"Awesome" is a word that fairly describes the capabilities of precision grinding shops. Those that combine the best of advanced technology and operator skill can consistently turn out parts requiring tolerances in the millionths and finishes as fine as 2 Ra (2 micro inches). Today, their specialty capabilities are increasingly in demand for parts such as gears, bearings, cylinders, and cams.

 

"Precision grinding is becoming increasingly important for the automotive, aerospace, medical-device, and electronics industries," said Anil Srivastava, manager of manufacturing technology at TechSolve, Inc. (Cincinnati), part of a team of industrial partners working with researchers at Purdue University to develop an "intelligent" system for improving precision grinding processes, according to innovations-report.com. "Grinding is often the final machining process for creating parts that require smooth surfaces and extremely fine tolerances."

 

While companies require precision, turnaround times are shortening. California Jig Grinding (Pico Rivera, Calif.), for example, turns around most jobs in 48 hours, and M&S Centerless Grinding, Inc. (Hatboro, Penn.) completes jobs in one week or less.

 

To maintain their competitive edge, many shops are deploying the latest advances in grinding machines and sophisticated abrasives. Wiscon Products, Inc. (Racine, Wis.), for example, specializes in complex form grinding between centers, using three new Junker 2-axis CNC universal angle head grinders. Wiscon also performs plunge centerless grinding with a new Tschudin CNC centerless grinder.

 

The new machines, having wheel speeds in the range of 50 meters per second, take advantage of new grades of ceramic wheels to attain higher feed rates, more metal removal, and better finishes, says Wiscon's owner, Rolfe Christensen. The machines also include automatic gauging for diameter, roundness, and like measurements. Wiscon gauges off-line as well.

 

Greater efficiency is also obtainable through a new generation of CNC grinding machines that give companies unprecedented flexibility for processing a wider variety of parts with shorter setup times. Absolute Grinding (Mentor, Ohio) realizes significant time savings with use of a Studer S31 CNC universal grinding machine from United Grinding Technologies (UGT, Miamisburg, Ohio). The firm's personnel can change over, within an hour, from an ID operation to an OD operation on a different part, according to Rob Murnyack, president of Absolute Grinding.

 

"We can't spend four hours on a setup," says Murnyack. "With other machines, I hear from people out in the field that they might spend four hours just writing the program," says Murnyack. "It takes us just five minutes to write these programs on the Studers."

 

Equipped with the Fanuc 16i CNC control system, the Studer S31 CNC universal grinding machine features a revolving wheel head that can be swiveled manually or automatically. It is particularly suited for grinding tooling and aerospace parts, especially parts that require close tolerances on angles.

 

Many shops specialize in one grinding technique, such as jig grinding or centerless grinding, or carry expertise in a skill such as straightening long, narrow parts. Boston Centerless, Inc. (Woburn, Mass.), for example, developed skill in straightening shafts prior to grinding. Steven Tamasi, the firm's CEO, says, "We do a lot of long shafts, such as rollers for the printing industry, and have developed expertise in hand straightening so we can successfully grind them to the finished tolerance."

 

Grinding shops may also focus on particular part sizes. Deryl Craig, president of California Jig Grinding, says, "Most parts we grind weigh 10 lb or less and can be hand-carried." Most of Wiscon Products' parts are long and narrow, up to 2-1/4 inches by 10 inches long.

 

"We grind parts that others say cannot be ground," says John Shegda, co-owner, M&S Centerless Grinding. For example, M&S grinds a sesame-seed-size medical part with dumbbell-shaped ends that are 0.030 inch +/- 0.1. "We've kept pretty busy during the recent lean times in manufacturing by pulling tiny intricate jobs from all over the country," Shegda says.

 

Stema Punch & Die (Cambridge, Ontario, Canada) uses a Studer S32 CNC punch grinder from UGT to rough and finish punch blanks of very hard M2 tool steel. Most of the firm's punches, ranging from 0.125-inch to 3 inches in diameter and from 2 to 6 inches in length, require a tolerance of +/- 0.0005-inch on the OD. Some, however, require an OD tolerance of +/- 0.0003-inch. According to Stema's owner, Stefan Lorbach, the Studer S32 CNC punch grinder is capable of holding a tolerance of +/- 0.0001-inch. Besides allowing Stema to handle 1-inch ground profiles, the punch grinder enables the firm to "easily tackle 2.5-inch to 3-inch profiles for custom punches," says Lorbach.

 

As often as specializing, grinding shops may offer a full range of grinding techniques. Boston Centerless provides cylindrical grinding in addition to through-feed and in-feed centerless grinding. "This capability allows us to look at the most economical way to grind a part," says Tamasi. "For example, we might not need to cylindrical grind the whole part, but through-feed centerless grind instead, then finish with cylindrical grinding." Boston Centerless often sets up jobs in a cell, operating two grinding machines in tandem to grind a part's ID at the same time as the OD.