A motion control error compensation method for a wax jetting 3D printer

Abstract

The application discloses a motion control error compensation method of a wax spraying 3D printer, opens a global compensation enable, acquires current actual coordinates and target coordinates of a printing shaft; by comparing the current actual coordinates and the target coordinates, determining the motion direction of this time; judging whether the motion of this time occurs a reversing action; if the reversing action occurs, using a reverse gap compensation amount to perform a preposition correction, obtaining a first modified target coordinate, and completing the preposition correction of a mechanical transmission gap error; if the reversing action does not occur, not performing the reverse gap compensation; then using a comprehensive error compensation amount to perform a postposition correction, obtaining a final motion instruction coordinate, and transmitting the motion instruction coordinate to a servo driving system for execution. It can be seen that the preposition reverse gap compensation of the application eliminates the mechanical gap during reversing, and then the postposition comprehensive error compensation corrects the screw pitch and the rail straightness error, the two-step correction cooperates, improves the positioning accuracy of the printing shaft, and ensures the wax printing forming quality.

Description

Technical Field

[0001] This invention relates to the field of wax spray 3D printer technology, and in particular to a method for motion control error compensation in wax spray 3D printers. Background Technology

[0002] Wax-spraying 3D printers rely on the layer-by-layer deposition of hot-melt wax to create wax models. With advantages such as high forming precision, good surface quality, and no support residue, they are widely used in investment casting fields such as aerospace, medical devices, and precision molds. Compared to conventional FDM and resin 3D printing equipment, wax-spraying printing requires micron-level precision in the positioning of motion axes, trajectory straightness, and repeatability. The motion error of the equipment directly determines the dimensional accuracy of the wax model and the quality of the subsequent casting. Currently, existing motion error compensation technologies for wax-spraying 3D printers have many inherent defects, severely limiting the high-precision wax model forming effect. Specific problems and their causes are as follows:

[0003] 1. The servo-based built-in fixed compensation has poor adaptability and cannot meet the precision molding requirements of wax spray printing. This solution only supports the correction of errors at fixed points with equal spacing, and can only correct single pitch errors. It cannot adapt to the straightness trajectory errors caused by uneven wear of the guide rail and assembly deviations in wax spray printers. At the same time, static gap compensation can only correct fixed values ​​and cannot adapt to the working conditions of frequent reversal and micro reciprocating motion during printing. It is very easy to cause defects such as trajectory deviation, layering, and deformation of fine structures.

[0004] 2. Traditional PLC dynamic compensation suffers from a fatal timing lag defect, leading to continuous error accumulation. Existing PLC compensation programs for wax spray printers generally employ a lag logic that reads the current actual axis position, calculates the compensation amount, and issues the next target motion command. The compensation amount always lags behind by one PLC scan cycle. However, wax spray printing involves continuous, layer-by-layer, high-frequency micro-positioning motion. A single small lag error will accumulate iteratively layer by layer, ultimately causing an overall dimensional shift in the wax model, failing to meet the tolerance requirements of precision investment casting.

[0005] 3. The lack of standardized coupling logic for multiple types of errors easily leads to overcompensation and undercompensation. The motion errors of wax spray printers include three core types: lead screw pitch machining error, guide rail assembly straightness error, and transmission mechanism backlash error. These three types of errors are coupled, affecting printing accuracy. Current technologies lack standardized multi-error hierarchical compensation logic, often employing single error correction or disordered superposition compensation methods. Reversing backlash correction and geometric trajectory compensation interfere with each other, frequently resulting in problems such as reversing overshoot, uneven straight-line trajectories, and repeated positioning deviations, making it difficult to achieve coordinated multi-dimensional error correction.

[0006] 4. The compensation logic is fixed and cannot adapt to the non-standard precision working conditions of wax spray printing. Traditional compensation schemes have fixed parameters and fixed points, and cannot customize the compensation points and correction values ​​based on the non-standard error data of the entire travel of the equipment measured by the laser interferometer. This results in poor adaptability to the high-precision, high-frequency reversing working conditions of wax spray printers, making debugging difficult and the accuracy improvement effect limited.

