Some simple mods for my Tormach

[LENS_CAD]

I thought I would share a couple of mods I made for my mill.

I have heard about several cases of the spindle door opening because of vibration which causes the spindle to stop. The axes continue to travel, usually breaking the cutter. I replaced the plastic knob with a handle which hangs down. The shaft was also replaced. The handle doesn't even have to be tightened as long as the latch is engaged.

Another potential problem I noticed was the top of the spindle drawbar. There was only about a 1/32" wide shoulder for the drawbar to seat on the top of the spindle and repeated tightening was starting to flare it. I turned back a short length and made a steel washer to fill the space. The drawbar now tightens more smoothly and it should last indefinitly.

Regards,
Len <><

[BlueFin]

Cool stuff, that is the exact washer thing that I wanted to make for my machine, the drawbar is too long winded to begin with and I was afraid of messing things up by too much use as well. If you don't might sharing washer dimensions I'd like to work one up.

[zephyr9900]

I like your door handle, Len. It reminds me of a suicide shifter on a chopper.

But Len and BlueFin, you've got me wondering now about the drawbar washer. Mine has had one since it was new, and I don't remember making it myself. I thought it came with the machine, but now I'm not so sure...

Randy

[R.DesJardin]

These are both things I have been planning on doing i the near future. The motor guard thing bit me yesterday so I guess that will get my first attention. I thought from the get go that the collet rod needed something different.
I am going to have a high school kid coming by on Friday afternoons for some OJT and the handle is planned to be his first cad/cam machining projects.

I made a tool rack out of 1/8" plate with four holes in it that I have mounted at the right hand corner of the guard, it lets the coolant dip back into the machine and easy to reach, an added bonus is doesn't get chips and coolant sprayed on them.

[BlueFin]

Originally Posted by zephyr9900 I like your door handle, Len. It reminds me of a suicide shifter on a chopper. But Len and BlueFin, you've got me wondering now about the drawbar washer. Mine has had one since it was new, and I don't remember making it myself. I thought it came with the machine, but now I'm not so sure... Randy

Hmmm I wonder if we are missing a part, like I said without the washer the drawbar screws way too far into the collet, about an inch or more on mine. Probably stealing linear force on the collet due to so much thread surface area causing friction loss when you tighten it. And three of us thought of the same thing when we looked at the setup. Plus you would need something like this to support the springs we have been talking about for an ATC.

[LENS_CAD]

This is a drawing of the drawbar mod and washer I made. It seems like something that should have been included with the machine.

The drawbar was packed separately from the machine when it was shipped but I don't remember seeing a washer with it. Some photos in the manual show a washer in place though.

Len

[BobWarfield]

Interesting that opening the door stops the spindle but not the axes. They should all be tied together so one e-stop shuts them all off. Shouldn't be that hard to wire it that way.

Best,

BW

[zephyr9900]

I agree, Bob, that's an excellent suggestion but that's probably a whole new discussion. Ideally the Machine Control Board would have circuitry (Mariss Freimanis published two examples on the Mach site) to monitor Mach's charge pump, and when the spindle contactor dropped out it would also put Mach into feed hold. The unknown would be how soon Mach pauses the motion and whether that would happen within the spindown time of the spindle, especially the Series II with the braking resistor.

We can't just dis-enable the drives, because the z axis on all but recent machines will back-drive the ballscrew and still break the cutter.

OR, since Tormach is doing this for safey, have something like a kitchen cabinet baby latch that will catch the door if the main latch lets go, and a safety switch with enough travel to accomodate this. Obviously Tormach selected the curent cam-latch to minimize vibration of the spindle door, but companies like Southco have many latches that would secure the door and not be hard to open on purpose.

Randy

[BobWarfield]

FWIW, in my own machine, I have the E-stop circuit wired to a relay that directly cuts power to the servo (in the Tormach case stepper) DC supply and the spindle. This is a dead simple circuit that does not involve Mach so there is no possibility for confusion there. The charge pump feeds this circuit as well as the servo error/fault signals. One could also put limits on the same circuit.

The shut down of the axes is pretty darned instantaneous when the AC to the DC supply quits, as is the spindle.

Cheers,

BW

[zephyr9900]

Bob, in the Tormach the spindle contactor (C2) is downstream of the main contactor (C1) that estop drops out. To duplicate your scenario the belt guard switch would just drop out C1--and lose the workpiece anyway.

As I pointed out, machine motion wouldn't all stop due to the backdriving head issue. Recent machines have a failsafe brake on the z-axis stepper to prevent this, but many machines in the field don't.

For something as trivial as the head door drifting open, something as drastic as an estop is hardly warranted. IMHO. One little bit of integration between the spindle subsystem and the axis drive subsystem would alleviate this problem entirely and possibly save workpieces without people jumpering the safety switch and defeating the safety interlock (I haven't, but know of people who have...)

Randy

[zephyr9900]

I don't know what I was thinking last night, Bob! There isn't a need to do anything with the charge pump--that only lets the machine know that Mach is in control. What is needed, is when the spindle contactor drops out, to send a code 1001 (feed hold) back to Mach. Since the parallel port I/O lines are already fully used, this would require a second parallel port. But it is easily doable. Another project to add to the list...

BTW, on the Tormach hitting a limit switch does seem to interrupt the charge pump signal, because the "ref'd" LED's go red, and the "Machine OK" LED goes blinking red. That's a little more drastic than I would want to happen for a head door come ajar. The Tormach is set for pretty good accel/decel so I think a controlled stop might work (though I know that in some cases, depending on the vector being processed it doesn't alway decel immediately and that could be a problem).

The more I think about it, the more the pragmatist in me votes for a baby catch (or similar to an automobile hood safety catch) next to the camlock, and a long-stroke interlock switch. That way if the camlock comes un-cammed during a run, the run will continue without a hitch and the door will just rattle a little until the next toolchange...

Randy

[BlueFin]

Originally Posted by zephyr9900 The Tormach is set for pretty good accel/decel so I think a controlled stop might work (though I know that in some cases, depending on the vector being processed it doesn't alway decel immediately and that could be a problem). Randy

Unless I am mis-understanding you or something if the door should come open and the contactor drops then there is no decel (just a dead motor). The few times it happend to me I heard the spindle slowing down on it's own. This was a good thing because I was able to run over and hit the mushroom and sometimes save the tool/part because it kept cutting while I was running! Finding 0,0 on the XY again sucked, but if during a roughing pass you still got some real estate to work with.