Additive and subtractive manufacturing method with spacer layer

Abstract

The invention relates to a metal additive and subtractive composite manufacturing technology field, in particular to a method for improving the surface quality of a subtractive machining surface of a part manufactured by additive and subtractive composite manufacturing. In the method, the additive method is powder laying type, the subtractive milling method is three-axis numerical control milling, and the building material finishing tool comprises a spacer milling cutter; the method comprises the following steps: a step of obtaining a metal material recess value; a step of designing and selecting a machining tool; a step of calculating a spacer layer height; a step of process planning; and a step of machining implementation. The technical scheme of the invention solves the problem that the existing machining method in the prior art causes recesses at the additive and subtractive interface, which affects the surface quality; if the surface quality needs to be improved, the machining tool needs to be selected; pulse laser impact machining can improve the forming quality and production efficiency, but the machining method cannot be used to machine the upper surface and the side surface of the part, and cannot be used to machine the lower surface of the part.

Description

TECHNICAL FIELD

[0001] The invention relates to the technical field of metal additive and subtractive composite manufacturing, in particular to a method for improving the surface quality of a subtractive machining surface of an additive and subtractive composite manufactured part. BACKGROUND

[0002] Additive manufacturing technology has the characteristics of flexibility, efficiency and high material utilization compared with traditional manufacturing processes, and can realize the direct forming of complex structure parts. The selective laser melting technology using powder laying method has high precision and dense internal organization, and is especially suitable for manufacturing complex structure parts. However, the surface of the part formed by pure additive manufacturing generally has defects such as step effect, powder bonding and spheroidization, which will lead to poor surface quality of the additive formed part and hinder its application.

[0003] Additive and subtractive composite manufacturing technology combines additive manufacturing and subtractive manufacturing processes, and uses an alternating forming and machining process. First, a certain number of layers of metal powder are melted / solidified by high-energy beam scanning, then milling machining is performed, and after subtractive machining, additive forming is performed again. This method not only improves the surface precision, but also improves the tool accessibility problem in the post-processing machining of complex additive parts.

[0004] However, the laser has a significant thermal effect on the bottom layer material during sintering. The volume shrinkage caused by the material cooling and solidification process when the additive and subtractive processes are alternated will introduce thermal residual stress. When the thermal stress exceeds the yield strength of the material, plastic strain occurs in the material, and the material deforms inwardly. When the additive layer has been subtractively machined to the designed size, continuing the additive process will cause thermal deformation of the lower layer material, resulting in the formation of a depression at the additive and subtractive alternating interface, affecting the surface quality.

[0005] Currently, research on powder laying type additive and subtractive composite manufacturing machining methods, such as the patent application of Dalian University of Technology (Method for determining alternating timing in additive and subtractive composite manufacturing, Publication No. CN113967737A), proposes to select appropriate tools according to the contour type and precision requirements of the part to be machined and plan the subtractive path to determine the optimal additive and subtractive alternating timing to improve machining efficiency. The technical solution focuses more on improving efficiency, and the protection of surface quality relies only on the selection of tools. The patent application of Xi'an Jiaotong University (Composite additive and subtractive machining forming device and method, Publication No. CN111957968A) proposes a method of using pulsed laser impact machining to process the surface of the part, which can improve the forming quality and production efficiency; but this method can only process the upper surface and vertical side of the part, and cannot process the lower surface of the part.

[0006] In view of the problems in the prior art, it is necessary to design a new additive and subtractive composite manufacturing method with an interval layer to overcome the problems in the prior art. SUMMARY

[0007] The existing processing method according to the prior art can cause the generation of a depression at the additive and subtractive interface, affecting the surface quality; if the surface quality needs to be improved, the selection of a tool is required; pulse laser impact processing can improve the forming quality and production efficiency, but this method cannot process the lower surface of a part and other technical problems, and an additive and subtractive composite manufacturing method with an interval layer is provided. The additive and subtractive composite manufacturing method mainly uses an interval layer introduced in the process planning of additive and subtractive composite manufacturing to offset the shrinkage caused by thermal stress in the additive process, so as to ensure the surface quality of subtractive processing.

