Hurco KMB-IS CNC update

Unfortunately, the hour meter is sorta there but all broken up and unreadable.

I've considered opening up the motor to look at the armature. But... based on Youtube videos, they say opening the motor is tricky business and you'll probably end up destroy the motor without the benefit of special tools and knowledge.

At this point the motor is useless so opening it up is an option. Can you offer any advice before I try this?

Good feedback on the brush condition. I really don't know what they are supposed to look like. Apparently the copper streaking is not a good sign. Perhaps those copper streaks are shorting armature segments together and causing the overcurrent.

I think the next step is to carefully take fine sandpaper to the brushes and get the copper off. Pretty low risk.

If that doesn't work (and maybe even if it does) take the motor apart and look at/clean up the armature.

I have come into possession of some scrap electro craft motors. They are generally smaller than the ones in the Hurco. I'm thinking about practicing disassembly procedures on them. I can find out what I'm up against.

The E-Stop doesn't work yet.

However, power to the machine is coming from a plug strip. This plug strip has a switch. This switch is serving as the E-Stop.

The quill looks to be reasonably lubricated. I've cleaned up the Y axis and its not dry. I'll put a little oil on it.

The X axis is completely covered by the table. The ways are not obviously visible. I'll try to see if I can look up inside and get some oil on the ways.

We've ordered some parts for the oiler, but they are not here yet.

_big_ wrote: Unfortunately, the hour meter is sorta there but all broken up and unreadable.

That is a downer as you could get a idea of how wore out it is...

_big_ wrote: At this point the motor is useless so opening it up is an option. Can you offer any advice before I try this?

Good feedback on the brush condition. I really don't know what they are supposed to look like. Apparently the copper streaking is not a good sign. Perhaps those copper streaks are shorting armature segments together and causing the overcurrent.

I think the next step is to carefully take fine sandpaper to the brushes and get the copper off. Pretty low risk.

I haven't taken one apart, so I can't say how it will be. I would definitely try cleaning the brushes gently, blow out the holes and then re-try the motor. But yes the smaller motors are what I would experiment with on taking apart.

Yes, like you are saying I also believe the copper on the brush is shorting between the copper lines. Just odd that the brush looks the way it does as I have never seen one have such defined lines on the brush like that. Usually just has some of the copper marred into the brush, but that one looks almost like it fused the copper on in perfect lines... just strange how it looks.

But yes, I would clean with sandpaper and blow everything out and try it before taking apart. With the thought that you may not get it back together without some type of special tool would push me down the path of trying all that I could before disassembly.


Sorry, wish I knew what you were up against on taking apart

Robert

Leith,

Ok I have been thinking about what you stated with needing special tools for disassembly. I can't think of anything other than the brushes that would be a issue for taking apart or re-assembly... and you would pull the brushes before taking apart. Not sure what would be needed for these. I can understand a different type of motor where you would need to stick a awl into the end and "pull" the brushes off the commutator to get it apart... similar to how a 1980's style GM alternator has the holes in the back where you put a awl in and hold the brushes off for re-assembly, then pull the awl the brushes pop down onto the commutator. Just not sure what is needed for special tools. I can see if it had a built in encoder and needed something special to get it apart, but for these old type brush motors just not sure what would be the issue other than the brushes which once again would be taken out

The encoder is on the outside of the motor and it is not a absolute encoder, so it is not critical to get the encoder back into a exact position. If it was an absolute, then the encoder would have to be timed to the keyed motor shaft so that when you put the motor back into the machine it would be exactly where it was taken out at. Incremental encoders are not the same and it is not a issue, so I have a feeling the videos you watched are probably talking about the encoder being the big issue, but this is all my speculation.

I can't say how the tach would be built, but once again those brushes would be removed also. That is the only thing that may need something special, but just can't think of what would be needed other than maybe a awl to get into a spot and push something out of the way. Definitely curious, as this is going to be a problem for me one day also.

Need someone to chime in that has done Electro-Craft motors. Maybe Tom can shed some light if he has come across one. I will try to do some research later and see what I can find.


Robert

OK. Took a closer look at the brushes. One in particular was pretty whacky.

There's sort of a plastic/metal carrier that aligns the brush to the armature. This carrier was actually rotated about 90 degrees from where it should be. Pretty bad sign. Not sure why I didn't notice this the first time through.

I managed to re-align the carrier close to where it should be. I also found a hole saw about same diameter as the armature and used that with some sandpaper to try and put the right shape on the brush.

Put it back together, but no difference. I thought it might at least see a little improvement.

This all begs the question about how the brush got turned 90 degrees in the first place? This 90 degree twist had to be the result of some previous trauma to the armature/brush.