Need Help!- Servo motor wont stop running

[cosurfer]

Thanks in advance for any help! I have a 5x10 practical CNC running WINCNC. I took apart the Z axis last week to clean it up and grease the rollers. Since then my Z axis has been running oddly. Sometimes it won't work at all, sometimes it runs great then stops mid program, sometimes it moves an inch and then locks up, sometimes it slips and locks up. WINCNC told me to check the wiring connections because practical CNC's don't have the best connections. I thoroughly checked and cleaned the connections and that doesnt seem to help. I took off the servo motor and tried to run it seperate from the CNC. When I hit the up or down it won't stop it just keeps running until I hit the other direction. I tried the 1" jump function and it moves but then locks up. I have a USdigital encoder and I don't know what brand the servo motor is. Any ideas on what's happening here? Do I have a faulty encoder? Thanks Adam

[MCPservice]

Post some pics of the z-axis itself and the servo, a name plate if the motor has one. What type of machine is this also?

[cosurfer]

Here are a couple of photos of my Z axis.
http://i876.photobucket.com/albums/a...ket_46933_.jpg
http://i876.photobucket.com/albums/a...ket_46934_.jpg

My machine is a "Practical" Cnc, they are out of business now. I have no idea what type of servos I have. There is not a name or model number on them. The encoder is a USdigital model no. e5d-500-250-HG. I fiddled with the wires again and the Z axis now runs fine. It must be an electrical problem with the connection or wire. What do you think? Thanks!

[MCPservice]

OK...then my question would be which wires did you fiddle with?

Check to see if there is any visible damage to the cable.

At the motor, look for the same thing the cable, connection, maybe the cable has been pulled at the connection, but it does sound like you have a suspect connection somewhere.

Hope this help.

[sch]

Motors look like brushed DC with attached encoders.
The two buttons on the ends with screw driver slots
look like brush holders.

[WinCNCGuy]

Hi cosurfer,

I am Mike at Wincnc. This is not our system and I don't have a lot of knowledge in this, but I will try to help you just a little.

First, your system uses Rutex drives. It has two connections from the drives to the motors. One is a cable with either 2 or 3 wires. That is the power for the motor. The other is an ethernet cable (RJ45), and that connects to your encoder. If the encoder wire comes loose the motor runs wild, I guess that's not happening.

That leaves the other set of wires and the mechanical part of your Z axis. First thing to do is to MAKE SURE that the wires on the screw terminal at the back of your drive box for the Z axis is in the connector and that the screws are tight. I've seen this happen, but it usually means that it just doesn't work - not a bunch of wierd motion.

The last thing I'd say is that it's more likely that it's mechanical. Something that you did when you had the Z stuff torn apart. Could you have put something in backward? Take some pics of everything there and paste them here. Could something be loose and binding?

Good luck. I might be able to give you a phone number of someone who used to work for Practical who might help you. But try to fix it yourself first.

Good luck,

Mike

[mike_Kilroy]

Originally Posted by cosurfer ...........I took apart the Z axis last week to clean it up and grease the rollers. Since then my Z axis has been running oddly. Sometimes it won't work at all, sometimes it runs great then stops mid program, sometimes it moves an inch and then locks up, sometimes it slips and locks up....

Adam, usually the last thing we do before something breaks is what caused it to break. That said, your taking Z apart most likely caused your problem. I would not mess too much INSIDE the control cabinet as you did not mess in there.

You are describing encoder problems. Either the wiring or the encoder itself. Did you have to use a hammer to bang the gear back on the motor after cleaning? did that break the glass disk in the encoder on the back of the motor? Please confirm that there is no other encoder or linear scale on the Z axis. Adam, why are there TWO motors? both Z?

[cosurfer]

Thanks for the responses. The machine seems to be running fine now. I think the problem is the connection to the encoder. The connection is an ethernet connection that is pretty loose. Its probably not a good design for a constantly moving part! I am just going to use some electrical tape and try to stiffen up the connection as best as I can. I assume the only way to truly fix the problem is buy a new encoder with a different connection style. When I took it apart I only removed a few of the aluminum plates and didn't mess with the screw and I didn’t pound on it so I don’t think I screwed up the alignment. Thanks for the help!

[WinCNCGuy]

Only one motor on Z, the other is for X..., it is rack and pinion. The motor only has one encoder and the RJ45 connector snaps directly into the encoder case. As Adam said, it is a problem joint. The ethernet cable is very stiff and the gantry is always moving.

I've seen these an ethernet cable come unsnapped and the motor run wild. It was on the X axis and it slammed into the side of the bridge. It bent to drive shaft for the X pinion.

Be careful about unhooking these and hooking them back up. If you connect them to the wrong axis or not get them completely snapped it... LOOK OUT!!!

I'm not sure how you'd get another type of connection. The drive has the RJ45. You might be able to run it into an intermediate box and break it out to another type of connector, I'm not sure.

Sounds like you might have found your problem. Glad you did.

Mike