Fixed position Tool touch-off vs "Zero off same side"

Post Reply
clintlmartin
Posts: 6
Joined: Wed Apr 29, 2020 5:05 am
Model of CNC Machine: Laguna Swift 4x8

Fixed position Tool touch-off vs "Zero off same side"

Post by clintlmartin »

Hello all!

I'm relatively new to CNC machining. I've been running a 4x8 CNC router for 9 or so months now and in looking at how to help speed up my work flow I wanted to look at using an fixed location touch probe. Right now I have one of those little "puck" type probes that you place under the spindle, wherever the spindle happens to be (or wherever you move the spindle to). (this is essentially a continuity type probe, not one of the cool button-type probes..)

my typical work today is 2-sided machining full-sheet (4x8) material, and I end up using the Zero off same side (Material surface) option in V-Carve for almost all my projects. Practically speaking, when I zero on the "TOP" side I put my probe directly on the material, and when I zero on the "BOTTOM" side, I put my probe on the wasteboard.

The prospect of using a fixed-position touch probe, however, has me wondering.. How exactly would I go about supporting these types of operations, if the height and location of the probe is "fixed"?

This question, I think, would be the same for machines which have an ATC as well -- ultimately they know which tool to pick up, they either already know the tool-length or they have one of those fixed-position probes (like I want to try)..

I assume the way the fixed probe works is by remembering the offset/difference between the machine's bed or wasteboard and the touch probe (in my machine, I have to calibrate this by setting the tool on the wasteboard OR on the material, then zeroing a tool to the touch probe) then each time a new tool is zeroed the effective length of the new tool is calculated by figuring out the delta.

This would allow either zeroing from the material surface OR from the machine bed.. but would require a re-calibration between sides of a sheet.

I guess I feel like I'm just missing something, and think it's probably a good idea to ask folks who are smarter/more experienced than I am..

any help is greatly appreciated.

User avatar
Adrian
Vectric Archimage
Posts: 14503
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Fixed position Tool touch-off vs "Zero off same side"

Post by Adrian »

I use a fixed touch off point which is set to be level with the spoilboard (it's threaded so I can raise/lower as the spoilboard changes) and I never have any issues with calculations etc.

There's nothing to worry about as the Vectric software does all the calculations for you when creating the code based on where you tell it you're setting z-zero and the thickness of the material. I don't do two sided operations but as long as you're zeroing to the touch off on both sides (with the relevant options set in the Job Setup form) it won't be an issue AFAIK.

With a puck the control software has to know (not Vectric) how thick the puck is and to compensate for that when you zero the Z.

clintlmartin
Posts: 6
Joined: Wed Apr 29, 2020 5:05 am
Model of CNC Machine: Laguna Swift 4x8

Re: Fixed position Tool touch-off vs "Zero off same side"

Post by clintlmartin »

If the tool touchoff is set/calibrated to the spoilboard, then in this case I wouldn't be able to actually zero off the material surface, right? you would always have to set up vcarve (or whatever) to use the "zero off machine bed" for all operations and both sides?

User avatar
Adrian
Vectric Archimage
Posts: 14503
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Fixed position Tool touch-off vs "Zero off same side"

Post by Adrian »

Correct. I always use the zero to Machine Bed option.

You can still use the Material Surface option without having to use a puck etc by zeroing the machine to the touch off, moving the z up by the material thickness and then resetting the z-zero in the control software. I've never had the need to do that though.

Post Reply