceleration endpoint. The offset can be based on the actual path length of the engraving toolpath, but cannot be directly offset according to the straight distance in space. Otherwise, the position may not be on the engraving toolpath in the curved texture or the folded texture. If the offset position falls between two toolpath points, the interpolation position between adjacent toolpath points can be used as the deceleration start point or deceleration endpoint. Alternatively, the toolpath point closest to this position and located in the direction corresponding to the processing sequence can be selected as the deceleration start point or deceleration endpoint.

[0092] In another alternative implementation, the preset speed reduction allocation table may not directly store the final target feed rate, but instead store the reduction ratio relative to the original feed rate. The target feed rate is then calculated based on the feed rate of the original engraving toolpath at the small curvature change section. This method is suitable for situations where the same set of table entries needs to be adapted to different processing materials or different machine tool feed rate limits.

[0093] Regardless of whether the target feed rate is stored directly or the reduction ratio relative to the original feed rate is stored, the object ultimately written into the subsequent process is still the target feed rate, and this target feed rate needs to together with the reduction start point and the reduction end point to form the local reduction allocation result.

[0094] For situations where multiple small curvature abrupt change segments are close to each other, the preset deceleration allocation table can be queried separately to generate their respective local deceleration allocation results. If the deceleration start and deceleration end points of two adjacent small curvature abrupt change segments overlap, the target feed rate with the lower value can be retained, and the foremost deceleration start and the last deceleration end point after the overlap can be used as the merged deceleration start and deceleration end points. This processing method is suitable for situations where multiple corners appear densely in leather textures or micro-text edges, and can avoid the engraving toolpath frequently switching the target feed rate within a very short distance. This supplementary processing does not change the query logic of the preset deceleration allocation table, but only connects the multiple local deceleration allocation results.

[0095] After the processing in step four above, each small curvature abrupt change segment yields a local deceleration allocation result. The local deceleration allocation result includes the deceleration start point, the deceleration end point, and the target feed rate. The deceleration start point reflects the distance that the tool needs to decelerate before entering the risk position, the deceleration end point reflects the distance that the tool needs to maintain a controlled speed after leaving the risk position, and the target feed rate reflects the feed rate that the tool should execute within this local range. Since this result is directly derived from the comparison results of three thresholds, the influence of the small texture width, residual height, and minimum spacing between adjacent toolpaths on the deceleration allocation can be reflected separately, providing clear data content for subsequently writing the local deceleration allocation result into the engraving toolpath.

[0096] Step 5: Write the local speed reduction allocation results into the engraving toolpath.

[0097] Please see Figure 4As shown, after obtaining the local speed reduction allocation results, it is necessary to implement the speed reduction start point, speed reduction end point, and target feed rate into the engraving toolpath. Since the previous stage has generated executable speed reduction parameters for each small curvature change segment, this stage deals with how these parameters enter the machining program so that the CNC machine tool executes the target feed rate within the corresponding toolpath range. This processing still occurs before the machining program is written into the CNC machine tool, without changing the geometry of the mold cavity model or the spatial direction of the engraving toolpath. It only assigns local values ​​to the feed rate at the corresponding position in the engraving toolpath.

[0098] In practice, first find the starting point and ending point of the deceleration corresponding to the local deceleration allocation result in the engraving toolpath. If the starting point or ending point of deceleration coincides with an existing toolpath point, the toolpath point can be directly used as the speed writing position. If the starting point or ending point of deceleration is located between two adjacent toolpath points, the insertion toolpath point can be generated according to the path of the engraving toolpath between these two toolpath points, and the insertion toolpath point can be used as the speed writing position.

[0099] The position of the insertion point on the toolpath can be determined by the path length of the deceleration start point or deceleration end point on the engraving toolpath. Instead of using a straight-line positioning that deviates from the engraving toolpath, this ensures that the feed rate after writing still acts on the original engraving toolpath path, avoiding the impact on the texture outline due to the speed writing position deviating from the toolpath.

[0100] After determining the starting and ending points of the speed reduction, the engraving toolpath between the starting and ending points is set as the target feed rate. If the original feed rate is higher than the target feed rate within this range, the feed rate of the corresponding toolpath point is rewritten to the target feed rate. If the original feed rate is lower than or equal to the target feed rate, the original feed rate is retained. This processing method can avoid the local speed reduction distribution result from reversely increasing the toolpath point that is already in a low-speed machining state.

[0101] For machining programs that use segmented feed rate commands, the target feed rate command can be written at the starting point of the deceleration and the original feed rate can be restored after the ending point of the deceleration. For machining programs that use toolpath points with attached feed rates, the feed rate of each toolpath point between the starting point and the ending point of the deceleration can be directly assigned as the target feed rate.

