Gantry movement problem

[Steve_k2400]

Hi!

I'm building a Proforge 4.2 which as I know is based on a Voron design. 
This is my first CoreXY printer and therefore I have a lot to learn and even more what I don't yet know.

Currently I have a problem with the movement of my Gantry. 
On every direction change it turns very abruptly with a "bang".
You can see it and hear it in this video.

When I watch videos where a CoreXY printer with a 3D Beacon does the bed mesh calibration, it is much smoother and without the drama.
On some videos the calibration is run much faster and the movement is still smooth.
This abrupt movement is also present when I pick up tools or do any other movement with direction change. 

I controlled my X rails, they are completely parallel. The Y rail has 90° angle to the X rails.

Without the belts, the gantry moves smoothly. (Not 100% silk smooth but the friction is minimal.)
I tensioned the belts the best I could. I tried with less tension and also with more. No difference.
As I don't have the knowledge, I have no more ideas.

The Proforge has 4 motors for the XY movement. (2 for each direction.)
Could there be a problem with synchronization?
I would be happy to hear any advice.
Thanks,
Steve

 

[claudermilk]

Welcome to the forum!

I'm not familiar with 4WD setups, but that could be it. 

[Steve_k2400]

Thanks. I asked this in the Proforge Discord as well but others have no such Problems. 
In theory I could disconnect 2 motors (1X and 1Y) and comment those out of the printer.cfg. Right?

[3DCoded]

30 minutes ago, Steve_k2400 said:

Thanks. I asked this in the Proforge Discord as well but others have no such Problems. 
In theory I could disconnect 2 motors (1X and 1Y) and comment those out of the printer.cfg. Right?

I don't have a 4WD printer, but I think the extra AB motors would add quite a bit of resistance, even if disabled. 

[Penatr8tor]

I have an AWD printer. 

I would do 2 things...

1. Tighten your belts. I can see them flopping around and that's a big no bueno.

2. Sync your motors. The way you sync them is to loosen the set screws on 2 of the motors so that the pulleys on those motors can spin freely. I want to stress not to loosen the set screws for A1 and A2 or B1 and B2... you want to loosen either A1 and B1 or A2 and B2. Next home X and Y, center the toolhead and tighten the two setscrews. Motors are now sync'd. You don't 100% need to home and TBH I don't think you even need to have the printer turned on, you just need to loosen the two pulleys, move the toolhead and re-tighten them.

I'm pretty sure this will, at a minimum, help with the banging.

Oh, one last thing... What's you acceleration set to? Small movements with high accel will sound like gun shots.

 

[Steve_k2400]

Thank you very much for the suggestions! I really appreciate it!
How do you tighten the belts correctly? 
I followed the instruction with the resonance frequency on a 15 cm length (110 HZ).

The problem is: when I have this short part of the belt set up tight, the long portion of the belt (and this is a large printer) is still not tight.
I find it very hard to route the two belts around two motors each and keep the tension between the motors tight.
I tried fixing the whole head assembly so that when tightening one belt, it doesn't pull it away.
It's really hard to properly tighten a CoreXY printer comapred to a "normal" printer I'm used to.
Is there a best practice to do this?

[NikosSprocket]

I use the BIQU Belter, Belt Tension Gauge for 3D Printers to adjust the tension on the belts. Read more at BiQU Wiki

They provide a nice spreadsheet to calculate proper tensions: Belter_tension_calculator.xlsx

[mvdveer]

4 hours ago, Steve_k2400 said:

How do you tighten the belts correctly? 

I too have an AWD printer and currently converting an Ender 5Plus to a Mercury one AWD.

Before tightening your belts or even before routing the belts - SQUARE YOUR GANTRY (Also known as Gantry Racking). See this video which is used as the gold standard.

1. Ensure the belts are cut to equal lengths - very important

2. Route the first belt and secure it to the gantry carriage on one side only

3. Route the second belt and secure this to the same side of the gantry carriage, making sure the exposed lengths after securing are equal lengths.

4. Then attach belt one to the gantry carriage on the opposite side and tighten just enough for the belt not to slip.

5. Do the same for the other belt, ensuring the protruded lengths are equal.

6. Tighten the belts from this side using one of the many belt tensioners available.

     a. A simple one on printables

     b. A more complex one on GitHub - This is the one I use

     c. A purchased one as mentioned by @NikosSprocket

7. Ensure the overlapping ends remain the same length.

8. Now sync your motors as described by @Penatr8tor, it is the easiest way to do it.

There are other ways to sync the motors on the VZBot but they require the VZBot macros. (Most YouTube videos involves these macros)

9. Trim your belt overlaps to allow enough belt to easily adjust the belts should you need to. I still need to do this in the above photos.

Hope this helps in getting you going.

[Steve_k2400]

Very, very helpful answer. Thanks for the detailed explanation.

I already made sure that the gantry is square so that should be no problem. 

I will try to route the belts as you suggested. I already cut the ends shorter and have to see if I'm able to properly see if they are the same length after tightening. 

If not, I will source a new belt. I have to source or print the gauge anyway.

Might take some days but I will report back as soon as I have done it. Many thanks!  

I wish you all a nice weekend.

