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Belt Slap causing Shifting Layer

Posted by clyevo 
Belt Slap causing Shifting Layer
May 10, 2017 02:41PM
I've calibrated the angle of the frame best i can. The XY motor is rated 34mm, 1.33 amps, 2.1ohm, 2.5mH, 2.3kgcm holding torque. I've adjusted the a4988 for both x and y at 0.5 (some miss step), 0.6 and 0.7. This video is taken at 0.6vref for both xy.
The 1st layer speed is 20mm/s when the shifting layer happen in the video. The motor is always much cooler than the print bed which is 58c. Previous prints, sometimes i get away with the problem until after 2-8 hours before shifting layers again. In between the shifting layering is very good and smooth. I've even switch extruder and z axis a4988 with x and y to no avail. I figure it might be the chinese knockoff mgn12h linear guide but when i move it, its ok. Well there is some binding if i exaggerated cantilever force on the linear guide. But is don see why this can cause the belt slap which ONLY happen 1 out of hundreds layers.

The belt slap]

Edited video (shows the where the layer shifted)

Edited 2 time(s). Last edit at 05/10/2017 04:33PM by clyevo.
Re: Belt Slap causing Shifting Layer
May 10, 2017 05:37PM
I would guess that you have a slipping belt. On my printer (prusa i3 deriv) I had some binding of a belt idler bearing as well as looseness in the belt and would hear a "pop" when it skipped a tooth. Result was a layer shift. Tightening up the belt and reworking the bearing. fixed the problem. I don't know coreXY that well (yet!) but your belts seem to have some slack in them - are they supposed to flap around that much?

Edited 1 time(s). Last edit at 05/10/2017 05:38PM by seattle_phil.
Re: Belt Slap causing Shifting Layer
May 10, 2017 08:29PM
Kudos for the slo-mo analysis!

I agree with seattle_phil- it looks like the belt tension is not what it should be. Another thing I see is that the belt segments attaching to the extruder carriage are not parallel to the X axis guide rail. That means belt tension will change with XY position of the extruder carriage. You tensioned the belts with the extruder carriage in one position but when it moves, the tension may decrease, possibly enough to allow one of the drive pulleys to skip a tooth or two on the belt. The variable length belt segments at the ends of the X axis need to be parallel to the Y axis guide rails for the same reason.

Then there's the usual suspect - acceleration set too high. I'd fix the belt path issue first, tension the belts and try again. If it still slips, usually when doing 45 or 135 degree infill because only one motor is moving both axes, you may have to reduce the acceleration/jerk/junction deviation.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt Slap causing Shifting Layer
May 11, 2017 02:25AM
If i put the belt tension any higher, the piece holding the belt idler on x gantry will deform and will damage the bearing on the stepper motor itself. As you can see the loud slapping noise is because of the belt tension. There is no slack. Anyway i have match the tension of both belts and at different higher and lower tension for few test prints, the problem still occur.

After further observation i conclude what happen is my linear guide bearing jammed randomly and caused this, however i have made sure the linear guide is parallel to the other side and the x linear guide is perpendicular to the y as best i can. So i am thinking to exhange it with the way more expensive original HIWIN linear guide. Well unless you guys have any other thoughts.
Attachments:
open | download - corexy tight linear guide and belt tension.jpg (67 KB)
Re: Belt Slap causing Shifting Layer
May 11, 2017 08:33AM
Ignore my previous post. My previous assumptions doesnt look right.

New video test print of shifted layers

In this new video its obvious the belt tension is ok, there is not slip in the gt20 tooth of motor x (upper right).
Doesnt look like normal misstep either because it look like the motor was turning at that time.
If the motor shutdown due to overcurrent then it should cause the east travel movement to deviate to southeast.
It is as if the motor reverse direction very suddenly at way higher speed than my minimum travel speed settings and miss stepping because of that.

Could this be the electronics?
I am not sure the sound is motor frequency sound or hitting the printed object sound or miss stepping motor, I have taken this into consideration so i made the z-hop 0.5mm and combing off in cura on this print.

Can someone identify this problem before i buy parts. I dont want to be waiting few weeks then not having it working right if i change the wrong thing.

Edited 2 time(s). Last edit at 05/11/2017 08:44AM by clyevo.
Re: Belt Slap causing Shifting Layer
May 11, 2017 09:29AM
What electronics do you use ?
Re: Belt Slap causing Shifting Layer
May 12, 2017 04:49AM
The good old ramps 1.4 and mega 2560. If its electronic i am thinking switching to this item :
3DSWAY 3D Printer Motherboard Lerdge Board with Thermistor ARM 32-bit Controller DIY Kit with 3.5" TFT Touch Screen
Re: Belt Slap causing Shifting Layer
May 12, 2017 04:20PM
Interesting board but it doesn't say what firmware it runs - my guess that means it's their own. Personally, I'd skip non-open source FW simply because you are at the mercy of the manufacturer's continued support.

