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Author Topic: Manual Tool Height Z Measurements  (Read 1108 times)

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Manual Tool Height Z Measurements
« on: December 15, 2017, 09:47:21 AM »
When I manually change the tool in MACH4 the new length must be input in the TOOL TABLE.  I do this manually by using the Z MEASUREMENT button in the Tool Table. This works ONLY if the tools get shorter. If the successive tool is longer the Z measurement is a POSITIVE reading which is incorrect. The correct Z height would be to ADD this positive Z measurement to the previous Z reading. I can do this math, but the possibility of making a simple mistake is large. Is there a way to manually set to tool so MACH4 references the length from a common starting height?  Is the probe page the way to do this... even if you don't have a probe? I attached a link to a drawing of this situation. Looking at the 3rd tool, left to right, the first two work ok, the 3rd longer tool is the problem. When the plate is touched the Z reading is +.4454. This is not correct for the Z height on the 3rd tool The actual height should be *-.2970.https://photos.app.goo.gl/FFa6nu7Dt9ouhvs43
Re: Manual Tool Height Z Measurements
« Reply #1 on: December 15, 2017, 05:00:08 PM »
The positive Z tool length for a tool longer than the one you used to set zero is correct.  You are confusing Z height with Tool Height which is properly called tool length.  Here is what happens when the tool length gets called.  If the tool was shorter than the reference tool and the Z axis was at 2" above the part it would move down until the shorter tool is 2" above the part before a cutting move.  Call a different tool with a positive length when the Z axis is at 2" then the Z axis will move upwards until the tool is 2" above the part before a cutting move.  This causes more confusion than almost anything else about CNC! 

I once worked at a shop where I replaced another guy and he had a huge valve forging in the machine.  There was a nice smooth slot cut in the top of the forging about 1/4" deep and 1" wide. I asked another machinist what that slot was for.  He said "He always does that. That is Z zero where he sets off all his tools!  OMG!!!  He clearly had no understanding of tool length offsets. So don't be discouraged, this guy had run the machine for 7 years.
Re: Manual Tool Height Z Measurements
« Reply #2 on: December 16, 2017, 08:54:47 PM »
Hi Gary, thanks for the assistance. I figured out the tool height. Its logical, I just assumed Mach 4 would keep track of the surface as long as you told it where the tip of the tool was. Anyway. I got my first complete part finished... with no errors. Small mold. Here is a link to google photos of the piece. Thanks again. Keith.