Tooth turning machining radial decreasing feed design method considering cutting force

Abstract

The invention discloses a tooth turning machining radial decreasing feed design method considering cutting force. The method comprises the following steps that the full-tooth-height cutting depth of a gear is calculated according to gear parameters; the proportion of the finish machining cutting depth to the full-tooth-height cutting depth and the maximum cutting force are set; initially determining the radial feed frequency of the cutter, and calculating the radial feed cutting depth of each time of rough machining; solving the chip thickness of each radial feed; calculating the cutting force of each radial feed; whether the cutting force is smaller than the maximum cutting force or not is judged, if not, the number of times of radial feeding of the cutter is increased till the calculated cutting force of each radial feeding is smaller than the maximum cutting force, and finally the cutting depth of each radial feeding is calculated and serves as the optimal feeding scheme. Compared with a traditional tooth turning machining equal-interval feeding method, the tooth turning machining radial decreasing feeding design method can effectively prevent the severe cutting condition that the cutting force is too large in the single-time feeding process of a tool, the service life of the tool is prolonged, and the tooth surface machining quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of gear processing, and in particular to a radial decreasing feed design method for gear processing taking cutting force into consideration. Background Art

[0002] Gears are the key basic parts of many equipments, and their processing technology level is of great significance to improving the performance of equipments in various industries. Power skiving is a new gear processing method, which has significant advantages such as high efficiency, high precision, and green dry cutting. It is becoming the preferred process for processing complex precision gears on industrial robot harmonic / RV reducers and automobile reducers.

[0003] In the actual gear turning process, due to the limitations of machine tool power, tool material strength and full tooth height cutting depth, the tool often needs to be radially fed multiple times in the full tooth height cutting depth direction to cut out a complete tooth shape. The gear turning feeding process is divided into roughing and finishing. Roughing is mainly used for tooth groove blanking, and its feed times depend on machine tool power, tool material strength, maximum chip thickness, etc.; while finishing is to cut out the correct tooth shape. In order to obtain better gear turning tooth surface quality, the cutting amount of finishing should be as small as possible, generally 1% to 5% of the full tooth height cutting depth is selected.

[0004] At present, the radial feed rate of gear turning tools is often distributed at equal intervals. However, gear turning is a generating process. As the radial cutting depth of the tool increases, the generating envelope area of ​​the tool and the chip thickness also increase, which leads to the continuous increase of cutting force during gear turning. Excessive cutting force will aggravate the wear of the gear turning tool and affect the processing quality of the tooth surface. Therefore, how to distribute the radial feed rate of the tool according to the load of the machine tool, so as to improve the tool life and tooth surface processing quality, is an urgent problem to be solved in gear turning. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a radial decreasing feed design method for gear turning that takes cutting force into consideration by calculating the chip thickness and cutting force of gear turning under radial decreasing feed conditions. The radial decreasing feed method for gear turning of the present invention can allocate the radial feed amount of the tool on the basis of considering the gear turning cutting force, which is beneficial to improving the tool life and tooth surface processing quality.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A radial decreasing feed design method for gear machining considering cutting force, comprising:

[0008] Step 1: Calculate the full tooth height cutting depth A of the gear according to the gear parameters p ;

[0009] Step 2: According to the material strength of the gear being processed and the tooth surface processing quality requirements, set the ratio of the finishing cutting depth to the full tooth height cutting depth p t , generally 1%-5% of the full tooth height cutting depth; according to the maximum output power of the gear turning machine and the material strength of the tool, the maximum cutting force during the radial feed of the tool is estimated, and based on this, the maximum cutting force of a single radial feed for roughing and finishing is set [F max ]; Combined with the full tooth height cutting depth A of the gear in step 1 p , the finishing cutting depth and roughing cutting depth are calculated;

[0010] Step 3: Initially determine the total number of radial feeds for roughing and finishing of the tool as n, of which the number of radial feeds for finishing is 1; based on the roughing cutting depth obtained in step 2, use the radial decreasing feed method to calculate the cutting depth a for each roughing cutting p(i) ;

[0011] Step 4: Cutting depth a for each feed according to finishing and roughing p(i) , calculate the chip thickness h for each radial feed i ;

[0012] Step 5: According to the chip thickness h of each radial feed in finishing and roughing i , calculate the cutting force F for each radial feed i ;

[0013] Step 6: Determine the cutting force F i Is it less than the maximum cutting force [F max ], if not, the radial feed times of the tool are n=n+1 and the process returns to step 3 until the calculated cutting force F is less than the maximum cutting force [F max ]; If yes, go to step 7; by accurately calculating the chip thickness and cutting force of each radial feed, the radial feed amount of the tool is calculated and allocated according to the set maximum cutting force.

