CNC Depot pneumatic draw bar control button location

Hi All,

I have the CNC depot pneumatic draw bar setup for the ATC, which I really like. There is one thing I would change about this however…. And that is the location of the draw bar release button (which is a software button on CNC depot screen setup). Has anyone else noticed that the draw bar release button and the spindle start button are right close together, and used while clicking the mouse and either placing or removing a tool into the spindle? I am extra careful with that, but it seems like it’s a setup for a an accidental spindle start while your hand is in there…… has anyone else noticed and perhaps fixed this for their setup? An even better answer might be a remote button at the spindle to operate the draw bar for hand tool changes…… anyone done that yet?

Before I reinvent the wheel, I thought I’d see if the correction already exists.


You can pretty easily move buttons around in the Mach 4 screen editor. I’m not in front of Mach right now to tell you exactly where to click but if look in the menus there is a way you can edit a screen set.

I’d recommend saving the one you have and copying it so that you can fool around with a new one.

If you just want to move a button on the screen, or copy it and its associated code to another screenset, it is pretty easy. I did a video on that a while back. Mach4 Screen Editing & new screen features for CNC laser support including laser touch plate support - YouTube


Where did your Mach ATC setup come from? Is it the Mach 3 setup in the CNC Depot downloads?

I saw this repo but haven’t looked at the details yet:

FWIW, I bought a CNC Depot spindle, but it’s still in the box.

It is not a full ATC setup. You still need to customize your own M6 script and add all the safety logic. You can get the screenset from CNC Depot’s website. I am not sure if you need to be logged in.

Here is a screen shot for clarity……

I have this exact set up. Just go to edit screen. And you should be able to click on any bottom on the screen and drag it to where ever you want. Then just save and you are good to go.

That is a scary button!

Personally I will stick with the override switch on the solenoid.

The problem with the AvidCNC controll box is it precludes the use of a locking harness so you don’t accidentally drop a tool while the spindle is in use.

As someone who has witnessed the spindle drop a tool at 20,000 RPM, I will describe it as an “underwear changing event!”

What happened with me is I had forgot to turn off the flood coolant for the tool which is what that relay they tell you to use is configured as.

Anyway, I unplugged all of that! Never again!

In my system I put the drawbar controll in the tool carousel controller. So you have to be in the middle of a M6 to activate that solenoid. Much safer.

I’d like to understand your setup and ATC in general better, if you don’t mind the questions.

So if I understand correctly, you have a solenoid valve (like this one?) on the compressed air line, and you press a button on that valve, which means you don’t need a button on your Mach screenset?

My search for “cnc atc locking harness” didn’t turn anything up. What is a locking harness? Is it in hardware or software?

Is your tool carousel controller a set of functions in your Mach software setup or is it something else?

If they did the screen right, they would have disabled the release button while the spindle was on, and disabled the spindle while the ATC was unlocked. That probably isn’t perfect, but would eliminate some accidents.

#1 If you look at the picture of that solenoid you will notice a little blue button on it. That button is the release button. If you press it will will activate the solenoid.

#2 The locking harness is two wires, essentially running to the relay that is built into the VFD. You then program the VFD to open the circuit when on and close it when off. One wire runs to the port that activates the drawbar from the controller and the second wire connects to the trigger for the relay that opens the solenoid. Thus when the spindle is on, there cannot be an errant signal to open the drawbar.

Since the AvidCNC setup is somewhat different from others it wasn’t an option. I believe the relay may be in use or the port on the VFD was configured differently and in use. Dunno, and I noticed that Alex has removed the docs from the downloads.

#3 My “tool carousel controller” is a control box for the fully retracting 10 tool carousel I built.

Since all tool changers (carousels, magazines, chain drives, etc) are nothing more than additional axis to the CNC machine I had to build an external controller. The reason is the AvidCNC breakout is only 5 axis.

So like for my little 10 tool carousel that is fully retracting, complimentary dust hood and the tool length sensor, I have an additional 3 axis (1 for retraction and extension of the carousel, 1 to spin the carousel and 1 to retract and extend the tool length sensor). I also added 2 pressure sensors (one for system level pressure, one for drawbar pressure so I can lift and seat correctly as well as error out if the pressure doesn’t reach the require settings) that is absolutely a must have (which you will figure out the first time you forget to turn on your compressor). Then I have three pneumatic channels, one for the drawbar, one to open and close the dust hood (dust shoe) so it doesn’t interfere with the tool change and the second to blow off the top of the tool length sensor so chips don’t give you a bad reading. There are also 3 proximity sensors to home all three axis.

