A method of progressive feed turning based on prolonging tool life

Abstract

The application relates to a progressive feed turning method based on prolonging tool life, and belongs to the technical field of machine tool cutting, which solves the technical problem of low tool life, and comprises the following steps: according to machining requirements, selecting a numerical control lathe turning tool, and installing the turning tool on the numerical control lathe; preparing a workpiece blank, and clamping the workpiece blank in a numerical control lathe clamp; measuring the tool length of the turning tool in the X direction and the Z direction, and inputting the tool shape compensation value corresponding to the tool number of the numerical control lathe; inputting the prepared progressive feed subprogram into the numerical control lathe, setting machining parameters, taking the feed speed calculated by the subprogram as the actual feed speed; implementing workpiece trial cutting machining according to the prepared program; measuring the structural size and surface roughness of the machined workpiece blank, adjusting the progressive feed subprogram, setting the feed speed and the decrement of each time, and implementing workpiece turning machining according to the adjusted progressive feed subprogram. The turning method is used for numerical control lathe turning machining.

Description

Technical Field

[0001] This invention belongs to the field of machine tool cutting technology, specifically relating to a variable feed turning method based on extending tool life. Background Technology

[0002] With the development of machine tool and cutting tool technology, post-heat turning is increasingly widely used in the machining of automotive transmission gear parts. Compared with traditional grinding processes, post-heat turning has advantages such as high machining efficiency, high flexibility, energy saving, and environmental protection. As the final finishing process, it requires a relatively low surface roughness value for the workpiece. In batch processing, excessive wear of the cutting tools often leads to out-of-tolerance surface roughness, posing a quality risk. In such cases, the cutting tool tip must be replaced, resulting in low tool life and high machining costs.

[0003] Taking the intermediate shaft gear of the transmission as an example, the surface roughness Ra of the inner bore after heating is required to be below 0.8. Figure 1 As shown in red, when using a rapid feed internal boring tool on a CNC horizontal lathe for boring, the surface roughness value is close to the upper limit of the requirement when the tool life reaches 400 pieces. At this time, the tool tip needs to be replaced, and the cost of a single tool is 0.69 yuan.

[0004] CBN inserts used in post-heat turning are relatively expensive. To reduce workpiece surface roughness, extend insert life, and lower machining costs, cutting speeds are typically reduced, but this decreases machining efficiency and is unsuitable for mass production. Alternatively, optimizing insert material to improve wear resistance often yields limited results. Therefore, extending insert life and maximizing insert value remains a critical technical challenge. Summary of the Invention

[0005] To overcome the short lifespan of machine tool cutting tools, this invention proposes a variable feed turning method based on extending tool life.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A variable feed turning method based on extending tool life includes the following steps:

[0008] Step 1, Prepare the knives

[0009] Based on the workpiece machining requirements, select the CNC lathe turning tool and install the turning tool on the CNC lathe.

[0010] Step 2, Prepare the workpiece blank

[0011] Prepare the workpiece blank by clamping it in the CNC lathe fixture.

[0012] Step 3, setting the knife

[0013] Measure the tool length of the turning tool in the X and Z directions, and input the tool shape compensation value of the corresponding tool number of the CNC lathe.

[0014] Step 4, Program Development

[0015] Create a variable feed subroutine, input the created variable feed subroutine into the CNC lathe, and set the machining parameters.

[0016] Add a subroutine call to the main program, and use the feed rate calculated by the subroutine as the actual feed rate.

[0017] Step 5, Trial Cutting Processing

[0018] Start the CNC lathe machining program and perform trial cutting of the workpiece according to the programmed procedure.

[0019] Step 6, Precision measurement and machining of the workpiece

[0020] According to the accuracy requirements of the design parameters, measure the structural dimensions and surface roughness of the workpiece blank after machining.

[0021] Based on the measurement results, adjust the incremental feed subroutine and set the feed rate and the amount of decrease each time.

[0022] Start the CNC lathe machining program and perform workpiece turning according to the adjusted incremental feed subroutine.

[0023] The above-described variable feed turning method, step 1, further includes:

[0024] With the workpiece boring as the machining requirement, the rapid feed boring tool holder is installed on the CNC lathe turret, and the rapid feed insert is installed on the tool holder, and the insert pressure plate screw is tightened.

[0025] The above-described variable feed turning method, step 2, further includes:

[0026] Using the intermediate shaft gear as the workpiece blank, the intermediate shaft gear is clamped in the CNC lathe fixture.

[0027] The above-described variable feed turning method, step 4, further includes:

[0028] Write a user macro program to set the initial feed rate, decrease value, and minimum feed rate in the incremental feed subroutine;

[0029] Add a tool life counter to the main program;

[0030] Then, in the subroutine, the decreased feed rate is calculated based on the current lifespan and set value, and the calculated feed rate is evaluated. If the calculated feed rate is greater than the minimum feed rate, the actual feed rate is the calculated feed rate; otherwise, the actual feed rate is the minimum feed rate. The main program then calls the actual feed rate at this time for machining.

