The aerospace industry is known for using materials that cannot be processed using traditional tools and techniques. The properties of these materials and their high strength at high temperatures enable components to survive in the harsh environment of aero-engines. These properties are the same as those that make them difficult to process.

Whether the part is cast, forged, or made of sintered powder metal, most parts will remove 50% or more of their original volume before reaching the final shape. This is usually done by turning, milling and broaching.

Due to the material properties and high value of the parts, these operations are usually run at conservative feeds and speeds to ensure that the tool does not malfunction or damage the parts.

Regardless of the parameters and part tolerances used in machining, the surface quality will decrease with tool wear, which will reduce the life of the parts in the engine.

In contrast, the grinding wheel is easy to dress-keeping the abrasive cutting edge sharp and the shape of the grinding wheel unchanged, thereby achieving a consistent finish within tight tolerances.

A good example is an aerospace customer who needs to cut grooves on the IN718 material disc and wants to compare the milling process with the grinding process.

Norton Engineers | Saint-Gobain Higgins Grinding Technology Center evaluated two different abrasives: one using Norton Targa ceramic alumina TG2 particles, and the other using Norton Quantum ceramic alumina 5NQX particles. Two IN-718 boards are stacked together, and four 1/2" wide grooves are ground to 1/2" deep in each case, without the need for wheel trimming. Choose a cutting depth of 0.100" arbitrarily, and increase the feed in increments of 20"/min. Until the wheel wear is considered too high. For the 5NQX grinding wheel, the feed rate of 70 ipm was reached before the wheel was considered to be worn too high. In the case of TG2 rounds, the feed is increased to 180 ipm. The material removal rates of TG280 and 5NQX46 grinding wheels were compared with the removal rates specified by different end mill manufacturers. Grinding has proven to be the most effective and efficient material removal process.

Compared with traditional materials (such as IN 718), the new nickel alloys used in aerospace may be more difficult to machine.

A customer encountered difficulty turning one of these new nickel alloy materials. Inclusions in the material can cause unpredictable tool failure, and due to the high strength of the material, the tool life is very low.

Using the new Norton Vitrium3 binder and extruded TG2 pellets, Norton engineers were able to grind parts at a feed rate of 0.025" per revolution and a working speed of 160 ipm, achieving a removal rate of 4.0in3/min/in.

Under these conditions, use 2 inch wide wheels to remove 8 cubic inches per minute. With the tool change function of today's machines, individual wheels can be used to machine and complete complex part geometries in roughly the same way as traditional CNC lathes.

If the surface needs to be ground after turning, the turning operation can be cancelled.

Cost savings in the aerospace manufacturing process can come from many sources, whether it is reducing capital expenditures, consumable tools, logistics, or shortening cycle time.

Today, engineers can find opportunities for abrasive solutions to outperform traditional machining processes.