Micro cutter breaking on Renshape


I am new to CNC machining and changing end mills to metrics cutters. I am using a very fine cutter on a simple job but somewhere in the tool settings the plunge rate is so high that it breaks the fragile end mill. Please see the attached tool setting for .5mm diameter cutter and let me know what is the suggested settings I should use. The job is a simple text carving on Renshpae.

Thank you!

That is a very tiny endmill!

Looking at your end mill setup, I see a couple of things that should be changed.

First thing is just suspicious - you have the flute length listed at 6mm - that seems awesfully long for such a short cutter. 0.5mm cutting edge diameter is about equivalent to an .010" bit, most of those have about .030" cutting length. Take a look at your tool and I think your flute length will be closer to 1.5mm.

I would change the Depth per pass to 0.125mm at most. As is, you have it set to half the diameter of your cutter. OK for larger cutters, but micro cutters like this should be handled with kid gloves.

That should help prevent you from breaking any more of those cutters.


In styrene with a 0.5mm cutter I have been using 0.13mm depth of cut, 100mm/min feed successfully on full-width cuts (i.e. slotting) using 10000 rpm. Renshape will likely need slower feed–styrene is very soft plastic. My cutter has 2mm long flutes (longer than the standard 3X that Edward correctly says) and I have not broken one yet. It is ramping into the material, but if I were plunging I would not go over 50mm/min.

It is set to DOUBLE the diameter of the cutter and for sure is way too deep.

Something doesn’t seem quite right about the cut design for engraving text. For a cutter that small, 1mm seems very deep and i question whether the y finishing should be necessary at all. When I do engraving I do it in a separate job.