In the bearing industry, bearing outer rings are generally thin-walled parts. Generally, CNC lathes use self-centering or multi-jaw chuck clamping methods when hard turning bearing outer rings. In view of the deformation problem caused by ordinary hydraulic self-centering or multi-jaw chuck clamping on the outer ring of hard turning bearings, a method of using electro-permanent magnetic chucks to clamp the outer rings of hard turning thin-walled bearings was proposed. At the same time, in view of the problem that the positive taper phenomenon occurs in the inner hole of the outer ring of a thin-walled bearing during hard turning, which leads to the excessive roundness of the inner hole, it is proposed to improve the positive taper phenomenon in the inner hole by changing the cutting depth and cutting path to ensure the hard turning of thin-walled bearings. The roundness of the inner hole of the bearing outer ring proves the feasibility of using electro-permanent magnetic chucks to clamp the outer ring of hard-turned thin-walled bearings.
01
Prefaci
As un de el més feble enllaços en dur gir, el coixinet subjectant i posicionament mètode té sempre estat a coll d'ampolla restricció el widespread application of hard turning technology in the bearing industry. The clamping method and clamping accuracy directly affect the machining accuracy. To achieve the accuracy of clinding processing in the hard turning process, it is molt important to choose the appropriate clamping method and how to maximitzar la subjecció precisió [1].
Self-centering or multi-jaw chucks have become the fixture of choice for turning operations due to their broad versatility, clamping reliability and centering accuracy. For the clamping method of self-centering or multi-jaw chucks, by changing the structure of the jaws, improving the accuracy of the jaws, and improving the layout of the jaws, the amount of hard turning deformation of the bearing can be limited and the clamping accuracy can be improved. Ren Minjie et al. [2] improved the structure of the claws of the hydraulic self-centering chuck of CNC lathes, which significantly reduced the deformation of the bearing hard turning outer ring and solved the problem of large deformation of the outer ring held by the three claws. Dr. Jeongmin Byun [3] of Purdue University in the United States systematically analyzed the self-centering chuck clamping. He not only found out the main factors affecting the clamping error of hard turning cylindrical parts, but also proposed a method to eliminate the tilt of the workpiece and reduce the clamping error. Methods to gradually improve clamping accuracy include maintaining redundancy, improving the machining accuracy of the jaws, and improving the accuracy of the jaw arrangement. The research results show that by processing cylindrical roller bearing rings on the basis of improving the clamping accuracy, the processing accuracy can reach the level of grinding processing, proving the feasibility of "replacing grinding with turning machines". At present, there are few cases of using electro-permanent magnetic chucks to clamp hard-turned bearings. This clamping method has obvious advantages and can avoid the deformation of thin-walled bearings caused by claw clamping. However, the disadvantages are not yet clear and need to be verified by experiments. J.M. Zhou et al. [4] from Lund University in Sweden found that when cutting rolling bearings, using a self-centering chuck for clamping can cause deformation of up to 20 μm, and recommended the use of a six-jaw chuck or electromagnetic chuck for clamping. Through experimental research on hard turning 100Cr6 ring parts with a hardness of 60 to 62HRC, they found that when using a self-centering chuck for clamping, the out-of-roundness error of the ring parts exceeded 10 μm; when using a six-claw chuck for clamping, the roundness error of the ring parts exceeded 10 μm. The out-of-roundness error of the ring parts is about 9 μm; when using electromagnetic chuck clamping, the out-of-roundness error of the ring parts is less than 4 μm.
Tot i que autocentrat o multimandíbula mandíbula mandíbula can millorar el deformació de parets primes coixinet anells anells dur dur gir per optimitzar el mandíbules, ells no poden completament resoldre el problema de dur gir deformació de de parets primes rodament anells exteriors. Per tant, usant Electropermanent magnètic mandril subjectant has esdevenir el millor mètode for hard turning prim-walled bearing outer rings. Aquest article conductes experimentals recerca per el primer temps usant an electropermanent magnètic mandril a pinça el anell exterior de a dur-girat prim-paret rodament. It verifica el viabilitat de el electropermanent magnètic mandril a pinça el anell exterior de a dur-girat prim-paret rodament. It també analitza el forat de el anell exterior de a a dur-girat paret coixinet. Quan el positiu taper fenomen ocorre, el rodonesa de el interior forat és forat de tolerància. It és proposat per millorar el positiu taper fenomen de el interior forat per canviant el tall profunditat i tallant camí.
