Converted Z-axis to Belt Drive

I have an ord bot and converted the z-axis to belt drive. If any one has an ord bot or similar type printer with lead screws, you might be interested in making the conversion. Here's a link to it on thingverse: [www.thingiverse.com]









Here's a video of it on youtube: [www.youtube.com]

Do you have any pics of prints from the machine?

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I forgot to mention I'm waiting on a new driver for my x-axis before I can start printing. Then I can fully test the belt system holding all the weight. Once I can get it printing I'll post a video of it.

I finally got my new Ramps driver and was able to do a a first print! I'm very happy with the first print. Still need to fine tune my steps/mm, but the layers looked really good. I got a little excited and tried to yank off my test cube while it was warm and deformed it, oops. Here are some pics:








Here's a video of it printing: [www.youtube.com]

Edited 1 time(s). Last edit at 02/18/2014 09:25PM by runninfarmer.

I have now implemented a counter balance pulley system so I no longer have to worry about my bed crashing on shutdown! Uses 2 lbs worth of lead sinkers and some 30 lb test fishing line. I will update my thingiverse page. Here are some pics:

Have you printed anything big yet? I am really curious to hear if this has completely eliminated Z-Banding.

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I have done a a couple football helmets for family memebers with pretty good results. One took 15 hrs and the other took 20 hrs. Layers are great at 0.2 mm, just didn't have any retraction so that shows with some artifacts. Here's some pics of the 20 hr one:









Edited 2 time(s). Last edit at 03/25/2014 10:53PM by runninfarmer.

I was wondering when someone was going to attempt this. I'have been contemplating doing this on my FrankenDel build to make it different. It would definitely eliminate any shake that may be induced by a acme rod that wasn't quite straight.

Any other results to post??

Edited 1 time(s). Last edit at 07/13/2014 11:59PM by RC-CnC.

Hi Rc-CNC,

I ended up selling my printer, but I have printed some nice objects with the belt driven Z axis. Here's a couple pics of a pulling tractor I printed, it's on my thingiverse page:





One of the main drawbacks with a belt driven z-axis is the "drop" once the motors are shut off. The counter pulley system works, but it does complicate it somewhat. You can't beat the fast response of the belts though, making them really nice for homing and calibrating. They also do get rid of the wobbling from screws, provided your linear rails are true. I'm working on my own design and I'm still unsure of using a belt driven z-axis for it or not.

Edited 1 time(s). Last edit at 07/16/2014 01:06PM by runninfarmer.

Couple things I can think of... Using a worm gear to drive the belts would prevent it from dropping, or use a servo or spring to extend a rest. Then use the custom end GCode in your slicer to lower the z down to set on the rest.

Wouldn't a pair of 280 oz-in NEMA 23s detent torque hold up the Z-axis.

Depending on the Z-axis configuration, NEMA 23's should have enough detent torque to hold it up. For the Ord bot, I don't think they will. When the x-axis is apart of the z-axis, the added weight from the x-axis motor is substantial (~200g or so). It's best to belt drive a Z-axis with table only, as opposed to an additional axis with it in my opinion.

Geared NEMA motors would be the ultimate way to prevent drop or the worm drive as mentioned by Mike. I think the worm drive could get complicated/costly to implement, though I don't know since I've never worked with one. Another issue with NEMA 23's is current requirement vs board limitations. I'm not sure how well RAMPs would support NEMA 23's.

voltage and current etc are what is important, you can get nema23 that work on pololus and even more on drv8825

you can easily get Nema 23s working with RAMPS via external Drivers.
I saw a schematic of someone attaching stepper driers like these:

[www.arceurotrade.co.uk]

to his ramps.

If anybody is interested, I can upload the schematic here for you guys to tinker with it.

Alex

You can also double, triple or quadruple the belts on a Z stage with pulleys to effectively gear down the Z motor and use a basic NEMA17. I'm doing a build at the moment with tripled belts on the Z bed lift (and CoreXY for the hotend), i.e. it takes 3 rotations of the 20T GT2 pulley to move the bed by 40mm (motor pulley circumference).

With 0.65Nm stepper, that's about 30kg of lifting force; I don't yet know if it will drop when powered off but I expect not (or at least slowly) due to the gear ratio.

A geared/wormed stepper seems a bad idea due to backlash if you ever intend to do Z-lifts while printing. Gearing via pulleys should have better backlash behaviour due to being under tension, and it does not increase the stress on the belt or pulley teeth.

Edited 1 time(s). Last edit at 10/08/2014 10:36PM by polyglot.

I have played with using more pulleys to divide up the force necessary to support the carriage. Problems can arise in terms of finding solid anchor points for the pulleys. I found I was running out of convenient extrusion space, until the design would get too complicated. It's definitely better to get something like that working than counterweights.

Edited 1 time(s). Last edit at 10/09/2014 01:09PM by runninfarmer.