[0007] In summary, existing motion compensation technologies for wax-sprayed 3D printers suffer from severe lag, limited error correction, chaotic error coupling logic, and poor adaptability to various working conditions. These shortcomings make it difficult to meet the molding accuracy requirements of micron-level precision wax molds. There is an urgent need to design a targeted motion control error compensation method that is lag-free, integrates multiple errors, and can be customized and adapted. Summary of the Invention

[0008] To address the aforementioned shortcomings, the technical problem to be solved by this invention is to provide a motion control error compensation method for a wax spray 3D printer. This method eliminates mechanical backlash during reversal through pre-reverse backlash compensation, and then corrects the lead screw pitch and guide rail straightness errors through post-comprehensive error compensation. The two-step correction works synergistically to improve the positioning accuracy of the printing axis and ensure the quality of wax spray printing.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0010] A method for motion control error compensation in a wax-sprayed 3D printer includes the following steps:

[0011] S10. Enable global compensation and obtain the current actual coordinates and target coordinates of the printing axis;

[0012] S20. Determine the direction of movement by comparing the current actual coordinates with the target coordinates;

[0013] S30. Determine whether a change of direction has occurred in this movement;

[0014] S40. If a reversing action occurs, obtain the backlash compensation amount, and then use the formula: First-level correction target coordinate = target coordinate + backlash compensation amount to calculate the first-level correction target coordinate, thus completing the pre-correction of mechanical transmission backlash error.

[0015] If no reversing action occurs, execute S50;

[0016] S50. Based on the first-level corrected target coordinates or target coordinates, obtain the corresponding comprehensive error compensation amount;

[0017] S60. Using the formula: Motion command coordinates = First-level correction target coordinates + Comprehensive error compensation amount or Motion command coordinates = Target coordinates + Comprehensive error compensation amount, calculate the final motion command coordinates and complete the subsequent correction.

[0018] S70 transmits motion command coordinates to the servo drive system for execution.

[0019] The preferred approach also includes the step of constructing a full-stroke error database for the printing axis, specifically:

[0020] Disable global compensation enable;

[0021] A laser interferometer is used to perform equal-division dot detection on the entire stroke of each printing axis of the wax spray printer. The screw pitch error and guide rail straightness error corresponding to each mechanical coordinate point are collected. According to the coordinate ascending order rule, a one-to-one corresponding coordinate array and a comprehensive error compensation array are established to realize the data solidification and storage of non-standard errors throughout the entire stroke.

[0022] The preferred method further includes the following steps:

[0023] With global compensation disabled, a laser interferometer was used to calibrate the backlash compensation of each printing axis of the wax spray printer.

[0024] In a preferred embodiment, S50 includes:

[0025] Using the first-level corrected target coordinates or target coordinates as the calculation benchmark, the interval to which it belongs in the pre-set comprehensive error compensation array is retrieved. By traversing the upper and lower limit coordinate indices of the matching interval, the corresponding comprehensive error compensation amount is calculated using the target position linear interpolation algorithm.

[0026] In a preferred embodiment, S50 further includes:

[0027] When the target coordinates of the first-level correction target or the target coordinates exceed the travel boundary, the comprehensive error compensation amount is the boundary fixed error compensation value.

[0028] In a preferred embodiment, the step of constructing the full-stroke error database for the printing axis further includes:

[0029] The spacing of the equally spaced dot detection is determined based on the print axis travel length and accuracy requirements. Each print axis is independently configured with a dedicated comprehensive error compensation array, and the compensation points fully cover the effective print travel of the device.

[0030] The preferred approach is to configure each axis with its own dedicated backlash compensation amount to adapt to the multi-axis linkage printing conditions of the wax spray printer.

[0031] The preferred approach is to rebuild the full-stroke error database of the printing shaft and / or recalibrate the backlash compensation amount, based on actual needs.