[0008] The technical means adopted by the present application are as follows:

[0009] In the additive and subtractive composite manufacturing method with an interval layer, the additive method is powder laying, the subtractive milling method is three-axis numerical control milling, and the additive finishing tool includes an interval milling cutter.

[0010] Further, the additive and subtractive composite manufacturing method with an interval layer includes the following steps:

[0011] Step (1), obtaining a metal material depression value: a depression value at the additive and subtractive alternation in the additive and subtractive composite manufacturing process of a metal material without an interval layer is obtained through a pre-experiment;

[0012] Step (2), designing and selecting a processing tool: an interval milling cutter for processing a vertical surface is designed according to the experimental results; and for upper and lower inclined surfaces, a ball end milling cutter and a drum-shaped cutter with a downward cutting capability are selected for processing;

[0013] Step (3), calculating an interval layer height: the maximum continuous additive height of each part of a part is calculated according to the geometric profile of the part, the overhanging angle of the surface to be processed, and the shape of the tool, and the height value is taken as the height of the interval layer in the additive and subtractive composite manufacturing;

[0014] Step (4), process planning: first, a laser additive path of the part is generated by using a processing software, and then a subtractive path is planned, that is, after the Nth continuous additive, the Nth continuous additive part is coarsely processed, and after the coarse processing, the N-1th continuous additive part is finely processed; after the fine processing, the N+1th continuous additive is performed; the additive and subtractive processes are repeatedly performed alternately in the above order;

[0015] Step (5), processing implementation: according to the interval layer height of each processing part calculated in step (3) and the process planning completed in step (4), the processing of the part is completed by using a three-axis additive and subtractive machine tool.

[0016] Further, the spacer milling cutter used for processing the vertical surface in step (2) should have a clearance portion, and the difference between the cutter radius and the clearance radius should be greater than the concave value obtained in step (1).

[0017] Further, the finishing allowance reserved for finishing in the rough machining in step (4) should be greater than the concave value obtained in step (1).

[0018] Further, the rough machining of the upper inclined surface in step (4) should use a ball-end milling cutter, and the rough machining of the lower inclined surface should use a drum milling cutter. The finishing of the upper and lower inclined surfaces should use a drum milling cutter, and the finishing of the lower inclined surface should not use the same drum milling cutter as the rough machining.

[0019] Further, the finishing of the upper and lower inclined surfaces in step (4) should use a drum milling cutter, and the finishing of the lower inclined surface should not use the same drum milling cutter as the rough machining.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The additive-subtractive composite manufacturing method with a spacer layer provided by the present application provides specific methods and theoretical basis for the development of three-axis additive-subtractive composite manufacturing process, and improves the concave at the additive and subtractive process alternation in the additive-subtractive composite manufacturing process.

[0022] 2. The additive-subtractive composite manufacturing method with a spacer layer provided by the present application can be applied to various machining surfaces by adapting different cutters to different types of machining surfaces, thereby meeting the high-quality additive-subtractive composite manufacturing of various complex parts.

[0023] 3. The additive-subtractive composite manufacturing method with a spacer layer provided by the present application can maximize the efficiency of additive-subtractive composite manufacturing on the basis of ensuring the quality of the machining surface by reasonably setting the axial feed amount of rough and finishing machining and the continuous maximum additive height value.

