Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Flatball takes the rub out of copying style inserts
Article Type: Equipment and software From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 4
A totally new generation of milling insert that claims to overcome problems associated with ball nose copying style inserts where zero cutting speed at the centre causes error of form and premature failure of the insert, has been developed by LMT’s Kieniger tooling division. The FlatBall indexable insert combines the advantages of both ball and toroidal style indexable inserts for die and mould and aerospace type applications in what LMT (UK) of Coventry describe as a “double-edger” geometry.
The design of the FlatBall, which has a 2 mm flat on a 10 mm diameter insert, totally overcomes the absence of cutting speed as the spindle rotates around the centre line of the tool which causes a normal carbide insert to suffer from the rapid rise in temperature created by the resulting “rubbing” rather than cutting action. The rubbing action also leads to increased wear of the insert, that progressively changes its geometry under cutting conditions leading to lost machining time to check components and input offsets at the machine control or even having to more frequently change tools.
LMT’s solution, as its name suggests, is to flatten the shape of the ball or more technically, reduce the radius of the insert until it becomes a double-edged cutter. This modification of form means the insert works at a constant speed in its centre but without loss of any advantages gained by the ball shape. This design also is said to prevent any accumulation of chips or built-up edge at the tip of the ball when an initial cut is made into a slope or a helix. In addition, it can also reduce the number of individual cutting paths required, thus shortening cycle times when complex contours have to be machined.
Recent trials at the Polish subsidiary of Comau, the Italian corporation that supplies the automotive industry with large cast iron, cast steel and tool steel alloy moulds, a LMT FlatBall was recorded with an in-cut running time of over 70 h. The material a GH240 steel casting with hardened inserts was machined using LMT’s WPB 16FB-70 der CBN faced cutting insert. The five-axis milling centre was run at its maximum speed of over 600 m/min and due to the improved security of the process, was able to be left to run unmanned.
A further hard milling trial to produce a trimming tool out of P20 tool steel, the LMT FlatBall was run at 400 m/min to produce a cutting distance of 3,960 m over an 11 h period and after that time displayed no appreciable signs of wear.
For further details, please contact: LMT (UK) Limited, Tel.: 024 7636 9770, Fax: 024 7636 9771, web site: www.LMT-tools.com