[0032] In a preferred embodiment, S20 includes:

[0033] Calculate the numerical difference between the target coordinates and the current actual coordinates.

[0034] If the numerical difference is greater than 0, it is determined to be forward movement; if the numerical difference is less than 0, it is determined to be reverse movement.

[0035] S30 includes:

[0036] Compare the current direction of movement with the previous direction of movement; if they are different, it is determined to be a change of direction movement.

[0037] The preferred method is to switch the global compensation enable switch to be on or off.

[0038] After adopting the above technical solution, the beneficial effects of the present invention are:

[0039] The motion control error compensation method for the wax-sprayed 3D printer of this invention, when global compensation is enabled, obtains the current actual coordinates and target coordinates of the printing axis; by comparing the current actual coordinates and target coordinates, the direction of the current motion is determined; then it is determined whether a reversal action has occurred; if a reversal action has occurred, the backlash compensation amount is obtained, and then the first-level corrected target coordinates are calculated using the formula: first-level corrected target coordinates = target coordinates + backlash compensation amount, completing the pre-correction of mechanical transmission backlash error; if no reversal action has occurred, no backlash compensation is performed; based on the first-level corrected target coordinates or the target coordinates, the corresponding comprehensive error compensation amount is obtained; using the formula: motion command coordinates = first-level corrected target coordinates + comprehensive error compensation amount or motion command coordinates = target coordinates + comprehensive error compensation amount, the final motion command coordinates are calculated, completing the pre-correction; the motion command coordinates are then transmitted to the servo drive system for execution. As can be seen, this invention provides a complete motion control error compensation process. It eliminates mechanical backlash during reversal by pre-reverse backlash compensation, and then corrects the lead screw pitch and guide rail straightness errors by post-comprehensive error compensation. The two-step correction works synergistically to significantly improve the positioning accuracy of the printing axis, ensure the quality of wax spray printing, and solve the problem of error accumulation in the high-frequency reversal, continuous micro-positioning, and layer-by-layer forming process of wax spray printing. It achieves micron-level precise positioning and trajectory correction of the printing axis throughout its entire stroke, improves the dimensional accuracy, straightness, and forming consistency of precision wax molds, and adapts to the production needs of high-precision investment casting. Attached Figure Description

[0040] Figure 1 This is a flowchart of the motion control error compensation method for the wax spray 3D printer in this invention;

[0041] Figure 2 This is a timing diagram of existing motion control error compensation methods;

[0042] Figure 3 This is a timing diagram of the motion control error compensation method in this invention;

[0043] Figure 4This is a schematic diagram of the structure of the wax-sprayed 3D printer used in this invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0045] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0046] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] like Figure 1 As shown, a motion control error compensation method for a wax-sprayed 3D printer includes the following steps:

[0048] Step S1: Disable global compensation, build a full-stroke error database for the printing axis, use a laser interferometer to perform equal-division point detection on the full stroke of each printing axis of the wax spray printer, collect the screw pitch error and guide rail straightness error corresponding to each mechanical coordinate point, and establish a one-to-one corresponding coordinate array and comprehensive error compensation array according to the coordinate ascending order rule to realize the solidified storage of non-standard error data for the entire stroke.

[0049] Step S5: Disable global compensation and use a laser interferometer to calibrate the backlash compensation of each printing axis of the wax spray printer.

[0050] Step S10: Enable global compensation and obtain the current actual coordinates and target coordinates of the printing axis;

[0051] Step S20: Determine the direction of movement by comparing the current actual coordinates with the target coordinates;

[0052] Step S30: Determine whether a change of direction has occurred in this movement;

[0053] Step S40: If a reversing action occurs, obtain the backlash compensation amount, and then use the formula: First-level correction target coordinate = target coordinate + backlash compensation amount to calculate the first-level correction target coordinate, thus completing the pre-correction of mechanical transmission backlash error.

[0054] If no reversal action occurs, proceed to step S50, which means that the preset reverse gap compensation amount is only superimposed at the moment of motion direction switching. The gap compensation is not superimposed repeatedly for continuous printing motion in the same direction to avoid trajectory deviation caused by overcompensation.