[0024] In summary, the technical solution of the present application solves the problems of the prior art, such as the generation of concave at the additive-subtractive interface, which affects the surface quality; if the surface quality needs to be improved, the selection of cutters is required; the pulse laser impact machining can improve the forming quality and production efficiency, but this method cannot process the upper surface and side surface of the part, and cannot process the lower surface of the part. BRIEF DESCRIPTION OF DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart of the method for alternating timing in the manufacturing of additive and subtractive composite materials with spacer layers according to the present invention;

[0027] Figure 2 This is a schematic diagram of the recess at the alternation point between additive and subtractive materials during the composite manufacturing process of this invention;

[0028] Figure 3 This is a schematic diagram showing the corresponding parameters of the interlayer milling cutter of the present invention;

[0029] Figure 4 This is a schematic diagram showing the corresponding parameters of the end mill of the present invention;

[0030] Figure 5 This is a schematic diagram showing the corresponding parameters of the ball end mill of the present invention;

[0031] Figure 6 This is a schematic diagram showing the corresponding parameters of the drum-shaped end mill of the present invention.

[0032] Figure 7 This is a perspective view of the part in Embodiment 1 of the present invention;

[0033] Figure 8 This is a cross-sectional view of the part in Embodiment 1 of the present invention;

[0034] Figure 9 This is a perspective view of the part in Embodiment 2 of the present invention;

[0035] Figure 10 This is a cross-sectional view of the part in Embodiment 2 of the present invention;

[0036] Figure 11 This is a perspective view of the part in Embodiment 3 of the present invention;

[0037] Figure 12 This is a cross-sectional view of the part in Embodiment 3 of the present invention;

[0038] Figure 13 This is a schematic diagram of the machining process of the inclined surface on the bowl-shaped part in Embodiment 1 of the present invention;

[0039] Figure 14 This is a schematic diagram of the machining process for the lower inclined surface of the bowl-shaped part in Embodiment 2 of the present invention;

[0040] Figure 15 This is a schematic diagram of the machining process for the vertical surface of the cylindrical part in Embodiment 3 of the present invention.

[0041] In the figure: D, tool diameter H, tool edge thickness L, tool relief length d, tool relief diameter T, tool edge number R, drum milling cutter arc radius. DETAILED DESCRIPTION

[0042] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0043] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0044] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of a feature, step, operation, device, component and / or combination thereof.

[0045] Unless specifically stated otherwise, the relative arrangement of the components and steps illustrated in these embodiments and the numerical expressions and values are not limiting of the scope of the present application. It should be understood that the dimensions of the various parts shown in the drawings are not necessarily to scale. Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the description of the present application. In all examples shown and discussed herein, any specific value should be interpreted as merely an example, and not as a limitation. Thus, other examples of the exemplary embodiments can have different values. It should be noted that similar reference numbers and letters in the following drawings represent similar items, and therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0046] In the description of the present application, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and in the absence of the opposite description, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0047] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0048] In addition, it needs to be noted that the use of "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0049] As Figures 1-6 As shown in the drawings, the present application provides a method for additive and subtractive composite manufacturing with an interval layer, the additive method is powder laying type, the subtractive milling method is three-axis numerical control milling, and the building material finishing tool includes an interval milling cutter;

[0050] The additive and subtractive composite manufacturing method with an interval layer includes the following steps:

[0051] Step (1), obtaining the concave value of the metal material: the concave value at the additive and subtractive alternating position in the additive and subtractive composite manufacturing process of the metal material without adding an interval layer is obtained by pre-experiment;

[0052] Step (2), designing and selecting a machining tool: according to the experimental results, an interval milling cutter for machining vertical surfaces is designed; and for the upper and lower inclined surfaces, a ball end milling cutter and a drum-shaped cutter with a downward cutting capability are selected for machining;

[0053] Step (3), calculating the interval layer height: according to the geometric profile of the part, the overhanging angle of the surface to be machined and the shape of the tool, the maximum continuous additive height of each part of the part is calculated, and this height value is taken as the height of the interval layer in the additive-subtractive composite manufacturing;

[0054] Step (4), process planning: first, the laser additive path of the part is generated using the machining software, and then the subtractive path is planned, that is, after the Nth continuous additive, the Nth continuous additive part is rough machined, and after rough machining, the N-1th continuous additive part is finished machined; after finishing, the N+1th continuous additive is carried out; the additive-subtractive process is repeated alternately in the above order;

[0055] Step (5), processing implementation: according to the interval layer height of each processing part calculated in step (3) and the process planning completed in step (4), the three-axis additive-subtractive machine tool is used to complete the processing of the part.

