Method for manufacturing flexspline of harmonic reducer

Abstract

A method for manufacturing a flexspline of a harmonic reducer. The manufacturing method comprises: S1, cutting a bar to perform blanking; S2, forging and shaping the bar by means of a forging die; and S3, carrying out a normalizing heat treatment on a blank; S4, turning a normalized flexspline blank; S5, carrying out a quenching and tempering treatment; S6, carrying out semi-finish turning on the flexspline; S7, conducting a stress relief treatment; S8, carrying out a grinding treatment; S9, carrying out flaw detection and burn detection; S10, carrying out a stress relief treatment; S11, carrying out drilling and tapping treatment procedures; S12, carrying out finish machining on the outer circle and the end face of the flexspline by means of a lathe; S13, carrying out stress relief treatment procedures; S14, machining flexspline teeth in place by means of a gear hobbing machine; and S15, carrying out a shot peening treatment.

Description

Manufacturing method of a flexible gear of a harmonic reducer TECHNICAL FIELD

[0001] The present application relates to a harmonic reducer, in particular to a manufacturing method of a flexible gear of a harmonic reducer. BACKGROUND

[0002] The harmonic reducer has the advantages of simple structure, small size, low noise, large transmission ratio and high transmission precision, and is used as an important component of a robot joint. The harmonic reducer is a gear mechanism that uses a flexible component to produce controllable elastic deformation to transmit power. The harmonic reducer mainly has three components: a rigid gear, a flexible gear and a wave generator. The wave generator is the driving part, and one of the rigid gear and the flexible gear is the driven part. The flexible gear is a thin-walled part that is easy to deform, and has a ring of teeth on the outer wall. Therefore, the flexible gear is the most difficult to process. At the same time, the flexible gear is also the most easily damaged part in the harmonic reducer, so higher requirements are placed on the processing and manufacturing of the flexible gear.

[0003] Because the flexible gear needs to withstand alternating loads during transmission in the harmonic reducer, the flexible gear is easily damaged during operation, so the fatigue strength of the flexible gear material, the wear resistance of the flexible gear and the manufacturing process technology of the flexible gear all have higher requirements.

[0004] After searching the Chinese patent publication No. CN116538268A, a new harmonic reducer flexible gear structure and its processing technology are specifically disclosed, which specifically includes the following steps: S1: selecting plastic particle raw materials required for flexible gear preparation, drying in a dehumidifying dryer, setting the drying temperature at 80-100 DEG C, drying for 2-2.5 h, and then transferring to an injection molding machine after heating is completed; S2: checking and preparing the ring-shaped metal insert, checking whether the appearance is damaged, whether cracks appear and whether burrs and protrusions are cleaned, and using a mechanical hand to clamp the ring-shaped metal insert on the mandrel in the mold cavity for injection molding; S3: injection molding S3.1: adjusting the mold preheating temperature to 60-80 DEG C, adjusting the barrel temperature of the cannon barrel to the nozzle in this section to be ladder type increasing, the starting temperature of the cannon barrel is 190-193 DEG C, and the ending temperature of the nozzle is 207-210 DEG C; S3.2: injection molding mold closing, injection molding machine shooting pressure setting is 88-92 par, fluid plastic enters the mold cavity through the nozzle, pressure maintaining for 2-3 seconds, pressure maintaining pressure setting is 48-52 par, cooling for 14-17 seconds, mold opening, and obtaining a flexible gear containing a ring-shaped metal insert.

[0005] However, the processing precision, fatigue resistance and wear resistance of the finished flexible gear in the existing flexible gear process are far from optimal.

[0006] SUMMARY

[0007] The present application aims at overcoming the defects of the prior art, and provides a manufacturing method of a flexible gear of a harmonic reducer, which is used to solve the problems of unstable precision, insufficient fatigue resistance and wear resistance of the flexible gear in the machining process.

[0008] The object of the present application can be achieved by the following technical solutions.