[0102] It should be noted that the deceleration start and deceleration end may contain multiple local deceleration allocation results corresponding to small curvature abrupt changes. If multiple local deceleration allocation results overlap on the same engraving toolpath, the target feed rate with the lower value can be retained within the overlap range, and adjacent deceleration start and deceleration end points can be merged according to the coverage range. This processing method is suitable for scenarios where adjacent corners appear densely, such as fine leather texture, fish scale texture, and micro-text edges. It can reduce the situation where the engraving toolpath frequently switches feed rates within a short distance. The merging here only applies to the already generated local deceleration allocation results, does not change the three threshold comparison results again, and does not extend to ordinary turning toolpaths that have not entered the local deceleration allocation results.

[0103] Before writing the engraving toolpath, it is also necessary to process the target feed rate difference between adjacent toolpaths in the same texture area. The purpose of the aforementioned steps to determine adjacent toolpaths is not only to determine whether the minimum spacing is lower than the toolpath spacing threshold, but also to reduce the processing energy difference between adjacent toolpaths in the final writing stage.

[0104] Specifically, when the projection range of the local speed reduction allocation results of adjacent toolpaths in the texture area overlaps in the mold cavity model, and the absolute difference of the target feed rate corresponding to the two local speed reduction allocation results reaches the speed difference threshold, the one with the higher target feed rate value among the adjacent toolpaths is reduced to no more than the sum of the target feed rate value of the one with the lower target feed rate value and the speed difference threshold, while keeping the one with the lower target feed rate value from increasing. This can reduce the probability of tool marks forming due to excessive speed difference between adjacent toolpaths in the same texture area, while not weakening the speed reduction protection of positions that have been identified as having higher risk.

[0105] The speed difference threshold can be predetermined based on the allowable degree of tool marks and joints on the surface of similar mold cavities. In one optional embodiment, the range of target feed rate differences when no visible joints appear between adjacent toolpaths in the same texture area can be statistically analyzed in the qualified machining records, and the upper limit of this range can be used as the speed difference threshold. Alternatively, it can be determined by trial cutting samples. Under the same mold material, the same tool diameter, and the same texture width, the target feed rate difference between adjacent toolpaths can be increased step by step, and the maximum target feed rate difference when no joints appear can be used as the basis for setting the speed difference threshold. This threshold is only used for speed difference processing between adjacent toolpaths and does not change the risk source of a single small curvature change segment that has already been obtained based on the comparison results of the three thresholds.

[0106] To determine if the projection ranges overlap, the starting and ending points of the deceleration corresponding to the local deceleration allocation results can be projected onto the surface of the mold cavity model to obtain the toolpath coverage range within the texture area. If the toolpath coverage ranges of two adjacent toolpaths overlap within the same texture area, then the projection ranges of their local deceleration allocation results in the mold cavity model are considered to overlap.

[0107] It is important to note that overlapping projection ranges should be judged within the same texture area. If two local deceleration allocation results are spatially close but located in different texture areas and separated by the texture boundaries on both sides, the target feed rate difference processing should not be performed to avoid mutual interference between different texture objects.

[0108] After processing the target feed rate difference, the final local speed reduction allocation result is written into the engraving toolpath. The written result should include at least three items: the speed reduction start point, the speed reduction end point, and the target feed rate. For common CNC machining programs, the target feed rate can be converted into the corresponding feed rate command and written into the toolpath segment corresponding to the speed reduction start point to the speed reduction end point. For scenarios where the machining software generates a machining program through post-processing, the local speed reduction allocation result can be written back to the machining software as a toolpath attribute, and the machining software can generate the corresponding feed rate command during post-processing. Regardless of the writing method used, the engraving toolpath after writing should maintain the original spatial path of the tool center point, and the feed rate should only be adjusted within the corresponding toolpath range.

[0109] In one optional implementation, if the original feed rate change command of the machining program is included between the deceleration start point and the deceleration end point, the feed rate command within this range that is higher than the target feed rate can be replaced with the target feed rate, while the feed rate command that is lower than the target feed rate is retained. If the original engraving toolpath has a recovery speed command after the deceleration end point, the original recovery speed command can continue to be used after the deceleration end point. If the original engraving toolpath does not have a clear recovery speed command, the original feed rate before the small curvature change segment can be written after the deceleration end point. This processing method can make the local deceleration allocation result compatible with the speed structure of the original machining program and reduce interference with the post-processing flow of the mature machining program.

[0110] After the writing process in step five above, each tiny curvature abrupt change segment in the engraving toolpath corresponds to an executable local speed reduction allocation result. After the tool passes the speed reduction starting point, it enters the target feed speed, and after passing the speed reduction ending point, it resumes the original speed arrangement of the engraving toolpath. When adjacent toolpaths have overlapping projection ranges in the same texture area, they are also constrained by the target feed speed difference. Thus, the risk judgment obtained from the aforementioned tiny texture width, residual height, and minimum distance between adjacent toolpaths is ultimately implemented as the speed control content in the engraving toolpath. This allows the local speed reduction allocation result to act on the fine engraving process of the mold cavity without changing the toolpath geometry, reducing the probability of fine texture corner contour trimming, narrow groove boundary sidewall scratches, adjacent toolpath joint marks, and local depressions.

