Electric/Mechanical brake issues

[Brian Holcombe]

I've edited this down, no reason to get into the nitty gritty I suppose.

Has anyone had a problem with a mechanical brake on an electric motor and what was the recourse?

[Jim Becker]

I have not heard of this happening. Perhaps it was the unlucky bad bolt or as you note, something wrong with the brake. It sounds like the remedy proposed by SCM is pretty good...replacing the whole assembly.

[Brian Holcombe]

I'm understanding it's fairly rare, so I guess that puts my mind to ease to some degree. New motor arrives tomorrow according to DHL.

I suppose when I check the brake function on this new motor after I install it I will know whether or not it was a problem of the previous motor or not. My understanding in how these work is that when power is 'on' the brake is open, and when power is 'off' the brake shuts. There is an override, and the override switch was not opening the brake on the previous motor so maybe something internal to the brake caused issue.

[Jim Becker]

That makes sense to me! And I think you'll be back up and running real soon.

[Brian Holcombe]

Sounds good, I’ll update with the results once it works out (or doesn’t lol)

[Lisa Starr]

My old, long gone RAS had a brake that occasionally wouldn't unlock. The "fix" was a sharp rap on the end of the motor shaft. Sold the saw before it became problematic.

[Jerry Bruette]

We used to have some machining centers at work that had brakes on the motors. When the brakes failed it was usually because they were just plain old worn out.

Usually a part of the linkage would wear out, or a spring would break.

All we would do is replace the brake. I don't think repair parts were available.

We have a case packer at work that has brakes on some of the motors and they last way longer than the ones on the machining centers, but the case packer motors only turn in one direction.

The brakes operate with a coil that is energized when the motor is and it disengages the brake. Then when the motor is de energized so is the brake and a spring engages the brake. I think this is also a safety feature, so that incase of a power failure the brake is on. Most of the motor/brake units I've worked on have a manual way to disengage the brake.

[Brian Holcombe]

Thanks Jerry, appreciate your insights.

[Phillip Gregory]

I have one piece of woodworking equipment with an electromechanical brake, a 20" single phase disc sander with a heavy cast iron disc. It hasn't given me any issues, but the sander is still pretty new. Electromechanical brakes typically only give issues when the friction assembly wears out, and replacing the worn parts fixes the issues. I have pulled trailers with electromechanical brakes and they also work very well, and if they have problems, it's either a bad connection from the tow vehicle, a failed brake controller, a bad ground, or worn out brake shoes. These failure modes should be identical to the similar setups in woodworking equipment.

I personally prefer purely electrical braking on woodworking equipment (injection braking) as there is nothing to wear out and with a good VFD with a braking resistor, it works very well. Electromechanical braking however is more effective as it stops the load notably more rapidly but you do need to service the parts when they wear out, and they will wear out.

[Brian Holcombe]

Thanks Phillip, It's starting to look like the brake did not fail at all (aside from the bolt busting) but instead something else caused the brake to close while the machine was running.

The new motor is in, I turn the override and it opens the brake but the motor does not turn under power. I assume it is attempting to because I did not hear the brake open but I did hear much electrical noise such that I assume the motor is attempting to work.

I'm pulling my hair out at this point, there is a gremlin left to chase.

My current solution is to pour a glass of Hibiki and see if that works.

[Phillip Gregory]

There could be a few things going on. I suspect the part you deleted may have had some additional information.

1. Did you power up the new motor by itself without the brake attached? If you did not, try to do so. Knowing that the motor starts and runs normally by itself rules out a lot of potential causes of the motor not running with the brake attached.
2. Does the motor shaft turn freely with the brake energized (released)? If not, the brake may be out of adjustment or broken. You mention a "bolt busting" so this is certainly possible.
3. If the motor starts and runs properly by itself, the motor shaft spins freely with the brake manually released, but the thing still won't start and run with everything all hooked up, then the brake regulator or relay may be bad.
4. If the Hibiki doesn't work, try Knob Creek 120 proof.

[Brian Holcombe]

Thanks Phillip, appreciate the insights.

The original issue is that the motor somehow damaged itself in normal use. I suspect the brake attempted to apply itself while operating under power. The result was that I discovered a broken bolt and washer in the fan housing which led to the discovery of a non-functional brake. I attempted to override at the time and the brake would not open. Recourse from the manufacturer was to send a new motor and then if it didn’t function we would further investigate. Unfortunately these things seem to happen on Friday afternoon so I get one call into tech before I need to hang it up and ponder for days.

I will try to power up the motor without the brake and see if it functions. The wiring bulk head (?) was identical in layout and the wire colors at each terminal were also identical from motor to motor. So in speaking with the tech he recommended swap wire for wire identical to the previous setup. I did that.

The brake does function manually when using the override switch, and when the brake is open the motor spins freely by hand. The brake is within the three specs provided (the spec listed on the first motor is different from that of the second which are both different from the owners manual...,haha!) I’m defaulting to the second motor being correct since it is newer and the air gap is about .005” larger than the ideal gap listed on the second motor but still smaller than that listed in the owners manual. Also, it functions so I’m leaving it as factory set at the moment.

Start the machine, electrical noise is heard but the ‘clunk’ of the brake opening is not. I plan to remove the fan housing again and visually inspect along with double checking the motor.

[Jim Becker]

Make sure you've accounted for all the safety micro-switches when you are testing things...it only takes one to keep things from working.

[Brian Holcombe]

Haha, funny you should mention that Either I was seeing things that weren't or something but I went over everything with a fine tooth comb today and it fired up and ran. I checked with the fan housing off and I could verify the gap each time.

I'm going to chalk this up to working too late into the evening, but I'm relieved to say the least.

Oddly enough the machine is considerably quieter with this new motor, so maybe what I had thought to be a loud machine was actually the previous motor having issues.