Fixing Pulley Innacuracy

[nick-foley 5]

All I'm saying is that even though a dead center isn't perfect on a lathe, it is certainly more effective than just slamming a wooden block (or a flat piece of metal) against the end of your workpiece - which is equivalent to the stock endcap solution of an Ultimaker (or the flat end of the machine screw in the printed upgrade variant).

Edited to add... (so this thread doesn't get even further off topic with more posts...) ... surely this isn't a necessary upgrade - but the argument for it not being an improvement seems pretty thin.

 

Your argument doesn't make sense to me.

 

 

[lars86 42]

All I'm saying is that even though a dead center isn't perfect on a lathe, it is certainly more effective than just slamming a wooden block against the end of your workpiece - which is equivalent to the stock endcap solution of an Ultimaker.

 

The solution is to print end caps, and use m3 bolts to locate the shafts axially. No preload, no cutting tapered holes into the shafts. It's far more simple than you are trying to make it. Just concede.

[nick-foley 5]

Edited my previous post to clarify, and prevent this thread from veering even further off course. And to bring it back:

My pulleys still suck. I don't know if mine are particularly eccentric, and I don't have a good way of measuring the force it takes to move across an axis, but I wouldn't be surprised if the necessary force periodically nearly doubled when moving by hand.

I want to purchase another set, but having missed the improved MXL batch coming from Markus, I'm looking for other options, and thinking about moving to GT2 in the process. Has anyone purchased the chinese GT2 pulleys from ROBOTDIGG?:

http://www.robotdigg.com/product/9/GT2-pulley-20-tooth-5mm-bore-for-6mm-gt2-belt

The 5mm bore ones seem appropriate, but don't have enough meat to open to 8mm... and the 8mm have an MOQ of 200qty. I'm sure they could be persuaded to take a lower quantity order... but are they a big enough improvement over the Adafruit version?

 

[snowygrouch 1]

IMO as soon as you start buying anything with a smaller bore and drilling it out later, you are always going

to have unnaceptable runout.

I think unless they are machined in one op. from the formed toothed bar blank, you are just stuffed from the start.

Once you have something as short as the finished pulley, getting it located in the chuck properly will be

very very hard.

Probably you could make up a nice little fixture to do it, and if you have a 4 jaw chuck you can sit

and tweak it all day until its running true. But then the issue is...true to what?

True to the original bore (which will in turn be slightly out from the pulley teeth), or true to the teeth...which

once you have the pulley with the belt flanges pressed on will be very hard to either measure or located onto.

I think the only way is to get them made like Markus. With the right spec from the start. I am sure there are firms

that can do it properly, but its just a question of finding them. Since it looks like Markus has already done so,

for me the reasons to look further just dissapeared (pending me testing them of course !)

C.

 

[johan 0]

Adafruit is selling Gt2 pulleys with 8mm bore.

Johan

[nick-foley 5]

Adafruit is selling Gt2 pulleys with 8mm bore.

Johan

 

Can anyone comment on the tolerances of these? I'm already somewhat disappointed that I have to replace my stock pulleys... I'd hate to purchase another set only to find that my new pulleys also started out in life as flywheels for pager motors.

 

[lars86 42]

I just wanted to thank Markus again for organizing this pulley order, and Joergen for handling the US shipment. I haven't installed them just yet, but the quality and runout (lack of) are top notch!

Cheers!

Lars

 

[illuminarti 18]

Hear, hear!! They look great - I hope I'll get a chance to install them soon. Thanks to both of you for making it happen.

Since I'm taking it all apart, I figure it's probably a good time to replace the belts too... anyone got any advice on what's the best thing to replace the stock belts with for use with these pulleys?

 

[lars86 42]

Good question! I'd love to hear some opinions too.

 

[owen 19]

I've just gotten a new set from UM. I won't be tightening them too much this time though. Over tightening doesn't help your prints but stretches the belts.

 

[johan 0]

@ Nick Foley:

I have bought a full set of them, and they look good. I haven't replaced them yet, but it fits nicely on the Misumi smooth rods I have bought to do the direct drive upgrade.

[mostlyatomicbob 34]

I added my set of pulleys to my machine at the weekend and there is absolutely no run out (visibly anyhow).

