Development of Ultra High-Speed Cutting Tester
This page has opened to public since May 15 2008.
All Rights Reserved by Jun Shinozuka.
Recently, a demand of high-speed machining has increased year by year. Improvement of spindle and feed mechanism are remarkable. However we do not know that cutting speed can increase up to how much speed. We do not know whether more faster cutting speed than cutting speed that we apply gives birth to advantages or not. Because there are a lot of unknown phenomena in high-speed and ultra high-speed cutting.
Then, we have tried to clarify the cutting phenomena under ultra high-speed cutting conditions by not only a FEM cutting simulations but also cutting experiments.
We have developed a cutting tester that can achieve high-speed and ultra high-speed cutting conditions.
In this study, condition whose cutting speed is faster than speed of the plastic wave of a workpiece is defined as ultra high-speed cutting condition.
Speed of plastic wave devends on the density and work hardening rate. Generally, speeds of plastic wave for a steel and an aluminum alloy are about from 200 m/s to 300 m/s in shear zone (12000 m/min-18000 m/min, 720 km/h-1080 km/h). While, for lead (Pb), it seems to be from 20m/s to 60m/s because of high density and very small work hardening rate.
In order to achieve high cutting speed over 200 m/s, a workpiece or a tool have to rotate in high rotation speed for a lath type of tester. For example, a workpiece of 0.3 m in diameter has to rotate in 12700 rpm if cutting speed is set 200 m/s. In such case, there are some difficulties; problems of critical speed of rotor and centrifugal force. Especially, low stiffness material such as lead easily deform plastically by centrifugal force.
Then we have developed a cutting tester of an airgun type. A tester of airgun type can achieve high speed relatively easily, mechanism is simple, and low stiffness material can be applied to workpiece.
Cutting speed depends on an acceleration pressure and an acceleration length. Acceleration pressure is up to 1.0 MPa.
High-Speed Cutting Tester (1999-2003)
This tester has two parallel slide rails. Cutting tool and workpiece are moving on these rails. They are accelerated with compressed air. Cutting achieves when they pass each other. Cutting speed is relative speed of them.
Image of the cutting tester
Overview of the high-speed cutting tester
Cutting force is measured with samll MEMS acceleration sensor.
Cutting speed is measured with a photo sensor. Of course, speed can be obtained by integrating the wave of acceleration that obtained with the MEMS sensor with time. Cutting tests of pure lead were performed up to cutting speed 65 m/s with the tester.
As the results, we found out that; shear angle and cutting force increase as cutting speed increases, the texture of the machined surface changes when cutting speed is faster than 40 m/s.
Ultra High-Speed Cutting Tester (2005-)
Patent: P4171808 Japan (P2006-181078, P2008-8821A)
In order to achieve much faster cutting speed and to investigate cutting phenomena in detail, newly tester have developed.
In this tester, a small cutting tool is installed into a small projectile. The small projectile with built-in the small cutting tool is accelerated with compressed air.
Projectile with built-in small cutting tool
Workpiece is set into a chamber. Cutting environment can be controlled to atomosphere condition, vacuum condition and gas condition. Acceleration length is 3 m. Cutting speed 150 m/s can be achieved in atomosphere condition. Cutting speed 250 m/s may be achieved in vacuum condition.
After cutting, chip is capctured into the projectile. Then chip that is very important to investigate cutting phenomena can be collected without damage.
Cutting tests of pure lead and aluminum alloy under atomosphere condition that cutting speed is up to 150 m/s were perfomed so far. We have found out some interesting phenomena.