Advancements in Single-Pass Bore Finishing - Systems Approach (pag. 6 of 10)

Advancements Manufacturers are continually pushing the envelope in regards to what can be accomplished with the singlepass Processo. Improved tool, fixture, and machine designs have allowed for increased production rates as well as improved bore precision. The following are some of the latest advancements that have been made. Soft Material: Soft, gummy, material such as aluminum and bronze can be successfully finished with the singlepass Processo. Normally an oil coolant would be recommended for these materials, but in some cases, specific waterbased coolant's can be utilized.

Crank bore being finished

Pin bore being finished

Case history #5 is a typical example of high production bore finishing of automotive connecting rods. The soft bronze material in the pin bores are being successfully finished to better than 0.5Ra, and with a waterbased coolant. For this Processo both crank and pin bores are finished simultaneously with four diamond singlepass tools apiece. The rods are held securely on a locating plate which is positioned on an XY (axis) floating fixture base. With this setup the radial alignment of the two bores (bend and twist), along with perpendicularity to the locating surface can be improved. The life of the diamond tools that are used on the forged steel crank bores average approximately 80,000 parts, while the life of the diamond tools used on the bronze pin bores often exceed 1,000,000. The total perishable tooling cost for finishing both bores is roughly $0.03.

	Crank bore			Pin Bore
Diameter:	56.876mm			21.018mm
Length:	23.85mm			23.85mm
Material:	Forged Steel			Bronze Bushing
Stock Removal:	0.076mm			0.076mm
Tool Pass #1:	56.836mm	Diamond	40/50	20.078mm	Diamond	60/80
Tool Pass #2:	56.861mm	Diamond	40/50	21.003mm	Diamond	60/80
Tool Pass #3:	56.871mm	Diamond	60/80	21.013mm	Diamond	100/120
Tool Pass #4:	56.876mm	Diamond	100/120	21.018mm	Diamond	200/230

Bore Quality	Required	Achieved	Required	Achieved
Size:	0.010mm	0.005mm	0.006mm	0.003mm
Roundness:	0.008mm	0.005mm	0.005mm	0.003mm
Surface Finish:	1 to 3um Ra	1.7um Ra	0.5um Ra	0.3um Ra

Machine Type:	Engis Model # 0025-24S (8 Spindle Machine)
Coolant:	Water-Soluble
Production:	300 Parts Per Hour