Comparison of Fine Grinding with Double-Disc Grinding — Хонинговальные головки

The selection of the appropriate technology for generating parts in the flatness range of 0.5 to 2 pm is becoming quite subtle. Technological advances in both processes are accelerating. The view just 5 years ago was that fine grinding held the better flatness but double disc held the better size control. However, with Koyo’s development of EDT dressing of metal bond wheels, flatness can now often be held to <0.5 pm. On the other hand, recent developments in magnetic probes for size control combined with new wheel technology for reduced wheel wear per load has dramatically improved size-holding capability for fine grinding. The drawbacks to fine grinding are that the process is a batch process, which is difficult to fully automate, and the process requires oil coolant. Disc grinding is a continuous feed process, which can be easily automated and runs well in water-based coolants. Fine grinding, due to the number of parts that can be ground simultaneously and the recent increases in wheel speeds and head pressures, probably has a higher throughput. Disc grinding requires constant postprocess gauging to monitor size; fine grinding being a batch process, size is checked just once or twice per load, which can be done manually with minimal labor cost. On the other hand, if there is a size error, the entire batch must be scrapped for fine grinding while it may only be a few parts for disc grinding.

Fine grinding is a technology driven by European machine tool builders, while disc grinding is driven by Japanese machine tool builders, and it is likely that this is influenced by the particular markets that they serve.

TABLE 16.14

Application Examples for Fine Grinding

Rough

Component	Material	Size	Stock	Removal	Grind	Flatness	//ism	Finish	Size	Wheel
			Amount	Rate	Time/Part				Control	Spec
		(mm)	(pm)	(pm/min)	(s)	(pm)	(pm)	(pm)	(pm)
bearing plate	bronze	119	330	45	18	<1.5	<2	<0.5 Ra	5	B
bearing race	steel 560 HrC	125/70	30	10	9	<1.5	<1.5	0.25 Ra	1.5	B
pair
cam-ring	steel 63 HrC	65	65	10	7	<1.5	<1.5	1.5 Rz	1.5	B
cam-ring	PM 95 HrB	35	150	16	2.5	<1	<1	<0.8 Ra	2.5	B76
cutting tool	M2 62 HrC	75	200	16	14	2.5	2.5	0.15 Ra	2	B46
gear	steel 62 HrC	20	25	7.5	2	<1	<1	<24 Rz	2	B
gear	PM 45 HrC	30.5	43	11	5	<1.2	<1.2	0.18 Ra	1.25	B46
injector plate	steel 61 HrC	20	60	20	2.3	<1	<1	0.15 Ra	1.5	B18/B30
oil pump gear	PM 43 HrC	57	157	20	3.2		<1	<0.35 Ra	1.25	B76
oil pump gear	PM 95 HrB	84	280	35	4.9	<5	<3	0.55 Ra	3	B76
piston ring	90CRMoV18	91.5	30	60	0.8	<2	<2	1.8 Rz/0.18 Ra	2	B
piston rod	aluminum	90	560	135	8	<1.5	<1.5	<3.7 Rz	10	B
plate	steel 62 HrC	95 x 75	35	35	33	<3	<2	<2 Rz	2	B
pump plate	PM 70 HrB	89	28	6.6	43	<2.5	<2.5	<0.2 Ra	1.25	B46
pump ring	steel 58 HrC	35	125	15	12	<2	<1	<.0.2 Ra	2	B46
pump rotor	PM D39	52	220	25	29	<1.5	<2	2 Rz	2.5	B
pump rotor	PM 52 HrC	44	100	25	3	<1.5	<2	3 Rz	1.5	B
pump stator	PM C11	60	200	40	25	<1.5	<2	2 Rz	2.5	B
slide disc	31CrMo12	136/55	400	28	86	<5	<2	<2.4 Rz	6	B
tappet shim	100Cr6	25	150	25	1-1.5	<2	<2	2 Rz	3	B
thrust-bearing	ss1819	200/192	71	10	0	<7	<3	<0.25 Ra	10	B
disk
valve plate	ss1819	100	355	30	3	<40	<2	<0.38 Ra	15	B
valve plate	steel 47 HrC	119	460	45	25	<2.5	<2	<0.6 Ra	2.5	B
seal disc	alumina	42	405	250	0.5	<2	<2	<0.4 Ra	5	D
seal disc	alumina	33/19	405	110	1.1	<2	<2	<0.4 Ra	5	D
seal disc	alumina	37	610	250	1	<2	<2	<0.4 Ra	5	D
seal washer	piezo ceramic	24	18	430	0.03	<1.2	<1.5	0.5 Ra	5	D
slide disc	alumina	23	140	19	6.3	<1	<2	<0.38 Ra	6	D
tile	SiC	63.5	1650	80	68	<5	<5	0.225 Ra	5	D
tool insert	alumina	32	250	16	19	<1	<1	0.25 Ra	2	D

Source: From Wolters 1998. With permission.

APPENDIX 16.1 LAPPING KINEMATICS A16.1.1 Introduction

Considerable research work has been carried out on grinding with lapping kinematics at the University of Berlin. Dr. Thomas Ardelt has provided detailed information on this research below.

During face grinding on lapping machines, several workpieces are moved simultaneously between two horizontally positioned grinding wheels (Figure A16.1). The parts are fixed in workpiece carriers that are led between two pin circles. This way, characteristic cycloidal path curves are generated between parts and grinding wheels that are similar to the movements in planetary gears. It was found that a variation of the types of planetary movement directly influences material removal rates and driving power and particularly the resulting quality of the produced parts [Ardelt 1999]. As a
basis of understanding these effects, kinematic possibilities of double-wheel lapping and grinding machines have to be analyzed.