[0014] Step 7: Calculate the cutting depth of each radial feed according to the number of radial feeds of the tool obtained in step 6, so as to obtain the optimal radial decreasing feed scheme for gear cutting.

[0015] In the above technical solution, further, in step 3, the radial decreasing feed method preferably uses an arithmetic decreasing method or an inverse function decreasing method, wherein the arithmetic decreasing method and the inverse function decreasing method are used to calculate the cutting depth a of each feed of rough machining. p(i) , the specific calculation formulas are shown in (1) and (2) respectively:

[0016] a p(i) =A p (p1+(i-1)·d) (1)

[0017]

[0018] Where: A p is the full tooth height cutting depth of the gear; p t is the ratio of the cutting depth of finishing to the cutting depth of the whole tooth height; n is the total number of radial feeds of the tool; i is the number of radial feeds; p1 is the ratio of the first feed cutting depth of roughing to the cutting depth of the whole tooth height; d is the tolerance of the radial arithmetic decreasing feed function; where p1 and d are given by the equation group The solution is obtained.

[0019] Furthermore, in step 4, when the cutting depth a of a certain feed is known, p(i) , the radius of the gear cutting tool is r t The installation axis angle of the gear cutting tool is Σ, and the feed rate per revolution of the gear cutting tool along the gear axis is f a Under the condition of, according to the relationship of gear turning motion, the chip thickness h of each radial feed i Calculate using formulas (3)-(8):

[0020]

[0021] Where:

[0022] A x =r t -a p(i) (4)

[0023]

[0024] Furthermore, in step 5, the cutting force F i Use formula (9) for calculation:

[0025]

[0026] Where: dF i is the cutting force on each microelement surface; K is the unit cutting force coefficient of the cut material; μ represents the chip thickness h i The influence coefficient on K; dA is the area of ​​each microelement surface.

[0027] Beneficial effects of the present invention:

[0028] The radial decreasing feed method for gear turning of the present invention takes into account the particularity of the gradual increase of the tool envelope area and chip thickness in gear turning. By accurately calculating the chip thickness and cutting force of each radial feed, the radial feed amount of the tool can be calculated and allocated according to the set maximum cutting force. Compared with the traditional gear turning equal-pitch feed method, the radial decreasing feed design method for gear turning of the present invention can effectively prevent the tool from experiencing a severe cutting condition with excessive cutting force during a single feed, which is beneficial to improving the tool life and tooth surface processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 The present invention is a flowchart of a radial decreasing feed design method for gear machining taking cutting force into consideration according to an embodiment of the present invention.

[0031] Figure 2 It is the generated envelope boundary of each radial feed in the rough machining and fine machining of the embodiment of the present invention.

[0032] Figure 3 It is the cutting force of each radial feed in roughing and finishing in the arithmetic feed method.

[0033] Figure 4 It is the envelope boundary of each radial infeed in roughing and finishing in the equal-pitch infeed method.

[0034] Figure 5 It is the cutting force of each radial feed in roughing and finishing in the equal-pitch feed method. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0036] In this embodiment, the gear is an internal helical gear with an involute tooth profile, and its main parameters are: number of teeth z w =79, modulus m n =1.7mm, pressure angle α n =22°, helix angle β w =12.5°(left-handed), tooth top diameter d a=136.464mm, tooth root diameter d f =144.937mm, displacement coefficient x n =0.812mm.

[0037] The main parameters of the gear cutting tool are: number of teeth z t =44, radius of gear cutting tool r t =39.887mm, gear cutting tool installation axis angle Σ = 16°, gear cutting tool helix angle β w =3.5° (left-hand rotation), the feed rate per revolution of the gear cutting tool along the gear axis is f a =0.2mm / rev.