[0031] The above-described variable feed turning method, step 5, further includes:

[0032] The intermediate shaft gear is boring.

[0033] The above-described variable feed turning method, step 6, further includes:

[0034] Measure the boring hole size and surface roughness values. Based on the measurement results, adjust the incremental feed subroutine and set the feed rate parameters and the amount of decrease each time.

[0035] The above-mentioned variable feed turning method also includes step 7, changing the turning tool, the specific process of which is as follows:

[0036] When the surface roughness of the workpiece blank reaches the set value after machining, replace the turning tool, record the turning tool life, and reset the counter in the CNC lathe to zero.

[0037] The above-mentioned variable feed turning method also includes step 8, batch processing, the specific process of which is as follows:

[0038] Follow step 6 to adjust the incremental feed subroutine, setting the feed rate and the amount of decrease each time.

[0039] Based on the turning tool life recorded in step 7, set the turning tool life in the main program.

[0040] Start the CNC lathe machining program to perform batch turning of the workpieces.

[0041] The beneficial effects of this invention are:

[0042] A variable feed turning method based on extending tool life differs from conventional turning, which uses a constant feed rate throughout the tool life cycle. Instead, it automatically calculates the appropriate feed rate based on the number of inserts already machined using a user macro program. This variable feed rate method achieves a more consistent workpiece surface roughness, delays insert wear, and extends insert life. Applying this method to the internal machining of intermediate shaft gears after heat treatment, the average cycle time remains the same, but the insert life increases from 400 pieces / cutting edge to 600 pieces / cutting edge, a 50% increase. The unit cost decreases from 0.69 yuan to 0.46 yuan, a 33.3% reduction. This method demonstrates significant cost reduction and life extension effects, resulting in good economic benefits.

[0043] A variable feed turning method based on extending tool life is proposed, applicable to post-heat turning scenarios where premature tool failure is caused by excessive surface roughness. It has a wide range of applications and good versatility. This method is automatically completed through program functions without manual intervention, making it convenient to use and requiring no change to the original tool model, resulting in zero cost for widespread application. Attached Figure Description

[0044] Figure 1 This is a diagram of the intermediate shaft gear;

[0045] Figure 2 This is a flowchart of the variable feed turning method according to an embodiment of the present invention;

[0046] Figure 3 These are comparison charts of cutting tool wear. The top chart shows the cutting tool for constant feed turning, and the bottom chart shows the cutting tool for variable feed turning. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0048] Example 1

[0049] Taking the hot turning of the inner hole of the intermediate shaft gear as an example, the application process of this incremental feed turning method is as follows:

[0050] 1) Prepare the cutting tool; install the rapid feed boring tool holder on the CNC lathe turret, install the rapid feed insert on the tool holder, and tighten the insert pressure plate screw.

[0051] 2) Prepare the workpiece; clamp the intermediate shaft gear blank in the machine tool fixture and tighten the workpiece.

[0052] 3) Tool setting; Measure the tool length in the X and Z directions inside the machine tool and modify the tool shape compensation value for the corresponding tool number.

[0053] 4) Program the machine tool; input the variable feed subroutine into the machine tool and set appropriate parameters. Add a subroutine call to the main program, using the feed rate calculated by the subroutine as the actual feed rate.

[0054] 5) Trial cutting; start the program and complete the boring process.

[0055] 6) Precision measurement of workpiece; determine the boring hole size and surface roughness values, and adjust the feed rate parameters and the amount of decrease each time in the subroutine according to the precision measurement results.

[0056] 7) Replace the cutting tool: When the surface roughness is close to the upper limit, record the tool life at this time and reset the counter (#701) to zero.

[0057] 8) Batch application: Based on the parameters adjusted in step 6 and the tool life recorded in step 7, set the tool life for automatic batch processing.

[0058] Example 2

[0059] To extend the life of cutting inserts after hot turning, this invention proposes a variable feed turning method. Because the surface roughness increases after the existing cutting insert reaches its lifespan, but the wear is still relatively small at this point, the method is based on the theoretical roughness calculation formula:

[0060]

[0061] In the formula, Rz = maximum profile height (μm), f = feed rate (r / min), and r = tool tip radius (mm);

[0062] Reducing the feed rate f can lower surface roughness. Based on this principle, this method gradually reduces the feed rate f as the tool has processed during the machining process, so as to delay the increase in roughness due to tool wear, increase the usable cutting edge length of the insert, extend tool life, maximize the value of the insert, and reduce machining costs.

