Anatomy of a Cut Motor 101

[Digitalwoodshop]

Today we are going to explore the Compucarve Cut Motor Model Number MWM A2 011 in your Illustrated Parts Break Down. Pay very close attention as there will be a TEST after we are through.

Yes, you have a Question?

Student: But "WHY"?

SON.... Because we CAN....


The Cut motor will come apart by removing the 6 Philip's screws including the one in the exhaust port after removing the brushes.

You will notice this motor uses Metric Bearings, a NSK 629V

9 mm d or bore
26 mm D
8 mm B1
Cr 4550
Cor 1970

Notice the bearings are sealed from dust on both sides.

The bearings on both ends are the same.

Note the position of the Magnet on the end of the shaft where the flex plugs in. It is held in place with what looks like glue and heat shrink heavier than I have ever seen.

Yes.... A Question?

Will the magnet throw the balance of the rotor off?

Yes, but since it's center of rotation is so close to the center it would be minimal.

See the picture that shows the grinding of the armature for balance. Note it is in the same plane as the magnet. A note should be made of the magnet position relative to the grinding marks as it looks like the armature could have been balanced AFTER the magnet was installed.

Note that you must remove the magnet to replace the bearings. A proper bearing puller should be used to remove the bearings as to not damage the shaft.

For re installation of the bearing use that hair drier you use to heat the quick release chuck. This will expand the bearing due to the heat and carefully slip the bearing over the cold thinner shaft.

Some hints about bearings that will come in handy on the TEST....

Ball bearings are very precise mechanisms that, in many cases, have geometrical tolerances measured in millionths of an inch. When handling, inspecting or mounting bearings, one should treat them as precision instruments. The user's poor handling techniques cause most bearing failures.

Foreign particulate matter entering a bearing shortens its life, and provides one or all of the following unsatisfactory operating conditions:

Increased Noise
Increased Friction
Increased Heat
Lessened Lubricant Life
Ball Skidding
And our favorite the CCM.....

Keeping the external surfaces and contiguous components (i.e., shafts and housings) contamination-free is also important. Contamination on bearing faces or mating shoulder of the housings or shafts will cause a bearing pair to be out of parallel. This will cause the balls to run in a non-circumferential plane within the raceways, causing ball speed variations, ball skidding and binding between the races. These phenomena increase friction, which produces heat. Heat causes the lubrication to oxidize, resulting in premature bearing failure. Follow these rules when handling bearings to eliminate contaminates and damage when working with bearings:

Bearings should never be handled with bare hands. Talc-free finger cots or talc-free surgical gloves should be worn.

Work areas must be clean, clean, clean (no food or smoking should be allowed).

Bearings should be kept in their original packaging until the moment that they are ready to be installed.

Do not clean housings and shafts with shop rags or cotton swabs, as these items usually will contribute to contamination. Clean Room wipes or swabs should be used.

The use of laminar flow workstations is strongly recommended.

Bearing work tools must be kept clean and burr free.

Bearings must be kept clear of any source of magnetism.

Bearings should be kept in a dry environment, as they are susceptible to corrosion. Moisture and acid from ones hands can cause a bearing to corrode.

Bearing mounting tools should assure that the bearings are mounted squarely on the shaft and into the housing.

Bearings should never be subjected to shock or impact load. Normally, a bearing will become Brinelled (dents in the raceways) if dropped from the workstation to the floor, or hammered into place.

When press fitting a bearing, force should be applied only to the ring that is being fitted. For example, if press fitting a bearing onto a shaft, force should be applied to the face of the inner ring only.

And MOST importantly...... Under no circumstances should the force be applied in a manner such that it is transmitted from one bearing ring to the other through the balls. Another way of saying NO HAMMERS.

That's all the time we have for today, the TEST will be next week.

Speaking of Next Week, we will dissect a Faulty Cut Motor with the CCM problem after 300 hours. Bring a sharp pencil.

AL


Written like I would do a Lesson Plan when I was a Navy Electronics Instructor....

