LaserUser.com Forum (formerly RDWorksLab)

I was trying to find it last night while skimming the Ruida manual. There is a third setting called Jerk in 3D printing and it isn't by Ruida They call it 'take off speed'. While you may not think that your steppers are idle during a job they do come to a 'stop' on change of direction momentarily so given the regular patterning worth a look too.

Takeoff Speed: it means the speed of the motion axle in direct start from the idle condition. If this value is excessively large, it will make the motor lose steps, jar and even squeak; if small, it will reduce the running speed of the whole figure. If the inertia of the motion axle is larger (the axle is heavier), you can set a smaller takeoff speed; if smaller (the axle is lighter), and you can increase the takeoff speed. example,the typical valueis 5~30mm/s.

If they were smaller in pitch from the actual track Moire or Ghosting would be the 3D printing equivalents and there is some other remedies to look at for those but yours are a gross error. Good luck

Hm, moire interference pattern never occured to me, but makes sense.
Will be doing more tests in couple of hours.
What are your jumpoff speeds, people ?

My current jumpoff is set to x-20 and y-15.

Setting jumpoff to 5 on both axes didnt help at all.

However, i think i found the culprit to all of this - flexible motor/shaft couplings.
I highly suspect windup, a form of backlash. Backlash is positional error, windup is torque error.
Damn couplings are springs that wind and unwind, bouncing everything around.
No way to fix this as motor is not inline with shafts and motor bracket is welded in, no adjustment.

Angle grinder it is... oof...(big facepalm about engineering of the machine.)

Correct me if i'm wrong... Please ?

You have something similar to these fitted to your Laser? If so give it a clean with some Acetone or IPA and add a wrap of cloth tape around and see it it reduces the effect?

Ignas Kaz wrote: Thu Jun 20, 2019 Setting jumpoff to 5 on both axes didnt help at all.

However, i think i found the culprit to all of this - flexible motor/shaft couplings.
I highly suspect windup, a form of backlash. Backlash is positional error, windup is torque error.
Damn couplings are springs that wind and unwind, bouncing everything around.
No way to fix this as motor is not inline with shafts and motor bracket is welded in, no adjustment.

Angle grinder it is... oof...(big facepalm about engineering of the machine.)

Correct me if i'm wrong... Please ?

Very interesting. Can you please post a photo of these couplings (assuming they differ from what Mr. Tim Mellor posted)?

Thanks!

No, they're exactly that.

The shot below is of the double ended stepper on my Y which works fine in my case. The Gantry is however a lot lighter than yours will be. Those couplings on the Z axis of my printers are also fine but they are inherently backlash tolerant as they 'generally' only drive up during a print. Apart from trying a tape wrap all you can really do is check they are aligned as close as you can laterally and radially and tighten them down. It is one of their benefits in that you can have shafts out of alignment and still rotate

The Couplers on my bigger Router are more like a bigger version of these https://www.ebay.com.au/itm/8mm-10mm-D2 ... %7Ciid%3A1

We used to use similar coupling for industrial high torque use but the alignment is much more important.

Tim, the photo looks suspiciously similar design to my laser, apart from motor location. Can you post a pic of entire work area ?
Side rails/drive interest me.

Also, i did purchase couple of spider couplers, the ones in second photo, see how they fare.

There is a bunch of photos and information on mine here https://www.eevblog.com/forum/reviews/4 ... msg1665956 and looking at yours it is a close cousin if not made in the same factory. The right hand side of my Y goes straight to a pulley on the right side unlike your extended shaft which I assume then goes to a pulley.

Looking at the setup of yours things to check. Check alignment of the Gantry to the Y axis rail. If one of your couplings has moved or was out of step you may be trying to drive the gantry at an angle to the Y rails causing them to grab or bind up causing a judder (rough sketch below)? Check the guide rollers on the right side to make sure they are running freely but still tight on their surface (bounce on change of direction causing your issue)?

Well, more tests.

1. Put the tape on couplers, lots of it. No change.
2. Did the "wedge in the table" test, no change.
3. Realigned X motor, was a bit crooked. And had to file down bracket mounting holes, as threads in the gantry were drilled too wide apart, and someone just slapdash redrilled bracket to suit. Crookedly. Had to widen slots to be able to move motor on them. Tightened X slide mounting screws. --No change--
4. Unscrewed one of the Y couplings AFTER belts were retensioned to relieve possible torsion/windup. Retightened EVERYTHING in drive system - pulleys, couplers, rails, etc, etc. - NO CHANGE (EDIT - now that i think on it theres idlers, albeit poor to relieve torsion in shaft/couplers...)

GAH!!!!!!!!!!!!!!