[0063] The technical solution process of this method is as follows: Figure 2 As shown, by compiling a user macro program, the initial feed rate, the decrement value, and the minimum feed rate are set in the subroutine; a tool life accumulation counter is added to the main program; then, the subroutine calculates the decremented feed rate based on the current life and the set value, and judges whether the calculated feed rate is greater than the minimum feed rate. If it is, the actual feed rate is the calculated feed rate; otherwise, the actual feed rate is the minimum feed rate, and the main program calls the actual feed rate at this time for machining.

[0064] Based on the above scheme and process, machine tool subroutines are compiled. Taking the FANUC CNC system as an example, the program is as follows:

[0065] %

[0066] O4001;…………………………………….….(Subroutine Name)

[0067] #1 = 0.45; ……………………………………..(#1 represents the initial feed / mm / r)

[0068] #2 = 5; ………………………………………………… (#2 means the first 5 items remain unchanged, and the number of items decreases starting from the 6th item)

[0069] #3 = 2; ……………………………………………….…(#3 means decreasing by one for every 2 items)

[0070] #4 = 0.0008; ………………………………… (#4 represents a decrease of 0.0008 each time)

[0071] #5 = 0.3; ………………………………………… (#5 represents the minimum feed / mm / r)

[0072] #6 = FIX[[#701-#2] / #3]; ……… (#6 represents the number of decrements)

[0073] IF[#701LE#2]THEN#1=#1;…………..…(First #2 pieces, feed rate remains unchanged)

[0074] IF[#701GT#2]THEN#1=#1-#6*#4;...(Calculate the decreasing feed rate)

[0075] IF[#1LE#4]THEN#1=#4;……………......(Actual feed rate is the minimum feed rate)

[0076] M99;…………………………………………...(End of subroutine, returns to main program)

[0077] %

[0078] In the above subroutine, #1 represents the initial feed rate; #2 represents that the feed rate remains unchanged for the first #2 pieces; #3 represents that starting from the #2+1th piece, the feed rate decreases by one for every #3 pieces; #4 represents the amount of each decrease; #5 represents the minimum feed rate; and #6 represents the number of decreases.

[0079] The main program needs to call its own subroutine and count the tool life. Taking the FANUC system as an example, the program is as follows:

[0080] %

[0081] O2001;…………………………………….….(Main program name)

[0082] ...

[0083] T0101;………………………………………….….(Call tool T1)

[0084] M98 P4001…………………………………………(Calls the feed rate calculation subroutine)

[0085] ...

[0086] G01 Z-50.0F#1…………………………………..(Use the subroutine-calculated speed as the current feed rate)

[0087] #701 = #701 + 1…………………………………..(#701 represents the number of times the tool has processed so far)

[0088] ...

[0089] M30…………………………………………………..(Main program ends, returns to the beginning)

[0090] %

[0091] In the main program above, #701 indicates that the tool life is counted, and #1 indicates the current feed rate.

[0092] The example program described above can be implemented with an initial feed rate of 0.45 mm / r. The feed rate remains constant for the first 5 pieces. Starting from the 6th piece, the feed rate decreases by 0.0008 every two pieces, reaching a minimum of 0.3 mm / r from the 382nd piece. After the 382nd piece, the minimum feed rate is maintained. When the surface roughness approaches the required upper limit, a tool change is necessary, and the #701 counter is reset to zero.

[0093] By applying the above example program, compared to the original constant feed rate of f = 0.35 mm / r, the usable cutting edge length of the rapid feed tool is extended, such as... Figure 3 As shown, the tool life has been increased from 400 pieces / cutting edge to 600 pieces / cutting edge, ensuring a surface roughness below Ra0.8, representing a 50% increase in tool life. The unit cost has decreased from 0.69 yuan to 0.46 yuan, a 33.3% reduction. This method uses the same rotation speed as the original, with the cycle time initially fast and then slowing down, resulting in an average cycle time that is essentially the same as before.

[0094] Example 3

[0095] A variable feed turning method based on extending tool life, taking the boring of intermediate shaft gears on a CNC lathe as an example, includes the following steps:

[0096] Step 1, Prepare the knives

[0097] Based on the requirements of the workpiece being machined, select the turning tools for the CNC lathe and install the turning tools on the CNC lathe.

[0098] Specifically, the rapid feed boring bar is mounted on the CNC lathe turret, and the rapid feed insert is mounted on the bar, and the insert clamping plate screw is tightened.

[0099] Step 2, Prepare the workpiece blank

[0100] Prepare the workpiece blank by clamping it in the CNC lathe fixture.

[0101] Specifically, the intermediate shaft gear is clamped in the CNC lathe fixture.

[0102] Step 3, setting the knife

[0103] Measure the tool length of the turning tool in the X and Z directions, and input the tool shape compensation value of the corresponding tool number of the CNC lathe.