[0111] Example 2: This embodiment provides a mold cavity curvature abrupt change segment deceleration allocation system to implement the mold cavity curvature abrupt change segment deceleration allocation method disclosed in Embodiment 1. The system includes a micro curvature abrupt change segment determination module, a texture region determination module, a threshold comparison module, a deceleration allocation module, and a toolpath writing module.

[0112] The micro-curvature abrupt change segment determination module is configured to acquire the engraving toolpath of the mold cavity, determine the curvature change between adjacent toolpath points according to the toolpath point sequence, and determine the continuous toolpath segment where the curvature change reaches the curvature change threshold and the length of the continuous toolpath segment is lower than the abrupt change segment length threshold as a micro-curvature abrupt change segment.

[0113] The texture region determination module is configured to read the texture boundaries on both sides based on the position of the small curvature abrupt segment in the mold cavity model, determine the minimum distance between the two texture boundaries as the small texture width, and determine the texture region from the two texture boundaries.

[0114] The threshold comparison module is configured to obtain three threshold comparison results based on whether the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, whether the height difference between the toolpath envelope formed by the engraving toolpath in the previous processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent toolpaths in the micro-curvature abrupt segment and the texture area is lower than the toolpath distance threshold.

[0115] The deceleration allocation module is configured to query a preset deceleration allocation table based on the comparison results of three thresholds to obtain a local deceleration allocation result including the deceleration start point, deceleration end point, and target feed speed. The preset deceleration allocation table records the deceleration start point adjustment amount, deceleration end point adjustment amount, and target feed speed corresponding to the comparison results of the three thresholds.

[0116] The toolpath writing module is configured to write the local deceleration allocation results to the engraving toolpath.

[0117] Since this system uses the mold cavity curvature abrupt change segment speed reduction distribution method in Example 1, it also has the same effect, which will not be repeated here.

[0118] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for allocating deceleration across abrupt curvature changes in a mold cavity, characterized in that, include: Obtain the engraving toolpath of the mold cavity, determine the curvature change between adjacent toolpath points according to the toolpath point sequence, and identify the continuous toolpath segment where the curvature change reaches the curvature change threshold and the continuous toolpath segment length is lower than the abrupt segment length threshold as a small curvature abrupt segment. The method for determining the micro-curvature abrupt change segment includes: identifying at least one peak toolpath point with the largest curvature change value within a continuous toolpath segment where the curvature change reaches the curvature change threshold; taking the peak toolpath point as the center, reading the curvature change of adjacent toolpath points along the forward and backward directions of the machining sequence, until the first toolpath point with a curvature change value lower than the fallback threshold is read; taking the toolpath point that first falls below the fallback threshold in the forward direction of the machining sequence as the front boundary point, taking the toolpath point that first falls below the fallback threshold in the backward direction of the machining sequence as the back boundary point, and determining the toolpath segment between the front boundary point and the back boundary point with a path length lower than the abrupt change segment length threshold as the boundary-corrected micro-curvature abrupt change segment; Based on the position of the small curvature abrupt change segment in the mold cavity model, the texture boundaries on both sides are read, the minimum distance between the texture boundaries on both sides is determined as the small texture width, and the texture region is determined by the texture boundaries on both sides. The method for determining the width of the micro-texture includes: taking multiple toolpath points on the micro-curvature change segment as ranging points, along the ranging direction perpendicular to the toolpath direction and pointing to the texture boundaries on both sides of the mold cavity model surface, reading the distance between the texture boundaries on both sides, excluding the distances where the ranging path is not located in the texture area, and determining the minimum distance among the remaining distances as the micro-texture width. The comparison results of three thresholds are obtained based on whether the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, whether the height difference between the toolpath envelope formed by the engraving toolpath in the processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent toolpaths in the micro-curvature abrupt segment and the texture area is lower than the toolpath distance threshold. Based on the comparison results of the three thresholds, the preset speed reduction allocation table is queried to obtain the local speed reduction allocation results, including the speed reduction start point, speed reduction end point, and target feed speed. The preset speed reduction allocation table records the speed reduction start point adjustment amount, speed reduction end point adjustment amount, and target feed speed corresponding to the comparison results of the three thresholds. Write the local speed reduction allocation results into the engraving toolpath.

