"One Perfect Part at a Time"

No Mistakes – Making My Point

I seldom, almost never make mistakes… HA! But I found one in my tool definitions for Vectric Aspire. Um… maybe I do make a few mistakes.

I use a very fine pointed, down to 0.003 tip tapered ball-end milling bits. Tapered ball-end milling bits are defined by their one side taper angle and the tip radius in the Aspire tool table. That was what got me. The tapered bits are identified by the manufacturer with total (combined) taper angle and the tip diameter.

So, what the maker defines as a 10-degree 0.005 tapered ball-mill is defined in Aspire as 5-degree taper bit with a 0.0025 tip radius.

I got the side angle correct but I was entering the full tip diameter as the radius. I realized the problem when I would define stepover as a percentage rather than specified absolute distance. The percentage calculation was showing twice the correct distance.

Therefore, Aspire was also calculating the tool path to be twice as wide as it actually was. That’s because that is what I specified.

Hmm… wonder how long I have been doing that!*

I am trying to imagine how that would affect the milling operation. Probably some dimensional errors, the program calculating the bit to be twice as wide as it actually was. With the tiny bits, there error would not be noticeable or of any importance. Pocket sidewall distance would be a couple of thou’ too small.

I think the biggest issue would be the stepover. If I wanted 20% it would be cutting 40% and surface finish might suffer, and the flute chip load would be high.

*I don’t think this has gone on for very long. I would have noticed before now. I bought an assortment of tapered ball-end mills a few months ago and added them to the tool database. They were 0.003, 0.004, 0.005, 0.010, 0.015, and 0.020 and have not yet been used in a project.

What saved butt in this discovery was I specified the 0.003 ball-end in the software but when I was about to run the project, I was going to substitute a 0.003 pyramid tapered bit (flat end) and it got me to thinking the flat end and the ball-end are both designated as 0.003 but I remembered Aspire asked for the RADIUS for the ball end taper bit. There is NO radius on a flat end bit. Brain-gears start turning.

In a minor panic, I went back to the drawing and the tool table and sure enough, I used the full diameter for the radius setting rather that the D/2 radius in the tool table. Stepover was wrong. My g-code was defective.

Is a mistake corrected still a mistake? How about an ex-mistake? Could be, it is a lesson learned…

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