Core XY belt alignment issue

Hello All,

I am building my core XY machine in 40*40 aluminium extrusion frame.
I have a problem with my belt arrangement. I am using Marlin 1.1.0
I am using NEMA 17 motor with 20 teeth MXL 2.03 mm pulleys. All pulleys are made in plastic with suitable idler.

Challenges:
1. When I move X axis, I need to apply little pressure to make it travel smoothly.
If I don't push it, then Y axis also moves along with X Axis.

Same thing happens when I try to move Y axis.

2. Pulleys at the crossed belt gets jammed and thus motor gets loaded and hot.

Pls suggest to get rid of these problems.

Pictures? It's normal to take some effort to move the extruder carriage manually- you're turning two motors when you do.

Here's mine:



Belts on two levels so they don't have to cross/twist. Linear guides on 1/4" tooling plate and bolted to 40x40 t-slot.

People usually twist the belts at the crossing point so the smooth back sides slide against each other.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

It almost sounds like your belts are too tight and the motors are having issues moving them or your motors don't have enough torque to move the head around.

The area your belts cross, are they perhaps stuck with teeth to teeth, or have you twisted it to make the teeth opposite of the crossing belt?

Also, it could be that the motor coils are shorted out, because you have all the wires bundled up. If the wires touch the coils short and then it is very hard to move the steps. Separate all the wires and you may find it moves easily. If all wires are NOT touching, then perhaps the belts are too tight.

With power off, can you easily rotate each motor pulley by hand?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks All for your valuable inputs.

It was a problem with belt tension and Center Distance between linear rails. Now I am facing another problem.

While moving axes manually everything works fine but when I start a print, ideally extruder should go to center of the bed i.e. X= 150, Y= 150
However once print is start, X goes to 25 mm and Y to 62.5 mm which means its skipping steps. What I have observed is, pulleys where belt crosses are getting jammed and motor is making noise and then
extruder is leaving its position and prints at some other location.

We are using 20 teeth plastic pulley. Its fixed at a height with the help of metallic bushes. I am afraid if these metallic bushes are pushing plastic pulleys restricting its free movement.

I am totally annoyed with this issue and need your guidance please

I pictures 1 and 3 I see belts tilting up and down, not parallel to each other. Why is that? Belts should meet the pulleys exactly perpendicular to their axes. If you are going to put the belts on one level do that, and if you're going to have them on two levels, do that, but this in-between stuff is bad unless you're also tilting the pulleys (but why on earth would anyone do that?).

If the pulleys have ball bearings you have to be sure not to compress the bearings inward with the mounting screw/bushing/spacer.

Have you calibrated the steps/mm yet? Maybe it isn't skipping, maybe it just doesn't know any better.

Edited 1 time(s). Last edit at 05/11/2017 10:36AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Hi. I will change the position of pulleys to ensure they are perpendicular to the axis.
Pulleys don't have bearings. Shall I put the bearings ? Also these are plastic pulleys.

I'm thinking of usiñg aluminium pulleys.

I have calibrated steps per mm as per belt pitch and pulley teeth count from prusa calculator

I will update results today after making belt perpendicular..

Guys.... I have now aligned my belts exactly perpendicular to axes with no sag.

This is what is happening right now.

1. I changed my Y Limit switch towards Y motor and hence changing home position to Left hand behind corner
2. When I give G1 X150 Y150 or any co-ordinates, it works fine
3. When I sliced a small cylinder of diameter 50 mm and height 5 mm just for the testing following things are happening,

A. Extruder does Homing
B. Ideally print should start from the bed center but in reality extruder goes to hardly 20, 20 mm in X and Y direction and then loses its direction and prints randomly anywhere.
C. Sliced files in 3 different slicers (Kisslicer, Cura,Slice3r) but the same problem. Extruder doesnt actually go to desired position.

D. X,Y Steps/mm = 80 ( 1.8 Deg Step angle and 20 teeth pulley with 2 mm pitch)

G code and Configuration.h files are attached.

Please help me in this

I suspect that your home position isn't defined right in the slicer. Where does the marlin think the home position is? Where are you telling the slicer that home is?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

HI,

Normally bed front left is supposed to be a home position which is treated as 0,0 by slicer and firmware both. However, Since I am using Core XY, if I put my Y limit switch to Front side then it becomes Y max distance as its away from motor and the whole calculation was getting wrong.

In repetier, in printer shape section I set following values to make repetier and actual home position same.

Xmin= 0, Xmax= 300 (left side from the front)
Y Min= -300, Y max= 0 (Towards Y motor)

Home= X Min, Y Max, Z Min

Now with this physical homing and repetier should match. However still problem persist after giving print.

I tried to even use relative positioning system but then it halts

I dont know what to do

In RH printer shape, did you allso set the 'print area width' and 'print area Depth' both too 300, this moves your cylinder G-code to the centre of the bed in my RH.

Yes I did that too. But it doesnt go to desired location.

Hi digital dentist and other friends,

I made all the belt sections exactly parallel and perpendicular but then now my motors are not able to pull it.

When they were little tilted, motors were able to move smoothly.

I am totally confused and annoyed with this. First it was not taking cordinates and now motors are not able to move axes.

Pulleys at the cross are getting jammed again. I have put washers under every pulley.

Refer photos pls.

Here's what I noticed right off. While I'm not saying that's the cause, I'd say you wanna clear it up. You should anchor the tops of your pulley mounts to the extusion, so they don't lean when you tension the belts.

For the issue, I'd take the belts off and make sure all the pulleys move easily and run a test without the belt just to make sure the motors are doing what they need be. Put the belts back on and be sure not to over tension them, you may be creating a force that the motors can't overcome.



Edit: Also how are your pulley's setup? It kind of looks like there's no bearing in them or the spacers/nuts are larger than the entire bearing and actually landing on the pulley.

Edit Again: Oh read the previous posts, plastic pulleys with metal bushings for spacers. Is there a bearing in them or are they riding directly on that bolt/rod there? I'd bet that would be picky to over tightening the nuts against them even with a washer.

Edited 6 time(s). Last edit at 05/26/2017 11:21AM by FA-MAS.