Gary Treichler, vice president and general manager of Rancho Santa Margarita, CA’s Form Grind Corporation, says that as a college student he had an internship with Mägerle in North Carolina, during which time he viewed large turn-key Mägerle systems built for a variety of customers, including Siemens, GE, Rolls Royce, etc.—several Mägerles lined up with dual spindles, automatic wheel changing, robotics and coordinate measuring systems communicating with the CNC controller providing complete automation for part handling.

“But in the job shop environment,” he says, “due to the variety of short run jobs we run, we do not require this level of sophisticated automation. We specialize in surface form grinding, and what we need is a machine that’s designed and built for rigidity, repeatability and consistent performance. Mägerle is the clear leader in surface form technology, and as an organization we’ve always tried to go the higher road in the sense that you get what you pay for. These machines, some of which are over 30 years old, keep producing great parts. In 1978 we opened shop with two FPA Mägerles in a 4,000 sq ft building. Today we’re in a 42,000 sq ft shop and have sixteen Mägerles, nine FPA machines and seven MFP CNC machines from United Grinding Technologies.”

The Grinding Process

Treichler says that approximately 70% of Form Grind’s business is in gas turbine blades for aerospace and power generation. He also says that the grinding process is like a chain, with each link being an important element of the process, with the weakest link being a potential failure point. The machine, however, is the most important link. “You need to have a solid, strong machine with ample power and rigidity. Then you need the proper wheel for the job, the proper work piece clamping, the proper coolant, proper settings and parameters, feeds and speeds. But by far the most important link—and the one on which you can least afford to cut costs—is the machine.”

Grinding Turbine Blades

Treichler notes that the grinding of gas turbine blades is a combination of art and science. The root serrations, known as fir trees, for example, have a tolerance band of ±0.0005” on the fir tree profile. “Our Mägerles can hold ±.0002” everyday,” he says.

With the smaller blades Treichler says they make multi-piece holding fixtures‚ guillotine-type fixtures that actually clamp on the airfoil.
“Then,” he says, “we try to orientate the blade where we’re grinding the least depth of cut so that, one, we can optimize the grinding wheel to use as much of the abrasive as possible and, two, we’re optimizing cycle time. If you don’t position the blades effectively, you may be grinding air or grinding an unnecessarily deeper profile than required. Typically we arrange the blades twelve per fixture and run two fixtures, or twenty-four pieces, at a time.”

Vertical Operation

Treichler notes that Form Grind is particularly lucky in that they are almost an entirely vertical operation; they rely on very little outsourcing (with the exception of diamond rollers).

“We do our own design and engineering,” he says. “We have operators and toolmakers who in many cases have been here twenty years. We make all our own multi-piece fixtures and crush rolls in house. We can prove out a process and be able to tool up and get into production almost immediately to meet customer needs.

Obviously, when we’ve got long runs and need a diamond dressing roll, we go outside, but usually not before we’ve done a prototype of the part, the form and profiles. So we prove out the process in house before we spend $1000 to $5000 on a diamond roll for volume production.”

Form Grind is also a master distributor of Winterthur abrasive wheels, which Treichler believes is a particularly good wheel for blade production. The Winterthur wheel is known as an open structure wheel, very porous, which permits having the right combination of coolant and chip size for the removal of large amounts of material without burning or cracking some of the exotic materials that blades require. Most turbine blades are made out of inconel 718 or 738 and are very heat sensitive, as well as being a very expensive investment casting. So, according to Treichler, ideally one wants to use a very porous wheel for maximum stock removal without burning and cracking the workpiece.

7 Minute Rule

Standardization or commonality of machines is also an important issue at Form Grind. Treichler notes that all of their Mägerles have 16” diameter wheels. One of the reasons for commonality is operator cross-training; operators can move from one machine to another, as the workload requires.

“We have a seven minute rule here,” Treichler notes. “What this means is that if the cycle time on a given job is more than seven minutes, the operator will be running more than one Mägerle. Depending on the job, a Mägerle doesn’t require a dedicated operator, especially the newer CNC machines. Over the years we’ve continued to add Mägerles and we’ve not really increased our number of operators.”

Treichler says that if you look over his shop you’ll see 30 years worth of Mägerles.

“We generally buy one every year or every other year,” he says. “And the reason is that they’re the leader in blade technology and surface form grinding. We think long term and buy the best. We’re still getting a good return on investment on machines that are close to 30 years old, to say nothing of the newer ones.”

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