I was running a toolpath to drill some .250" holes in some HDPE seaboard .5" thick drilling through with a 3 flute EM designed for plunging as it center cuts. The swarf would not clear off the bit and ruined the material by making huge swirl scratches in the textured finish of the material. $160 sheet of material ruined. I have ran this same bit many times using the same parameters of plunge speed and RPM never having a problem but this time it was a disaster.
I would have caught it sooner but I was running a 2nd CNC machine that required frequent tool changes and by the time I looked it had pretty much ruined the whole 4x8 sheet.
I am changing tools from here on out to a special drill bit designed for plastic the problem is it really tears up my spoilboard because it has such a long taper at the point I have to drill .250" into the spoilboard to get a hole through the .5" material.
I wonder why all the sudden this same tool path I have been using does not work. I tried a new bit and got the same results again. I have been doing it this way for over a year with great results. I am not really looking for an answer I am just venting.
Mike