Accurate, heavy duty timing belt

Hey all,

I'm building a relatively large coreXY printer and I wanted to get some advice on belts.



Here's the legend for the image above:
Orange square = print bed
Blue stars = leadscrews driving the Z axis
Green diamond = Nema 23
Red stars = Drive assembly connecting the Nema 23 and the individual leadscrews

I'm using a piece of tooling plate for the print bed, which is quite flat but unfortunately quite heavy (it's about 10kg / 22lbs). That's without the heating silicone attached too, or the level adjusting hardware (probably another kilo). Since it's a large bed I'd expect that maybe an extra kilo or two might be added in plastic. So overall we're probably looking around the 14kg (31lbs) mark.

I was thinking the purple belts connecting the leadscrews to the drive assembly might be fine as standard 6mm GT2 belt. There'll be reduction gearing by the size of pulleys between the Nema 23 and the leadscrews, so if they can handle an equivalent of 5kg each it should be fine. Yes, I've got a tensioner for each of them.

What's got me stumped is what I should do for the pink belt, connecting the Nema 23 to the drive assembly. Would 9mm GT2 be fine or is there something else that could be suitable? It would benefit from the gearing so wouldn't ever have to move the full load very fast at all...

Does anyone see anything wrong with any of this too? Even if you doubt a Nema 23 could handle that load I'd be interested to know.

Calculate the torque required using [www.orientalmotor.com]
The torque needed will be a function of the screw pitch, gear ratios, load being lifted, etc.

Check belt manufacturer's info on maximum belt loading.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

So 10 lb on each leadscrew, they won't mind it at all.
What type /size leadscrew?

Pink belt may not afford enough tooth contact to transmit the power.

For good torque transmission need > 6 tooth contact

Ref: [sdp-si.com]

Why not eliminate the pink belt by stacking red pulleys on motor.
or
if you need reduction make a four stack
with pink belt having 180 deg pulley contact.

Why this configuration instead of triangle circuit
around lead screw pulleys?

I'm not that worried about the leadscrews, it's mostly the belts which hold my concern. I won't be using standard 20-tooth pulleys but rather 32-tooth at the minimum, maybe much larger in some instances. This should ensure a decent number of teeth have contact with the belt at any one time.

I'm also more than happy to place bearings at various places to guide belts to have more contact.

Finding ratings for the belts have been quite difficult.

Having a number of pulleys on a single rod would be a fine solution but it's a pretty inefficient use of space. I did consider it but my Z height would suffer unnecessarily.

Your leadscrews are giving you tremendous mechanical advantage.
Will you bed be lifting very heavy weight?

Quote
pugzor
Finding ratings for the belts have been quite difficult.

What ratings? Power Transmission?

[sdp-si.com]

[www.gates.com]

The larger the pulley the larger movement per step of motor?

Beware non-standard back and forth motion -- not pure rotation power transmission.

You are using these for mechanical positional operation very little and very slow power transmission.

You really don't care about rating, your going to get cheap Chinese belts and pulleys
and get on with life