MXL vs. GT2 - print results

[ataraxis 51]

Hi everyone, I installed new pulleys and belts (GT2) on my Ultimaker Original

and - at first - didn't recognized any difference . But when you take a photo through a macrolens

you can see how much difference there actually is:

size:

MXL:

GT2:

The other settings where exactly the same, therefore i really really can recommend it to everyone that owns an UMO.

You have to change the steps/mm to 80.00! (thanks )

Have a nice day,

Ataraxis

Edited May 22, 2015 by Guest

[lars86 42]

Very nice! The motion definitely looks cleaner.

I have upgraded pulleys on the original belts, and am considering a GT2 upgrade. My heated bed upgrade just arrived, so I'm excited to get that rolling as well.

Where did you get the parts? What sized belts and how many teeth on the pulleys?

Edited May 12, 2015 by Guest

[ataraxis 51]

Hi lars, I ordered at robotdigg.com

GT2 Pulley 20 teeth, 8mm Bore

GT2 Belt, 303 teeth, 606mm long, 6mm wide, closed-loop

http://www.robotdigg.com/product/23/GT2-Pulley-20-Teeth-8mm-Bore

http://www.robotdigg.com/product/275/606mm-long-6mm-wide-closed-loop-gt2-belt

[lars86 42]

Cool, thanks. How did the belt length work out for you? Are you using tensioners? What kind?

[ataraxis 51]

The length is perfect, therefore I do not use tensioners anymore.

I read that - when you use the GT2 belts - there is no need for tensioners at all.

I don't know if that is still true after some hundred prints but at least at first it is.

Edited May 13, 2015 by Guest

[macua85 52]

Wow thats quite a difference. Did you have to make any software/firmware changes with this setup?

[ataraxis 51]

hey macua, no - since the diameter is the same as before you don't have to change anything else (but the belts and pulleys) ;)on the other hand i really recommend new x/y-blocks!

chopmeister's design is my personal favourite. i tried some others too but i prefer the easy to print and solid design of chopmeister's:

https://www.youmagine.com/designs/twisterblocks

they also include a GT2 clamp that does not lead to any tension at the belt.

Edited May 14, 2015 by Guest

[macua85 52]

Great thanks for the info. I have tried ordering the parts, just waiting for Robotdigg to get back to me. Its a strange web store, check out means sending an email to the owner to verify, at which point they send you an invoice.

Looking forward to applying this upgrade. Going for direct drive at the same time too, hopefully see some noticeable improvements.

[lars86 42]

Yeah, just got my quote today. Shipping is a little high.

[macua85 52]

$2us for me...the only perk of living in china

[ataraxis 51]

@lars86: you can also choose china post (as i did), to germany it was 4 USD

tell them to stick the invoice on the outside of the package, otherwise it will be handed to the customs. shipping was around 2 weeks from china to germany, and and additionally week it was at the customs...

@macua85: mine is also direct driven, i can recommend it. but be careful what kind of couplings you install, otherwise you will have some backlash again. you should easily get some metal bellow couplings (which are backlash free) in china i guess

Edited May 15, 2015 by Guest

[macua85 52]

Whoa, my robotdigg parts turned up today! 2 days from order to delivery, not bad! Quality looks good, just printing those xy blocks now so I can install.

[ataraxis 51]

nice @macua85, could you do some before/after pictures of an high quality print maybe? would be nice if you confirm my results.

[lars86 42]

Have you guys scrutinized the concentricity of the pulleys? That is my biggest concern, because once fastened to the rods, if there is any eccentricity to the cogged surface, the print head motion will have sinusoidal accel / decel instead of constant velocity.

[ataraxis 51]

the pulleys are WAY better than the original ones, there is almost no play and also two set screws on every pulley

Edited May 17, 2015 by Guest

[macua85 52]

Well, I spent all afternoon on this. So, first problem...the rods i bought are a different size! They are I think h6, 8mm. So the bearings etc take some force to get on. I got past that however. The bronze guide bearings seem ok, still pretty loose. However, on assembling it all with the new xy blocks, its all super stiff...cant move properly. I'm trying to troubleshoot now. If I loosen the 6mm rod points on the XY blocks, it gets much easier to move around. Maybe its an alignment problem on the print head. The old system was maybe more forgiving?

