jerk and noisy travel on Y axis after a smooth start

[Matadormac]

Good day to the list. I have recently acquired a lightly used 6040Z CNC router which appears to be in excellent condition. I am basically a newbie at this but not at some basic metal machining. While exercising the machine and getting to know it I have found that on the Y axis and only the Y axis that after an indefinite but not long travel after starting that the Y axis stops with a jerk, pauses for what is not likely even a second and then continues to travel but now there is what sounds like a grinding noise. This occurs both in the + and - directions. There doesn't seem to be a set distance of initial smooth travel before this occurs but it is not more than an inch or so. I have moved the machine head to various positions along its possible travel and tested for this jerk and grind and it seems to happen wherever along the full 60 cm full travel. Once it does the jerk thing and the noise starts, it doesn't jerk stop and start again but the "grinding" sound continues until the travel is stopped.

This machine is only a year or so old, is being driven by a laptop running Windows 7.1 pro, usb connection, SXCNC controller.

The software has all axes set to 320 steps. I tried 400 steps for the Y axis and this did not help.

The machine is clean and has done only one or two projects prior to my acquiring it.

When I get home tonight I am going to carefully clean the ways of the Y axis, lightly lubricate and see if this helps.

I would appreciate any thoughts toward identifying and then solving the issue(s).

Regards

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[mattcnc123]

Hi

you can contact me to work together to fix your problem.
It could be from settings or electronic
My contact info is in my signature.

Matt

[Sterob]

Easy things to look at:
Wind the Y axis through it whole travel with power off......It must be easy and smooth.Any notchyness or resitance in either direction is bad.
Check motor speed and acceleration settings in Mach 3. ( I assume your using Mach3? ) reduce incrimentaly and see if that makes a differnce.....

Also. I would not use a Laptop. ( some people do ) but I think its not a good idea.

[Matadormac]

Easy things to look at:
Wind the Y axis through it whole travel with power off......It must be easy and smooth.Any notchyness or resitance in either direction is bad.
Check motor speed and acceleration settings in Mach 3. ( I assume your using Mach3? ) reduce incrimentaly and see if that makes a differnce.....

Also. I would not use a Laptop. ( some people do ) but I think its not a good idea.

Okay, solved. I took your suggestions and used them, thank you.

I was all set to rewire with heavier, shielded cabling when I decided to have a closer look at how the thrust washer on the Y axis was working. Well, that was the issue. The machine half of the thrust washer had worked somewhat loose so that it worked forward, toward the machine body a bit. Also, the Y-Axis shaft was bit chewed up after this. Also, after inspecting the stepper motor half of the thrust washer I noticed that where it bore on the other half now sported a step which helped I think with the jerk when it cammed over the mating half. Also, it appeared that the machine body half of the unit couldn't get tight enough on the shaft. I used sandpaper to open up the split a bit and then made sure that when it was fitted back onto the Y-Axis shaft that it was not set so far in. I was able to get this half tight enough that it didn't slip on the shaft anymore and the resetting of its position made for a much tighter fit of the two. Also, I had used a file to redress the stepper side of the thrust washer to remove the "step" and keep the correct angle.

All in all it took quite a few trials but it is now working as it should with smooth travel and no grinding noise!

Thank you and to the list for helping me with this.

Best

Matadormac

[Sterob]

Okay, solved. I took your suggestions and used them, thank you.

I was all set to rewire with heavier, shielded cabling when I decided to have a closer look at how the thrust washer on the Y axis was working. Well, that was the issue. The machine half of the thrust washer had worked somewhat loose so that it worked forward, toward the machine body a bit. Also, the Y-Axis shaft was bit chewed up after this. Also, after inspecting the stepper motor half of the thrust washer I noticed that where it bore on the other half now sported a step which helped I think with the jerk when it cammed over the mating half. Also, it appeared that the machine body half of the unit couldn't get tight enough on the shaft. I used sandpaper to open up the split a bit and then made sure that when it was fitted back onto the Y-Axis shaft that it was not set so far in. I was able to get this half tight enough that it didn't slip on the shaft anymore and the resetting of its position made for a much tighter fit of the two. Also, I had used a file to redress the stepper side of the thrust washer to remove the "step" and keep the correct angle.

All in all it took quite a few trials but it is now working as it should with smooth travel and no grinding noise!

Thank you and to the list for helping me with this.

Best

Matadormac

Well done finding the problem! Glad to help.
I'm a little confused by when you say 'thrust washer'. You are not talking about the Flexible Coupling between the motor and ball screw are you?
Can you post a pic for us please?
Steve

[Matadormac]

Yes, you are correct, my bad. As soon as I posted that I thought I might have used the wrong term. It is the flexible couple however. Now the question is perhaps is it supposed to be one piece or two. When I found my problem and took the stepper motor off the Y axis I found the coupling in two pieces. I was puzzled how it coupled in both directions when it really only fitted together and drove in one direction. I just did some research and see that my coupling is indeed broken.

OK, my machine is a Chinese 6040Z, which dimensions should I be looking for to buy a replacement coupling?

Would this be the correct flexible coupling?

https://www.ebay.com/p/Id6-35mm-D19l...2951289&chn=ps

Thank you for making me rethink my so called "fix"!

Now to find the right size and fix it for sure.

Regards

[Sterob]

Yes, you are correct, my bad. As soon as I posted that I thought I might have used the wrong term. It is the flexible couple however. Now the question is perhaps is it supposed to be one piece or two. When I found my problem and took the stepper motor off the Y axis I found the coupling in two pieces. I was puzzled how it coupled in both directions when it really only fitted together and drove in one direction. I just did some research and see that my coupling is indeed broken.

OK, my machine is a Chinese 6040Z, which dimensions should I be looking for to buy a replacement coupling?

Would this be the correct flexible coupling?

https://www.ebay.com/p/Id6-35mm-D19l...2951289&chn=ps

Thank you for making me rethink my so called "fix"!

Now to find the right size and fix it for sure.

Regards

No problem......it makes sense now.
There are several version of flexible couplings. I use these type.
All you need to do is measure your stepper shaft dia and the ball screw shaft dia and get some that match.

Any 'flats' on you stepper shafts and/or ball screws? They help to prevent slipping.