Shavings in Z motor

[DianMayfield]

Hi Guys,

Just replaced my Y motor and while the cover was off, went to tighten everything and found this....I have what looks like metal shavings in my Z motor. Any idea what might be wearing?:confused: It is not ferrous.


Thanks in advance!

[fwharris]

How does the disc look? All of the black lines this on it? Anything around the shaft look like it has been rubbed?

[bergerud]

Can you tell what it is? Aluminum, solder, brush dust? How is the bushing on the motor shaft?

[Digitalwoodshop]

Does the Motor have a CLEAR encoder cover? That is pretty COOL....

I got similar dust in my Y Motor... My dust was sawdust... Have you ever cut any plastic or litho's?

AL

[DianMayfield]

Hi Al, It IS clear :)

Hubby says it could be aluminum dust, or even plastic. Feels like talc, smears like graphite. It looks to be the same material as in Al's picture number 6 from this post http://forum.carvewright.com/showthread.php?27799-Z-Axis-Stall-E06-0313&p=250335#post250335. Butch thought it could also be solder spalling (I forgot what he called it, but corrosion/degradation of the solder)

It also looks like the plastic "foot" on the bottom side of the reader is slightly melted next to the solder.

The encoder disk looks ok, as compared to Al's pics in the above post. I will take it apart and look at the shaft and bushing.

[Digitalwoodshop]

I have never taken a servo motor apart but I bet if I do I will find some of this dust inside from the stator and magnet rubbing slightly.... Remember if you ever do open the servo motor it will never be the same... It looses some of it's magnetic properties. I did a post on that years ago with a quote from a servo motor repair company that the customer opening it damaged it... They have a machine to re magnetize it... See Step 2.... http://www.servotechusa.com/servo-motor-repair/

AL

[Rocketman]

I have never taken a servo motor apart but I bet if I do I will find some of this dust inside from the stator and magnet rubbing slightly.... Remember if you ever do open the servo motor it will never be the same... It looses some of it's magnetic properties. I did a post on that years ago with a quote from a servo motor repair company that the customer opening it damaged it... They have a machine to re magnetize it... See Step 2.... http://www.servotechusa.com/servo-motor-repair/


(http://www.servotechusa.com/servo-motor-repair/)

AL

Are you sure about that? While it's true that stepper motors should not be taken apart for the reasons you mention, I don't think that applies to servo motors. Following is a quote from Mariss Friemanis; the designer of the world famous Gecko drives: "This topic came up in another group. The stator acts as a magnetic "keeper" for the rotor.

Nothing like running an experiment to know if something is true or not.

I had a motor I didn't care for (MO62-FD04), so I ran dyno test (http://rover.ebay.com/rover/1/711-53200-19255-0/1?toolid=10029&campid=CAMPAIGNID&customid=CUSTOMID&catId=220&type=2&ext=291648481106&item=291648481106)s on it that showed 112 in-oz low-speed torque. I removed the rotor for 5 seconds, then replaced it and re-ran the dyno test.

The low-speed torque now was 70 in-oz, or only 62% of what it was before disassemby.

You may not notice the loss in torque but it is real and it is there.

Mariss"

Mariss not only makes some of the best stepper drives in the industry but he also makes servo drives. I'd like to mention that there are plans all over the internet for adding an encoder to the back of a plain old electric motor to convert it into a servo motor. While the resolution may not be high enough for certain applications using everyday electric motors, they still do work in many applications. DC or AC motors can be converted to servos and since AC motors don't have magnets I know they won't mind being taken apart.

One of the first home brew CNC machines I studied back in the 80's was built using car alternators as stepper motors. The plans came on a VHS tape and showed how to take apart the alternators and snip the winding's and rewind them to make them into 4 pole stepper motors. While the resolution was crude, they were very powerful stepper motors and could be used to build very large CNC machines.

The link you posted has much information but I think the information you were looking for is here: http://www.servotechusa.com/blog/bid/31931/Disassembling-your-own-DC-Servo-Motor/

And that information is only relavant for specific types of DC servo motors. Here's what I think you might have read:
Separate the Armature from Its Magnetic Field without Causing Demagnetization There are many types of magnets. The most popular types used in servo motors are Neodymium Iron Boron (NdFeB or NIB), Samarium Cobalt (SmCo), Alnico, Ceramic, Ferrite and Rare Earth. Certain magnet types require that their fields not be broken. If a motor or tachometer armature is removed from the wrong type of field frame, the magnets will loose their strength effectively ruining the servo. The only way to rectify demagnetized field frames on a disassembled servo motor is to recharge the magnets. Otherwise the servo will never run properly.

If there's a part number on the motor somewhere you could look up the motor specs to determine it's type and whether it's safe to take it apart or not. Another example of why I wish the Carvewright makers would be a little bit more forthcoming with various machine spec's. Has Carvewright ever published a schematic or motor spec's?

[bergerud]

The motor is very common. Just Google RS 555PH. The ones with the longer shaft out of the back for the encoder are harder to find. I (and I think Al) bought some for fun off of ebay. I do not think they are the "strong" field type which would be damaged by removing the armature. These are higher speed motors, not high torque stepper motors. (I think the magnets are cylindrical and magnetized across the diameter. The armature would not make a good "keeper" anyway.)

I would not think twice about taking one apart.

[Digitalwoodshop]

Yes, I bought 2 on eBay.

http://www.ebay.com/itm/MABUCHI-RS-555PH-HIGH-TORQUE-MOTOR-GENERATOR-12V-5500RPM-/291527706846?hash=item43e067c8de

AL

[Rocketman]

Thanks for the motor number. I just ordered one from here: http://www.ebay.com/itm/230438229146

In the description it mentioned "Additional data sheet upon request". I'm looking forward to playing with it.

As cheap as these motors are, I too would not worry about taking them apart.

Did anyone get the part number off the encoder too? These sound like great parts to play with using linux found here: http://linuxcnc.org/

I've got another stepper cnc system I've been wanting to convert to servos. These may do the trick. (small lathe)