Delta pulley and idler dimensions question

I have just realized you replied while I was editing my previous post so I'll post the edit in a new reply. Here it is:

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realthor
Edit1: If I were to print a belt clamp with the two reversed negative shapes for the belt, I am afraid that will be quite long and I would still reduce the Z max. But I'll have to measure that on the real distance between the idler and the top carriage position.

Edit2: I just realized that timing belts can clamp on themselves to lock, so that might be the ticket to be able to achieve the third diagram without modifying the existing carriage. The clamp shouldn't be higher than the existing teeth lock on the carriage, which run for about 8 teeth worth of length, which, at 2mm pitch would be around 16mm. I have measured the existing embedded clamp and it has 22.6mm, while the distance from the end of the carriage to the pulley is about 30mm. This looks definitely feasible.

Edited 3 time(s). Last edit at 12/16/2015 06:40AM by realthor.

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I'm thinking about going over to 16 tooth drive pulleys and these idler pulleys [pages.ebay.com] that should improve resolution and provide reliable idlers. The 3mm bearing will wear on the 3mm bolt but at an acceptable rate.

Why not use quite large idler pulleys to reduce their rate of rotation, this should reduce noise/vibration and bearing wear?

Edited 1 time(s). Last edit at 12/24/2015 03:53AM by DjDemonD.

If the idler and stepper motor pulleys do not have the same diameter, then the belts will not be quite vertical. So I suggest you choose idler pulleys with the same number of teeth as your stepper motor pulleys. Also make sure that the pulley diameter is compatible with the position of the slot in the carriage for the return belt.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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DjDemonD
I'm thinking about going over to 16 tooth drive pulleys and these idler pulleys [pages.ebay.com] that should improve resolution and provide reliable idlers. The 3mm bearing will wear on the 3mm bolt but at an acceptable rate.

The resolution gain is minimal I don't know how much you would be gaining if you aim for that. I went to 20tooth pinion and 2 flanged bearings that have a difference of 0.4mm in diameter difference when the belt rides on them with the teeth on the bearing; if I reverse the belt then the diameter of the pinion+belt should be about the same with the idler+belt.

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DjDemonD
Why not use quite large idler pulleys to reduce their rate of rotation, this should reduce noise/vibration and bearing wear?

Please check the sketch I have attached in my first post. I subscribe to the larger idler idea and would have used it from the beginning should I have designed my own printer. You only have to make sure the driving side of the belt is perfectly vertical so you would have to offset the idler center to one side somehow.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff