not cutting straight

[gene]

Can a bit that is not as sharp as a new bit or a bad collet effect the straightness of a cut ? not the quality of the cut.
i am cutting mdf 3/4 deep at 5 ips plunge is 2 ips . the edge of the cut is ok . the bot seems tight no play in the carrage or the z axis . if i cut in 2 passes then there is a slight line in the center of the edge. is this just bit deflection because i am pushing it too hard ? it doesnt seem to do it when i cut 3/4 plywood . the spindle speed is the same on both 13000 . if i rerun the file it seems to straighten the cuts up . :confused:

Thanks for your help

[bobmoore]

Gene. Let me start by saying there are a lot more qualified people to answer this than I am, however, I have the same witness lines in hardwood that you are getting in the MDF. I believe the bit is deflecting a little. What I have done to negate the problem is to run the cutout as a climb cut which deflects the bit out to the scrap area. I then run a coventional cut in one pass at full depth on the same line. The deflection seems to slightly pull the bit into the "good" area and clean up the witness lines made from the first cut.
Bob

[dlcw]

Bob and Gene,

There is enough flex in the Shopbot that you do need to make cutouts in two passes. Climb cut first and conventional cleanup cut in a second pass.

I haven't been doing this as long as many people on this forum, but I've run a few hundred sheets of plywood, MDF and melamine through my machine and have learned that this two cut approach is what delivers the best results. Yes, it takes more time but the cut cleanup is eliminated when the parts come off the table. I can take parts directly from the table straight to my edgebander without any intermediate work needed.

[jerry_stanek]

I run a Biesse at the place I work and I get the same thing when cutting. It is just bit deflection.