A safety domain-based force-controlled efficient CNC machining method for aircraft metal additive parts

Abstract

The present invention provides a force-controlled and efficient CNC machining method for aircraft metal additive parts based on a safety domain, which belongs to the field of aviation manufacturing, and the steps include: scanning to obtain the contour model of the manufactured additive part and comparing it with the three-dimensional digital model of the part to obtain the cutting allowances of different feature positions; determining the safety domain boundary of each cutting segment; segmenting each cutting segment of the machining path; adjusting the safety domain boundary plane; solving to determine the cutting force of each segment; solving to determine the tool feed speed; compiling a CNC machining program and performing simulation to verify the correctness; machining the additive part according to the generated CNC program. The present invention can accurately quantify the safety domain distance, which can not only reduce the risk of damage to the tool when cutting into the additive part, but also improve the efficiency of air cutting; based on this method, stable tool cutting of the additive part under different cutting allowance conditions can be achieved, thereby improving the tool life and the surface quality of the workpiece.

Description

Technical Field

[0001] The present invention belongs to the field of aviation manufacturing and relates to a safety domain-based force-controlled efficient numerical control machining method for aircraft metal additive parts, which is used to improve the machining efficiency and precision of aircraft parts and reduce tool costs. Background Art

[0002] The rapid development of aircraft is the future development trend. As a disruptive technology, additive manufacturing technology has the advantages of supporting complex structural design, moldless trial production, rapid response, and saving raw materials, and has gradually been applied to aircraft metal structural parts. However, due to the spheroidization effect of metal powder, aircraft additive parts cannot meet the dimensional accuracy requirements, and usually require manual support, filing, machining, grinding and other post-processing processes, resulting in high labor intensity for workers and poor consistency of manual grinding accuracy. In addition, due to the uneven size allowance of additive parts, the cutting force varies greatly during the cutting process, and the tool is prone to chipping and severe wear, which makes the cost of processing tools high. Worn tools are in an uncontrolled state, which increases the risk of tool breakage. In severe cases, they will damage parts, causing significant economic losses and affecting the delivery progress of aircraft products. Therefore, a new technical method is urgently needed to solve the above problems. Summary of the invention

[0003] The present invention provides a safety domain-based force-controlled efficient CNC machining method for aircraft metal additive parts, which not only reduces labor intensity, but also solves the problems of poor consistency in manual polishing precision, easy breakage of tool cutting, and low machining efficiency, thereby reducing tool costs and improving the machining efficiency and precision of additive parts.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A force-controlled efficient CNC machining method for aircraft metal additive parts based on a safety domain, the CNC machining method comprising: first, obtaining an additive part by an additive manufacturing method; second, scanning the additive part to obtain an additive part contour model; third, solving to obtain cutting allowances at different feature positions; fourth, determining the safety domain boundary; fifth, segmenting each cutting segment of the machining path; sixth, adjusting the safety domain boundary plane; seventh, determining the cutting force F of each segment; c ; Eighth, determine the tool feed speed f; Ninth, based on the size of the actual part, combine the cutting force and feed speed of each section to compile a CNC machining program; Tenth, perform cutting simulation to verify the correctness of the CNC machining program; Finally, process the additive part according to the generated CNC machining program. The CNC machining method specifically includes the following steps:

[0006] Step 1: Use additive manufacturing methods, combined with the three-dimensional digital model of the part, to print the part to obtain an additive part.

[0007] Step 2: Scan the contour of the additive part to obtain a contour model of the additive part.

[0008] Step 3: Compare the contour model of the additive part with the three-dimensional digital model of the part to calculate the cutting allowances at different feature positions.

[0009] Step 4: Determine the safety zone boundary. On the machining path, the tool entry point S of each cutting segment is far away from the cutting position, and a plane parallel to the tool axis is defined as the safety zone boundary plane P of each cutting segment. c , then the tool cuts into the workpiece point S and the corresponding safety zone boundary plane P c The area between them is the safety zone of the cutting segment, and the vertical distance between them is the safety zone distance L0, so L0 = part manufacturing deviation + (2mm~5mm).

[0010] Step 5: Divide each cutting segment of the machining path into segments. Define the tool starting point of each cutting segment as O, the cutting end point as E, and the tool starting point O to the safety zone boundary plane P c The area between is the empty cut area, and the safety zone boundary plane P c The area between the cutting end point E is the cutting area; set the division distance to L slit , starting from the cutting end point E of each cutting segment and ending at L slit The length of the corresponding cutting segment is divided into segments. After the division, the boundary points of each segment are M0, M1, M2, etc. i , where 2mm≤L slit ≤5mm.