[0056] Further improve the processing efficiency under the premise of ensuring the surface quality, a larger axial feed rate can be selected during rough machining, and the axial feed rate during finishing is related to the theoretical residual height value and the radius of the drum-shaped milling cutter. The theoretical maximum axial feed rate should be calculated according to the surface quality requirements of the part, and the actual value should be slightly less than the theoretical maximum value.

[0057] The spacer milling cutter used for machining vertical surface in step (2) should have an avoidance part, and the difference between the tool radius and the avoidance radius should be greater than the concave value obtained in step (1) experiment.

[0058] The finishing allowance reserved for finishing in rough machining in step (4) should be greater than the concave value obtained in step (1) experiment.

[0059] When selecting subtractive machining tools, the geometric profile of the part and the machining precision requirement should be considered to select from end milling cutter, ball nose milling cutter, drum-shaped milling cutter and spacer milling cutter. The corresponding parameters of end milling cutter, ball nose milling cutter, drum-shaped milling cutter and spacer milling cutter are shown in Figure 3 、 4 , 5, 6.

[0060] In step (4), ball nose milling cutter should be used for rough machining of the upper inclined surface, and drum-shaped milling cutter should be used for rough machining of the lower inclined surface. Drum-shaped milling cutter is used for finishing of the upper and lower inclined surfaces, and the same drum-shaped milling cutter is not used for finishing and rough machining of the lower inclined surface.

[0061] In step (4), drum-shaped milling cutter is used for finishing of the upper and lower inclined surfaces, and the same drum-shaped milling cutter is not used for finishing and rough machining of the lower inclined surface.

[0062] Example 1

[0063] As Figure 7 ,8 As shown, the present invention provides a composite manufacturing method for additive and subtractive materials with spacer layers to process a bowl-shaped part with a minimum diameter of 10cm and a height of 8cm; the part material is GH3536, the laser power is set to 400W, the scanning speed is 1750mm / s, the subtractive material feed speed is 1000mm / s, and the spindle speed is 20000r / min.

[0064] As attached Figure 1 As shown, the indentation value of GH3536 during the additive and subtractive composite manufacturing process without the spacer layer was first obtained through experiments. Then, the spacer cutter for machining the vertical surface was designed and end mills, ball end mills and drum end mills were selected. The tool diameter of the four types of end mills was selected as 6mm. The difference between D and d of the spacer cutter was determined according to the experimental results of step one, and the radius R of the drum end mill was taken as 0.25mm.

[0065] For bowl-shaped parts without overhanging surfaces, since the inner wall surface resembles an upwardly inclined surface, a method is adopted. Figure 13 The processing method shown is used to process the inner wall surface.

[0066] Example 2

[0067] like Figure 9 , 10 As shown, this invention provides a composite manufacturing method for additive and subtractive materials with spacer layers to process an inverted bowl-shaped part with a minimum diameter of 10cm, a height of 8cm, and a hanging angle of 70°. The part material is GH3536, the laser power is set to 400W, the scanning speed is 1750mm / s, the subtractive material feed speed is 1000mm / s, and the spindle speed is 20000r / min.

[0068] As attached Figure 1 As shown, the indentation value of GH3536 during the additive and subtractive composite manufacturing process without the spacer layer was first obtained through experiments. Then, the spacer cutter for machining the vertical surface was designed and end mills, ball end mills and drum end mills were selected. The tool diameter of the four types of end mills was selected as 6mm. The difference between D and d of the spacer cutter was determined according to the experimental results of step one, and the radius R of the drum end mill was taken as 0.25mm.

[0069] For inverted bowl-shaped parts, due to their overhanging characteristics, the maximum continuous additive height must first be determined based on the overhang angle and tool parameters, and then... Figure 14 The processing method shown is used for processing.

