Multi Grind: Turning Performance

Minnesota shop succeeds by being good at many different part-grinding methods.

Minnesota Grinding has grown a lot in its 53 years in business.

It was founded by two partners in 1959 as a small tool grinding shop in a garage behind a White Castle restaurant in Minneapolis. In 1961, the partners built a 6,000-sq.-ft. facility in Minneapolis and began to add employees. That facility was expanded several times until it became landlocked at 23,000 sq. ft.

All images courtesy Minnesota Grinding

John Glatczak of Minnesota Grinding programs one of the shop’s Studer S40 grinding machines.

In 2005, Minnesota Grinding moved into its current 43,000-sq.-ft. facility with high bays, overhead cranes for handling large pieces and 35 employees working three shifts, 5 days a week. As you might expect, business is very good—but it took some work to get there.

“We gradually expanded into centerless, cylindrical and thread grinding,” said David Schranck, human resources manager and information technology manager (and manager of “the intangibles”) at Minnesota Grinding.

“In the 1980s and early 1990s we added horizontal machining capabilities, but being a job shop we found it difficult to compete with high-volume, production-type operations,” Schranck said. “We realized our greatest strengths were in precision grinding and advising customers on how they could modify parts or manufacturing processes to achieve a better end product, often at a lower cost. Eventually, we added machines for flat grinding, honing and lapping.”

In 1995, the company began focusing on precision grinding. It eliminated much of its machining capacity and continued to add grinders—mostly CNC machines. By 2005, Minnesota Grinding had outgrown its building and moved into its current Crystal, Minn., plant.

The company offers centerless, cylindrical and thread grinding, lapping, honing, double-disc grinding, Blanchard and surface grinding, and some CNC turning and Swiss-style machining. Industries served include medical, automotive, aerospace, food processing and roofing.

“We could be centerless grinding bar stock, and a few hours later the same machine could be grinding pins for hard drives,” Schranck said. “We may be repairing a large roller for a roofing customer in one department, while thread grinding titanium bone screws in another. We like to be challenged. We pride ourselves on doing work right the first time, on time and with impeccable quality.”

Workhorse Grinders

The grinder brand of choice is Studer from United Grinding Technologies Inc., Miamisburg, Ohio, said Harlen Gibbs, operations manager at Minnesota Grinding. “They’re real workhorses,” Gibbs said. The company has four Studers: an S20, two S40s and a new S33. The company’s first Studer, the S20, was purchased in 1988.

Operations Manager Harlen Gibbs with Minnesota Grinding’s new Studer S33 grinder.

“We found the rigidity of the Studers is key to our precision and repeatability requirements, and the service we’ve received from UGT, the technical support—whether it’s helping with a programming issue or just fixing or adjusting the machine—has been remarkable,” Gibbs said. The shop’s S20 has been running every work day for 24 years.

Minnesota Grinding’s Studer grinders achieve tolerances of ±0.0001 ” to ±0.0004 ” and impart surface finishes from 8µin. Ra to 16µin. Ra. Gibbs said the machines can tackle just about any workpiece material, including aluminum, titanium, Hastelloy, stainless steel, Inconel, carbide and plastic.

“We just had a job that was made of rhenium, an exotic, expensive material,” Gibbs said. “Not the kind of stuff that leaps out at you from the periodic table.” The part was an aerospace coupler that required ID, OD and thread grinding.

Before the shop decided to buy the S33, Minnesota Grinding looked at other, less-expensive grinders, but they were less rigid and lacked the service and support track record UGT provides, according to Schranck.

The S33 grinds a 16 “-long shaft that requires nine different diameters.

The S33 has the latest generation of high-frequency, internal grinding spindles that have maximum speeds of 120,000 rpm, allowing the grinding of very small bores, according to UGT.

The basic wheelhead on the S33 can be indexed at 0° or 30° for straight and angular plunge grinding. A universal turret wheelhead swivels manually or automatically, permitting OD, ID and face grinding in a single setup. The machine features a Hirth coupling B-axis with a 1° indexing that repeats within 0.08 arc-seconds. This permits extremely accurate ID-to-OD runout and concentricity.

Also, the S33 has a shoulder probe and a B-axis that automatically rotates the wheelhead to do different kinds of features, such as ID grinding.

“In the past, we probably quoted jobs based on running a part on multiple machines,” Gibbs said. “The new Studer, with its Fanuc 0i-TD control, allows us to do a job with multiple diameters and multiple faces and shoulders in one setup in a single machine versus using multiple manual machines. This makes us more productive, more competitive and more cost effective. Also, the S33 will open up other market opportunities because the machine is much more precise, faster and more flexible than any other cylindrical CNC grinder.”