[Digitalwoodshop]

More Pictures

[Digitalwoodshop]

More Pictures

[rpringle]

Al,

Are trying to tell us that you took your motor to far apart when you replaced the brushs?

Or that the brushs were only part of the 290hr problem?

I have an idea that after all your warnings that most of us will just order a new motor.

Russ

[Greybeard]

Hi Al.
Good one - but I think you may be giving yourself a job for life :)
It will certainly give more confidence for those who are prepared to follow your lead, and deter those who feel a bit wobbly about tackling it, as Russ suggests.
Win, win, I think.
Regards
John

[Digitalwoodshop]

Sitting hear painting signs last night about midnight hearing the carver still going in the wood shop through the intercom. My nearest Neighbor is almost a mile away and a wood worker, plus with the door closed you can't hear it.

I kept thinking about the motor. The one I took apart is the motor I got from a fellow Carver that has a open winding. I stoled the brushes from this motor.

I just pulled the 348 hour motor out to take apart.

Look for pictures soon.

AL

[liquidguitars]

CW is sending me a new cut motor this week, any way of fixing the old one? its got a about 12 hrs on it. "CCM"

LG

[Digitalwoodshop]

Here is the Readers Digest Version... It's FIXED !!!!!! The (MY) CCM problem.

It was the Magnet, it had popped off when I was moving the motor around with the flex cable still attached. Grease GUNK at the end of the flex cable housing must have gotten moved around and when the motor started the heat and friction must have caused the shrink holding the magnet to give way. Found the magnet in a fling pocket designed to hold junk that makes its way through the flex cable like over lubrication. The face of the flex housing and the armature do not touch but it is close. When that gap fills the friction starts working on the heat shrink.

Stand by for pictures. It now takes 3 seconds to spin up for a bit change and NO CCM.... Tried 3 times before writing this.

AL

[Digitalwoodshop]

I start every class out with a quick joke so here it goes..... Looking at all the pictures I have posted, I guess it is kinda good that my Ex Wife and I never had any Children....... :)

I believe I have solved the CCM problem, at least for me. Feedback will tell otherwise.

Opened the old cut motor and found it to be in very good shape for about 400 hours. The Commutator only had a slight groove and it is a QUALITY PART with what I would guess to be another 3000 hours of life in it. Time will tell. The bearings turned out to be a name brand dispelling all the roomers I had heard about stuff from China. In this case the LHR Designers and QA is supplying us with a QUALITY MOTOR. I don't see a single improvement needed.

I was relieved to see the Magnet missing from the end of the Armature. That answered the question of what was causing the CCM problem for ME.

As the pictures show it was found in the Fling Pocket designed to catch grease and junk thrown off by the armature. Mainly EXCESS Lubrication.

I am putting the removal of the Flex Shaft on a 50 hour maintenance schedule to remove and clean the end. I believe I caused this problem with the CCM when I pulled the cut motor out and left the flex shaft attached. I spun the shaft in the holder getting access to the bottom brush and must have moved the junk around. Forcing it in and around the magnet. I didn't get the CCM until the second project after replacement of the brushes. Next time I will remove the Flex, it's only one screw.

So if your unit has the CCM error or spins up more than 3 seconds for a bit change then I would remove the Flex and L@@K inside the end and see if your magnet is still there. Bet it's gone.

With the CCM problem Bit Change Spin up took 7 seconds and ended up SCREAMING at full speed. After the fix, spin up took 3 seconds and about half speed.

I did not see any glue in the magnet so I did not use any. I used some electrical Heat Shrink I have a pile of. Anyone attempting this repair and can't find any heat shrink, drop me a email and I will send you 2 inches of shrink in a first class envelope. Donations can be made to papal digitalwoodshop@aol.com Snicker Snicker.... Save $77.00 when they are out of warranty.

