View Full Version : Chinese Laser X axis vibrating noise?

Zach Browning
01-10-2016, 1:24 AM
This recently started happening with my G.Weike laser. https://youtu.be/ef3a66eIQdc
I can't identify where exactly the noise is coming from, because the noise itself is coming from the whole machine vibrating. So I guess I need some advice on what could be causing the vibrations, bad stepper motor, bad axis bearing? It only happens when the head is moving left to right.


Matt McCoy
01-10-2016, 10:34 AM
Is there light lithium grease on the rail?

Zach Browning
01-10-2016, 12:06 PM
There is some thick yellowish grease from the factory, whatever that stuff is. I've only had the machine a month, if that helps anything.

Bert Kemp
01-10-2016, 12:13 PM
Wipe all that heavy grease off, thats put on heavy to protect it from salt in sea transportation. most likely its full of grit from you using it. Clean all the rails really well and apply a very thin coat of lithium grease and see if that solves the problem.:D

Kev Williams
01-10-2016, 1:01 PM

I tore the whole X axis apart, every head bearing, every pulley bearing...

The problem is the stepper motor. Mine does is badly at 500mm per second. Not so bad at 400, or even 600. Mine started about a year ago, I'm just working around the vibration using different speeds. I've been going to call Triumph about getting another one, just haven't as yet (the machine isn't used constantly so...)

But I'll 99% guarantee it IS the stepper motor. I even have a video of mine off the machine, it's pretty obvious. I'll try to locate the vid and post a link to it...

Zach Browning
01-10-2016, 1:27 PM
I actually may have fixed it. With the machine turned off I moved the laser head by hand and it seemed to have a lot of resistance compared to the y axis, so I loosened the tension a tiny bit between the stepper and the reduction wheel (not sure if that's the right term). Moving it by hand is now much more in line with the resistance of the y axis, and I am able to run 700mm/s+ (didn't test higher), whereas before it would make horrible noises from 385 (speed in the video) to 500mm/s, and would skip steps (or not even move) any higher than that. It seems the tension was set too high from the factory, causing too much shear force on the stepper. I'll still replace the heavy nasty grease with some thin lithium. Kev, did you try messing with the tension on the stepper? If it was happening for a long time, your stepper may have been damaged. Mine just started doing it yesterday.

Kev Williams
01-10-2016, 2:08 PM
Tension definitely plays a factor. I'm not all that smart-wise about steppers, since over the years I've haven't had much problem with them. But it seems the one my Triumph likes SOME tension. I found the video, and the testing I did during the video was with stepper only connected to the first drive pulley, so other than the pulley's bearing tension- which was nil, the motor is 'free-floating'. During the test, the motor basically wouldn't work right at 500mm/s but slowing it down helped...

So just a few minutes ago I ran a test to see if I could get it to make some noises at different speeds. It's uploading as I type this, I'm just waiting for it to finish...
As you'll see what happens, I'm thinking I should be ordering me a new stepper tomorrow!

fair warning, I'm terrible at making videos...

first vid:
https://youtu.be/9jkOy2xbfrc (https://www.youtube.com/watch?v=9jkOy2xbfrc)

new vid:

In watching the new vid, the noise didn't seem so bad on camera, but the vibration does cause the box to echo. Some days are worse than others, today wasn't too bad, until switching speeds... Wonder if ambient temp has anything to do with, the garage is pretty cool this morning.

-Now, I'm NOT saying the stepper is BAD, it's possible I suppose that the X controller may be to blame? But I'm 100% certain, at least with my machine, that it's not goofy grease or bearings, the stepper IS the source of the vibration...

As for tensioning my belts, I did some adjusting, tighter made it worse, looser may have helped a little, but my engraving suffered. I'm sure new backlash settings would've taken care of it, but I didn't notice enough of an improvement to warrant another 2 or 3 hour session of speed testing for new lash settings! ;) So my belts are basically tensioned the same as I got the thing. And I'll say this about Triumph, the ONLY adjustment I had to make whatsoever was leveling the table. Everything else was dead-to-rights spot-on.