[0055] Step S50: Obtain the corresponding comprehensive error compensation amount based on the first-level correction target coordinates or target coordinates;

[0056] Specifically, after a pre-correction is performed when a motion reversal occurs, the target coordinates of the first-level correction are used as the calculation reference. When no motion reversal occurs, the target coordinates are used as the calculation reference. The corresponding interval in the pre-defined comprehensive error compensation array is retrieved, and the corresponding comprehensive error compensation amount is calculated by traversing the upper and lower limit coordinate indices of the matching interval and employing a linear interpolation algorithm for the target position. This linear interpolation algorithm continuously calculates the error compensation amount between discrete measurement points, ensuring both smooth continuity of compensation and real-time calculation efficiency, making it suitable for high-speed motion control scenarios.

[0057] Step S60: Using the formula: Motion command coordinates = First-level correction target coordinates + Comprehensive error compensation amount or Motion command coordinates = Target coordinates + Comprehensive error compensation amount, calculate the final motion command coordinates and complete the post-correction.

[0058] Step S70: Transmit motion command coordinates to the servo drive system for execution;

[0059] After the invention has been running for a period of time or as needed, the full-stroke error database of the printing shaft can be reconstructed and / or the backlash compensation amount can be recalibrated to cope with parameter drift caused by wear, replacement or environmental changes of mechanical parts, and to ensure the long-term stability of the compensation effect.

[0060] like Figure 1 As shown, the motion control error compensation method for the wax spraying 3D printer of the present invention, by constructing a full-stroke error database of the printing axis, performing pre-correction of the reverse clearance of motion reversal, calculating the geometric error of the target position pre-interpolation (linear pre-interpolation calculation of the target position), performing multi-error hierarchical coupling correction and issuing lag-free commands, abandons the traditional lag compensation logic based on the current position, and realizes dynamic correction of wax spraying printing motion error without accumulation.

[0061] This invention adapts to the high-frequency reversing and continuous layer-by-layer printing conditions of wax spray printers by establishing a hierarchical coupling logic that prioritizes backlash correction and postpones pitch and straightness geometric error correction, thus avoiding overcompensation and undercompensation problems caused by the superposition of multiple errors.

[0062] This invention employs a target position linear pre-interpolation algorithm to precisely correct the segmented non-standard error data collected by the laser interferometer throughout its entire stroke, overcoming the limitations of servo fixed-point compensation and adapting to the non-standard mechanical error characteristics of a single wax printer.

[0063] As can be seen, this invention provides a complete motion control error compensation process. It eliminates mechanical backlash during reversal by pre-reverse backlash compensation, and then corrects the lead screw pitch and guide rail straightness errors by post-comprehensive error compensation. The two-step correction works synergistically to significantly improve the positioning accuracy of the printing axis, ensure the quality of wax spray printing, and solve the problem of error accumulation in the high-frequency reversal, continuous micro-positioning, and layer-by-layer forming process of wax spray printing. It achieves micron-level precise positioning and trajectory correction of the printing axis throughout its entire stroke, improves the dimensional accuracy, straightness, and forming consistency of precision wax molds, and adapts to the production needs of high-precision investment casting.

[0064] It should be noted that the wax-spraying 3D printer used in this invention includes a PLC and a global compensation enable switch, a storage unit, a motion mechanism, and a laser interferometer calibration module, all electrically connected to the PLC. The laser interferometer calibration module is used to calibrate the backlash compensation amount and construct a full-stroke error database for the printing axis.

[0065] This invention allows users to switch the global compensation enable function on or off by operating a global compensation enable switch. This facilitates temporarily disabling the compensation function during the debugging phase or troubleshooting, and enables quick comparison of the effects before and after compensation, thereby improving the flexibility of system debugging and maintenance.

[0066] This invention utilizes a storage unit to store preset backlash compensation amounts and comprehensive error compensation amounts, etc.

