[nlancaster]

I have a JoesCNC 2006 that is having a shaking problem only in the y-axis.

Here are some pictures to show you what is going on:



The blue on on the left was cut at 120ipm, the red on the right at 50ipm.

Ger21, has given me many suggestions but they have not panned out.

I have also added the moving knot cable system that did help a little.

The biggest thing I notice, is the x-axis moves with almost no noise, while the y-axis rumbles as it moves at speed. This happens weather cutting or just making free air moves.

Things I have tried with no luck:

1. Microstepping 1/2 1/4 and 1/16.
2. Various amounts of tension on the y-axis bearing/rail assembly.
3. Various amounts of tension on the y-axis 5-start acme screw.
4. sanded the rails smooth, they are galvanized.
5. added threaded rod and square tubing to the sides of the gantry, it is very stiff now. with extra rod just below the x-axis carriage in the middle of the gantry sides.
6. carefully cleaned the y-axis bearings.
7. Various bits, up/down cut 2flute qaurter inch, v-bits.
8. moved x-axis stepper motor to y-axsi position, no change.
9. rattler style damper on the y-axis no change. (Works great on z went from 40ipm to 80ipm)

Please help, I can see many videos of JoesCNC2006 models cutting at 100-150ipm on youtube, but mine cannot give me a decent quality. Only thing I have been able to do is roughing passes at 120ipm then a finish pass at 50ipm. But this of course slows things down.

[jckstrthmghty]

Sorry to hear you are having so many problems.

Have you tried moving the gantry without the leadscrew in place? If it's a rail or bearing issue then without the leadscrew it should still exibit the same rumbling/shaking. If it slides smooth then you know it has to do something with the leadscrew. Just trying to narrow down the options.

[nlancaster]

no i have not. I will try that.

[ger21]

It may be resonance. If the stepper has dual shafts, I'd try adding a damper.

[nlancaster]

Yes made a damper. No change. Added to the fix attempts above.

[nlancaster]

Pulled the leadscrew out of the y-axis, still making noise when I move it by hand. It is also very stiff, but I think that is the moving knot at work. Can't feel any major vibration when moving it by hand even if I move it as fast as possible.

So could that be something wrong with the 5-start leadscrew? Would be pretty expensive to test by replacing that lead screw, $60. And that may not fix it.

[jckstrthmghty]

In your other post you said it wasn't but I'm thinking it's leadscrew whip.

[nlancaster]

I don't see how it could be. the 5start just isnt spinning very fast, and it is pulled tight by the dumpster clamp and coupler. Can't see or feel any whip while it is moving, it feels very smooth.

[jckstrthmghty]

ah ok then it's not. Sorry I know this all be very fustrating.

[nlancaster]

one thing I have wondered about. Could the drive end of the screw be off centerline? Could that cause this behaviour?

And if it is the screw whipping, what can I do about it?

[nlancaster]

If whip is the issue. would adding thrust bearings to the system help? Because I would be able to pull more tension on the scew without binding the regular ball bearings that are currently on the machine.

[louieatienza]

Are you sure it's not flex at the saddle/carriage assembly? If you rotated the part 90 degrees in CAM and re-machined it (parallel to the gantry beam) does the same problem persist?

Not many items left to check:

- The stepper itself can be bad.
- The connectors for the steppr wires, the wires themselves, can also be bad.
- The drive can be bad
- Cleaning the bearings doesn't necessarily remedy the situation. Skate bearings are so cheap, it's better to just replace them. And test them first before installing.
- Have you checked the leadscrew bearings? Also, if they're just radial BBs, they are not intended for resisting axial loads, so if you try to tension the screw that may cause issues. Also if the seats on the bearings are not 100% flat and parallel, you'll pull your screw into a bow no matter how much you tighten those bearings.
- I would also realign both bearing blocks just to eliminate that as a possible cause.

I did have a similar issue with my xylotex drive. It turned out the Molex connector for my Y axis worked a little loose, which caused arcing in the connector and eventually fried the Y axis chip on the board. Still have it here and still haven't sent it for repair....

As you've already chased your tail a couple times around trying to solve this issue, it doesn't seem constructive to keep wasting time and effort. If it were me, I would retrofit supported round rail in place of the gas pipe/skate bearings. And you'd only need one rail per side.

[nlancaster]

Louie, those are some good ideas to try. I will recheck the connections, and even change the driver and see what happens.

As far as the direction of shake it only seems to appear in the y-axis direction, no matter what oreintation of part.

And yes the leadscrew bearings are just radials. I will try flipping them and pulling less tension.

As far as moving to linear shaft. I will just live with slow speeds on this machine and save up for either a cncrouterparts kit, or build my own with linear shafting and steel weldments, I know a guy with a cnc plasmacutter

[Khalid]

Shaking may be due to binding of Lead screw.
Out of square gantry.
Tension on sliding rails/bearings at certain positions/locations.