[Steve_k2400]

On 6/27/2025 at 10:25 PM, NikosSprocket said:

I use the BIQU Belter, Belt Tension Gauge for 3D Printers to adjust the tension on the belts. Read more at BiQU Wiki

They provide a nice spreadsheet to calculate proper tensions: Belter_tension_calculator.xlsx

 

Hi! I got the tool now, but I'm a bit disappointed that they have not put in a properly manufactured tool tip.
The rear printed parts are no problem, but depending on how you printed the tool tip and how far you can push it on to the shaft, it will give different values.
If you have time, could you measure the length of the shaft including your tool tip? 
Is there a given distance somewhere how long the complete assembly (tip + shaft) should be? (I could not find any related number.)
On the A/B belts they recommend around 8 mm distance. Can you achieve that with your belts?

Thanks for any info. 

 

[NikosSprocket]

On 7/1/2025 at 12:33 PM, Steve_k2400 said:

If you have time, could you measure the length of the shaft including your tool tip? 
Is there a given distance somewhere how long the complete assembly (tip + shaft) should be? (I could not find any related number.)
On the A/B belts they recommend around 8 mm distance. Can you achieve that with your belts?

Thanks for any info. 

My 300 mm Voron 2.4r2 the AB belts are at 6 mm. The total length is 29.11 mm.

[Penatr8tor]

16 hours ago, Steve_k2400 said:

The rear printed parts are no problem, but depending on how you printed the tool tip and how far you can push it on to the shaft, it will give different values.

The subject of belt tension on 3D printers is like the WD-40 chain lube discussion on motorcycle forums. Everyone has a different method and or opinion.

IMO, it would be best to measure the tension either one of two ways. 1) With the toolhead right in the very middle of the bed and 2) with the toolhead centered in X with Y full forward or at the back. I guess that's 3 ways LOL. Regardless, you need to ensure two things, 1) that you have adequate belt tension and 2) that the two belts have equal tension. The tension itself has a pretty generous range at which it will operate effectively.

So the tool you have will get you close enough on tension without worrying about the tip you have or don't have, and it will 100% do the most important part of belt tensioning and that is equal tension of all belts.

[Steve_k2400]

15 hours ago, NikosSprocket said:

My 300 mm Voron 2.4r2 the AB belts are at 6 mm. The total length is 29.11 mm.

Fantastic, thanks!

I was wondering how to achieve the 8 mm suggested by the conversion table. I gave up to try to achieve it. 

I have 7.something on both belts and that seems to be good enough. 

 

[Steve_k2400]

3 hours ago, Penatr8tor said:

The subject of belt tension on 3D printers is like the WD-40 chain lube discussion on motorcycle forums. Everyone has a different method and or opinion.

IMO, it would be best to measure the tension either one of two ways. 1) With the toolhead right in the very middle of the bed and 2) with the toolhead centered in X with Y full forward or at the back. I guess that's 3 ways LOL. Regardless, you need to ensure two things, 1) that you have adequate belt tension and 2) that the two belts have equal tension. The tension itself has a pretty generous range at which it will operate effectively.

So the tool you have will get you close enough on tension without worrying about the tip you have or don't have, and it will 100% do the most important part of belt tensioning and that is equal tension of all belts.

Yeah, like those engine oil threads in my Youngtimer car forums.

Thank you all for your help! I greatly appreciate it! 

I set up the belts now correctly (same length, good tension, synchron) and it is moving now much smoother. For now, I will leave it like this and go to the next task.

I have to dig myself deeper into bed mesh calibration. The mesh image I got from Beacon3D calibration looks very tilted. I have to read into what that bed mesh image actually mean. 

If you don't mind, I might come back later with some more questions. 

I'm an old guy and to be honest I much more prefer these "old fashioned" forums. I can't keep up with discord...

[NikosSprocket]

1 hour ago, Steve_k2400 said:

Fantastic, thanks!

I was wondering how to achieve the 8 mm suggested by the conversion table. I gave up to try to achieve it. 

I have 7.something on both belts and that seems to be good enough. 

I just measured my 350 Voron 2.4r2, with motors off and gantry all the way back, and I got 6.25 mm on both sides.

Btw, besides all the other miraculous properties of WD40, it works great for cleaning print beds etc. ; NOT!!! 

[claudermilk]

21 hours ago, Steve_k2400 said:

Yeah, like those engine oil threads in my Youngtimer car forums.

Thank you all for your help! I greatly appreciate it! 

I set up the belts now correctly (same length, good tension, synchron) and it is moving now much smoother. For now, I will leave it like this and go to the next task.

I have to dig myself deeper into bed mesh calibration. The mesh image I got from Beacon3D calibration looks very tilted. I have to read into what that bed mesh image actually mean. 

If you don't mind, I might come back later with some more questions. 

I'm an old guy and to be honest I much more prefer these "old fashioned" forums. I can't keep up with discord...

 I remember those oil threads. Also the filter threads. Good grief, we were on religious crusades with those.

Discord has its place with immediate(-ish) responses if you are in the middle of a project. But I also prefer old school forums; a bit more relaxed pace, easier to find conversations, and the information is retained & relatively easy to find again (Discord search suuuu-uuuuu-<deep breath>-uuuucks).