# Clamps



## edison auto (Nov 13, 2015)

I use the aspire program and have a nebula running Linux. My question is there a way to program where your clamps are so the spindle will not hit them. Most of what I cut I screw down to my spoil board but am looking at etching glass and also have some walnut that I don't want to waste by screwing it down. I have had to stop the spindle remove a clamp go past the clamp area, reinstall the clamp and start cutting on a couple of projects. Or even if I could preview the spindle route I could move my clamps or make the spindle go from tool length sensor to the middle of my table at the end then go the y axis to the project at least I would know where it was going. Thanks on advanve


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## 4DThinker (Feb 16, 2014)

Nearly every cut I make is held down by clamps, and although mine have a few encounters with spinning bits that happens less and less as I get more experienced using linuxCNC and Aspire. 

It starts with the drawing in Aspire. I'm already considering where I'll put clamps when I see the toolpath previews. I make a note of where there are gaps in the toolpaths (2 inches from the left end on the bottom edge, etc.) and refer to those notes at the CNC.

In LinuxCNC once the toolpaths are loaded and you've zeroed out X,Y, and Z, the preview screen shows the bit relative to the paths it will take. With the bit high, I'll jog it around to the edges of the the tool paths, near any clamps I've put in place. Looking at both the screen and the bed of the CNC to verify that my clamps are "safe". 

In aspire you can set the safe Z height so that all travel is above your clamps. This will keep unexpected travel between cuts from passing through a clamp. 

4D


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## beltramidave (Jan 6, 2016)

Mark,

I modified the Probotix tool length sensor code (one line) to raise the Z axis up all the way after a tool change and then move to your projects' X/Y origin before continuing on with the program. I would think that this would work for you as you usually set your X/Y origin to the center of the material.

This was a very easy change, if you are interested.

Dave


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## edison auto (Nov 13, 2015)

Thanks for the tips 4D I will try the preview next time I set one up for cutting. Dave when I get back in town I would love to change the line that controls the height. Thanks to both of you


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## cjskelton (Feb 27, 2015)

Mark, 
My method for holding the work piece in place is to screw down a 2" strip of plywood, thinner than the piece being cut, along the bottom of the X axis and another along one edge of the Y axis. I place the material to be carved in the inside corner of these two pieces and then screw down 2 short strips along the remaining sides while holding pressure against it. Your work piece will be boxed in by the plywood strips and held in place by friction. This has worked well for me unless using an up-cut bit. In that case I'd use low profile wood clamps, like 4D makes, and raise the Z travel high enough to pass over them. The May 2018 issue of Wood Magazine has an article on securing CNC stock.

Jay


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## JOAT (Apr 9, 2010)

I'm curious, would a vacuum table work to hold down the work?


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## beltramidave (Jan 6, 2016)

Here is the tool change routine (downloaded from the Probotix wiki site). On my machine, the file is located in Probotix>linuxcnc>nc_files>subs folder.

This change would only be valid when using the G54 work coordinate system. My change is the second line from the bottom (G54 G0 X0 Y0). As the Z axis is already at G53 Z0 (Homed location), it should be all the way up. So what my edit does, is move X&Y to where ever you have previously set up your XY origin before exiting the tool change program and resuming your loaded toolpath file.

Use at your own risk, but it works fine for me. After editing the file, you may need to restart your PC for the change to take effect.

Dave


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