02
Introducció a electro-permanent magnètic portabroques
El electropermanent magnètic mandril és fet de permanent imants en canvi de electroimants, i el magnèticament permeable blocs són normalment permanents imants. Quan it comença treball, el electropermanent magnètic mandril és energitzat i magnetitzat. Quan el set magnètic força és assolit, el poder és automàticament tall apagat a mantenir el magnètic força. Perquè allà és no necessitat per contínua potència subministrament durant el treball procés, it will not generate calor durant continuous operation, preventing the workpiece from being deformed by heat.
El electromagnètic chuck is made based on the principle of the magnetic effect of electricity. The magnetic force depends on a continuous electrical current. The desadvantage of this type of suction cup is that when the current stops, it will release the workpiece. If this happens during work, it will cause flying parts and the operator at risk of injury. At the same time, after the electromagnetic chuck has been running for a period of time, the continuous flow of current will generate heat, causing the workpiece to be heated and deformed, and the machining accuracy cannot be guaranteed.
This test uses an electric permanent magnet chuck, model X61-500. The controller model is LMSDVPL2VH301, as shown in Figure 1.
imatge
a) Electropermanent magnètic mandril b) Controlador
Figura 1 Elèctric permanent imant mandril i controlador
El electro-permanent magnètic mandril llauna absorbir i pinça el anell exterior anell de parets primes rodaments través força magnètica. It té no radial subjecta força on la peça i evita subjecta deformació. Aquesta electropermanent magnètica mandril té a total de 16 nivells de força magnètica, i el força magnètica és controlada per ajustant s corrent.
03
Experiment on el exterior anell de parets primes rodaments subjectat per electropermanent magnètic mandrils mandrils
3.1 màquina eina equip selecció
The CNC vertical lathe T6-85H independently developed by General Technology Group Shenyang Machine Tool Co., Ltd. was selected for the test. The workpiece is clamped vertically so that the center of gravity of the workpiece coincides with the center of gravity of the spindle to avoid roundness errors caused by gravity during horizontal clamping and ensure the roundness of the workpiece [5]. At the same time, the self-weight of the workpiece makes the contact with the fixture datum surface exact and close, byby obtaining high positioning accuracy and stable processing accuracy.
3.2 Peça selecció
The hard turning test selects the outer ring of the cylindrical roller bearing as the test object. The wall thickness is 6.5mm, which is a thin-walled bearing [6]. The material is GCr15, and the hardness after quenching is 60~64HRC. The end face and outer circle of the sample are both rough grinding surfaces, with good dimensional consistency and surface quality. Since rough grinding of the inner hole is inefficient and prone to burns, this test only hard-turned the inner hole, using hard turning instead of rough grinding. After hard turning, there is also a fine grinding process and a super-finishing process. The test piece requires that the inner hole size after hard turning is 136.82~136.86mm, the inner hole roundness is 0.011mm, the inner hole cylindricity is 0.011mm, the coaxiality between the inner hole and the outer circle is 0.02mm, the verticality between the inner hole and the end face is 0.011mm, and the inner hole is 0.011mm deep. The hole surface roughness value Ra=1μm, as shown in Figure 2.
imatge
a) Patró
imatge
b) En blanc
Figura 2 Cilíndric rodet rodament exterior anell
3.3 Procés pla
El procés pla consisteix de dues eines per dur gir el interior forat de el anell exterior de el cilíndric rodet rodament. el tall paràmetres són: rotació velocitat 250r/min, feed rate 0.1mm/r, single-sided cutting depth of the first tool {{}}.{08mm, and single-sided cutting depth of the second tool 0.07 mm. CBN inserts are used, i el eina punta radi és 0,8mm, as mostrat en figura 3.
