I’m using Vcarve to make a pocket toolpath, I use a 1/8" downcut bit for the initial pocket and then a 1/4" upcut for the clearance. I rehome the “Z” between running each but no matter what I do there seems to be a small step between the two toolpaths. Any help in correcting this would be much appreciated…
Hey Todd,
what do you mean with “rehome”? Homing has to be done only once, after initial power-on of the machine. What you would do in these cases is just to zero z after the bit change.
Note that stall homing on the Original or PRO Series is not very accurate (poor homing repeatability). Retrofitting inductive proximity sensors brings perfect positioning repeatibility.
Anyway, no need to re-home a machine that works correctly during operation.
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Should have been more specific, not doing a total rehome, just zeroing the bits between toolpaths as you indicated.
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and how do you zero? Do you use the XYZ touch plate?
Note that depending on downcut or upcut bits used, the workpiece could get lifted.
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Looking closely at the photo, it looks as if the height of the step varies. Could your workpiece could be moving a little bit in the vertical direction? If it has any internal stresses, it may well bow a little when you cut into it, depending on how you’re fastening it down.
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Yes I use the XYZ touchplate and I try to place the touchplate in the same location on the wood each time I zero. I’m securing the piece with screws in each corner. could the bits still cause lifting ?
I use compression bits for just about everything and I have this same type of problem even when I use the same exact spot for zeroing (X,Y,Z block) between bits and it doesn’t matter how I fasten my material down, it still happens sometimes.
Sometimes the step between bits is lower OR higher, and sometimes they are exactly the same height. I know it’s not flex in my table or gantry.
My DOC is usually .075 or less with a 1/4" bit, and .05 or less with a 1/8" bit, and speeds are reasonable, (I’m retired, what’s the hurry!)
I’ve just been putting up with it so I’ll be interested to see what the replies are.
Pony
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If the problem was simply inconsistent zeroing of the bit heights, I’d still expect you to get consistent step heights (on a given run).
The rule of thumb for accurately dimensioning lumber with conventional tools is to “sneak up” on the final dimensions. In other words, don’t cut all the way to finish dimension on the first pass, because the wood may move when you cut some of it away and relieve its internal stresses.
It would be very interesting to see if you could get consistent results by roughing out everything first, saving maybe 0.02" of material to remove with a final finishing pass. If that gives good results, your wood is probably moving when you cut into it.
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