[0011] Step 6: Adjust the safety zone boundary plane. When the boundary point M of the last cutting segment divided in step 5 is i When located in the security domain, the security domain boundary plane P c and the safety zone distance L0 remains unchanged; when the boundary point M i When in the empty cut area, adjust the safety zone boundary plane P c P c ',P c 'Parallel to P c , and the boundary point M i In plane P c ', the safety zone distance is adjusted accordingly , That is, the tool enters the workpiece point S and the plane P c ', where Calculate according to formula (1):

[0012] (1)

[0013] Where Mi P c Representing the boundary point With plane P c The vertical distance between.

[0014] Step 7: Determine the cutting force F for each segment c Finite element analysis or empirical formula method is used to fit the cutting force F of each segment in each cutting segment. c , and a constant cutting force is used in each segment, where the cutting force F in the safety region c The cutting force of the segment where the tool of the corresponding cutting segment cuts into the workpiece point S is located.

[0015] Step 8: Determine the tool feed speed f. To characterize the tool position, define the tool position point as T po To improve machining efficiency, the tool uses a dynamic feed rate, that is, each segment uses a different feed rate but the feed rate in each segment remains unchanged; specifically: when the tool position T po When in the air cutting area, the feed speed f adopts the set fast feed speed f max ; When the knife position T po When in the cutting area, the feed speed f adopts the cutting feed speed f in , cutting feed speed f of each segment in According to formula (3), when the tool position T po When in the safety zone, the feed speed f also uses the cutting feed speed f in , the specific cutting feed speed of the segment where the tool of the corresponding cutting segment cuts into the workpiece point S is adopted, as shown in formula (2) and formula (3):

[0016] (2)

[0017] (3)

[0018] Where ES represents the cutting area from the point where the tool enters the workpiece S to the cutting end point E; SM i Represents security domain; OM i Represents the empty cutting area; K c is the cutting force correction factor; a p is the cutting depth; a e is the cutting width; m is the feed speed coefficient; n is the cutting depth coefficient; k is the cutting width coefficient.

[0019] Step 9: Based on the actual part size and the cutting force and feed speed f of each segment determined in steps 7 and 8, CAM software is used for CNC machining programming.

[0020] Step 10, performing cutting simulation on the compiled NC machining program to verify the correctness of the NC machining program.

[0021] Step 11, machining the additive part according to the generated NC machining program.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a safety zone-based force-controlled efficient CNC machining method for aircraft metal additive parts, which can accurately quantify the safety zone distance, not only reducing the risk of tool breakage when cutting into the additive parts, but also improving the air cutting efficiency; based on the force control method, stable tool cutting of additive parts under different cutting allowances can be achieved, thereby improving tool life and workpiece surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the efficient force-controlled CNC machining method for aircraft metal additive parts based on the safety domain.

[0025] Figure 2 Schematic diagram of a three-dimensional model of a three-way pipe in the embodiment.

[0026] Figure 3 It is a schematic diagram of safety domain solution and cutting path division in the embodiment. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention clearer, further detailed description is given below in conjunction with specific embodiments.

[0028] This embodiment takes a certain three-way pipe as an example to further illustrate a force-controlled efficient CNC machining method for aircraft metal additive parts based on a safety domain provided by the present invention. The overall scheme of the CNC machining method is as follows: Figure 1 The detailed steps are as follows:

[0029] Step 1: Use additive manufacturing methods to combine the three-dimensional digital model of the part (such as Figure 2 As shown in the figure), the parts are printed to obtain a three-way pipe additive part, the material of which is AlSi 10 Mg, powder size specification is 15-53μm.

[0030] Step 2: Use a contour scanning measurement device to perform contour scanning on the three-way pipe additive part to obtain point cloud data of the three-way pipe additive part, and perform preprocessing and model surface reconstruction on the point cloud to generate a contour model of the three-way pipe additive part.

[0031] Step 3: Compare the contour model of the tee pipe additive part with the three-dimensional digital model of the part to calculate the cutting allowances at different feature positions.

[0032] Step 4: Determine the safety zone boundary. On the machining path, the tool entry point S of each cutting segment is far away from the cutting position, and a plane parallel to the tool axis is defined as the safety zone boundary plane P of each cutting segment. c , then the tool cuts into the workpiece point S and the corresponding safety zone boundary plane P c The area between them is the safety zone of the cutting segment, and the vertical distance between them is the safety zone distance L0, then L0=part manufacturing deviation+(2mm~5mm), and in this embodiment, L0 is 3mm.

