help locating supplier for motor brushes

[bherr]

Have a Bridgeport Series II Interact 4 that has been giving me fits with the spindle motor shutting down. finally started searching for the motor brushes which a forum member suggested checking. Found them, one was completely gone, so I need to find some brushes.

The motor has the following info on it:
Hubner Elektromaschinen AG Berlin
Typ: GT 9.06/420F
Nr. 467082
20v 3ma 1000 1/min. max 8000 1/min.
I've attached a photos of the brush housing. I can't seem to remove the spring loaded retainer that holds the brushed in place. do I need to remove this retainer to install the new brushed? Also I'm assuming this brushed don't use a spring to keep tension on the brushed, since there were no springs. I can't find a part number, because the brushes are completely gone. Can anyone provide these?

Anyone know were I can order these??? PLEASE & THANK YOU.
Ben

[Al_The_Man]

The brushes are usually held in place by a coil spring that pushes against the top of the brush, this is lifted up to insert the new brush?
If you have a problem finding originals, try Helwig Carbon, either for replacements or something you can use in place of.
In a real pinch, ones that are close can be shaved or sanded down to the required size, care must be taken however to avoid movement or slop in the brush holder.
That appears to be a extraordinary long commutator to have only one brush set, especially for a spindle motor, I would have expected to see two brushes, side-by-side.
Al.

[bherr]

there is another brush a little further to the right of the one in the picture..
The brushes didn't have any springs attached. the metal clip you can see, which is out of the brush holder is held in place by a tension clip located on the back side.
Ben

[UKRobotics]

I know a place in the UK which will sell you a set for about $300 if you cant find anywhere locally.

Looking at that photo now might be a good time to take it out and get it profesionally serviced.

Get the housing stripped down, carbon dust cleaned out, bearings replaced, new brushes in the motor + taco and get the comm skimmed and undercut.

It wont be a cheap service but it could save you a lot of money in the long run.

[bherr]

Originally Posted by UKRobotics I know a place in the UK which will sell you a set for about $300 if you cant find anywhere locally. Looking at that photo now might be a good time to take it out and get it profesionally serviced. Get the housing stripped down, carbon dust cleaned out, bearings replaced, new brushes in the motor + taco and get the comm skimmed and undercut. It wont be a cheap service but it could save you a lot of money in the long run.

I think I try and find them locally. What is taco and comm skimmed and undercut mean. Never heard those terms before, although I'm not a machinists by trade. Motor is quiet as a mouse, so I think the bearings are good.

Ben

[bherr]

Originally Posted by UKRobotics I know a place in the UK which will sell you a set for about $300 if you cant find anywhere locally. Looking at that photo now might be a good time to take it out and get it profesionally serviced. Get the housing stripped down, carbon dust cleaned out, bearings replaced, new brushes in the motor + taco and get the comm skimmed and undercut. It wont be a cheap service but it could save you a lot of money in the long run.

UK,
I need to slide the DC spindle motor out and because I don't have a manual I'm not exactly sure how to do that. It looks like I can take the four large allen head bolts that are in the slots out, then unthread the adjustment bolt at the rear of the motor for fine adjustment of the belt tension. then I assume I have to remove the top part of the motor ( located just above the belt)to remove the belt and then the motor will slide out to the rear on the rails. Is this the proper procedure?

I ordered brushes, but they were the ones for the tachometer on the bottom of the motor. Got a company searching for the correct ones now.
Ben

[UKRobotics]

You have the right idea but it should be possible to take off the belt and remove the motor without removing the top part of the motor.

[bherr]

UK,
Here's some photos of the top part of the motor. As you can see there's no way to get the belt up and over the top without removing this top round black thing, whatever it is.

[Al_The_Man]

If the brushes are completely gone, there is bound to be a build up of carbon dust, apart from the problems of worn brushes down to the wire, the carbon can cause ground faults to occur.
If you have enough brush to mic. the width/length (the OA height you will have to guess), Have you checked the Helwig carbon site?
They list some Hubners amongst their products, you could compare the measurement with those, if you do not have enough brush to measure, mic the slot dimensions, you may be able to match it up to some of their other metric brushes.
Al.

[HelicopterJohn]

Hi Ben,

If you can take one of the brushes off of the motor as a sample you might want to take it to a local electric motor repair shop. Just get all the appropriate information from the motor name plate. I needed some brushes for one of the servo motors on one of my CNC mills and found the locally.

If you end up removing the motor I would take it along to the electric motor repair shop. They may be able to better tell the correct length of the brushes and answer any questions you may have on how tension is applied to the brushes for proper operation.

As others have stated the comm did not look very good and may need servicing. You could try the brushes first and if it gives you any further trouble you always remove the motor again to get it rebuilt. Just have to evaluate how much your time is worth removing and re-installing the motor.

Just something you might want to consider.

John

[UKRobotics]

Some definitions and terms:

The tacho is the round lump on the bottom end of the motor. It is effectivly a rotary encoder which allows the control to see how fast the motor is spinning so it can adjust the voltage/current accordingly.

It uses a system of closed loop control where there is a continious negative feedback loop to ensure the motor is maintaining the predefined speed. For example if you start cutting through thick steel this could slow down the motor a bit. Provided it has the power available, using the signal from the taco as a reference it will be able to boost the power to the motor accordingly.

The comm/commutator is the copper part of the armature which the bushes contact with. While the brushes wear down over time, the comm wears down also. The comm is split into many different sections with an insulating epoxy resin between each one.

Undercutting is the proces of using a lathe to put a groove into the epoxy so it is not level with the copper. This is because the resin is a lot more abrasive than the copper and if the copper wears down as far as the epoxy your brushes will be destroyed very rapidly.

Skimming is based around the same area but levels out the entire comm, removing the deep grove worn into it by the brushes. Putting new brushes onto a heaviy worn comm will reduce their lifespan, especially if the new brushes are a slightly different shape/size.

Considering the motor has to be totally stripped to perform those tasks it makes sense to go for a bearing replacement and get the carbon dust cleaned out at the same time.

You are right about removing the round black thing on the top. I thought you were refering to the yellow casting beneath it. The item in question is actually the spindle brake. An electromagnetic brake which prevents the spindle from moving during tool changes etc. It operates from a 24vdc supply which is connected when ever the spindle is turning.

If you plan to remove the motor entirely please be careful as it is stupdily heavy. (about 200lbs!) We had to use a merlo (tractor/forkflit) to remove the motor in my machine. Bear in mind if you drop it you will be looking at over $4000 for a replacement which is probably more than you paid for the machine itself.

How are you powering this machine? Do you have 3 phase in your workshop or are you running it through a phase convertor?

[gridley51]

The motor info given in the first post is actually for the tacho and not the motor.