imatge
a) Fulla b) Eina
Figura 3 CBN fulles i tall eines
04
Experimental procediment
The rated magnetic force of the electro-permanent magnet chuck used in the test is 160N/cm2, and the axial adsorption force on the outer ring of the cylindrical roller bearing is 2432N. According to the contact surface principle, the friction coefficient entre the workpiece and the magnetic positioning block of the electro-permanent magnet chuck is 0.15, the friction force is 364. 8N, i el combinat força de el principal tall força i el radial tall força de la peça en dur gir és sobre 120N. Per tant, el electropermanent magnètic mandril llauna completa adapta a la subjecció necessitats de dur gir.
Ja que el exterior anell de el coixinet és posicionat per a magnètic chuck on el final, allà és no centrat mesura on el circumferència. In fet, it és molt difícil a centre el anell exterior amb a circumferència metre. Per tant, an arc pas amb a profunditat de 5 mm is girat on el posicionament magnètic bloc a fer el pas circular. El gap entre el arc i el coixinet exterior anell should be as small as possible. The gap is about 0.01mm, as shown in Figure 4. At the same time, when self-turning the step surface, it is necessary to ensure that the surface quality of the contact surface between the magnetic conductive block and the bearing outer ring is good. After the parts are processed, the magnetic disassembly will be very fast. Easily, it only takes 5 segons a càrrega i descàrrega peces.
imatge
Figura 4 Esquemàtic diagrama de dur gir i subjecció de el anell exterior de cilíndric rodet rodaments rodaments
Parts No. 1 to 5 were hard turned according to the above clamping method and cutting parameters. After turning, the parts were inspected by three-dimensional coordinates, as shown in Figure 5, and the surface roughness was inspected by a roughness meter, as shown in Figure 6. The test results are shown in Table 1, and the status of the parts after hard turning is shown in Figure 7.
imatge
Figura 5 Trescoordenades detecció
imatge
Figura 6 Superfície rugositat detecció
Taula 1 Cilíndrica corró rodament (No. 1~5) anell anell interior forat inspecció resultats (unitat: μｍ) imatge
imatge
Figura 7: El estat després dur gir
It can be seen seen from the data in Table 1 that after the outer ring of the cylindrical roller bearing is clamped by the electro-permanent magnetic chuck and the inner hole is hard-turned, the roundness of the inner hole, the coaxiality between the inner hole and the outer circle, the perpendicularity entre the inner hole and the end face, and the surface roughness of the inner hole The degree can all complir els requisits de el dibuix, i el cilindricitat de el forat interior majoritàriament compleix el requisits, però it és també tancar a el límit tolerància requerit per el dibuix. A lleuger acumulació de altres errors voluntat superat el tolerància i causa el part a ser unqualificat. El_motiu és que el diferència entre el superior i inferior cercles de el el forat interior és gran, causant a endavant taper fenomen en en el interior forat.
For this positive cone phenomenon, as shown in Figure 4, the analysis reason is that under the axial clamping of the electro-permanent magnetic chuck, when the height of the self-turning arc step can contact the outer circle of the bearing ring, the vertical lathe starts from the top. During the hard turning process of the inner hole of the thin-walled bearing outer ring, the insufficient rigidity of the bearing outer ring causes radial deformation of the tool during the cutting process. The upper circular part of the inner hole of the bearing outer ring undergoes elastic deformation due to the cutting force, and the cutting amount becomes smaller, resulting in actual The cutting depth is inconsistent with the nominal cutting depth. The deformation of the lower circular part of the inner hole is small due to the bottom surface of the magnetic block, the suction force of the side steps and the pressure of the side steps. The cutting amount is larger than that of the upper circular part of the inner hole. The outer ring of the bearing has a positive taper phenomenon in the inner hole.