It is hard to quantify improvements as I added them at the same time as switching over to direct drive.

Overall with both upgrades my prints are better and well worth the money.

 

[thingster 0]

At least after my notices a direct drive system has less impact on print quality than play-free pulleys like the ones from foehnsturm. These new pulleys are truly a great deal. So what a shame Ultimaking uses such crappy pulleys for their stock machines. The Ultimaker is not a cheap 3d printer, so I think everyone could expect a bit more quality from its components...

[gluetools 0]

I received mine this week. I have to head out for a business trip, so I can't install mine right away.

Can anyone that has installed these describe what they experience?

Markus,

When I visit München this fall, I would like to meet up an say "hi"!

Thanks for the R&D!

bob..

 

[gadgetfreak 7]

Lars and Nick, thanks for your comments and sorry for my late reply.

I actually did drill V-shaped indents into my rods to prepare for a future improvement, but after reading Lars reply I'm unsure.

I haven't really been able to assess the new pulleys/belts as I've encounted another annoying extrusion problem (I've started another troubleshooting thread on that) so I'll leave this until the extrusion problem is solved.

Later I can put up pictures of the lathe drilling and if I modify the end caps.

Has anyone else done before/after calibration prints to assess the new pulleys? Would be nice to see

Cheers

Daniel

 

[foehnsturm 969]

Hi all,I'm very happy that you appreciate the parts. I will forward the compliments to the manufacturer.@Bob,

I would be very happy to meet you this fall. Like beer gardens?

 

 

@Everyone who asked for pulleys since then,

 

There will be a second batch!

I will reply to your messages when I'm clear about the schedule.

 

 

Markus

 

[smoother 0]

Hi Markus.

Received the parcel. Pulleys are made perfectly. Thank you so much.

Sergey.

 

[makingzone 2]

Hi all,

I'm very happy that you appreciate the parts. I will forward the compliments to the manufacturer.

@Bob,

I would be very happy to meet you this fall. Like beer gardens?

@Everyone who asked for pulleys since then,

There will be a second batch!

I will reply to your messages when I'm clear about the schedule.

Markus

 

 

 

Ok we waiting about !!! Thanks in advance

 

[piranha 1]

Hi Markus, good news!

We are waiting next batch!!!!!!!

[snowygrouch 1]

Pulleys received with thanks, currently installing - and taking opportunity to replace XY blocks

with MoonCactus`s printed ones...I hope they work ok.

Will post results late tonight, have to pause in installation to go outside* to get food.

(* A desolate barren place with no printers)

 

Ughhh I really really need to get a proper camera...these pics are useless

 

[tz-advantage 0]

If there will be another batch i would like to reserve a full set.

 

[makingzone 2]

+1000 for the batch ?

What was the price of the pulleys ?

 

[snowygrouch 1]

Will post pics later, but result for me is postitve.

 

Good points = vertical lines in print corresponding to pulley tooth pitch are almost gone now

Bad points = improved accuracy reveals even more the negatives from the Z carrige wobble and vibration.

 

 

[lars86 42]

Will post pics later, but result for me is postitve.

 

Good points = vertical lines in print corresponding to pulley tooth pitch are almost gone now

Bad points = improved accuracy reveals even more the negatives from the Z carrige wobble and vibration.

 

 

So, it's not just me! I am also noticing a lot more randomness in the XY plane (obviously no fault of the pulleys). I even have large weights glued to the front underside of my bed, and rubber bands pulling it to one side, in order to take the lash out of the 12mm bearings, and make it less resonant. Over extrusion definitely makes it worse, as it increases the force that the nozzle exerts against the part/bed. I've been printing a new print head, which is a very long print, and to avoid the occasional layer of under-extrusion (thin bit of filament?), I've tuned for slight overextrusion, so I get a strong part.

If we can just get the bed rock solid, the prints are going to look amazing!

How are you liking the XY blocks? (besides the limit arm misalignment) I've printed mine, but need a little more hardware to install.

 

[tz-advantage 0]

If you want to straighten out the bed you could use some reinforcements on the outer case and use a "moving knot".

The CNC guys use this to make sure the gantry moves on both sides exactly the same.