5,5kW ATC spindle problem, tool release

[Daniel Araya]

Hi,

A quick update!
I decided to take it apart and as soon as I did it was obvious what had happened. Someone changed tool with the spindle moving at some point and the return springs for the cylinder got crooked. After enough cycles some of them broke and got stuck so that the cylinder couldn't move past a certain point, I guess the last one that made it impossible to change tool just lodged itself in there the other day!

I'm going to get new springs and try to put it all back together! I had to desolder a few wires but it was not especially hard.

[Brian Lamb]

Looks like there should be some sort of pin or keyway to hold the piece from rotating. That is probably what broke the springs, upper and lower spring pockets got out of line with each other and destroyed everything.

[Daniel Araya]

Looks like there should be some sort of pin or keyway to hold the piece from rotating. That is probably what broke the springs, upper and lower spring pockets got out of line with each other and destroyed everything.

As far as I could see there is no keyway. The center brass insert in the push rod is spring loaded, that might protect it somewhat but it looks very sensitive to damage if the thing is run with pressure applied to the cylinder! You can see the heat damage to the rod, it turned blue from the friction!

[Brian Lamb]

There should be a limit switch that prevents the motor from coming on with the cylinder depressed. That would mean the tool is loose, you wouldn't ever want the spindle turning in that case.

[Daniel Araya]

There should be a limit switch that prevents the motor from coming on with the cylinder depressed. That would mean the tool is loose, you wouldn't ever want the spindle turning in that case.

The limit switches were not connected and the release function was manually actuated with a valve. And a note saying "do not change tool with the spindle spinning"...

Well, I ordered some new springs and will be taking some photos to help other people in the future if this happens. And I got a much better understanding of how this thing works now, it doesn't feel so intimidating to fix anymore.

[Brian Lamb]

I see, well it would be wise to wire up the limit switch as it should have been to prevent something like this. Good that you figured it out and can get the parts to repair it.

[bobby milam]

Good to see you are getting comfortable with it and hopefully your repairs solve all of your problems.

[Daniel Araya]

Good to see you are getting comfortable with it and hopefully your repairs solve all of your problems.

Thank you for all the encouragement and advice!

[Wes Grass]

In normal operation, no part of the drawbar should be in contact with the rotating spindle. In some cases, without a toolholder in place, the drawbar can come up far enough to make contact. So running the spindle without a toolholder in it can burn things up.

It's also possible one of the springs failed from fatigue, and got things twisted out of alignment, causing a cascade failure of the rest. But, yeah, the interlock should be hooked up if possible. If nothing else, it might prevent a tool from being ejected from the spindle at high RPM. I know someone who had this happen on a VMC with a 40 taper holder bouncing around in the enclosure. Major eye widener.

[Daniel Araya]

Here is an update!
At first I managed to order the wrong type of springs, I did not realize that there was a parameter called "median diameter" that was different from "outside diameter" in the spring world so I had to reorder.
But then it was quite straight forward, I cleaned everything, put the new springs in and made a mark so I could align the holes in the cylinder and the piston and screwed it all together!
I had to turn the pressure up a bar because the springs was a bit stiffer I think and after a couple of cycles it grabbed and released the tool fine!
I will see how it holds up of course but now I know how it works and that it contained no magical parts! No water or air leaks either!

I wired up the sensors also but the current control system doesn't allow for expansion so either I will use a small PLC that I have laying around or take the plunge and go for Pokeys and Mach4 to make it safe.

springs.jpg

Thank you for all your help!

[Brian Lamb]

Glad you got it working. I don't know anything about Mach 4, my experiences with Mach 3 are enough to prevent going down that road. You might want to check out Centroid Acorn, I'm running one of their All in One DC Servos systems on my CNC mill and really like it.

[David Buchhauser]

I don't know anything much about Mach4, but I am running Mach3 on one of my Avid cnc routers and Centroid Acorn on the other Avid machine. I have not personally had any problems with Mach3 for the limited amount of cnc wood routing that I do. I like Mach3 and enjoy using it, but upgraded from Mach3 to Centroid Acorn on my newest machine.
David