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| Systems Approach |
Advancements
Manufacturers are continually pushing the envelope in regards to what can be accomplished with the singlepass process. 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 process. Normally an oil coolant would be recommended for these materials, but in some cases, specific waterbased coolant’s can be utilized.
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| Crank bore being finished |
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| Pin bore being finished |
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Case History #5: (Connecting Rod)
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 process 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. |
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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 |
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| 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 |
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| Machine Type: |
Engis Model # 0025-24S (8 Spindle Machine) |
| Coolant: |
Water-Soluble |
| Production: |
300 Parts Per Hour |
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