[0009] According to one aspect of the present application, a manufacturing method of a flexible gear of a harmonic reducer is provided, which comprises the following steps:

[0010] Step S1, cutting a bar material for blanking;

[0011] Step S2, heating the bar material, and forging and shaping the bar material into a blank through a forging die;

[0012] Step S3, normalizing heat treatment is performed on the blank;

[0013] Step S4, the flexible gear blank after normalizing is subjected to turning machining through a lathe;

[0014] Step S5, the flexible gear after turning machining is subjected to quenching and tempering treatment;

[0015] Step S6, semi-finishing machining is performed on the flexible gear through a lathe;

[0016] Step S7, stress relief treatment is performed;

[0017] Step S8, grinding treatment is performed;

[0018] Step S9, flaw detection and burn detection are performed;

[0019] Step S10, stress relief treatment is performed again;

[0020] Step S11, drilling and tapping treatment is performed;

[0021] Step S12, the flexible gear is subjected to finish machining of the outer circle and the end face through a lathe, and all dimensions of the flexible gear are turned to the right position;

[0022] Step S13, stress relief treatment is performed again;

[0023] Step S14, the flexible gear teeth are machined to the right position by using a gear hobbing machine;

[0024] Step S15, the flexible gear after Step S14 is subjected to shot blasting treatment.

[0025] As a preferred technical solution, the bar material in Step S1 is a medium-carbon alloy steel base material.

[0026] As a preferred technical scheme, the normalizing heat treatment in the step S3 is specifically: setting the normalizing temperature to 900-920 DEG C and keeping for 2-3 hours, and after keeping, the flexible gear blank is air-cooled to room temperature with the furnace.

[0027] As a preferred technical scheme, the normalizing heat treatment process in the step S3 is performed for 2-3 times, the metallographic structure grain size of the processed flexible gear blank reaches 9 or above, and no banded ferrite is allowed.

[0028] As a preferred technical scheme, the parameters of the quenching and tempering process in the step S5 specifically include: quenching temperature 860 DEG C ± 20 DEG C, and tempering temperature 530-550 DEG C.

[0029] The metallographic structure of the flexible gear after the quenching and tempering process should be troostite, and the grain size reaches 11 or above, and the hardness of the flexible gear reaches 35-38 HRC.

[0030] As a preferred technical scheme, the stress relief process includes annealing treatment, and the annealing temperature is below Ac1, and the keeping time is 2-4 hours.

[0031] As a preferred technical scheme, the grinding process in the step S8 first adopts a surface grinder to grind the convex end surface of the flexible gear, and then adopts a compound grinder to grind the inner hole and the outer circle of the flexible gear, and after grinding, the concentricity of the inner hole and the outer circle reaches within 0.003 mm.

[0032] As a preferred technical scheme, the surface residual stress of the flexible gear after the step S15 is greater than 600 MPa, and the surface coverage reaches 200%.

[0033] As a preferred technical scheme, the machine tool adopts a CNC lathe.

[0034] According to another aspect of the present application, a harmonic reducer flexible gear is provided, which is manufactured by the manufacturing method.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] 1) The die forging process of the present application saves materials and improves material utilization, and the mechanical properties and metallographic structure of the materials are better;

[0037] 2) The grinding process of the present application adopts a compound grinder, which improves the machining precision of the flexible gear;

[0038] 3) The combination of the multiple heat treatment processes of the present application improves the grain size of the flexible gear, refines the grains, and improves the fatigue resistance;

[0039] 4) The shot blasting treatment of the present application makes the flexible gear obtain a good surface stress state. BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 is a flow chart of the method of the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the protection scope of the present application.

[0042] The present application belongs to the technical field of manufacturing a flexspline for a harmonic reducer, and discloses a manufacturing method of a flexspline for a harmonic reducer. The manufacturing method comprises the following process steps in sequence: blanking, forging, normalizing, CNC lathe turning, quenching and tempering, semi-finishing turning, stress relief, grinding, flaw detection, drilling and tapping, finishing turning, stress relief, gear hobbing, and shot blasting. The high precision requirement of the flexspline is ensured by the grinding process, and the fatigue resistance and wear resistance of the flexspline are ensured by multiple heat treatments and the shot blasting process. Finally, the harmonic reducer has excellent transmission precision and the ability to maintain precision for a long time.