[0067] like Figure 4 As shown, the motion mechanism in this invention includes an X-axis printing motion mechanism, a Y-axis printing motion mechanism, and a Z-axis printing motion mechanism; wherein the X-axis printing motion mechanism includes an X-axis servo driver, an X-axis servo motor electrically connected to the X-axis servo driver, and an X-axis lead screw and transmission mechanism connected to the X-axis servo motor; wherein the Y-axis printing motion mechanism includes a Y-axis servo driver, a Y-axis servo motor electrically connected to the Y-axis servo driver, and a Y-axis lead screw and transmission mechanism connected to the Y-axis servo motor; wherein the Z-axis printing motion mechanism includes a Z-axis servo driver, a Z-axis servo motor electrically connected to the Z-axis servo driver, and a Z-axis lead screw and transmission mechanism connected to the Z-axis servo motor.

[0068] In some embodiments of the present invention, when constructing the full-stroke error database of the printing axis, the spacing of the equally spaced detection points is determined according to the stroke length and accuracy requirements of the printing axis. Each printing axis is independently configured with a dedicated comprehensive error compensation array, and the compensation points fully cover the effective printing stroke of the device. That is, by using a laser interferometer to equally space the entire stroke for detection, a coordinate-comprehensive error compensation array is established, which solidifies and stores non-standardized mechanical errors, providing an accurate and reliable data foundation for subsequent real-time interpolation compensation, and achieving controllable errors throughout the entire stroke range.

[0069] In addition, each printing axis in this invention is independently configured with a dedicated backlash compensation amount, which is suitable for multi-axis linkage printing of wax spray printers, ensuring the accuracy of the reversal compensation value, avoiding over-compensation or under-compensation due to inaccurate gap measurement, and further improving the positioning accuracy at the moment of reversal.

[0070] In other embodiments of the present invention, when the primary correction target coordinates or the target coordinates exceed the travel boundary, the comprehensive error compensation amount is a fixed boundary error compensation value. This fixed boundary error compensation value prevents situations where no data is available or compensation is abnormal when the target coordinates exceed the measurement range, thus enhancing the robustness and security of the compensation algorithm.

[0071] In some embodiments of the present invention, the step of comparing the current actual coordinates and the target coordinates to determine the direction of movement specifically includes:

[0072] Calculate the numerical difference between the target coordinates and the current actual coordinates.

[0073] If the numerical difference is greater than 0, it is determined to be forward movement; if the numerical difference is less than 0, it is determined to be reverse movement.

[0074] To determine whether a change of direction has occurred in the current movement, the direction of the current movement is compared with the stored direction of the previous movement. If the two are different, it is determined to be a change of direction.

[0075] This invention uses a dual judgment method of numerical difference and historical direction comparison to accurately identify the direction of motion and reversing action, providing reliable triggering logic for backlash compensation and avoiding misjudgment or omission.

[0076] Compared with existing wax-sprayed 3D printer error compensation technologies, this invention has significant technical advantages and improved accuracy:

[0077] Completely eliminates compensation timing lag and prevents layer-by-layer error accumulation. This invention employs a target position pre-interpolation compensation mechanism, completing all compensation calculations before the motion command is issued, replacing the traditional current position lag calculation mode. This addresses the error iteration and accumulation problem in continuous layer-by-layer forming and high-frequency micro-positioning processes during wax spray printing from the algorithmic root. Actual measurements show that when the equipment continuously prints more than 50 layers of thin-walled structures along the Z-axis, the cumulative dimensional deviation is reduced from ±0.03mm in the traditional method to within ±0.008mm, significantly improving forming consistency.

[0078] This invention achieves precise correction of multiple errors through integrated solutions, adapting to the precision conditions of wax spray printing. It establishes a hierarchical coupling compensation logic to simultaneously correct three core errors: backlash, lead screw pitch, and guide rail straightness. This solves the problems of single compensation dimensions and chaotic error superposition in traditional solutions; the straightness accuracy of the printing trajectory is improved by more than 40%, and the repeatability accuracy stably reaches the micrometer level.

