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Discussion Starter · #1 ·
Recently I've cut 2 clocks using 1/16" end mill for detail and 1/4" end mill for milling larger clearance using 0.125" depth. I used the "Auto Tool Zero" function in Mach3 in the same spot for both tools. On each clock, the 1/16" end mill cut slightly deeper than the 1/4" clearance. It's enough deeper that there is a visible outline around each item in the clock. Since the depth of cut stays constant on both cutters with any change, is there a way to correct for this problem? I'm using Aspire 9.512 and Mach3.:help:
 

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Which order did you cut and how was material held down? Sometimes material will flex or bow up as material is removed. Did you use a down cut 1/8 and up cut 1/4? That can also lead to the issue as the up cut will tend to lift.
 

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Discussion Starter · #3 · (Edited)
The 1" thick circle is very flat and was held down with 6 clamps. 1/4" DC 2 flute end mill being the first, clearance toolpath and 1/16" up-cut for the second pass. The clearance pass is dead on 0.125" deep. The second pass appears to be 2 to 3 thousands deeper. If the 1/16 bit slipped in the collet the pass would be shallower rather than deeper.

I'm wondering if there is a way to raise Z in Mach3 after the 1/16" tool change and zeroing before "Cycle Start".
 

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The 1" thick circle is very flat and was held down with 6 clamps. 1/4" DC 2 flute end mill being the first, clearance toolpath and 1/16" up-cut for the second pass. The clearance pass is dead on 0.125" deep. The second pass appears to be 2 to 3 thousands deeper. If the 1/16 bit slipped in the collet the pass would be shallower rather than deeper.

I'm wondering if there is a way to raise Z in Mach3 after the 1/16" tool change and zeroing before "Cycle Start".
I've added a few thousandths on Z before cutting text using the offsets tab in Mach3. Bumping the feed down to around 30% to start with being careful where you start the tool again. Probably not the right way to do it. I'm interested in hearing all the experts approach on this.
BTW, I really like the clock.
 

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David
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Very nice looking clock, Bob! I don't use Vectric products but in Mach4, when I do cuts like this where I have to change bits, I make sure my second bit is just above zero so that I don't have what you've experienced.

Since I have yet to build a zero touch off plate I still use a piece of paper to set zero. But when I do the second bit I fold the paper and start there. If the toolpath is a short one I just let it run to completion and then drop Z zero a couple of thousandths to run again. If it's a long toolpath I'll stop it and lower Z zero before it goes too far. I'd rather sneak up on it than go too far. Every once in a while I hit it right on the first pass but most often I run two passes with the smaller bit.

David
 

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Mike
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The smaller bit may not be making good contact with the touch plate so it is going farther down before it completes the circuit and zero is set for the Z axis. Might help to make sure there is not chip build up or possibly pitch build up on your bit before trying to zero.

I figure you can adjust your Z height in Mach3 but my question would be how much do you need to adjust it each time. It will all depend on how the touch plate reading works each time. I have had problems with smaller bits with my touch plate and it is usually because of poor contact from build up on the bit.
 

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Discussion Starter · #7 · (Edited)
The smaller bit may not be making good contact with the touch plate so it is going farther down before it completes the circuit and zero is set for the Z axis. Might help to make sure there is not chip build up or possibly pitch build up on your bit before trying to zero.

I figure you can adjust your Z height in Mach3 but my question would be how much do you need to adjust it each time. It will all depend on how the touch plate reading works each time. I have had problems with smaller bits with my touch plate and it is usually because of poor contact from build up on the bit.
This was a brand new bit so it's not a buildup problem. I do think your first sentence is likely the problem. I've had this problem before with small bits on the 2nd pass.

I'm going to try David's approach and try to do some adjusting in Mach3.

Now I need to wait for all of the ice we have to melt so I can step outside and spray the masked area!
 

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instead of guessing on the depth offset, maybe machine a few passes on a scrap board (on the table at the same time) with the two bits - after zeroing both bits off your (clock) material top. then you can measure the depth offset with calipers and adjust your z setting in the program.

remember to touch pad off the same location of your project each time.
 

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Theo
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Design feature.
 
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