Tool Touch-off

[trnsfrmr33]

hi All,

please forgive me if this was covered in another thread.

I've been working with an old Shopbot PRT, but I'm looking into getting a cncdepot ATC spindle at some point.

I have a few questions, some theory.. some practical:

1. how does tool touch-off work in relation to your Z location? If you're working on a multi-op project and you're finished with the first tool, and you've loaded too#2 (either with ATC or even by hand) and you run over and do a tool touch-off, is there a script or something that actually does the math to compensate for the variable in tool height? Or do you have to do something different so the machine's Zero is still the same?

2. I have a feeling that CNC12 handles things like touch-off and probing differently than SB3, but can anyone explain sort of generally how it all works? (leading to question 3).

3. Is it even possible to use either the TT-1 or TT-4 with my SB3 software? I am planning on moving over to Centroid.. My wife has heard me talk about Gary Campbell for years at dinner like he's someone I actually know

4. and I guess my last question is to see if people can chime in and let me know their experience if they've switched from a Shopbot machine to Centroid. I started with a home-built Mach3 machine and I got by, but there was just so much I didn't know at the time. Shopbot is like braindead simple.. but I have a feeling that I'm missing out on a lot of functionality. (some of which I don't fully grok yet).

anyhow, many thanks in advance for people's insights.
-J

[cnckeith]

i moved this post into the Acorn forum.

related links,

https://www.centroidcnc.com/shopbot_gcnc.html

https://centroidcncforum.com/viewtopic.php?f=60&t=6149

[Sword]

Hey J,

You can use your original SB touch plate and also a fixed tool touch off. With an ATC, your tools are measured and saved in your tool library. The offset from the table surface to the fixed touch off is saved and applied for all tools. That's a simple explanation. With both, you have the option of routines, built in as a custom M6 macro (verbose), or with Swissi's great Probe App.

Going from SB3 to Acorn is one of those "Great Awakening" kind of moments!

Here' a video I did for some of my customers that shows my normal daily workflow using the plate and fixed tool touch off with Swissi's Probe App.

[Gary Campbell]

J...
By your numbers:
1) tool length offsets are stored by the system. My recommended version is to store them referencing machine Zzero (top). Once measured with a fixed tool touch off device you will not have to remeasure unless you change the physical bit in the holder. You can use a portable z setting device to set the part zero to top of material or machine bed. Once set, all tools are set (zeroed) to that location. You will not have to reset Z part zero until you change the material height if zeroing to the top of material. If set to the bed, then you are good until you resurface.

2) Good news is that you will find that Centroid software remembers everything. Bad news is that SB3 remembers nothing. So, you will have to relearn every procedure. That said, ask around to the other SB'ers on here... doesn't take that long and is more than worth the effort.

3) It might be possible, but the SB probe is a 5v version and if I remember correctly, others have tried and failed.

Some things you want to know:
The PRT is a marginal frame to install an ATC on due to their age and ancient design
You will need to upgrade to modern more accurate sensors for homing on all 3 axes.
You do not want to install an ATC on an open loop stepper system. Closed loop steppers or servos are just about mandatory, and servos will overpower the frame, so...
Swap to Acorn control and use the machine for a bit before you attempt the ATC upgrade
IF you do go ATC, make sure you upgrade the OEM Z axis to the 8 V roller design
Due to the limited Z height you may have to mount your tool rack and tool measure switch below the table surface
If you follow my suggestions above, your wife can now hate me for the money I just cost you!
Find a way to replace the OEM SB conductive Z plate