[0079] Customizable flexible compensation adapts to the error characteristics of non-standard equipment. This invention overcomes the limitations of fixed built-in compensation parameters and fixed points in servo motors. It allows for customized compensation points and correction values ​​based on the measured error data of the laser interferometer for each wax printer. This precisely adapts to the assembly deviations and guide rail wear errors of individual devices. Compared to general fixed compensation schemes, the individual device accuracy adaptability is significantly improved, and debugging is more convenient.

[0080] Specifically designed for high-frequency reversal and continuous molding conditions in wax spray printing. Optimized gap compensation trigger logic for the specific conditions of wax spray printing, which involve frequent micro-reversals, continuous trajectory movement, and multi-layer stacking. Gap correction is only applied at the moment of reversal, with no redundant compensation for unidirectional movement, perfectly adapting to the molding needs of precision microstructures and thin-walled wax molds.

[0081] It boasts strong versatility and controllability. It is compatible with precision motion control PLCs and servo systems, and the three axes can be quickly reused and ported. It supports one-click switching of compensation enable, facilitating equipment accuracy comparison, fault debugging, and working condition switching, and is suitable for standardized application in industrial mass production wax printing equipment.

[0082] Compared with existing error compensation technologies for wax-sprayed 3D printers, this invention is detailed in [reference needed]. Figure 2 and Figure 3 .

[0083] To better understand this invention, specific examples are given below:

[0084] Case 1:

[0085] The test platform was built based on an industrial-grade wax spraying 3D printer, AM522PLC, and IS660N servo. The equipment has an effective printing stroke of 0~950mm and is suitable for precision investment wax molding.

[0086] Implementation of single-axis fixed-point precise positioning compensation (X-axis)

[0087] A laser interferometer was used to perform point detection every 50mm along the entire X-axis stroke of the wax printer from 0 to 950mm, and 20 sets of coordinate-error correspondence data were collected and entered into the PLC's global comprehensive error compensation array.

[0088] The X-axis backlash of the wax spray printer was calibrated using a laser interferometer, and the X-axis backlash compensation value was set to 0.006 mm.

[0089] Enable global compensation. The device receives the print positioning command with a target coordinate of 500mm. The PLC reads the current axis's actual position of 300mm in real time, determines that this is a forward movement and forms a reversal action with the previous reverse movement, and preferentially adds a 0.006mm backlash correction to obtain the first-level target coordinate of 500.006mm.

[0090] Based on this coordinate, interval linear interpolation was performed, and the comprehensive compensation value for pitch and straightness at this point was calculated to be -0.003mm; the final synthesized and issued coordinate was 500.003mm.

[0091] The servo performs the positioning action;

[0092] Finally, the laser interferometer was used for retesting.

[0093] Conclusion: The actual positioning deviation was reduced from 0.021mm (uncompensated) to 0.007mm, and the positioning accuracy was greatly improved with no hysteresis error accumulation.

[0094] Case 2:

[0095] This embodiment uses a three-axis wax-spraying 3D printer as an example, with printing strokes of 300mm for the X-axis, 200mm for the Y-axis, and 150mm for the Z-axis. Each axis uses ball screw drive and is guided by linear guides. The servo driver receives motion command coordinates and drives the motor to rotate.

[0096] Preliminary calibration

[0097] Construct a full-stroke error database:

[0098] Turn off the global compensation enable switch. Use a laser interferometer to perform full-stroke equally divided point detection on the X, Y, and Z axes.

[0099] X-axis: travel 300mm, equal interval of 5mm, a total of 61 measurement points (including start and end points).

[0100] Y-axis: travel 200mm, equal interval 5mm, total 41 measurement points.

[0101] Z-axis: travel 150mm, equal interval of 5mm, a total of 31 measurement points.

[0102] At each measurement point, record the screw pitch error and guide rail straightness error. The algebraic sum of the two is the comprehensive error compensation for that point.