Just finished the first 50 min project with CCM Fix. Started fine but the upper left Z Truck bearing is loose... Need to get to the back of the bearing... I think the top pin pulls out.... I guess I will find out.... And so shall you in pictures.... I shut it down for now.

The hair dryer was just not hot enough, I ended up going to the house and using the gas range to heat the heat shrink.

Well, enjoy the pictures.

Class Dismissed.

AL

[Digitalwoodshop]

Playing Peek a BOO with the magnet..... I SEE YOU....

[Digitalwoodshop]

You must type something in this block to post pictures.....

[Jeff_Birt]

Al,

You don't need to pull the Z-truck to adjust the bearings. You need a thin 14mm(?) open end wrench to fit over the hex head of the axle. Hold the Phillips head screw in place with a screwdriver and get it loose enough to back the screw out and apply a drop of lock-tite. Tighten the screw with the screwdriver until it becomes snug, then hold the screw in place with the screwdriver and finish tightening with the wrench. Holding the screw and don't the final tightening with the wrench prevents the screw head from being stripped. The right side is basically the same, except the bearing are on eccentric axles. You adjust the eccentric to remove play in the Z-truck.

[Digitalwoodshop]

Used 2 layers of Shrink, one at a time. Next time I do it I will cut back the shrink a 1/16 of an inch from the end. This will give the junk less of an area to grab.

AL

Remember if you need shrink tube let me know and I will send you some in a first class envelope.

[Digitalwoodshop]

In the last picture I post a picture of the HALL Effect Transistor used by the computer to count pulses as to how fast your motor is going.

In this web page http://www.simplemotor.com/hemotor.htm It gives a write up on how a Hall Effect Sensor works. I put the magnet in both ways as the shaft is ferris metal and it stuck. As per the web page only the south pole triggered the sensor, so why I put that in is that I did not try it but it might only work correctly if the South pole is out. Only doing the shrink twice will answer the question..... So if it does not work change the magnet.

Hope you enjoyed the pictures. Left a message for Chris to call me as I had a SCREW LOOSE..... as in the upper left Z Bearing.... Need to get to the back of the bearing to the nut.

Remember, want to turn the used parts into cash, let me know.... I would like some bad motors and sensors.

AL

[Digitalwoodshop]

Let me try that.

AL

[Digitalwoodshop]

Jeff, wish it was that bearing....

It's this one....

AL

Just had a thought looking at the last picture. Do the hardened rails slip out the bottom freeing the Z assembly?

Edit: I was looking in the wrong place, picture 2 is my fault, wrong.... Not Jeff's area he mentioned. The right side of the Z is what he said... My fault

AL

[Jeff_Birt]

Al,

The right side bearings can be loosened as I mentioned. The 14mm hex head is on the 'inside' (or housing side) of the bearing, so you need a skinny, bicycle style wrench. I do not remember how the axle is held on the left side. To removed the head, you loosen the right bearing, the rails will fall out (as you guessed), you have to unplug the little ribbon cable, loosen the tensioner for the drive belt, and get the timing belt off the Z-motor drive pulley.

[Digitalwoodshop]

Jeff, I looked in the WRONG place... Talked to Hope on the phone and finally saw the eccentric nuts on the right side. Ended up damaging the left bearing trying to tighten it so I ordered 8 bearings and 8 screws. Replace the Y and Z.

If this were the 60's TV show Lost in Space the Robot would be flailing it's hands and saying "Warning young Will Robinson.... DANGER.... "... Too late.

I have all the carving done for the show... Wasted most of today playing technician when I should have been working.... I fixed the bearing but it is still damaged so I will just wait for the replacement....

I will post the repair.

Turned out for some reason the upper left screw became loose and in the end the ONLY way to tighten it was to strip it down to this point. I had a 14 mm flat wrench from something in the last 30 years of collecting tools and the special screw driver for the hollow nuts.... Had one of them too.... Used on Navy Switchboards for lug screws...

The 14 mm wrench came with my HVLP sprayer to remove the guts of the gun.... Just an idea if you need one.