[ataraxis 51]

hey macua, yes the original ones are f8 (minus-minus-tolerance) and also hard-chrome-plated (as i describe here). it's important for the ease of movement and especially for the original bearings to keep that tolerance (i also ordered h6 at first but had then contact to someone "who knows it better" ). I had no problems with the linear slide bearing (the bronze ones) and the f8 shafts.

therefore I would suggest to buy new rods again,

or - if this is cheaper - new bearings (maybe linear ball bearings? i also thought about that).

Edited May 17, 2015 by Guest

[lars86 42]

Well, I spent all afternoon on this. So, first problem...the rods i bought are a different size! They are I think h6, 8mm. So the bearings etc take some force to get on. I got past that however. The bronze guide bearings seem ok, still pretty loose. However, on assembling it all with the new xy blocks, its all super stiff...cant move properly. I'm trying to troubleshoot now. If I loosen the 6mm rod points on the XY blocks, it gets much easier to move around. Maybe its an alignment problem on the print head. The old system was maybe more forgiving?

Macua, the bronze bushings are super prone to being distorted by the XY blocks. If they involve a bolt that clamps the XY block together, it needs to be almost finger tight. I ended up adding some super glue to restrain the bushing while avoiding any real clamping.

[lars86 42]

Also, having the 6mm rods out of square with the 8mm's will cause bind.

Try out my squaring arms: https://ultimaker.com/en/community/view/15770-lars-xy-axis-square

[ataraxis 51]

I don't like to contradict @lars86, you may have your reasons, but i didn't faced that problem and I think the only reason to tighten your screws that much is the fear that the screws could loose more and more. in that case I would suggest spring washers, as - in my eyes - everyone should use at moving parts.

[lars86 42]

I don't like to contradict @lars86, you may have your reasons, but i didn't faced that problem and I think the only reason to tighten your screws that much is the fear that the screws could loose more and more. in that case I would suggest spring washers, as - in my eyes - everyone should use at moving parts.

Too many variables to just say you can or can't fully tighten the bolts on a clamp style XY block.

Even if you are printing the exact same model as someone else, the calibration of the extruder, XY steppers, flow rate, filament size, etc, means that the size of the bore you print will vary. It's possible that the XY block halves seat against one another before exerting much force on the bushing. It is also possible that the bore touches the bushing first, in which case, a large force can be put on the bushing for a very small torque on the bolt (this is why we love threaded fasteners!)

What can be said without question, is that the bushings are extremely prone to deformation and binding (even the amount of force needed to compress a spring washer). It is an easy test to loosen the bolts and look for an improvement in the force needed to move the print head.

Edited May 18, 2015 by Guest

[ataraxis 51]

he should measure the diameter of the printed part for sure,... this is a good example of "separation of concerns". real deviations are not part of the responsibility of the modeler - something he could/should think about are tolerances.

if chopmeister makes a model that fits "in theory", it is up to you an me to adjust the settings (hard- or/and software) so that the reality fits the theory (with some tolerances for sure).

Edited May 18, 2015 by Guest

[macua85 52]

So I managed to get it working, the problem was indeed the bearings getting pinched. However, I now face my next problem. The holes are not round when it prints circular items. Any ideas on what could cause this? The old setup printed perfectly round holes.

[ataraxis 51]

do you already have installed direct drive? is it still the h6 shaft?

first idea: still too much friction and therefore you are losing steps in - at least - one direction.

 

• is it possible to you to move the printhead by "two fingers"?
  
• is there more force necessary in one direction than in the other?
  
• what happens when you increase the steppers current to it's maximum? (see here)
  

 

second idea: check your pulleys (and couplings), maybe some of them are loose. you can also mark the position to see if they move.

Edited May 20, 2015 by Guest

[macua85 52]

Hey, thanks for the reply. I am still using the H6 shafts, as the bronze linear bearings seem to have 'worn in' now. I can move printhead as freely as I could on my previous setup, one hand etc. its a curious one, as it appears that all of the pulleys are tight. They certainly are on the h6 shafts as they have some natural grip with the tolerances. I'll mark them as you suggest and see if thats the problem..

If i can't solve it, i'll go back to the belts...but keep the GT2 system. Would it be possible to use the MXL short belts and keep the GT2 long belts, or will I get some step/movement mismatch on the prints? i.e they come out smaller/larger etc than design.

Edited May 20, 2015 by Guest