[0038] like Figure 1 , is a radial decreasing feed design method for gear machining considering cutting force provided by an embodiment of the present invention, which specifically comprises the following steps:

[0039] Step 1: Calculate the full tooth height cutting depth A of the gear according to the gear parameters p =(d f -d a ) / 2=4.237mm.

[0040] Step 2: Set the ratio of finishing depth to full tooth depth t = 3%, the maximum cutting force of a single radial feed for roughing and finishing [F max ]=1550N;

[0041] Step 3: Initially determine the number of radial feeds of the tool n = 8, where the first 7 radial feeds are for roughing and the 8th is for finishing. Use the radial arithmetic decreasing feed method, and calculate formula a by the arithmetic decreasing method p(i) =A p (p1+(i-1)·d) Calculate the cutting depth of each feed of 7 rough machinings to be a p(1) =1.027mm, a p(2) =0.881mm, a p(3) =0.734mm, a p(4) =0.587mm, a p(5) =0.440mm, a p(6) =0.294mm, a p(7) =0.147mm, where: A p is the full tooth height cutting depth of the gear; p t is the ratio of the finishing cutting depth to the full tooth height cutting depth; n is the total number of radial feeds of the tool; i is the number of feed cutting depths; p1 is the ratio of the first feed cutting depth of roughing to the full tooth height cutting depth; d is the tolerance of the radial arithmetic decreasing feed function; where p1 and d are given by the equation group It can be solved that p1=0.2425, d=-0.0346.

[0042] The 8th finishing feed cutting depth is a p(8) =p t *A p =0.127mm.

[0043] like Figure 2 It is the envelope boundary of each radial feed in roughing and finishing in the arithmetic feed method. Figure 3 It is the cutting force of each radial feed in roughing and finishing in the arithmetic feed method. It can be seen from this that the envelope area and cutting force of the tool will be different when the tool radial feed cutting depth is different in gear turning. Moreover, when the workpiece parameters, tool parameters and tool installation parameters change, the relationship between the tool radial feed cutting depth and the envelope area is complex and difficult to describe with a mathematical formula. The chip thickness and cutting force need to be calculated to evaluate whether the tool radial feed cutting depth is reasonable.

[0044] Step 4: According to the development motion relationship of gear cutting, when the cutting depth a of a certain feed is known, p(i) , the radius of the gear cutting tool is r t The installation axis angle of the gear cutting tool is Σ, and the feed rate per revolution of the gear cutting tool along the gear axis is f a Under the condition of Calculated, where A x =r t -a p(i) ,

[0045] That is, the chip thicknesses of a total of 8 radial feeds in roughing and finishing are: h1=0.127mm, h2=0.120mm, h3=0.113mm, h4=0.105mm, h5=0.094mm, h6=0.079mm, h7=0.058mm, h8=0.054mm respectively.

[0046] Step 5: By formula The cutting forces of 8 radial feeds in roughing and finishing are calculated to be F1=1083N, F2=1238N, F3=1443N, F4=1519N, F5=1494N, F6=1146N, F7=683N, and F8=736N. i is the cutting force on each microelement surface; in this embodiment, the gear material is 42CrMo, so the unit cutting force coefficient of the cut material is K = 2452N / mm 2 ; Chip thickness h iThe influence coefficient on K is μ=0.26; dA is the area of ​​each microelement surface.

[0047] Step 6: Determine the cutting force F for a total of 8 radial feeds in roughing and finishing i and maximum cutting force [F max ]=1550N, and it is found that they are all less than the maximum cutting force. Therefore, there is no need to return to step 3 to increase the number of feeds, and go directly to step 7. By accurately calculating the chip thickness and cutting force of each radial feed, the radial feed amount of the tool can be calculated and allocated according to the set maximum cutting force.

[0048] Step 7: Get 8 radial feed cutting depths, as shown in Table 1, and use it as the optimal radial decreasing feed scheme for gear turning. In the gear turning process, the radial decreasing feed scheme can effectively improve the tool life and tooth surface processing quality.

[0049] Table 1 Cutting depth of each radial feed in this embodiment

[0050]

[0051] As shown in Table 2, the cutting depth of each radial feed of the tool is calculated using the traditional equal-pitch feed method and the same gear and tool parameters, that is, the cutting depth of the tool for 7 radial feeds in rough machining is the same 0.587mm.