Zach Browning
01-10-2016, 2:38 PM
I'm thinking ambient temps may have been a factor for me as well, as the last two days have been around 20F and the garage is not heated. Likely the tension was a bit tight from the factory, but the belt shrunk a bit in the cold temps and caused too much tension.

Mine did the same thing yours did in your new video - locking up at high speeds, which yesterday was about 500mm/s. Today I can run 700mm/s+ with no issue or vibrations, and engravings look just as good. Tension on that small belt shouldn't have much, if any, effect on backlash. Have you played with the tension between the stepper and the first drive wheel? That's where my issue was. The tension of the long belt that actually moves the laser head isn't the issue, it's the small belt between the stepper and first reduction wheel. Too much shear force on the steppers drive shaft is not good. Since you might be replacing the stepper, might as well mess with the tension there.

I have a custom build camera dolly, which is basically a single axis CNC that moves the camera along a 6ft rail. It's driven by a nema 23 stepper motor, and if I have the drive belt too tight, it will bind exactly the same way as in the laser. That's how I knew to take a look at the tension on the laser's stepper. There's a sweet spot between not enough tension, and too much.

Edit: I just put together a video of the laser running at 385(speed in the original video), 500, 700, and 1000mm/s. https://youtu.be/lZP3GMGi4cE
I didn't even think 1000mm/s was possible, it's the max LaserCut will let me set.

Kev Williams
01-10-2016, 3:51 PM
Haven't loosened the first small belt. It's fairly tight, but there's about 1/8" of 'easy slack' between pulleys... Off track here a little, the Y-axis small belt on my Gravo LS900 is brutally tight, there's no 'easy' slack at all, it's pretty snug. However, there's a bearing fixture that supports the shaft that protrudes past the gear wheel...
So the outer bearing supports nearly all the belt tension stress, and the stepper motor bearing gets little if any of the tension, with virtually no side-loading. The bracket is simple and does the job, it's screwed to the bracket the stepper is mounted to, so it's all a 'unit'. As for the X-axis on the LS900, the main belt is connected directly to the stepper motor, so no secondary tension issues there. However, the X belt is quite tight itself, and the X stepper shaft is supported in the same manner...

I suppose it's all in the interest of high accuracy to have these belts so tight- However, moving on to my IS7000 tool machine, it's X-axis recirculating-ball lead screw is driven via a stepper-to-larger secondary gear reduction cog, and to me, that belt is sloppy loose! Yet- the machine cuts perfectly round, repeatable holes thru 1/8" aluminum. If the 'apparent' belt slop was of any issue, this wouldn't be the case, and this is a machine where the steppers must exert substantial force in both directions to do their job. So I have to ask, if this machine's seemingly loose belt has no effect on output even when exerting substantial forces, then why do laser's belts have to be so tight?

Zach Browning
01-10-2016, 4:08 PM
I would definitely try loosening the small belt and see if that helps.

My guess would be that with no secondary reduction gear, any slop will be more obvious. With a reduction gear, slop would be reduced by whatever the gearing ratio is, not to mention the belts between the servo and reduction cog are very short, leading to even less slop. So in the instance of your lead screw driven machine - the lead screw is very accurate, so really the only slop would be in the belt between the servo and reduction cog, which doesn't need to be super tight as the belt is too short to have much play and what play there is is minimized by the reduction ratio.

With the externally supported stepper shafts, the belts can be insanely tight without doing damage to the servo removing the need for the reduction cog.

Robert Schmiede
01-11-2016, 10:40 PM
If this has just started without problems before you will probably find that stepper motor is not getting full voltage. Taking the load of the stepper by loosening the belts will falsely give you the impression the belts are to tight. You most likely have a loose wire to your control box. Grease causes resistance ,use a light oil like sewing machine oil.