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DIY 4th Axis with Brake

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PekkaNF:
Great work. Is that RoboDrill? How does that brake works? Is the rotating disc aluminium or which part is stationary, which rotary and which is actuated by the coil? Maybe I need to have another look.

mukanico:
Thanks. It's a Brother TC-215, or at least the mechanics of one (I have done a full retrofit in the past with a new controller, drives and servos...).

The aluminium disk is attached to the main shaft and rotates with it when the brake is disengaged (i.e. the coil is energised). The disk is sandwiched between a stationary aluminium housing and a steel pressure plate (that's attracted by the coil).

Here is a photo of the brake unit assembly where you can see the steel pressure plate and the 8 belleville spring stacks. The fingers in the middle of the assembly belong to the disk brake (this bolts on to the main shaft).


I hope this helps explaining it.

Cheers

RotarySMP:
Nice design and workmanship.
Mark

PekkaNF:
OK. Thank you. I get it now. The brake disc has high radial stiffness to spindle and the bell housing is fixed to main housing. The pressure plate doubles as a solenoid "plunger" and it does not need be indexed accurately into housing.

The construction looks very good and sound design.

philf:
Wow!

That's superb.

Much more substantial than mine!

My 4th axis also uses a Harmonic Drive but mine's 200:1 and is driven by an ordinary stepper so the speed is very slow. (The Harmonic Drive came out of a semiconductor silicon dicing saw which had been scrapped so was free = otherwise I'd have gone for 100:1 or 50:1.) I also use taper rollers in my design.

I've really only used mine for engraving so the cutting forces are low. Mine has a threaded nose to take Myford accessories so I do worry about damaging the Harmonic Drive when I'm tightening or undoing a chuck or faceplate. I have included slots for a c-spanner to oppose those forces but it's difficult to not try to turn the spanner when you're fitting or removing something.



Phil.

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