[0033] Step 5: Divide each cutting segment of the machining path into segments. Define the tool starting point of each cutting segment as O, the cutting end point as E, and the tool starting point O to the safety zone boundary plane P c The area between is the empty cut area, and the safety zone boundary plane P c The area between the cutting end point E is the cutting area; set the division distance to L slit , starting from the cutting end point E of each cutting segment and ending at L slit The corresponding cutting segment is divided into segments, and the boundary points of each segment are M0, M1, M2, etc. i , where 2mm≤L slit ≤5mm, in this embodiment, L slit Take 3mm; Figure 3 Taking a cutting segment in this embodiment as an example, a segment is divided every 3 mm from the cutting end point E of the cutting segment, and a total of 4 segments are divided, and the boundary points of each segment are M0, M1, M2 and M3 in sequence. i .

[0034] Step 6: Adjust the safety zone boundary plane. When the last boundary point M of each cutting segment after being divided in step 5 is i When located in the security domain, the security domain boundary plane P c and the safety zone distance L0 remains unchanged; when M i When in the empty cut area, adjust the safety zone boundary plane P c P c ',P c 'Parallel to P c , and the boundary point M i In plane P c ', the safety zone distance is adjusted accordingly to , that is, the tool enters the workpiece point S and P c ', where Calculate according to formula (1):

[0035] (1)

[0036] by Figure 3 Take the middle cutting section as an example, the boundary point Mi Located in the empty cutting area, therefore, the safety zone distance of the cutting segment is adjusted to , and according to Adjust the safety zone boundary plane P of the cutting segment c P c '.

[0037] Step 7: Determine the cutting force F for each segment c The finite element analysis method is used to fit the cutting force F of each segment in each cutting segment. c , and a constant cutting force is used in each segment, where the cutting force F in the safety region c The cutting force of the segment where the tool of the corresponding cutting segment cuts into the workpiece point S is; Figure 3 As shown in the embodiment of the present invention, a cutting section is taken as an example. Through the finite element analysis method, it is found that in this cutting section, the cutting force of the EM0 segment is 413.6N, the cutting force of the M0M1 segment is 206.8N, the cutting force of the M1M2 segment is 74.5N, and the cutting force of the M2M i The segment is located in the safety domain, and the cutting force of this segment is the same as that of the M1M2 segment where the tool cuts into the workpiece point S, which is 74.5N.

[0038] Step 8: Determine the tool feed speed f. To characterize the tool position, define the tool position point as T po To improve machining efficiency, the tool uses a dynamic feed rate, that is, each segment uses a different feed rate but the feed rate in each segment remains unchanged; specifically: when the tool position T po When in the air cutting area, the feed speed f adopts the set fast feed speed f max ; When the knife position T po When in the cutting area, the feed speed f adopts the cutting feed speed f in , cutting feed speed f of each segment in According to formula (3), when the tool position T po When in the safety zone, the feed speed f also uses the cutting feed speed f in , the specific cutting feed speed of the segment where the tool of the corresponding cutting segment cuts into the workpiece point S is adopted, as shown in formula (2) and formula (3):

[0039] (2)

[0040] (3)

[0041] by Figure 3 As shown in the embodiment of the present invention, a cutting section is taken as an example. In this cutting section, the fast feed speed f is set in the empty cutting area. max 2200mmpm, EM0 segment cutting feed speed f inThe M0M1 segment cutting feed speed is 1691.09 mmpm. in The M1M2 segment cutting feed speed is 1703.74mmpm. in 1833.42mmpm, M2M i The segment is within the safety zone, and the cutting feed rate f of the segment is in The same as the M1M2 segment where the tool enters the workpiece point S.

[0042] Step 9: Based on the actual size of the three-way pipe additive part and the cutting force and feed speed f of each section determined in steps 7 and 8, CAM software is used for CNC machining programming.

[0043] Step 10, performing cutting simulation on the compiled NC machining program to verify the correctness of the NC machining program.

[0044] Step 11, machining the additive part according to the generated NC machining program.

[0045] The CNC machining method used in this implementation case can accurately quantify the safety zone distance, reduce the risk of tool breakage when cutting into the additive part, and improve air cutting efficiency; based on the force control method, stable tool cutting of additive parts under different cutting allowances can be achieved, thereby improving tool life and workpiece surface quality.