By the way, have you tried trimming back acceleration? When I first upgraded to Marlin 1.1 my acceleration was too high and got missed steps that translated into a layer shift.
Re: Belt Slap causing Shifting Layer
May 15, 2017 11:27AM
Some update, i switch the x and y motor, bump up the vref to 0.82 on both the 1.33A motor (fan on shroud on both motors), and tighten one of the belt to match the tension of the other. I am not sure which did it, but so far no miss step for a few short duration prints. I am now trying a 18 hours print. I have a feeling it will go well. Hope it will go well.

Quote
seattle_phil
Interesting board but it doesn't say what firmware it runs - my guess that means it's their own. Personally, I'd skip non-open source FW simply because you are at the mercy of the manufacturer's continued support.

By the way, have you tried trimming back acceleration? When I first upgraded to Marlin 1.1 my acceleration was too high and got missed steps that translated into a layer shift.

I didnt change acceleration, but i bump up the motor current - addresses the same issue i hope.

yeah its proprietary, but good review and cheap for 32bit with no coding hassle for noob like me. Then i cant think of any advances in 3d printing that need further firmware updates. I read it already support so many features: multipoint bed geometry leveling, pause change filament , automatic resume after power failures.

Edited 1 time(s). Last edit at 05/15/2017 11:37AM by clyevo.
Re: Belt Slap causing Shifting Layer
May 15, 2017 11:51AM
The thing about that board is that it uses crappy steppers and if you want to ever expand you'll toss that one in the scrap bin.
Re: Belt Slap causing Shifting Layer
May 15, 2017 04:21PM
It's not advances/new features I'd worry about, it's good old fashioned bugs getting fix. Also, I agree with Qdeathstar about the stepper drivers as well. Blow one, you blow the board (or have to do PCB surgery if you can).

But, hey, you should go ahead and buy it if it makes you happy.
Re: Belt Slap causing Shifting Layer
May 21, 2017 09:32AM
i am not buying anything yet, so far what i have done in previous post is working, i think its the equalizing belt tension and the vref voltage tuning that solves it.

But i still have some inconsistency in extrusions, there is moire about 1mm apart in 50mm/sec printing vertically align, i think most probably cause is the pulsing of the filament because i am not using any gears on extrusion at 1/16th microstepping. There is also the overextrusion every 10-15 layers most likely is my cheap china pla filament not having equal diameter. I am thinking buying a new stepper motor that comes with 1:5.18 planetary gears. I would have posted a new thread on this new problem but googling the reprap forum led me to that idea.
Re: Belt Slap causing Shifting Layer
May 22, 2017 02:50AM
Hello everyone,

I have built Core XY and I am finding lot of vibrations at Y motor compared to X motor. Also when printing at 45 Degrees, one of the motor should be non moving.
But in my case its moving by 1 revolution. Please see below video and suggest.

[youtu.be]
Re: Belt Slap causing Shifting Layer
May 22, 2017 09:52AM
The video is unavailable.
Re: Belt Slap causing Shifting Layer
May 22, 2017 12:24PM
If both motors are turning when moving at 45 or 135 degrees, you probably have not told the firmware on the controller that you are using a corexy mechanism. There should be a way to do that. Once you correct the firmware, only one motor should turn when you tellit to move at 45 or 135 degrees.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt Slap causing Shifting Layer
May 29, 2017 03:23AM
hi... I could solve the above problem. However I am observing lot of vibration in belts. these vibrations are getting passed on to the entire assembly and the whole assembly is vibrating.
including bed. this is ruining my prints badly. pls help.
Re: Belt Slap causing Shifting Layer
May 29, 2017 11:17AM
If the B motor is vibrating, try powering off the printer, move the extruder carriage to the center area of the bed, and swap the cables for the A and B motors. Turn the power back on and try jogging in each direction. If the problem occurs in the A motor, it's a cable problem or driver problem. If the problem stays with the B motor, it's a motor or load problem.

If you are using little plug-in driver modules, it's probably a problem with current setting or a bad driver chip. Those modules are very poorly designed and easily damaged or destroyed. If you set the current too high, which is easy to do because you never really know how much current you've set, the chips heats up and the tiny circuit board can't remove the heat. You can get away with this for a little while, but eventually, the driver chip burns itself up. Also, pulling off or plugging in motor cables while the machine is powered up can result is damage or destruction of the driver chips, so don't ever do that. I suggest you keep several spare driver modules handy unless you don't mind being shut down while you wait for replacements to arrive. If you eventually tire of the unreliability, look into 32 bit controller boards that have the driver chips soldered to the board. They usually have current set in firmware configuration so there are no tiny pots to adjust/break, and thermal performance is better, so you're unlikely to burn the chips up.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt Slap causing Shifting Layer
June 06, 2017 09:29AM
Hi Digital dentist,

Thanks for the detailed reply. I am using MKS Base V1.5 board on which drivers are soldered. Also I have checked resistance in each arm and found to be within range.
My observation is that belt vibrates more in Y direction when printing in 45 or 135 Degrees. there is very less or almost no vibration when printing at other angles.

May be motor B is getting loaded as Motor A is off during 45 Degrees!

sagar
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