[0103] Arrange the coordinates in ascending order and establish the X-axis coordinate array Pos_X

[61] and the comprehensive error compensation array Comp_X

[61] respectively. Similarly, the Y-axis and Z-axis are also established. The data is stored in the storage unit of the PLC.

[0104] Backlash compensation calibration:

[0105] Keep global compensation enabled off. Also use a laser interferometer to measure the backlash on each axis.

[0106] First, move forward to a certain position and record the actual position; then move backward by the same commanded distance and record the actual position deviation. This deviation is the backlash compensation amount.

[0107] Repeat the process multiple times and take the average value. The measured backlash is 12 on the X-axis, 8 on the Y-axis, and 5 on the Z-axis. Store these values ​​in the variables Backlash_X, Backlash_Y, and Backlash_Z, respectively.

[0108] Motion control compensation process (taking a single X-axis motion as an example)

[0109] Assuming the current actual X-axis coordinate is 100.000mm, the host computer sends the target coordinate as 150.020mm.

[0110] S10: Enable global compensation (set via the global compensation enable switch in the PLC or CNC system). Read current actual coordinates = 100.000, target coordinates 150.020.

[0111] S20: Calculate the numerical difference Δ = 50.020 > 0, and determine it as positive motion. Record the current motion direction as positive, and update the stored previous motion direction (assuming the previous one was negative).

[0112] S30: Compare the current direction of motion (forward) with the stored previous direction of motion (reverse). If they are different, determine that a change of direction has occurred.

[0113] S40: Obtain the X-axis backlash compensation amount = 0.012mm. Since this is a switch from reverse to forward, calculate the first-level corrected target coordinates according to the predefined sign rule (adding backlash during forward movement):

[0114] The first-level corrected target coordinates = 150.020 + 0.012 = 150.032 mm;

[0115] Complete the preliminary corrections.

[0116] S50: Using the first-level correction target coordinate of 150.032mm as a reference, search the X-axis error database.

[0117] The adjacent points in the Pos_X array are 150.000mm and 155.000mm, respectively, with corresponding comprehensive error compensation values ​​of +3.8μm.

[0118] Linear interpolation algorithm is used:

[0119] The overall error compensation is 0.003204 mm.

[0120] S60: Calculate the final motion command coordinates: Motion command coordinates = First-level corrected target coordinates + Comprehensive error compensation = 150.032 + 0.003204 = 150.035204 mm;

[0121] Complete the subsequent corrections.

[0122] S70: Transmit the motion command coordinates 150.035204mm to the X-axis servo driver, and drive the motor to run to that position.

[0123] Boundary case handling

[0124] If the target coordinates exceed the travel boundary (e.g., X-axis target coordinates 305mm), then the fixed boundary error compensation value is directly taken in S50 (e.g., compensation value at the maximum travel point of the X-axis = +4.5μm), and no further interpolation is performed.

[0125] Multi-axis linkage application

[0126] For three-axis simultaneous printing tasks (such as printing inclined straight lines), the X, Y, and Z axes execute the above process independently. The program modules for each axis are completely identical; only their respective comprehensive error compensation arrays and backlash parameters need to be loaded during initialization. For example, the Y-axis backlash is 8μm, and the Z-axis is 5μm, respectively, by calling the corresponding calibration data.

[0127] Function of compensation enable switch

[0128] During the debugging phase, the compensation function can be turned off by using the global compensation enable button on the host computer interface. At this time, S10 skips all compensation steps and directly sends the original target coordinates to the servo, which is convenient for comparison and verification of the compensation effect.

[0129] Recalibration of the database and backlash

[0130] After one year of operation, if the X-axis backlash increases to 18μm due to lead screw wear, compensation can be disabled again, the X-axis backlash can be recalibrated using a laser interferometer, and the new value can be written to the Backlash_X variable. Similarly, if a significant deviation in the travel error is found, the full travel error database for that axis can be rebuilt.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made within the spirit and principles of the present invention, or improvements to the motion control error compensation method of an equivalent wax spray 3D printer, should be included within the protection scope of the present invention.