[0052] Table 2 Cutting depth of each radial feed of the traditional equal-pitch feed method

[0053]

[0054] Figure 4 It is the envelope boundary of each radial feed in roughing and finishing in the traditional equidistant feed method. Figure 5 It is the cutting force of each radial feed in roughing and finishing in the traditional equal-pitch feed method. Figure 4 and Figure 5 It can be seen that although the cutting depth of each radial feed of the tool in rough machining is the same, the cutting force shows a trend of increasing with the increase of the number of feeds. Among them, the cutting force of the 6th feed is 1712N, and the cutting force of the 7th feed is 2112N, which is obviously larger than the cutting force of other feed times. Larger cutting force will increase cutting heat, make the cutting conditions of the gear cutting tool worse, and reduce the service life of the tool.

[0055] Therefore, compared with the traditional equidistant feed method for gear turning, the radial decreasing feed design method for gear turning of the present invention can effectively prevent the tool from experiencing severe cutting conditions with excessive cutting force during a single feed, which is beneficial to improving the tool life and tooth surface processing quality.

Claims

1. A radial decreasing feed design method for gear machining considering cutting force, characterized in that: The method comprises the following steps: Step 1: Calculate the full tooth height cutting depth A of the gear according to the gear parameters p ; Step 2: Set the ratio of finishing depth to full tooth depth t , and the maximum cutting force [F max ]; Combined with the full tooth height cutting depth A of the gear in step 1 p , the finishing cutting depth and roughing cutting depth are calculated; Step 3: Initially determine the total number of radial feeds for roughing and finishing of the tool as n, of which the number of radial feeds for finishing is 1; based on the roughing cutting depth obtained in step 2, use the radial decreasing feed method to calculate the cutting depth a for each roughing cutting p(i) ; Step 4: According to the cutting depth of each feed of finishing and roughing, the cutting depth of each feed is a p(i) , calculate the chip thickness h for each radial feed i ; Step 5: According to the chip thickness h of each radial feed in finishing and roughing i , calculate the cutting force F for each radial feed i ; Step 6: Determine the cutting force F i Is it less than the maximum cutting force [F max ], if not, the radial feed times of the tool are n=n+1 and the process returns to step 3 until the calculated cutting force F is less than the maximum cutting force [F max ]; if yes, go to step 7; Step 7: Calculate the cutting depth of each radial feed according to the number of radial feeds of the tool obtained in step 6, so as to obtain the optimal radial decreasing feed scheme for gear cutting.

2. A radially decreasing feed design method for gear machining considering cutting force according to claim 1, characterized in that: The radial decreasing feed method in step 3 is implemented by an arithmetic decreasing method or an inverse function decreasing method.

3. A radial decreasing feed design method for gear machining considering cutting force according to claim 2, characterized in that: The arithmetic decreasing method is used to calculate the cutting depth a of the i-th rough machining feed p(i) , the calculation formula is as follows: a p(i) =A p (p1+(i-1)·d) (1) Among them, p1 is the ratio of the first feed depth to the full tooth height depth in rough machining; i is the number of radial feeds; d is the tolerance of the radial arithmetic decreasing feed function; among them, p1 and d are given by the equation group The solution is obtained.

4. A radially decreasing feed design method for gear machining considering cutting force according to claim 2, characterized in that: The inverse function decreasing method is used to calculate the cutting depth a of the i-th roughing feed p(i) , the calculation formula is as follows:

5. The radial decreasing feed design method for gear machining considering cutting force according to claim 1, characterized in that: Chip thickness h per radial feed i The calculation method is: Given that the radius of the gear cutting tool is r t The installation axis angle of the gear cutting tool is Σ, and the feed rate per revolution of the gear cutting tool along the gear axis is f a Under the condition of i Calculate using formulas (3)-(8): Where: A x =r t -a p(i) (4) 6. The radial decreasing feed design method for gear machining considering cutting force according to claim 1, characterized in that: The cutting force F of each radial feed in step 5 i Use formula (9) for calculation: Where: dF i is the cutting force on each microelement surface; K is the unit cutting force coefficient of the cut material; μ represents the chip thickness h i The influence coefficient on K; dA is the area of ​​each microelement surface.

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