Ord Bot X-Axis Leadscrew

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Ord Bot X-Axis Leadscrew

Postby evil2002usna » Sat Apr 12, 2014 7:49 pm

I have never really been happy with the belts on my 3d printer. No offense to Bart, the original idler brackets worked but were difficult to tension IMHO. Online idler brackets like Flurin's worked better but eventually the belt would stretch and start to wear so your prints would start out great and then eventually over time get worse. Over the past couple of months I have been trying to decide if there were any other options and what the best option was. I have seen Prusa's with Rack and Pinion Drives, I have seen the threadless ball screws on Thingiverse, and I have seen some leadscrew driven printers as well. The rack and pinion is expensive and difficult to implement with the space I have allotted for my Ordbot. Inexpensive leadscrews are slow, and I have heard that the threadless ballscrews slip alot.

A couple of months ago I decided to spend the money and buy a really nice all aluminum extruder. It has been one of the best purchases I have made for my printer so far. As such I realized that if I wanted my printer to work the way I expect it to, I am going to have to spend the money to make it better. So i decided to buy one of the high speed leadscrews from Trinity Labs. It is the same leadscrew that they are using on the aluminatus. The screw and the nut are only $100.00 so it is expensive but not out of my price range.

Now all I have to do is redesign the x-axis carriage mounting to work with a leadscrew design. I have already started with the x-axis gantry left and right plates. The left plate has an integrated motor mount for a Nema 17 motor. I have left the rest of the design true to Barts original. On the right, no changes were made except to increase the thickness to make it stronger since it is made out of PLA. I have designed an idler thrust bearing block to hold the shaft on the right side that just screws into the Makerslide. I did have to buy a longer piece of makerslide for the x-axis to give myself the room to print on the 200mmx200mm bed. My extruder sticks out pretty far to the right on my carriage. I am at the point now that I have to design the extruder carriage. Anyways, I just wanted to show you guys how far the design has come. As I make progress on the extruder carriage, I will update with more pictures. Once I get everything done, I will upload everything to Thingiverse. If anyone is working or has worked on anything similar I would love to see it.
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Re: Ord Bot X-Axis Leadscrew

Postby orcinus » Sat Apr 12, 2014 8:07 pm

Online idler brackets like Flurin's worked better but eventually the belt would stretch and start to wear so your prints would start out great and then eventually over time get worse.


I've used the MXL belt for about a year, then used the GT2 belts for about a year.
Must admit i've never noticed any stretch or wear.

But even so, there are other solutions to the problem - like switching to a much heavier duty belt, e.g. Laszlo's T2.5 belts:

Image

They're tough enough that cutting them with diagonal wire cutters isn't a one-snip job (they're much stiffer too and virtually impossible to stretch).

But given enough funds, multiple start leadscrews should definitely be a nice option.
I'm very interested in how they perform, considering they make the platform way more constrained than a belt-driven system can ever be.

So please post some updates as soon as you get some results! :)
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Re: Ord Bot X-Axis Leadscrew

Postby evil2002usna » Sat Apr 12, 2014 11:55 pm

I may try those belts for my y-axis. For some reason, I have not had as many problems with that axis as I have with the x-axis. However, it is starting to stretch a little after over half of a year of use.
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Re: Ord Bot X-Axis Leadscrew

Postby r691175002 » Sun Apr 13, 2014 1:05 pm

It's interesting to see so many reports of stretch because one of the characteristics of timing belts is that they do not stretch because of the steel/kevlar/fiberglass reinforcement. A 3d printer is really a very low load application for belts as well. Could the apparent belt stretch just be other parts shifting over days/weeks of vibration?

I could see knockoff timing belts stretching over time, but genuine belts really shouldn't.
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Re: Ord Bot X-Axis Leadscrew

Postby orcinus » Mon Apr 14, 2014 1:49 pm

There's another possible source of "stretch" - clamps. Even when you think your clamps are very tight, there can still be some deformation and slippage. I usually stuff thin plastic shards (print leftovers scraped off the bed) between the belt and the clamp walls. When I can't get them in by finger anymore, I hammer one or two more in there with the screwdriver handle.

Mounts loosening over time are a good point too, though. I've put foam padding on the undersides of my mounts (the side that's in contact with the makeslide. That's pretty effective at preventing any slipping due to vibration, even if they're not tightened 100%.
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Re: Ord Bot X-Axis Leadscrew

Postby evil2002usna » Thu May 08, 2014 5:46 am

Update, I finally have all the parts printed and was able to perform a motion test tonight. Seems to work pretty good. I will post some print samples when I get the motor hooked up and the wiring cleaned up. Here is a picture and a video.

https://www.youtube.com/watch?v=_tA0cX0WMNE&feature=youtu.be
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Re: Ord Bot X-Axis Leadscrew

Postby evil2002usna » Mon Jun 02, 2014 3:13 am

It took a while and some tinkering, but I now have the leadscrew working well. As of this point, I have only done the x-axis. I will let the y-axis belts ride for as long as they last and then I will decide if they need to be upgraded. I have attached some print samples. Right now I am very happy with the print quality. I still need to design a fan mount for the hot end, but that is not what everyone came to see. Here are the prints. I printed a cube and my iphone alarm clock mount. Additionally, I have linked the Thingiverse webpage. Their is s video of it printing on the webpage. I am still making some modification to the parts that I think will improve the design. I have already added a new x-idler and I am working on changes to the rest as well.

http://www.thingiverse.com/thing:346429
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IMG_0881.jpg
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Re: Ord Bot X-Axis Leadscrew

Postby orcinus » Thu Jun 12, 2014 5:25 pm

Are the variations in layers visible in the prints present on both axes or are they limited to just the belt or just the screw?
How's the "shadowing"? Any less artifacts around holes perpendicular to the leadscrew axis?
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Re: Ord Bot X-Axis Leadscrew

Postby evil2002usna » Fri Jun 13, 2014 11:34 pm

The variations in layers are consistent on both axis. I am pretty sure whatever is causing the variation is something to do with my z-axis, extruder, or Marlin settings. All of my holes come out very round with no gaps between the infill and the hole perimeters. When I look at my infill on both axis, it is very consistent leading me to believe that the lines come from elsewhere in my printer.
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Re: Ord Bot X-Axis Leadscrew

Postby orcinus » Sat Jun 14, 2014 9:56 pm

Probably extruder, then.
Have you tried reducing the microstepping on the extruder driver?
Assuming everything else is tight and backlash-less, it might help.

Any luck reducing vibration artifacts (ghosting/shadowing) using the lead screw instead of belt?
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