[0104] Step 4, Program Development

[0105] Create a variable feed subroutine, input the created variable feed subroutine into the CNC lathe, and set the machining parameters.

[0106] Add a subroutine call to the main program, and use the feed rate calculated by the subroutine as the actual feed rate.

[0107] Step 5, Trial Cutting Processing

[0108] Start the CNC lathe machining program and perform trial cutting of the workpiece according to the programmed procedure.

[0109] Specifically, the intermediate shaft gear blank is subjected to boring machining.

[0110] Step 6, Precision measurement and machining of the workpiece

[0111] According to the accuracy requirements of the design parameters, measure the structural dimensions and surface roughness of the workpiece blank after machining.

[0112] Based on the measurement results, adjust the incremental feed subroutine and set the feed rate and the amount of decrease each time.

[0113] Start the CNC lathe machining program and perform workpiece turning according to the adjusted incremental feed subroutine.

[0114] Specifically, the boring hole size and surface roughness values ​​are measured, and the incremental feed subroutine is adjusted based on the measurement results, setting the feed rate parameters and the amount of decrease each time.

[0115] Step 7, Change the turning tool

[0116] When the surface roughness of the workpiece blank reaches the set value after machining, replace the turning tool, record the turning tool life, and reset the counter in the CNC lathe to zero.

[0117] Step 8, Batch processing

[0118] Follow step 6 to adjust the incremental feed subroutine, setting the feed rate and the amount of decrease each time.

[0119] Based on the turning tool life recorded in step 7, set the turning tool life in the main program.

[0120] Start the CNC lathe machining program to perform batch turning of the workpieces.

Claims

1. A variable feed turning method based on extending tool life, characterized in that, Includes the following steps: Step 1, Prepare the knives: Based on the workpiece machining requirements, select the CNC lathe turning tool and install the turning tool on the CNC lathe; Step 2, Prepare the workpiece blank: Prepare the workpiece blank by clamping it in the CNC lathe fixture. Step 3, setting the knife: Measure the tool length of the turning tool in the X and Z directions, and input the tool shape compensation value of the corresponding tool number of the CNC lathe; Step 4, Programming: Create a variable feed subroutine, input the created variable feed subroutine into the CNC lathe, and set the machining parameters; Add a subroutine call to the main program, and use the feed rate calculated by the subroutine as the actual feed rate; In the variable feed subroutine, set the initial feed rate, the decrease value, and the minimum feed rate; Add a tool life counter to the main program; Then, in the subroutine, the reduced feed rate is calculated based on the current lifespan and the set value, and the calculated feed rate is judged. If the calculated feed rate is greater than the minimum feed rate, the actual feed rate is the calculated feed rate; otherwise, the actual feed rate is the minimum feed rate. The main program calls the actual feed rate at this time for machining. Step 5, Trial Cutting Process: Start the CNC lathe machining program and perform trial cutting of the workpiece according to the programmed procedure; Step 6, Precision measurement and machining of the workpiece: According to the accuracy requirements of the design parameters, measure the structural dimensions and surface roughness of the workpiece blank after machining; Based on the measurement results, adjust the incremental feed subroutine and set the feed rate and the amount of decrease each time. Start the CNC lathe machining program and perform workpiece turning according to the adjusted incremental feed subroutine.

2. The variable feed turning method according to claim 1, characterized in that, Step 1 further includes: With the workpiece boring as the machining requirement, the rapid feed boring tool holder is installed on the CNC lathe turret, and the rapid feed insert is installed on the tool holder, and the insert pressure plate screw is tightened.

3. The variable feed turning method according to claim 2, characterized in that, Step 2 further includes: Using the intermediate shaft gear as the workpiece blank, the intermediate shaft gear is clamped in the CNC lathe fixture.

4. The variable feed turning method according to claim 3, characterized in that, Step 5 further includes: The intermediate shaft gear is boring.

5. The variable feed turning method according to claim 4, characterized in that, Step 6 further includes: Measure the boring hole size and surface roughness values. Based on the measurement results, adjust the incremental feed subroutine and set the feed rate parameters and the amount of decrease each time.

6. The variable feed turning method according to claim 1, characterized in that, It also includes step 7, changing the turning tool, the specific process of which is as follows: When the surface roughness of the workpiece blank reaches the set value after machining, replace the turning tool, record the turning tool life, and reset the counter in the CNC lathe to zero.

7. The variable feed turning method according to claim 6, characterized in that, It also includes step 8, batch processing, the specific process of which is as follows: Adjust the incremental feed subroutine according to step 6, and set the feed rate and the amount of decrease each time; Based on the turning tool life recorded in step 7, set the turning tool life in the main program. Start the CNC lathe machining program to perform batch turning of the workpieces.

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