@Martin_Bleakley - Did you make any special requests on the leadscrew (like @D_Rob has, asking for the ends to be turned down) or just bought it “off the shelf”?
I’ll probably go the 4mm lead for the reason’s you’ve listed / divides into a wider array of z heights more evenly.
My custom was for 12mm as well
What material are they?
I was thinking of just ordering them and turning them down myself if necessary (I have a serious lathe and carbide / CBN tooling)
@Jarred_Baines
I had it machined here in Auckland , in hind sight I would of had them do it at the factory, as it ended up costing me 80 and that was the cheapest that I could find here
@Jarred_Baines
Chrome plated steel. however they have a ballnut and if your machining them you need to secure in place else you have a ton of small ball bearings loose all over the place
@Martin_Bleakley I have tonne of small bearings in a jar because no one ever gave me that advice before I took apart a ball screw 
ha ha ha Yep! I’ll hold onto that tip boys, cheers 
No worries machining them here then, I’ll do that as then I can fine-tune lengths and fits
hah yeah I made sure I knew what I was doing before pulling things apart
@Martin_Bleakley In fairness I was very careful and it had to be done as there was some contamination in the race but those things are a nightmare to put back together - one day I will get around to it. Something to note with ballscrews in fact is that the cheaper ones often only have one silicone seal to protect the race and if a piece of plastic or metal get’s past it, it can make the movement rough.
Ive been lucky with mine not getting crap in it and it was wrapped well before it was machined
@Martin_Bleakley - Are you able to upload an entire assembly to youmagine (or link here) I’m interested in your xy setup now as well as the Z… They’re ‘blocklike’ but look tough and, on closer look, they seem like a really great design! Have you managed to have the belts drive point on the x/y ends the same height as the rods AND the rods of the ends and the middle shaft also at the same height? (It looks that way from pictures).
When you get around to it of course
@Jarred_Baines from what I can make out. I looks like the belts are aligned above or below the outer shafts so the distance between shafts would be constrained by the size of the pulleys driving the belts. Looks like 20 tooth gt2 pulleys to me, I assume Martin had those custom machined to 10mm bore.
@Tim_Rastall I asked for 20 tooth from robotdigg but they said the smallest they could do is 32 in a standard. Ive looked ad the wall thicknesses on a 20 tooth (eyeballed it) and it doesnt look like they have enough meat for a 10mm bore
Good point. The ones @Martin_Bleakley is using look smaller than 32/36 and it looks like he’s using 10mm shafts… Hopefully he can comment.
You guys would have prefered 20t to 32t?
I understand you can fit stuff easier with 20t but wouldn’t 32t be better for tracking the belt?
ultimaker uses 20t
Ultimaker’s also scaled down 33% from your machines though… It’s fitting that it uses a 20t pulley and we’re using 30+ in that sense…
I’m not the most learned when it comes to toothed pulleys and the advantages / disadvantages of a smaller / larger pulley, except for the more obvious points, I don’t know which is preferable… 20T gives more torque and smaller footprint, 32T gives more speed, less resolution and is available with bigger bores…
:-/
I’m going to use 10mm shafts on the outside, was going to use 32T pulleys simply because I saw you ordering a bunch rob (robotdigg are making it a standard item I think: http://www.aliexpress.com/item/GT2-Pulley-32-Teeth-10mm-Bore/1704280978.html)
But if 20T is ABSOLUTELY (not maybe, absolutely) good enough, I’d just go with them to reduce the footprint and fit in my custom X/Y setup easier.
Perhaps @Martin_Bleakley can vouch for 20T pulleys once he’s back on
those benefits/disadvantages are really more dependent on the pulley to pulley ratio. if I use 32t in my stepper and 32t on mr rods then its a 1:1 no matter how you slice it. however if I change the pulley on my motor to sat 20 then the pulleys on the rods only turn 5/8 of a rotation for every full rotation of the stepper pulley. its the same as doing gear ratios. if 20t would fit it would be ideal for the outside. then you could play with ratios to get faster speeds/lower res or slower/more intricate moves
Sorry… brainfart on my end - you’re 100% correct.
I’m thinking of direct-drive motor anyways, so it HAS to be 1:1 between my pulleys. So given that fact, there’s probably 2 main concerns;
The SIZE of the pulley (for footprint / design purposes) and the OD of the pulley (as I understand it, a larger OD has less tendancy to slip and places less stress on the teeth as it spreads the load over more teeth, therefor it is possibly better in demanding situations also)
ugh… wish I had more experience with belts… I’m so used to leadscrews and pneumatics on the machinery I’ve been involved with…
what we need is the middle ground where limited to no possibility of slipping for the forces at work and as small a footprint as possible. basically the bang for the buck er… space