Claims

1. A method for compensating motion control errors in a wax-sprayed 3D printer, characterized in that, Includes the following steps: S10. Enable global compensation and obtain the current actual coordinates and target coordinates of the printing axis; S20. Determine the direction of movement by comparing the current actual coordinates with the target coordinates; S30. Determine whether a change of direction has occurred in this movement; S40. If a reversing action occurs, obtain the backlash compensation amount, and then use the formula: First-level correction target coordinate = target coordinate + backlash compensation amount to calculate the first-level correction target coordinate, thus completing the pre-correction of mechanical transmission backlash error. If no reversing action occurs, execute S50; S50. Based on the first-level corrected target coordinates or target coordinates, obtain the corresponding comprehensive error compensation amount; S60. Using the formula: Motion command coordinates = First-level correction target coordinates + Comprehensive error compensation amount or Motion command coordinates = Target coordinates + Comprehensive error compensation amount, calculate the final motion command coordinates and complete the subsequent correction. S70 transmits motion command coordinates to the servo drive system for execution.

2. The motion control error compensation method for a wax-sprayed 3D printer according to claim 1, characterized in that, It also includes the step of building a full-stroke error database for the printing axis, specifically: Disable global compensation enable; A laser interferometer is used to perform equal-division dot detection on the entire stroke of each printing axis of the wax spray printer. The screw pitch error and guide rail straightness error corresponding to each mechanical coordinate point are collected. According to the coordinate ascending order rule, a one-to-one corresponding coordinate array and a comprehensive error compensation array are established to realize the data solidification and storage of non-standard errors throughout the entire stroke.

3. The motion control error compensation method for a wax-sprayed 3D printer according to claim 2, characterized in that, It also includes the following steps: With global compensation disabled, a laser interferometer was used to calibrate the backlash compensation of each printing axis of the wax spray printer.

4. The motion control error compensation method for a wax-sprayed 3D printer according to claim 2, characterized in that, The S50 includes: Using the first-level corrected target coordinates or target coordinates as the calculation benchmark, the interval to which it belongs in the pre-set comprehensive error compensation array is retrieved. By traversing the upper and lower limit coordinate indices of the matching interval, the corresponding comprehensive error compensation amount is calculated using the target position linear interpolation algorithm.

5. The motion control error compensation method for a wax-sprayed 3D printer according to claim 4, characterized in that, The S50 further includes: When the target coordinates of the first-level correction target or the target coordinates exceed the travel boundary, the comprehensive error compensation amount is the boundary fixed error compensation value.

6. The motion control error compensation method for a wax-sprayed 3D printer according to claim 2, characterized in that, The step of constructing the full-stroke error database for the printing axis also includes: The spacing of the equally spaced dot detection is determined based on the print axis travel length and accuracy requirements. Each print axis is independently configured with a dedicated comprehensive error compensation array, and the compensation points fully cover the effective print travel of the device.

7. The motion control error compensation method for a wax-sprayed 3D printer according to claim 3, characterized in that, Each axis is independently configured with a dedicated backlash compensation amount, adapting to multi-axis linkage printing conditions of wax spray printers.

8. The motion control error compensation method for a wax-sprayed 3D printer according to claim 3, characterized in that, Based on actual needs, rebuild the full-stroke error database of the printing axis and / or recalibrate the backlash compensation amount.

9. The motion control error compensation method for a wax-sprayed 3D printer according to claim 1, characterized in that, S20 includes: Calculate the numerical difference between the target coordinates and the current actual coordinates. If the numerical difference is greater than 0, it is determined to be forward movement; if the numerical difference is less than 0, it is determined to be reverse movement. S30 includes: Compare the current direction of movement with the previous direction of movement; if they are different, it is determined to be a change of direction movement.

10. The motion control error compensation method for a wax-sprayed 3D printer according to any one of claims 1 to 9, characterized in that, By operating the global compensation enable switch, you can toggle global compensation enabled or disabled.

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