Help! One of my servos has a lot of noise

[davaro]

I finished my home cnc router but I have not been able to get rid of the noise I have on x axis. I have done a lot of troubleshooting like changing the servo, encoder, driver, re-routing the cables to make sure they are well isolated, tuning servos with driver, etc. Something that helps some times to temporary reduce or eliminate the noise is when I move or lift the encoder. The problem is that the noise comes back again having the servo vibrating and getting hot. The noise is causing the axis to not move accurately and having mistakes on my work.
I am using a Keling servo KL 23-120-36, an encoder AMT 102 and a Gecko drive G320, and a power supply KL 600 48.

I hope you can help me to resolve the issue and finally use my cnc router.

Thanks

[Al_The_Man]

As a general rule, the two causes of this are Tuning, too much gain etc, or mechanical problem, have you tried it with the motor disconnected from the load?
When you say 'lift the encoder' is this on the end of the motor?
Al.

[H.O]

Hi,
With the AMT encoders it's sometimes reported that the "splines" doesn't mesh properly, introducing an ever so small backlash between the shaft and the encoder. A drop of glue or silicone usually takes care of it.

/Henrik.

[davaro]

Al the man, I have tried the servo by disconnecting the servo from the ball screw and the noise is present too. I chanage the servo, I change the encoder and the noise stills there.
The only way to eliminate the noise (some times), is by separating and leaning the encoder from the top of the servo where the econder is inserted onto the servo shaft.
Thank you Al the man for your comments.

[davaro]

H.O. Thanks for the tip. Just to make sure I understand correctly.
When you insert the encoder onto the servo shaft, there is a white and black rings that you insert first and by a separator you give the proper distance to the rings. These rings are held at that distance given by the separator. Then you insert the encoder and engages with the black/white ring. When the servo shaft rotates, it also makes the encoder to rotate. Your suggestion is to glue only the ring with the shaft? or glue the ring and the rotatory part of the encoder with the shaft? I think the second is the correct but HO please let me know.
Thanks HO for your feedback, I appreciate your help.

[davaro]

HO, I will glue the rotating spline with the ring and the shaft tomorrow. I will let you know the results.

Al the man and HO, another question. In Mexico it is not mandatory to use ground on the houses. Therefore, I am not using the third wire (white) of the servo which it suppose to be connected to ground. I am only using black (-) and red (+). Do you think that not using ground could be causing the noise?

Thanks
DVR

[H.O]

Hi,
Correct, I meant to glue the "ring" (mounted to the shaft) to the rotating hub of the encoder. The spacer tool is supposed to make the parts fit tightly but I (and others) have experienced that it's not always the case. From your description of the problem it sounds like this is it. Use some "rubbery" glue like RTV (silicone) or something so that you still CAN still take it apart if needed. (No superglue etc)

If your motors are mounted to a metal surface of the machine and the machine is properly grounded (mandatory or not you really should ground the machine properly for your own safety!) the motor housing will get grounded thru the machine frame.

If they are not mounted on a grounded metal frame of the machine then you may get some capacative coupling from the windings to the motor housing which might upset the encoder.

I don't think not having the motor housing grounded is your problem but you really have nothing to loose by doing a proper job and grounding them.

/Henrik.

[davaro]

H.O. Thank you very much for your suggestion. I applied silicone to the encoders and the noise was reduced a lot. I feel very happy, since I tried everything and nothing was reducing the noise.
Now, I will go ahead and start building some cabinets. I am working on a project to build furniture and I could not start until having the cnc done.
Are you also working wood?

Thanks again H.O.
david

[davaro]

H.O. , maybe you can also help me up with this one. My x axis is the slowest axis, and when I work wood, it takes too long to finish the jobs.
I am using a 1" ball screw and 23 Nema servo motor connected with 1 to 2 gear belts. I am also using Mach 3 to move my servos and I increase all speed in the set up program and I do not have a major change.

I hope you can help me.
Thanks
David

[H.O]

Hi,
I'm glad you got the vibrations sorted, it seems to be a reccuring issue with the AMT's.

If you, in the motor tuning dialog in Mach3, increase the velocity you are changing the maximum speed the Mach3 will be able/allowed to command the motors to move (in other words the rapid or G0 speed). If you have a program which specifies a certain feedrate changing the velocity in motor tuning will not affect the actual feedrate - you have to change that in your G-code program. G1 X50 F100 will move at 100units/min etc

If you ARE doing that but don't see an increase in velocity it might be that your motors simply can't turn faster with the powersupply voltage you have. However that should quite quickly result in a following error tripping the servo drive so I don't think that is the case.

Me, I don't do much wood. I'm currently in the process of converting an Abene knee-mill but the progress is and has been slow for about a year - hope to pick it up again shortly.

/Henrik.

[davaro]

H.O. Thanks for the tip on the speed. I will try that tomorrow.
I read the link of your project to convert that into a cnc machine.
Since I also want to work with hard metal (hobbie) I plan to purchase a used machine in USA and import it to Mexico and then make the conversion too.
But first I need to complete the router and play with it a little bit long.

You surprised me with all electricall work you have done to the machine. It is not simple and takes a lot of time. Actually, in the machine that I am finishing has taken to me more than 1 year to purchase components and building it.

Thank you for sharing your knowledge.
keep in touch
David