[0043] As shown in Fig. 1, a manufacturing method of a flexspline for a harmonic reducer comprises the following process steps, specifically:

[0044] Step S1, blanking preparation, cutting a bar stock for blanking;

[0045] Step S2, heating the bar stock, and shaping the bar stock into a blank by a forging die, the blank reserving a machining allowance;

[0046] Step S3, normalizing heat treatment is performed on the blank, the normalizing temperature is 900-920 DEG C, and the blank is kept for 2-3 hours, and after keeping, the flexspline blank is air-cooled to room temperature in the furnace;

[0047] Step S4, turning machining is performed on the flexspline blank after normalizing by a CNC lathe;

[0048] Step S5, quenching and tempering treatment is performed on the flexspline, the quenching temperature is 860 DEG C ± 20 DEG C, and the tempering temperature is 530-550 DEG C;

[0049] Step S6, semi-finishing turning is performed on the flexspline by a CNC lathe, and the machining allowance of the flexspline is removed twice;

[0050] Step S7, stress relief process;

[0051] Step S8, grinding process;

[0052] Step S9, flaw detection and burn detection;

[0053] Step S10, stress relief process;

[0054] Step S11, drilling and tapping;

[0055] Step S12, finish machining the outer circle and end face of the flexible gear by a CNC lathe, and turning all dimensions of the flexible gear to size;

[0056] Step S13, stress relief process;

[0057] Step S14, machining the flexible gear teeth to size using a gear hobbing machine;

[0058] Step S15, shot blasting, high-speed pellets are sprayed onto the surface of the flexible gear to cause plastic deformation of the surface of the flexible gear, thereby forming a strengthened layer with high residual stress.

[0059] Specifically, the bar material in step S1 is a medium-carbon alloy steel base material, such as SNCM439 or 40CrNiMoA.

[0060] Specifically, the heat-treated blank obtained in step S3 has a metallographic structure grain size of 9 or more, and no banded ferrite is allowed.

[0061] Specifically, the normalizing process in step S3 can be performed 2-3 times.

[0062] Specifically, the flexible gear obtained in step S5 has a troostite metallographic structure and a grain size of 11 or more, and a hardness of 35-38HRC.

[0063] Specifically, the stress relief treatment is performed after each turning operation.

[0064] Specifically, the stress relief treatment includes annealing treatment at an appropriate temperature below Ac1 for 2-4 hours.

[0065] Specifically, in step S8, the flexible gear is first ground on the convex end face using a surface grinder, and then the inner hole and outer circle are ground using a compound grinder, and after grinding, the inner hole and outer circle are concentric to within 0.003mm.

[0066] Specifically, in step S15, the surface residual stress of the flexible gear should be greater than 600MPa, and the surface coverage should reach 200%.

[0067] Example 2

[0068] As shown in FIG. 1, a manufacturing method of a flexible gear for a harmonic reducer includes the following process steps, specifically:

[0069] Step S1, blanking preparation, cutting the bar material for blanking;

[0070] Step S2, heating the bar material, and shaping the bar material into a rough piece through a forging die, the rough piece reserving a machining allowance, 3mm on a single side;

[0071] Step S3, normalizing heat treatment of the rough piece, normalizing temperature being 920℃ and holding for 3 hours, and the flexible gear rough piece being air cooled to room temperature after holding;

[0072] Step S4, turning machining of the flexible gear rough piece after normalizing through a CNC lathe, leaving a machining allowance, 1.5mm on a single side;

[0073] Step S5, quenching and tempering treatment of the flexible gear; quenching temperature being 860℃, and tempering temperature being 540℃;

[0074] Step S6, semi-finish turning machining of the flexible gear through a CNC lathe, removing the machining allowance of the flexible gear for the second time, leaving 0.1mm on a single side;

[0075] Step S7, stress relief process, temperature being 220℃, and holding for 12 hours;

[0076] Step S8, grinding process, grinding the boss of the flexible gear to the final size of the drawing, and grinding the inner hole and the outer diameter of the gear part to the final requirement of the drawing;

[0077] Step S9, flaw detection and burn detection;

[0078] Step S10, stress relief process, temperature being 220℃, and holding for 12 hours;

[0079] Step S11, drilling and tapping to the requirement of the drawing;

[0080] Step S12, finish machining of the outer circle and the end face of the flexible gear through a CNC lathe, turning all the sizes of the flexible gear to the right position;

[0081] Step S13, stress relief process, temperature being 220℃, and holding for 12 hours;

[0082] Step S14, machining the gear of the flexible gear to the right position by a gear hobbing machine;

[0083] Step S15, shot blasting treatment, high-speed pellets are sprayed to the surface of the flexible gear, so that plastic deformation occurs on the surface of the flexible gear, and a strengthened layer with high residual stress is formed.

[0084] Specifically, the bar material in step S1 is a medium-carbon alloy steel base material, such as SNCM439 or 40CrNiMoA.

