Part Wobble (Formerly: [need] Gates GT2 Belt[?])

wilriker

Do gates belts have ID marks on them?

I think so but that does not stop people from copying them. I will only switch to Gates belts once my no-name belt is... no longer what I am happy with.

DocTrucker

On reflection I think I've been barking up the wrong tree. The wobble appears belt related but not necessarily bounce, as I'd expect that to drop quicker.

So maybe belt tension related...

I'll let the acceleration test finish before tweaking anything else. May find a better value for features even if it doesn't fix my wobble.

DocTrucker

20t drive and toothed idler.

No belt twisting.

Seems to be worse when the slicer slows a layer down due to it being short.

deckingman

@doctrucker That's not just infill showing through is it? The part looks thin so I guess it's solid with no infill but just a thought.....

DocTrucker

Good check, that's had me before!

PLA @180C, 0.4mm nozzle (E3D V6, std thermistor), 0.24mm layer, 0.42mm wide extrusion, 50mm/sec perimeter, 40mm/sec external perimeter, 20mm/sec small perimeter, 0% infill, three perimeters, 3 layer solid base.

https://www.thingiverse.com/thing:1478258/files

I'm ignoring the numbers on the part, just using it as something super simple (been burnt by test pieces trying to do too much at once) and currently trying to fix the simplest feature of all - vertical wall! Set Slic3r to tweak the settings for me based on z height eg:

; Layer [layer_num] jerk change gcode.
{if [layer_z] < 10.0}M566 X1700 Y1700;
{if [layer_z] >= 10.0}{if [layer_z] < 20.0}M566 X1500 Y1500
{if [layer_z] >= 20.0}{if [layer_z] < 30.0}M566 X1300 Y1300
{if [layer_z] >= 30.0}{if [layer_z] < 40.0}M566 X1100 Y1100
{if [layer_z] >= 40.0}{if [layer_z] < 50.0}M566 X900 Y900
{if [layer_z] >= 50.0}{if [layer_z] < 60.0}M566 X700 Y700
{if [layer_z] >= 60.0}{if [layer_z] < 70.0}M566 X500 Y500
{if [layer_z] >= 70.0}{if [layer_z] < 80.0}M566 X300 Y300
{if [layer_z] >= 80.0}{if [layer_z] < 90.0}M566 X100 Y100

mrehorstdmd

@doctrucker That looks like ringing to me. Changing the belt won't cure it. The motor, current, acceleration, and speed all affect it. Take a look here: https://forum.duet3d.com/topic/5951/periodicity-of-ringing

DocTrucker

Cheers for the link. Clearly got a big chunk of reading and fiddling to get through. Slightly complicated by slower external perimeters, but fixed global jerk.

Acceleration is currently 500 on the perimeters, jerk 1000, and speeds as before from 1.8 small steppers running at 1000mA.

JamesM

@doctrucker You may want to try a wider extrusion width with a .4mm nozzle. General rule of thumb is 1.2x the nozzle width for the minimum line width so .48mm should be your base line. At .42mm you could be sacrificing some strength in layer adhesion. Think of it this way, you are laying down a molten tube of plastic at .4mm width and when it lies down on top of the previous layer it will want to squish outward and flatten a little bit.

DocTrucker

I'll test the line thickness later.

I noticed the worst of the problem is at line start, and when I did a test dropping extrusion multiplier from 100 - 80% on the 80% end of the scale it appear that the undulation was thickness, rather than position. To add yet another thing to the mix this maybe extruder related!

I'm one filament guide short of a titan extruder (git it in a bundle of e3d parts on ebay) so I'll give that a go after printing a guide!

Edit: current extruder is ormerod 2 style with printed helical gears.

Phaedrux

Can I ask what steps per mm and microstepping you're using?

I can't tell for sure from your picture, but it looks more like ghosting than vertical ribbing in that it fades away. I've had ribbing occur from belts meshing poorly with the toothed idler. I ended up using a twist in the belt to run the smooth side on a pair of flanged bearings. Ribbing gone.

Wyvern

It would be worth trying dynamic jerk control.

If it helps it would support the fact if it is indeed ringing or extrusion issues.

I used it on my machine, and the little bit of ghosting I was trying to eliminate is essentially gone.

I used 40x40 XYZ calibration cubes with 1 perimeter and no infill with a print speed of 60mm/s on the walls.

DocTrucker

I thought dynamic jerk was Duet 2 only? Will check though.

Edit: Dynamic jerk is not available on v0.6 or v0.8.5 boards.

16 microstepping, 80 steps per mm. Extruder is around 420.

bot

Those belts do not look anything like gates GT belts.

Gates GT is a curvilinear tooth profile. Your teeth look very much like trapezoidal teeth. These teeth profile are made for transferring materials, not precise locating.

DocTrucker

They're also too cheep to be gates too! I was just using that one as a size guide to show the major ripple and the belt have a similar pitch. Not the same as the belts on the machine.

Edit: My question about ID markings for the gates was so I could tell if I had recieved gates or normal if I ordered new belts.

AlexLin

just upgraded to e3d gates belts on my corexy (yes they are genuine) what also improved quality is replacing all china pulleys/idler with the gates from e3d. They have a 5mm inner diameter. I can see less/no wobble in the Y axis when moving in X, i did with the china ones iwth 3mm inner diameter. They were not true center, even the more expensive ones.

DocTrucker

Yes, the off centre pulleys are a particular frustration of mine!

DocTrucker

Some better pictures of current state. There is a little ghosting but these are mostly constant.

First side (Parallel to Y). The section of the part with text seems to effect the side after. I'm assuming the tool is being moved slightly faster here.

Second Side (Parallel to X)

Third Side (Parallel to Y)
![0_1550785895082_DSC_3064_red.JPG](Uploading 100%)

DocTrucker

@bot Thanks for making me double check my belts! The belts that I had on where a semi-circle section on the tooth, but one of the belts I had lying around weren't. No idea where it came from but scrapped it. I have now replaced the belts with other belts I had as the alternatives were a little thicker. Very slight improvement in finish but not solved the problem.

I've now replaced each of the following one at a time with a test print between:

X-axis belt. - Minor improvement,
Replaced sprung loaded bed adjustment with a locked up nut/bolt alternative like the standard Ormerod set up. - No observable difference.
Y-axis belt. - In test.

I'm now printing a re-designed base to my z axis that will make that joint more rigid.

Failing that I may need to replace the ply bed support with the alloy alternative that I run on my other two Ormerodishes.

DocTrucker

Y axis belt change had little effect.

Flipping the belt to run over a pair of 10mm bearings has had little effect.

I've ordered a set of polymer LM12UU bearings just incase the better z-axis base doesn't fix it. The bearings are from a second hand machine I never ran so they may be bad.

Edit: I don't think this is extruder related any more because the pattern would be equally bad on the x-axis parallel surface of the square test. The motor currents are set high at 1000mA, and the settings for x and y axis are currently the same acceleration, jerk, and current.

UnderDoneSushi

@doctrucker Gates LL2MR06 PowerGrip GT2 -- this is the designation for the standard GT2 belts.