Why does this pocket cut plunge three times? (Newbie)

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Rhys
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Joined: Thu Sep 24, 2015 5:59 am

Why does this pocket cut plunge three times? (Newbie)

Post by Rhys » Thu Oct 01, 2015 2:11 am

My first cut with the SO3 worked perfectly except for a couple of minor things:

Order of cuts was pretty un-optimized (I think I can fix this by doing a pocket cut for each element instead of the entire group).
Three passes/plunge operations were made when I expected two.

The first issue doesn't bother me too much since I think I already know the solution. The second one is a curiosity since I was expecting completely different behavior. The values I used were:
Target depth: -0.0625
Step down: 0.03125
sylvia.JPG
pocket settings
sylvia.JPG (49.38 KiB) Viewed 1144 times
Since my step down was half of my target depth, I assumed it would complete the job in two passes. However, it did three.

Part turned out fine, but I was curious about the unexpected behavior.
DSC00363.jpg
Finished part
DSC00363.jpg (261.55 KiB) Viewed 1144 times
My second job was made with a target depth of .5 and a step down of .251 and it completed in two passes as I expected. Is this just a matter of not making (step down * # of passes) equal to exactly the target depth?

As mentioned in the title, I'm a newbie to CNC so the more knowledge I can glean, the better.

WillAdams
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Re: Why does this pocket cut plunge three times? (Newbie)

Post by WillAdams » Thu Oct 01, 2015 2:30 am

Probably it needed the third pass to make up for rounding off.

Yes, making the step down slightly more than one would ideally need addresses that.
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cvoinescu
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Re: Why does this pocket cut plunge three times? (Newbie)

Post by cvoinescu » Thu Oct 01, 2015 9:21 am

WillAdams wrote:Probably it needed the third pass to make up for rounding off.
There's an easy way to verify that it's a rounding error. Make the step down 0.0313, or even 0.03125001, and see whether that makes it do only two passes.
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