Teòricament, aquest taper fenomen can be reduït o eliminat per dos mètodes. El primer és a canvi el tall profunditat per reduir el radial tall força, tal as reducció el tall profunditat quan acabat el interior forat de el exterior anell de a a prim-paret rodament; el segon és per canviar el tallar camí, tal as quan acabar el forat interior de el anell exterior anell de a paret prima rodament, acordar a el positiu taper mida, ús a cert invers taper to tall el inner hole, so that the cutting amount of the lower circle of the inner hole Less than or equal to the cutting amount of the upper circle of the inner hole, reducing o eliminating the forward taper phenomena of the inner hole.
05
5.1 Verificar el efecte de canviar el tall profunditat on el endavant taper fenomen
El procés pla consisteix de tres eines per dur girar el interior forat de el exterior anell de el cilíndric rodet rodament. el tall paràmetres són: rotació velocitat 250r/min, feed rate {{}}}.1mm/r, single-sided cutting depth of the first tool {{7d}.{08mm, and single-sided cutting depth of the second tool 0.05 mm, the cutting depth of of the second tool 0.05 mm, the cutting depth of el tercer ganivet on un costat és 0,02mm. El subjecta mètode restes inalteració, i el dur-girat peces No. 6 to 10 are provat per tridimensional coordenada inspecció i superfície rugositat metre després del gir. El prova resultats són mostrats en Taula 2.
Taula 2 Cilíndrica corró rodament (No. 6 a No. 10) anell anell interior forat inspecció resultats (unitat: μｍ) imatges
It can be seen from the data in Table 2 that by changing the cutting depth, the finishing cutting amount changed from 0.{{}}}7mm to 0.02mm on one side. After hard turning the inner hole of the outer ring of the cylindrical roller bearing, all geometric toleràncies and surface roughness were tested to meet the drawings. Require.
5.2 Verificar el efecte de canviar el tall camí on el endavant taper fenomen
El procés pla consisteix de dues eines per dur girar el interior forat de el exterior anell de el cilíndric rodet rodament. el tall paràmetres són: rotació velocitat 250r/min, feed rate {{}}.1mm/r, single-sided cutting depth of the first tool 0.08mm, and single-sided cutting depth of the second tool 0.07 mm. En conseqüència a el dades en Taula 1, la mitjana diferència entre el superior i inferior cercles de el coixinet interior forat i el amplada de el coixinet, el taper ràtio és 1:2.6493. Quan girar el segon eina, el tall profunditat restes inalteracions, taper compensació és performat, i el tall camí és el camí corresponent a el invertit taper relació. el mètode de subjecció restes inalteracions, i el dur-girat parts No. 11 to 15 are tested. After turning, the parts are tested by tridimensional coordinate inspection and surface roughness meter. The test results are shown in Table 3.
Taula 3 Cilíndrica corró rodament (No. {{}}}) anell exterior anell interior forat inspecció resultats (unitat: μｍ) imatges
It can be seen from the data in Table 3 that by changing the cutting path, the taper ratio is obtained based on the known forward taper phenomena. The cutting depth remains unchanged during cutting, and the cutting path is the corresponding inverted taper ratio path. After hard turning the inner hole of the outer ring of the cylindrical roller bearing, Check that all geometric toleràncies and surface roughness meet meet the drawing Requisits.
06
Conclusió
Objectiu at el problema que autocentrat o multimandíbula mandíbules voluntat causa deformació de el anell exterior de parets rodaments quan pinçament dur girat parets primes rodaments, aquest paper proposa el ús de electropermanent magnètic mandrils a pinça el anells exteriors de dur-girat de parets primes rodaments, i demostra que el electro-permanent magnètic mandril és utilitzat a pinça el anell exterior de gir dur parets primes rodaments el viabilitat de utilitzant magnètic mandril a pinça el anell exterior de gir dur parets primes rodaments.
Per el problema de endavant taper fenomen en el anell exterior anell de dur girar muralla rodaments, dos mètodes són proposats per optimització. Un és per canviar el tall profunditat, i el altre és per canviar el tallar camí. A través experimental verificació, it és trobat que canviant el tall profunditat és millor que canviant el tallant camí. .
