X parallelism problem without explanation!

Rudy2A

Good morning all,

I will try to be as precise as possible!

I explain, without changing any parameters in my Config.g. My slicer or mechanically ... a problem has just occurred!

When I put my X Y axes to 0 (home) and I move my X to 200 (for example). I see my cart moving in X, make a curve towards the middle by putting parallelism X across ...

I made a small diagram, I hope it will be understandable!

In blue the belt A
in green the belt B

In dotted red, moving my head (trolley) that makes a curve ...

At startup, making X200, I see my cart X get in the side of the editor B and when I do X-200, my cart X is crosses also motor side A ... And this only happens near the 2 motors (front of the machine) or doing a G29 at the beginning.

If I print in the center of my bed, the impression is successful without any parallelism defects? Do you have an idea ?

dc42

The first thing to check IMO is that the belt sections that have variable length depending on print head position are parallel to the motion axes. Look for the diagram posted by @mrehorst in several different posts.

Rudy2A

@dc42
Once again, thank you ... I found what you recommended me, remains more than read and digest all this!

For those who would interest!

https://drmrehorst.blogspot.com/2018/08/corexy-mechanism-layout-and-belt.html

mrehorstdmd

Can you post a photo of the xy stage?

Is this a new printer? A new problem?

Rudy2A

@mrehorstdmd said in X parallelism problem without explanation!:

Pouvez-vous poster une photo de la scène xy?
Est-ce une nouvelle imprimante? Un nouveau problème?

So, unfortunately for me, impossible to make a video!

I will try to be a little more specific.

In the picture, we take the reference cart that is in the center of my bed ... if I move my cart to Xnn, we see the support with the pulleys (Y right) back 2 to 3 mm from the engine ... In reverse, if I move my cart to -Xnn, we see the same problem, but on the left?

This is actually a new printer that I just built, and before I encountered this problem, I printed a 30 hours without encountering this type of problem ...

I thought at first belts, too much or not enough tension, I took everything back to 0 for 2 days without result!

There, I confess that I am lost and that I need expert to save me from there!

Thank you .

JamesM

The first thing I would do is get rid of the steel core belts...For them to work reliably you need big pulleys for them to go around which from the looks of it your printer has standard small pulleys.

mrehorstdmd

Agreed. Steel core belts and small pulley corexy are a bad combo. The steel wires in the belts break due to excessive flexing around the small diameter pulleys, and then the belts stretch over the broken wires. It will cause all sorts of weird behavior.

Rudy2A

@JamesM said in X parallelism problem without explanation!:

La première chose que je ferais serait de me débarrasser des courroies à âme en acier

@mrehorstdmd said in X parallelism problem without explanation!:

les petites poulies corexy sont un mauvais combo

Thank you...

I observed the belts and indeed to an irregular shape and ungully, when it passes on the pulley of the engine, I hear a noise of clack. I think the soul of steel is broken on one side!
I will order new range, but also new pulleys.

On this subject, I do not quite understand when you say big pulley. Currently, I have 20 teeth GT2 which exact model should I take for the belt and the pulleys (do you have a type to communicate to me)?

Thank you.

JoergS5

@Rudy2A If you change the pulleys, you will change the belt alignment also, so I would not change them (I mean the number of teeth, the diameter). For alignment rules, please check the image samples of wrong construction of Mark Rehorst on https://drive.google.com/drive/folders/1Fdp4ah8Wh1CzPStKwDIiN_boE0fUlqfv where the images are commented by him.

Rudy2A

I still had a new belt length (same belt previously installed) ... I just changed the belts to test and the problem was that, a belt with a broken steel core inside ... I could have thought of it! Frankly, a little over a year ago, I hardly knew what a 3D printer was! And here today, I built my own printer (inspired here and there ... but each piece was thought and modeled by myself in part thanks to this forum)

So, I'm going to order another type of belt, to start with and see for the pulleys and by documenting all your links!

In any case, thank you all for your advice!

mrehorstdmd

@Rudy2A by "big pulley" I mean large diameter. I don't know the minimum diameter that will allow the steel core belts to last a long time, but based on the size of the "cables" that make up the core, the diameter should be at least 25 mm, but bigger would be better. That includes the drive pulleys!

Rudy2A

@mrehorstdmd said in X parallelism problem without explanation!:

par "grosse poulie" j'entends grand diamètre

Alright I understand ! Indeed, the steel souls of the belts being very thin, to be constrained on a greater diameter will avoid to the souls to heat and to break!

I also did a little research on different forums and the report of unreliable steel belts. So I will invest in other types of belts ... remains to see which!

whosrdaddy

I have these: https://e3d-online.com/gates-powergripr-gt2-belt-6mm-x-100mm
It's genuine Gates and is not too expensive!

Rudy2A

@whosrdaddy said in X parallelism problem without explanation!:

J'ai ceux-ci:

Yes indeed, I had seen them earlier in my research and as soon as I have to make an order at e3d, I will not hesitate to take them!

Thank you

JoergS5

@whosrdaddy Your recommended Gates belt are 2GT which is not the same as GT2, the profiles are according to https://reprap.org/forum/read.php?1,842583 different (2GT: circular, GT2: curvilinear). I would use the Gates 2GT belt only with their 2GT pulleys.

P.S. personally, I change all my belts and pulleys to 9 mm GT2.

P.S.2: there are GT2 belts from Gates 6 mm: LL2MR06 https://www.biedlers-belts.com/long-length-belting/long-length-powergrip-gt2-belting/2mm-pitch/gates-ll2mr06-belt.html

whosrdaddy

@JoergS5 : I am using their pulleys so I did not encounter the "wrong profile" issue