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Old 12-25-2011, 07:59 PM   #1
Sshire
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Default Dead mill

So there I was. Milling another part for Elmer's Grasshopper and the BF20 mill started, stopped, started, stopped.
That's it. Stopped. Fuse fine. Unplugged and replugged every connector in the control box. Used my patented, "smack the part with my hand" technique. Nothing. The RPM indicator is lit and shows 0 RPM. Motor not turning.
I'll call PrecisionMatthews in the morning. Unless someone has an idea, I'll start on part I can make on the lathe.
At least I can look at my new Bison 5C Set Tru chuck until its faceplate arrives
Bummer

Stan


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Old 12-25-2011, 08:09 PM   #2
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Default Re: Dead mill

Have a look at teh brushes

J


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Old 12-25-2011, 09:07 PM   #3
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Default Re: Dead mill

I would start troubleshooting with a multimeter see where the power is not getting through could be the motor could be the power supply/ Pusle width modulator. sounds like you ruled out a loose connection could be something as simple as a broken wire or bad connector. IIRC that is under warranty so would not go any further than part level troubleshooting. Sometimes something simple.
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Old 12-26-2011, 01:35 PM   #4
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Default Re: Dead mill

IT'S ALIVE!!!
Jasonb gets the prize. Thank you, thank you.
I pulled the motor cover and was going take Tin's suggestion to get out the multimeter and start checking voltages, etc. when I remembered Jason's post. Took out brush #1. Slipped out very smoothly and was clean and shiny. Brush #2 was stuck. VERY gentle pulling and wiggling followed. Finally popped loose. The brush was very dull looking. 600 grit around a 0.25 dowel and got it clean and shiny. Replaced brush. Fingers crossed. IT WORKED!!! Christmas miracle.
Thanks for all the suggestions. Having a very limited knowledge of motors, can someone explain what caused one brush to get stuck and dull looking? Is it something I did?
Anyway, we now return you to your regularly scheduled milling.
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Stan
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Old 12-27-2011, 07:35 AM   #5
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Default Re: Dead mill

Can't tell you why apart maybe from poor fit to start with. Had a similar problem with my lathe where one brush had worn more than teh other, got hot and softened the spring.

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Old 12-27-2011, 08:04 AM   #6
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Default Re: Dead mill

Looking at the r/h brush I think it would be worthwhile ordering a new set

Bob
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Old 12-27-2011, 08:33 AM   #7
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Default Re: Dead mill

I did better than that, ordered a new set and another as a spare you know that if they fail again it will be just at the wrong time.

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Old 12-27-2011, 11:55 AM   #8
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Default Re: Dead mill

Quote:
Originally Posted by Sshire
can someone explain what caused one brush to get stuck and dull looking? Is it something I did?
Almost certainly nothing that you did - sometimes a small fragment chips off and wedges the brush - other times its simply build up of dust - they can also get stuck fom overheating - particularly if they were a tight fit in the first place.

Always a good idea to pull them out once a year and give the motor a blow out with compressed air - put the brushes back the exact same way they came out.

Inspect the trailing edges of the brushes and the com for signs of arcing, brush bounce etc - if the com looks a mess - it might be in need of a skim.

Ken
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Old 12-27-2011, 04:19 PM   #9
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Default Re: Dead mill

I had that same problem with the starter motor on my scoot. I opened up the starter and found the brush slot had never been deburred. The brush had hung up in the slot. A new starter would have cost over $100. I cleaned up the slot with some jewellers files, reassembled the starter, and put it back on the scoot. It spun the engine over faster than it ever had before.


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