2. The method for speed reduction distribution in the abrupt curvature segment of a mold cavity according to claim 1, characterized in that, Methods for establishing a preset speed reduction allocation table include: The query conditions are as follows: whether the ratio of tool diameter to micro-texture width reaches the width threshold, whether the height difference reaches the residual height threshold, and whether the minimum spacing is lower than the toolpath spacing threshold. For each query condition combination, the deceleration start adjustment amount, deceleration end adjustment amount, and target feed rate are configured.

3. The method for distributing the deceleration of the mold cavity curvature abrupt change segment according to claim 2, characterized in that, Methods for obtaining local deceleration distribution results include: When the ratio of the tool diameter to the width of the micro-texture reaches the width threshold, the corresponding target feed rate is lower than the target feed rate when the width threshold is not reached. When the height difference reaches the residual height threshold, the corresponding deceleration starting adjustment amount is greater than the corresponding deceleration starting adjustment amount when the residual height threshold is not reached, and the corresponding target feed rate is not higher than the original feed rate of the original engraving toolpath at the small curvature change section. When the minimum spacing is lower than the toolpath spacing threshold, the corresponding speed reduction endpoint adjustment amount is greater than the corresponding speed reduction endpoint adjustment amount when it is not lower than the toolpath spacing threshold, and the corresponding target feed rate is not higher than the original feed rate of the original engraving toolpath at the small curvature change section.

4. The method for distributing the deceleration of the mold cavity curvature abrupt change segment according to claim 2, characterized in that, Methods for generating the deceleration start and deceleration end points include: The starting toolpath point of the small curvature change segment is shifted forward in the machining sequence according to the deceleration starting point adjustment amount to obtain the deceleration starting point; The end point of the small curvature change segment is shifted in the direction of the later machining sequence according to the speed reduction endpoint adjustment amount to obtain the speed reduction endpoint.

5. The method for distributing the speed reduction of the mold cavity curvature abrupt change segment according to claim 1, characterized in that, Methods for writing local speed reduction allocation results into the engraving toolpath include: When the local speed reduction distribution results of adjacent toolpaths in the texture area overlap in the projection range of the mold cavity model, and the target feed rate difference is greater than or equal to the speed difference threshold, the toolpath with the higher target feed rate value will be reduced until the target feed rate difference is lower than the speed difference threshold, while the toolpath with the lower target feed rate value will not be increased.

6. The method for speed reduction distribution in the abrupt curvature segment of a mold cavity according to claim 1, characterized in that, Methods for determining height differences include: Based on the engraving toolpath and tool cutting edge shape that precede the processing sequence, a toolpath envelope surface is generated. The target surface of the mold cavity model is read at the corresponding position of the small curvature change segment. The maximum height difference between the toolpath envelope surface and the target surface along the outer normal direction of the target surface is used as the height difference compared with the residual height threshold.

7. The method for speed reduction distribution in the abrupt curvature segment of a mold cavity according to claim 1, characterized in that, Methods for determining the minimum spacing between adjacent toolpaths include: The engraving toolpaths with adjacent processing order within the texture area and those whose projection distance in the mold cavity model is lower than the adjacency threshold are all selected as candidate toolpaths. Candidate toolpaths not located within the texture area are eliminated, and the engraving toolpath closest to the small curvature abrupt change segment among the remaining candidate toolpaths is selected as the adjacent toolpath.

8. A deceleration distribution system for a mold cavity curvature abrupt change segment, used to implement the deceleration distribution method for the mold cavity curvature abrupt change segment as described in any one of claims 1-7, characterized in that, include: The micro curvature abrupt change segment determination module is used to obtain the engraving toolpath of the mold cavity, determine the curvature change between adjacent toolpath points according to the toolpath point sequence, and determine the continuous toolpath segment where the curvature change reaches the curvature change threshold and the length of the continuous toolpath segment is lower than the abrupt change segment length threshold as the micro curvature abrupt change segment. The texture region determination module is used to read the texture boundaries on both sides based on the position of the small curvature abrupt segment in the mold cavity model, determine the minimum distance between the two texture boundaries as the small texture width, and determine the texture region from the two texture boundaries; The threshold comparison module is used to obtain three threshold comparison results based on whether the ratio of the tool diameter to the width of the micro texture reaches the width threshold, whether the height difference between the tool path envelope formed by the engraving tool path with the processing sequence and the target surface of the mold cavity model reaches the residual height threshold, and whether the minimum distance between adjacent tool paths in the micro curvature abrupt segment and the texture area is lower than the tool path distance threshold. The deceleration allocation module is used to query a preset deceleration allocation table based on the comparison results of three thresholds to obtain local deceleration allocation results including deceleration start point, deceleration end point, and target feed speed. The preset deceleration allocation table records the deceleration start point adjustment amount, deceleration end point adjustment amount, and target feed speed corresponding to the comparison results of the three thresholds. The toolpath writing module is used to write the local deceleration allocation results into the engraving toolpath.

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