Printer Friendly

'93 V8 crankshafts microfinishing.

Dimensional accuracy and surface finish to tolerances of [+ or -]5 microns at production rates to 100 pph will be achieved on a new nodular iron crankshaft using an innovative microfinishing process and machine.

The microfinishing machine with in-process size control, built by IMPCO, Lansing MI, for GM's Powertrain Div, will be used to finish the bearing journals of crankshafts for the 1993 4.6L Northstar 32-valve V8 engine for Cadillac.

The microfinishing process eliminates the need to match journal diameters to inventoried bearings and will result in improved engine performance due to improved geometry and surface finish. Bearing life will also be increased because the contact area compared with conventional finishing is increased. Another anticipated benefit will be the crankshaft's ability to deliver the high torque demanded by the engine without the need for running in.

The patented IMPCO process, called Generating Bearing Quality (GBQ), is the key to finishing the crankshaft bearings and correcting geometric errors such as lobing and waviness. Conventional crankshaft grinding typically produces parts with differing geometry and form errors as a result of process inconsistencies and differing material hardness.

The IMPCO process uses a noncompressible abrasive film, developed by 3M, pressed against the workpiece by nonresilient "shoes" machined to conform to the diameter of the workpiece. This tooling provides a much more predictable performance than does abrasive stone, according to IMPCO.

Workpieces are rotated in both directions during a finishing cycle while the tooling oscillates to achieve the optimum cross-hatched surface finish qualities. According to IMPCO, the insert and the film provide the stiffness to generate improvements in roundness and straightness. The company claims that roundness of diameters using the IMPCO GBQ process can be improved 50% to 80%, and microfinishes typically in the range of 2 to 3 microinches (Ra) result.

The IMPCO size control checks each journal diameter as it is being processed. A post-process gaging station provides closed-loop feedback on journal diameters and geometry to the machine control. In this way, the machine monitors process trends and the effect of the microfinishing. Stock removal at each tool is adjusted automatically as required.

"This size control capability is vital to holding size because stock removal rates vary in microfinishing operations depending on incoming surface finishes and journal geometries and material hardness," explains Norm Judge, IMPCO marketing vice president.

In the estimated 40-sec cycle, the IMPCO machine produces an aggression-free surface finish on four pin and five main journals in three levels. Ra readings are in the 0.05 to 0.1 micrometer range. Within the cycle the machine also breaks the corners on oil holes and fillet undercuts.

Crankshafts are transferred from the grinding line and automatically loaded into the microfinishing machine for three-level microfinishing. In the first finishing station, all journal diameters are sized to mean part print plus six microns, allowing stock for further finishing at the remaining two stations. Stock removal at this station can be up to 27 microns. In subsequent finishing stations, the journals are improved further and final finished. Front and rear thrust walls and oil seal surface finishes are improved.

"Following all finishing, the post gages check each workpiece and automatically update and recalibrate all in-process gages to compensate for process trends," explains James Vasilenko, IMPCO VP-sales. "The IMPCO 2400FX Microfinisher is actually the final inspector of the crankshafts prior to assembly and will provide the engine builder invaluable data about the manufacturing process upstream."

The machine control also stores historical run data and provides histograms and run charts for the automaker's statistical process control program. Should the machine detect any out-of-specification journal diameters, the control can stop the machine and notify the operator.

For more information on microfinishing machining from IMPCO, circle 277.
COPYRIGHT 1992 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:microfinishing machine with in-process size control built by IMPCO
Publication:Tooling & Production
Article Type:Product Announcement
Date:Mar 1, 1992
Previous Article:Training corner: setting an agenda for US education.
Next Article:The laser's edge: catching the wave in welding.

Related Articles
Microfinishing hard-turned parts.
Microfinishing: it's making a name for itself in the auto industry.
New components call for new processes.
Flexibility for crank finishing. (WIP).
Closing in on machined perfection: bearing surfaces benefit from microfinishing solution. (Automotive).
Lathe microfinishing attachment. (Product Spotlight).
Flexible crankshaft finishing: microfinisher allows manufacturer to handle longer parts.
Centerless microfinishing.
Micro systems prove perfect for world-class crankshafts.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters