Rebuilding Old Crankshaft Grinders

Jan. 12, 2010
Remanufacturing 50-year-old machines such as centered grinders requires creative thinking to apply current technology to decades-old designs.

According to KRC Machine Tool Solutions, Independence, Ky., remanufacturing 50-year-old machines such as centered grinders requires creative thinking to apply current technology to decades-old designs. A recent job, for example, involved rebuilding old crankshaft grinders with indexable, adjustable chucks for grinding shafts and shaping throws for large cranks. The 6 to 12-m-long cranks are used in compressors, marine engines, and stamping presses that require a crank or eccentric shaft to move a ram.

The customer had purchased several Friedrian Schmalts manual crankshaft grinders decades ago. One went into production and the others into storage. Years later, the company needed to put all the machines into production. Problem was, the grinders in storage were a mess — the beds had somehow ended up outside, stacked up on each other and exposed to decades of weather. To make matters worse, the headstocks, tailstocks, saddles, and other mechanisms were scattered around on pallets and in piles. Scrapping the machines and buying new ones would have cost to the tune of $2 million.

“Of course we couldn’t get our hands on any prints,” says KRC Systems Sales Manager Matt Collins. “So we eyeballed the working machine to see where major components such as the headstock, tailstock, and carriage should go. It then became a process of sorting out parts, castings, and assemblies for tear down and remanufacture. We purchased some replacement parts from local suppliers and altered them in-house. The mechanical remanufacture was mostly a matter of building up wear surfaces and scraping-in hard bed surfaces,” says Collins. The company also had to custom fabricate many of the carriage, dressing, and gauging components, build mountings for servomotors, and rebuild wheel guards, as well as craft plumbing and manifolds for the lubrication systems.

In terms of programming the controls, much of the learning curve was associated with the unique grinding process, says Collins. “We had a lot to learn about crankshaft grinding to fashion a workable control program with all the steps in the correct sequence. Here, we worked hand in hand with the customer to ascertain what we were looking at, step-by-step. In one example, the customer said it has pin-chaser-style grinders for in-process rework. Unfortunately, the old grinders just allowed loading a crankshaft, finishing it, and moving on to the next. Should something happen during a grind, there was no way to just repeat a small section of the grinding program. To build a flexible control, we included a step in the program that lets the operator leave the routine and go back and rework an area before proceeding.”

Edited by Leslie Gordon

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