[0085] Specifically, the rough piece after heat treatment obtained in step S3 has a metallographic structure grain size of 9 or above, and no banded ferrite is allowed.

[0086] Specifically, the normalizing process of the step S3 can be performed 2-3 times.

[0087] Specifically, the flexspline obtained in the step S5 should have troostite metallurgical structure, and the grain size reaches 11 level or above, and the hardness reaches 35-38HRC.

[0088] Specifically, the stress relief treatment is needed after each turning.

[0089] Specifically, the stress relief treatment includes annealing treatment, and the annealing temperature is appropriate temperature below Ac1, and the holding time is 2-4 hours.

[0090] Specifically, in the step S8, the flexspline is firstly ground by a surface grinder to grind the convex end face, and then is ground by a compound grinder to grind the inner hole and the outer circle, and the concentricity of the inner hole and the outer circle after grinding reaches within 0.003mm.

[0091] Specifically, in the step S15, the surface residual stress of the flexspline should be greater than 600MPa, and the surface coverage reaches 200%.

[0092] The flexspline obtained by the embodiment has obviously improved fatigue resistance and wear resistance, and has greatly improved the service life and precision maintaining ability of the harmonic reducer, and the service life and wear resistance of the harmonic reducer of a certain type are averagely improved by about 30% compared with other flexspline manufacturing schemes.

[0093] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of manufacturing a flexspline of a harmonic reducer, characterized by, The method comprises the following steps: Step S1, cutting the bar to prepare for blanking; Step S2, heating the bar and shaping the bar by a forging die to form a rough piece; Step S3, normalizing heat treatment of the rough piece; Step S4, turning the normalized flexible gear rough piece by a lathe; Step S5, quenching and tempering treatment of the turned flexible gear; Step S6, semi-finishing turning of the flexible gear by a lathe; Step S7, stress relief treatment process; Step S8, grinding treatment process; Step S9, detection of flaws and burns; Step S10, stress relief treatment process again; Step S11, drilling and tapping treatment process; Step S12, finishing turning of the flexible gear by a lathe to finish turning of all dimensions of the flexible gear; Step S13, stress relief treatment process again; Step S14, machining of the flexible gear teeth by a gear hobbing machine; Step S15, shot blasting treatment of the flexible gear machined in step S14.

2. A method of manufacturing a harmonic reducer flexspline as defined in claim 1, wherein, The bar in step S1 is a medium-carbon alloy steel base material.

3. The method of claim 1, wherein the harmonic reducer flexspline is manufactured by the steps of: The normalizing heat treatment in step S3 is specifically setting the normalizing temperature to 900-920℃ and keeping for 2-3 hours, and after keeping, the flexible gear rough piece is air-cooled to room temperature in the furnace.

4. The method of claim 1, wherein The normalizing heat treatment process in step S3 is performed 2-3 times, the metallographic structure grain size of the treated flexible gear rough piece reaches more than 9 levels, and no banded ferrite is allowed.

5. The method of claim 1, wherein the harmonic reducer flexspline is manufactured by the steps of: The parameters of the quenching and tempering treatment in step S5 specifically include quenching temperature 860℃±20℃ and tempering temperature 530-550℃. ​ The metallographic structure of the flexible gear after quenching and tempering treatment should be troostite, and the grain size reaches more than 11 levels, and the hardness of the flexible gear reaches 35-38HRC.

6. The method of claim 1, wherein The stress relief treatment process includes annealing treatment, and an annealing temperature below Ac1 is adopted and kept for 2-4 hours.

7. The method of claim 1, wherein the harmonic reducer flexspline is manufactured by the steps of: The grinding treatment process in step S8 first adopts a surface grinder to grind the flexible gear boss end face, and then adopts a compound grinder to complete grinding of the flexible gear inner hole and outer circle, and after grinding, the inner hole and outer circle concentricity reaches within 0.003mm. ​ 8. The method of claim 1, wherein the harmonic reducer flexspline is manufactured by the steps of: The surface residual stress of the flexible gear treated in step S15 is greater than 600MPa, and the surface coverage rate reaches 200%. ​ 9. The method of claim 1, wherein the harmonic reducer flexspline is manufactured by the steps of: The machine tool adopts a CNC lathe. ​ 10. A harmonic reducer flexspline characterized by, The flexible gear is manufactured by the manufacturing method in any one of claims 1-9.

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