[0070] Example 3

[0071] like Figure 11 , 12As shown, the application provides a kind of additive and subtractive composite manufacturing method with spacer layer to process the inner diameter of a cylindrical part 10cm, height 15cm;Part material is GH3536, laser power is set to 400W, scanning speed 1750mm / s;Subtractive feed speed is 1000mm / s, spindle speed is 20000r / min.

[0072] As shown in the accompanying drawings Figure 1 First, the concave value generated in the additive and subtractive composite manufacturing process of GH3536 without setting the spacer layer is obtained by experiment, then the spacer milling cutter for processing vertical surface is designed and the end milling cutter, ball milling cutter and drum milling cutter are selected;The tool diameter of the four milling cutters is selected as 6mm;The difference between spacer milling cutter D and d is determined according to the experimental results of step one, and the arc radius R of drum milling cutter is 0.25mm.

[0073] For cylindrical parts, vertical milling cutter and spacer milling cutter are used to process the inner wall surface according to the processing method shown in the drawings. Figure 15

[0074] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, but not to limit it;Although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features;And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.​

Claims

1. A method for additive and subtractive composite manufacturing with spacer layer, characterized in that: the additive method in the method for additive and subtractive composite manufacturing with spacer layer is powder laying type, the subtractive milling method is three-axis numerical control milling, and the subtractive finishing tool comprises a spacer milling cutter; the method for additive and subtractive composite manufacturing with spacer layer comprises the following steps: step (1), obtaining a metal material recess value: a recess value at an additive and subtractive alternate position in an additive and subtractive composite manufacturing process without adding a spacer layer is obtained through pre-experiment; step (2), designing and selecting a machining tool: a spacer milling cutter for machining a vertical surface is designed according to an experimental result; and a ball-end milling cutter and a drum-shaped cutter with a downward cutting capability are selected for machining upper and lower inclined surfaces; step (3), calculating a spacer layer height: a maximum continuous additive height of each part of a part is calculated according to a geometric contour of the part, a cant angle of a surface to be machined and a tool shape, and the height value is taken as a height of the spacer layer in the additive and subtractive composite manufacturing; step (4), process planning: laser additive paths of the part are generated by using a machining software, and then subtractive path planning is performed, that is, after N times of continuous additive, rough machining is performed on the N times of continuous additive, and after the rough machining, finishing is performed on N-1 times of continuous additive; after the finishing, N+1 times of continuous additive is performed; and the additive and subtractive processes are repeatedly performed alternately in the above order; and step (5), machining implementation: the part is machined by using a three-axis additive and subtractive machine tool according to the spacer layer height of each machining part calculated in step (3) and the process planning completed in step (4).

2. The method for additive and subtractive composite manufacturing with spacer layer according to claim 1, characterized in that: the spacer milling cutter for machining the vertical surface in step (2) should have an avoidance part, and a difference between a tool radius and an avoidance radius should be greater than the recess value obtained through the experiment in step (1).

3. The method for additive and subtractive composite manufacturing with spacer layer according to claim 1, characterized in that: the finishing allowance reserved for finishing in the rough machining in step (4) should be greater than the recess value obtained through the experiment in step (1).

4. The method for additive and subtractive composite manufacturing with spacer layer according to claim 1, characterized in that: the rough machining of the upper inclined surface in step (4) should use a ball-end milling cutter, the rough machining of the lower inclined surface should use a drum-shaped milling cutter; the finishing of the upper and lower inclined surfaces should use a drum-shaped milling cutter, and the finishing of the lower inclined surface should not use the same drum-shaped milling cutter as the rough machining.

5. The method for additive and subtractive composite manufacturing with spacer layer according to claim 1, characterized in that: the finishing of the upper and lower inclined surfaces in step (4) should use a drum-shaped milling cutter, and the finishing of the lower inclined surface should not use the same drum-shaped milling cutter as the rough machining. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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