BUE is the phenomenon where the actual cutting edge of a tool is violated as it is working and results in cutting without its proper cutting edge and angle. Dirty MWF (coolants) promote this event.
When an operation is running with poor or no filtration, the debris of particles in the fluid grows in concentration to where they become trapped in the interface between the tool and workpiece. The high concentration of hardened particles and the elevated heat at the point of cut, allows the captured debris to “weld” to the tool’s cutting edge. The accumulation of welded material is called “built-up edge.” It affects the shear angle and the tool’s normal cutting edge. The tool’s edge is not cutting the workpiece anymore. The BUE is. Figure 1 (below) shows the built-up edge is making a mess of the machined surface and the part is probably rejected. The added heat shortens tool life.
Almost everyone in this industry knows that this situation can exist. They also know that continuous cleaning of the MWF reduces the occurrence and extends the tool life. It is difficult to correlate tool life to coolant cleanliness because of all the other variables which affect tool performance. Therefore, any attempt to measure the impact is usually qualitative and approximated. Many of us would like to quantify the correlation, but very few companies can take the time to isolate the coolant cleanliness factor and only measure its impact on tool life.
However, a few years ago one plant took the time to conduct controlled tests to measure the difference in machining performance with filtered versus unfiltered coolants.
They set up two identical machines; machine A had filtered coolant while machine B operated with unfiltered coolant. The filtered coolant machine A maintained an average of 1200 workpieces per cutter re-grind. The unfiltered coolant machine B produced 125 workpieces per cutter re-grind. To insure that there was no machine bias, the filtration system was taken off machine A and placed on machine B. After a suitable run time machine A dropped to 150 workpieces, while machine B climbed to 1200 workpieces.
There have been other correlation tests as well. Remember this scenario is only a guide and that the tests were measuring filtered coolant versus unfiltered coolant. If there is some filtration already on the machine or if the coolant is dumped routinely, the results should still be favorable but probably not be as dramatic.
Here, the term “filter” is the loosely used jargon for any device which cleans coolant. Therefore, in addition to filters, cleaning devices can be magnetic, retention, flotation, and centrifugal. Obviously each device would be selected for its applicability to operation’s needs. There are many ways to incorporate effective coolant filtration systems.
James J. Joseph is the principal/owner of Joseph Marketing, located in Williamsburg, VA. You can reach him at firstname.lastname@example.org.
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