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IMPCO.MACHINE.TOOLS

Transfer System Streamlines Crankshaft Microfinishing

Southeast Machinery & Industrial News, July 2002

An innovative machining process and statistical process control performed by a new type of microfinishing (superfinishing) system will be used to guarantee correct circular and other geometry characteristics and surface finish of a steel automotive V-8 crankshaft.

"An innovative linear synchronous transfer system within the two-station IMPCO Machine Tools microfinisher (superfinisher) costs 50% less and uses 20% less floor space than a gantry type transfer system and is quicker to install. The internal transfer can be loaded manually or with automation and provides a 25% faster part transfer time. Automotive companies are constantly looking for ways to reduce the cost of manufacturing and IMPCO's innovation is a direct response to that objective," said a company spokesman.

"The engine plant will save manufacturing cost and improve part quality by utilizing the new Worldstar Model 1640 microfinishing system with two levels of microfinishing to improve circular geometry, straightness and surface finish of main and pin journals and other surfaces on the 30" crankshaft. The microfinishing (superfinishing) process will eliminate the need to match journal diameters to bearing sand will help improve engine performance. Production rates will be up to 60 pph with the patented FlexShift part transfer solution and 120 parts per hour with a standard tooling arrangement," continued the spokesman.

Crankshafts are transferred from the grinding line and automatically loaded into the first station. The part is centered between a fixed quill headstock, which provides servo-driven part rotation, and a pneumatically operated tailstock. The abrasive film is applied by horizontal arms which close around the part and press the abrasive against the part at predetermined pressures for specific time to achieve the desired surface finish and geometry. Independent of part rotation, the part is also oscillated while rotated. Within each station, the crankshafts are Flex-Shifted left to right to present journals tot he tooling, saving time, space, and machine cost. According to the spokesman, this procedure also allows the manufacturer to use less tooling to complete each part without inhibiting required production.

Surface finish achieved on main and pin journals was statistically held to a part print spec maximum limit of 0.15 micrometers (mu). Ra. Circular geometry was reduced to less than 2 micrometers (mu), typically better than 50% over incoming condition and less than one-half of the part print allowance. The IMPCO microfinishing system was designed to reduce material handling cost and improved production quality and efficiency while allowing the manufacturer flexibility to accommodate future production.

Manufacturers of precision shafts are increasingly using microfinishing to achieve tight part surface finish and geometry specifications required for many products from pumps and compressors to instruments and automotive engines and transmissions. IMPCO microfinishing (superfinish) process is widely used in the auto industry to improve the geometry and surface finish of crankshaft bearings, increasing bearing life by increasing the contact area.

All tooling maintenance is accomplished from a single location at the front of the machine. Microfinishing tooling is within easy, safe reach from the front of the machine, and operators can easily observe tooling. it is also designed to be simple to changeover or expand for future production needs.

Worldstar's modular design and quick tooling changeover provide the flexibility needed to keep up with changing part specifications and production volumes, and the machine design is expandable to accommodate changes in plant layouts.

The patented IMPCO process is called Generating Bearing Quality (GBQ) and is the key to finishing crankshaft bearings and correcting geometric errors such as lobing and waviness. As they arrive at the microfinisher, parts typically exhibit geometry and form errors as a result of previous processes and differing material hardnesses. The Impco GBQ process uses a noncompressible abrasive film pressed against the workpiece by nonresilient "shoes" precision-machines to create the desired diameter on the workpiece. This tooling provides a predictable performance. Most vehicle crankshafts produced in North America and many in Europe and Asia are treated to GBQ Generating Bearing Quality microfinishing.

IMPCO Machine Tools

3417 West St. Joseph Street, Lansing, Michigan USA 48917

Phone: (517)484-9411 Fax: (517)484-0502

Email: Sales @IMPCO.com