AL

[Digitalwoodshop]

At about 50 hours my CCM started again. A quick check of sensors found only a "0" for the Cut Sensor while rotating it. My magnet had let go again.

Had a new Cut motor and a L@@K in the end saw a thicker magnet retainer. This peeked my in interest so off goes the cover and out comes the camera... New IMPROVED design.... Good Job LHR !!!! That ends the CCM problem for me. The thicker design helps keep the oil junk from getting inside the motor area.

Good Job LHR !!!!

AL

[Jeff_Birt]

So is it a collar with an internal slot that slips over the armature shaft (holding the magnet in place)? Seems like it could be a good field upgrade.

[rjustice]

I would venture a guess that the material of the shrink tubing isnt impervious to petroleum products (grease)... and it ends up softening the tubing which alows it to split under the cintrifugal force of the magnet.

AL, can you confirm whether the shaft size and magnet size are the same or whether they changed them?...

Ron

[Digitalwoodshop]

Shaft size looked like the 9 mm with a 10 mm lip to keep the bearing in place. Can't see the magnet. Almost looks like it was hot molded then machined down to a size slightly smaller than the hole area from the rubber shaft.

The cut motor sensor was missing and the screw hole was stripped out but I made it work.

Cut for 4 hours tonight with no problems.

AL

I wonder if JB Weld would work to hold the magnet?

[Digitalwoodshop]

DEGA L@@K Here to find your answer....

AL

[newcarver]

I tore into mine to see if it was fixable by me, no go. the magnet was intact, there was a lump of stuff on the hall efecct transistor. After cleaning it all up and reassmbling it. It ran for around 2 min, then quit, hit enter for the ccm error and the machine starts moving but without the motor. Did this 3 times the last time it slowly stopped, winding down in rpm's then quit. The magnets were worn about half way from your pics i saw. The ups guy was here to pick it up, I was never told by the lhr guy to even get it ready for return. I will send it ack on monday(his 3rd attempt), I have little knowledge of motor repair.

[Digitalwoodshop]

Bump......

[yatrgatr]

did i see a posting or pdf on the removal of the cut motor? can someone point me in the right direction?

[hotpop]

yatrgatr

There are only three screws holding the cut motor in place and one screw holding the flex shaft in place. There is a small plastic like box hiding the two motor power supply wires. There a small metal bracket attached to the "Y" rail that is held in place with one screw. Remove the bracket and the plastic to expose the power supply wires. Unplug the wires. Also remove the little plug at the flexshaft end. The motor is now free.

I'm not sure but I think there is only four screws holding the two halves of the motor together. Be sure to remove the brushes before opening the motor.


See the exploded view in the parts manual.

[Digitalwoodshop]

Anyone with over 100 hours on the cut motor should order a set of cut motor brushes and have them on hand. A short brush could cause the motor to not start.... I broke a bit the first time.... Pay me now or pay me later... About 10 bucks for a set of brushes and ? much for a new bit..... Replace the brushes as part of "Preventive Maintenance" not a repair....

At 150 hours I would replace them.

AL

[Digitalwoodshop]

I bumped this back to the top as the CCM has been rearing it's ugly head and the lessons learned here could be of some use.


AL

[Dan-Woodman]

Al
Are you saying that you are having CCM issues again or just other people.
I just read all these threads. Is the new magnet available or does it only come with a new motor?
later Daniel

[fwharris]

Al
Are you saying that you are having CCM issues again or just other people.
I just read all these threads. Is the new magnet available or does it only come with a new motor?
later Daniel

Daniel,

You can order the new magnet retainer seperate. I believe it is $5.00 plus shipping. Might make sense if you need other items to order at the same time to save some shipping $$$.

[Digitalwoodshop]

Al
Are you saying that you are having CCM issues again or just other people.
I just read all these threads. Is the new magnet available or does it only come with a new motor?
later Daniel


Yes, on some Centerline Text files it get the CCM error, my magnet is fine. I think it is a software issue.

AL