So just in that little example above you have more “things” than can fit in your AvidCNC box even if you had just the basic 3 axis setup.

So that is why I built an external controller for all of that. I also wrote the software to use the ModBus protocol making integration into Mach4 a snap (sort of, actually Mach4’s ModBus plugin is broken :crazy_face:).

If you do the math, you can’t have 10 tools lined up across the back of your machine, even if you are like me and have a PRO60120. And if you have static masts for the tool forks you have just reduced the size of the work area you paid all that money for.

Anyways, hope that helps.


Ha! Once you have witnessed a loose ISO30 tool holder with a 4 inch end mill spinning around your shop at 20,000 RPM you will have a whole new respect for what you are playing with.


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Ya, I’ve seen a 3" panel raising bit come out of a router table. Things get exciting in a hurry :slight_smile:

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Sorry this might be a little off topic but not by much. I to use the CNC Depot spindle but don’t use the the drawbar button in Mach 4 at all. I first installed a foot switch then last week I added what I think is a much better solution. A button right next to the spindle.


Since some tools are too long to fit in my carousel I have it set up so that any tool with a slot number of -1 will trigger the tool change to move to the side and wait for a manual load or unload. Right now I have an ugly switch but I will have something nice like yours when I get that part finalized.

What I wanted to do is have it so that the light will turn on in the button to signal that you can long press it to actuate the drawbar. It will be solid blue to signal it’s available but turns red on release and green for secured. In either the red or green state if it’s the wrong state for the operation (load or unload) it will flash and the machine will not allow you to hit the OK button to continue.

But I like your polish. Looks good.

My solution was easy and dead simple. Your design will do all the cool stuff I think we would all like to have in the end. I hope you’ll share your progress. I will have to print something else for the switch when I have a mill vise mounted. That will create a whole new set of problems as I wouldn’t be able to use a traditional spoilboard of MDF as I’ll need coolant when cutting metal.

I’m excited Avid has put up this site so we can help each other. I’m in the final stages of my install. Building a dust collection system that didn’t drive me out of my shop with it’s noise has taken me much longer than I expected.

Actually, keep the MDF but get a real Fog Buster because the micro-droplets are just better than the other brands. There is a reason JPL uses them exclusively.

Then get a Vortex cooler like this one:

The trick is the vortex cooler is pointed down from the spindle to cool the part and clear the chips but not exactly at the tool. Use the Fog Buster to lubricate the tool and not get everything wet. The droplets will evaporate very quickly leaving the lubrication on the tool.

I have a metal bracket that I drop the half gallon Fog Buster into on the back of the Z axis and use relay 1 to control it. Relay 2 then becomes the vortex cooler.

The key here is the vortex cooler blowing the chips and cooling the part keeps it from changing dimensions on you. The lubrication using micro-droplets really makes the tool last much longer and the finish much better.

One last thing about this setup! You will need a nice compressor that can keep that flow going to the vortex cooler!

Nice looking install though. I need to get a better setup for mine. If you think the vacuum system is noisy? Try a 4 motor flow through fixture! Ear protection required!

I think I’ll open a new threat as we’ve gotten a bit to far off topic.

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James put in a 2nd valve and wired it to the Spindle VFD.

I’ll be doing this - but I like @rwoerz switch near the spindle better than a foot pedal for a machine with a large table.

Actually you won’t if you have the AvidCNC controller and VFD. In fact the factory ( has removed those instructions from the AvidCNC setup.

You will find that the relay #1 is attached to the coolant in Mach4 so you will spin up and the drop your tool because you forgot to turn off coolant for that tool in your CAM.

It was an UCE… undewear changing event.

I completely removed all of that on my machine because I cut non-ferreous metals and need the coolant but also the interlock part doesn’t exist or is repurposed on the AvidCNC setup. I forget what the deal was but some time back somebody brought up the instructions had vanished from the web site.