“For other blades we may do some creep feed passes and then some reciprocating and fi nal dressing at the very end. There is some tribal knowledge, or black magic if you will, in the art and science of grinding.” Form Grind begins process planning with a team that includes marketing, tool designers, toolmakers and produc- tion managers. “We try to see what makes the most sense in terms of the best way to break down a process,” Treichler said. “We will at times break up the operations to where we use certain machines for the fi r tree operation then we’ll do another feature in a separate operation. There is no real clear- cut best way to do things. When you start a job you have to
Blade dimensions are verifi ed through dual inspection methods. Treichler said Form Grind always submits the parts it grinds to two methods of inspection: “We check fi rst articles in the inspection room where we have a CMM and a 30" [762 mm] optical comparator, then we empower the operators to perform in-process inspection.” At each of the more than 25 different grinders on the shop fl oor, there is a surface plate where the operator can use hard tooling and different types of go/no go and plug gages that verify certain part features. For fi nal inspection, the CMM holds parts in a free state to check and verify the six point nest dimensional features on the blade. Such overall verifi cation is not possible in-process when a part moves from machine to machine for different operations. “Turbine blades tend to have 100 percent in- process inspection, and in fi nal inspection we do a statistical process sampling,” Treichler said.
Additional Services In addition to providing standard grinding services, for some customers Form Grind grinds parts and also manages subcontract suppliers for secondary operations such as coat- ing, shot peening, and heat treating and stress relief. Treichler jokingly calls the all-encompassing work Form Grind’s “blade in a bag” service. “OEMs are getting larger and trying to cut their supplier base, so a one-stop shop is the kind of supplier they are looking for,” Treichler said.
Form Grind produces hyperbolic rods used in mass spectrometers that have traveled to Mars in NASA space probes.
be pragmatic and look at what the goal is, what the volume is and what it potentially could be, and how elaborate your tooling should be to maximize effi ciency. It is all about easing cycle time out of the process and achieving the most output.” Shorter cycle times, however, must be achieved while maintaining process security. Intricate casting processes and new workpiece materials have pushed up the cost of rough blade castings, with some valued at $1000 or more. As a re- sult, much effort goes into establishing and verifying a reliable process. “It is important to have an open structure grinding wheel and speeds, feeds and coolant locations set so that you are removing the material as fast as possible, but also without burning or cracking parts,” Treichler said. “We are very proud that we have less than one tenth of one percent of scrap; OEMs tell us that that when they ship us a set of 100 blade castings, we will send 100 blades back.”
Form Grind also supports its customers’ in-house grind- ing operations with its Form Products division, which makes crush rolls and provides resharpening services for shops that perform cylindrical grinding. In addition, Form Grind distrib- utes a variety of abrasive products.
The Future of Grinding Treichler is a fi rm believer in the key role of grinding in
the production of precision parts, especially of gas turbine components. “A company tries to mill a feature then sends the part out to heat treat and gets distortion. Then they try to fi x those distortions,” he said. “Milling can be consistent and accurate, but for features such as fi r trees with 0.002" [0.05 mm] tolerances, the speed and capability of the diamond dresser to dress all those points on a conventional wheel and grind them all at once offers a clear advantage. The beauty with creep feed grinding or profi le grinding is that you can grind hardened materials directly to size.”
This feature edited by Senior Editor Michael Anderson from information provided by United Grinding Corp.
105 — Aerospace & Defense Manufacturing 2015
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