Efficient machining of workpiece materials with poor thermal conductivity

Solid carbide tools were chiefly used for trochoidal milling in the past. Together with SolidCAM and its iMachining software, MAPAL has now demonstrated that the highly efficient machining technology also offers advantages for milling with indexable inserts. An aeroplane part made of titanium was used as a demo object.

The torsion link is a component of the main landing gear of aeroplanes and is made up of two parts. It connects the two cylindrical parts of the landing leg. This design allows the damper cylinders to retract and extend without twisting. The torsion link thus maintains correct positioning of the wheels and ensures the directional stability of the aeroplane when the landing gear is extended.
Due to the resulting high loads, torsion links are made of titanium. Other than parts for a few mass-produced aeroplanes where production of forged blanks is worthwhile, both parts for the torsion link are usually milled from solid. Because titanium is a poor thermal conductor, trochoidal milling is a suitable machining strategy as the tool only briefly comes into contact with the workpiece. Part characteristics like constrictions that have to be machined, deep cavities and grooves all speak for this method.

THE BETTER MACHINING STRATEGY
For conventional roughing (groove milling), a wrapping angle of 180° is stipulated for the milling cutter. This has various disadvantages: long chips, high thermal loads, big machining forces. This limits infeed depths, feed rates and cutting speeds. By superimposing a circular movement of the tool over the feed movement, the contact conditions can be positively influenced with trochoidal milling.

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