[0046] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A safety domain-based force-controlled efficient CNC machining method for aircraft metal additive parts, characterized in that: The numerical control machining method comprises the following steps: Step 1, manufacturing additive parts; Step 2, scanning the additive part to obtain an additive part contour model; Step 3, compare the contour model of the additive part with the three-dimensional digital model of the part, and calculate the cutting allowances at different feature positions; Step 4: Determine the security domain boundary; Step 5, dividing each cutting segment of the processing path into segments; Step 6: Adjust the security zone boundary plane; Step 7: Determine the cutting force F for each segment c ; Step 8, determine the tool feed speed f; Step 9, based on the actual part size, combined with the cutting force and feed speed determined in steps 7 and 8, perform CNC machining programming; Step 10, verifying the correctness of the NC machining program compiled in step 9; Step 11, machining the additive part according to the generated NC machining program; Steps 4 to 8 in the CNC machining method are specifically as follows: Step 4: Determine the safety zone boundary. On the machining path, the tool entry point S of each cutting segment is far away from the cutting position, and a plane parallel to the tool axis is defined as the safety zone boundary plane P of each cutting segment. c , then the tool cuts into the workpiece point S and the corresponding safety zone boundary plane P c The area between is the safety zone of the cutting segment, and the vertical distance between them is the safety zone distance L0; Step 5: Divide each cutting segment of the machining path into segments; define the tool starting point of each cutting segment as O, the cutting end point as E, and the tool starting point O to the safety zone boundary plane P c The area between is the empty cut area, and the safety zone boundary plane P c The area between the cutting end point E is the cutting area; set the division distance to L slit , starting from the cutting end point E of each cutting segment and ending at L slit The length of each cutting segment is divided into segments. After the division, the boundary points of each segment are M0, M1, M2, etc. i ; Step 6: Adjust the boundary plane of the safety zone; when the last boundary point M of each cutting segment after being divided in step 5 is i When located in the security domain, the security domain boundary plane P c The distance L0 from the safety zone remains unchanged; when the boundary point M i When in the empty cut area, adjust the safety zone boundary plane P c P c ',P c 'Parallel to P c , and the boundary point M i In plane P c ', the safety zone distance is adjusted to L'0, that is, the tool cuts into the workpiece point S and P c 'The vertical distance; Step 7: Determine the cutting force F for each segment c ; Fitting to obtain the cutting force F of each segment in each cutting segment c , and a constant cutting force is used in each segment, where the cutting force F in the safety region c The cutting force of the segment where the tool of the corresponding cutting segment cuts into the workpiece point S; Step 8: Determine the tool feed speed f; the tool uses a dynamic feed speed and defines the tool position point as T po , when the knife point T po When in the air cutting area, the feed speed f adopts the set fast feed speed f max ; When the knife position T po When in the cutting area, the feed speed f adopts the cutting feed speed f in ; When the knife position T po When in the safety zone, the feed speed f also uses the cutting feed speed f in .

2. The method for force-controlled efficient CNC machining of aircraft metal additive parts based on safety domain according to claim 1 is characterized in that: In step 4, the safety zone distance L0 = part manufacturing deviation + (2mm~5mm).

3. The method for force-controlled efficient CNC machining of aircraft metal additive parts based on safety domain according to claim 1 is characterized in that: In step 5, the distance L is divided slit Range: 2mm≤L slit ≤5mm.

4. The method for efficient force-controlled CNC machining of aircraft metal additive parts based on safety domain according to claim 1, characterized in that: In step 6, L′0 is calculated according to formula (1): L′0=L0+M i P c (1) In the formula, M i P c Represents the boundary point M i With P c The vertical distance between.

5. The method for force-controlled efficient CNC machining of aircraft metal additive parts based on safety domain according to claim 1 is characterized in that: In step 7, the cutting force F of each segment in each cutting segment is c Solved by finite element analysis or empirical formula method.

6. The method for efficient force-controlled CNC machining of aircraft metal additive parts based on safety domain according to claim 1, characterized in that: In step 8, the knife point T po The mathematical expression of the feed speed f in different areas is: Where ES represents the cutting area from the point where the tool enters the workpiece S to the cutting end point E; SM i Represents security domain; OM i Represents the empty cut area.

7. The method for force-controlled efficient CNC machining of aircraft metal additive parts based on safety domain according to claim 1, characterized in that: In step 8, the cutting feed speed f of each segment in the cutting area is in According to formula (3), we can get: In the formula, K c is the cutting force correction factor; a p is the cutting depth; a e is the cutting width; m is the feed speed coefficient; n is the cutting depth coefficient; k is the cutting width coefficient.

8. A safety domain-based force-controlled efficient CNC machining method for aircraft metal additive parts according to claim 1 or 7, characterized in that: Knife point T po Cutting feed speed f within the safety zone in Use the cutting feed speed of the segment where the tool of the corresponding cutting segment enters the workpiece point S.

9. The method for force-controlled efficient CNC machining of aircraft metal additive parts based on safety domain according to claim 1, characterized in that: In step 10, the correctness of the CNC machining program is verified through cutting simulation.

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