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Alu reprap

by larsie, published

Alu reprap by larsie Jan 8, 2012
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This is partly a derivative of http://www.thingiverse.com/thing:14208 (which is a variant of the printrbot). I recommend the printrbot variant on Thingiverse (the link above), as it's a nice and compact design. The files required from the above design are slightly modified and are provided here http://www.thingiverse.com/thing:15634 (separately due to GPL licensing of the original parts). The x-carriage can be used straight from the original design, but change the rod size to 8mm.

On this design, the smooth rod has been changed to be on the outside, and the frame uses an aluminium sheet instead of rods. I'm still calling it a reprap, as it relies on lots of printed parts to be operational.

The z-belt has been replaced by a printed rack, which partly based on http://www.thingiverse.com/thing:11642 and inspired by http://www.thingiverse.com/thing:6011 and http://www.thingiverse.com/thing:14537. The x-axis still uses a belt, and a printed pulley. I doubt the Y-axis rack is better than a belt, but it remains to be seen. The design supports a printrbot-type Y-belt if you want to use that instead.

I've tried to make this printer really small, and the print area is too small right now to be usable. I either have to mount the extruder 90 degrees to what it is now (might be the simplest), use a bowden extruder, or use an entirely new not yet invented extruder, I'm aiming for a print area of about 120 mm, which should be possible. This is the main thing I have to fix before this printer is good enough. I haven't printed with it yet, but it feels very stable and I think it'll do well.

The bot is 250 mm wide, but could of course be made wider. The stepper for the x-axis (printrbot-variant design) goes outside 'the box' (alu sheet). I've been toying with the idea of making a different x-axis end which keeps the extruder inside 'the box', for example by turning it 90 degrees and having it upside down like this: http://www.thingiverse.com/image:96329

The bars are 8mm. I use NEMA17 for the z-axis and NEMA17 for the extruder, and NEMA14 for the X and Y axis. The printrbot variant files can be edited to use NEMA17 all over instead if you wish. If you use his files, you'll need to fix the distance between the smooth and threaded Z rods also. Mine are 27 mm apart, between the centers.

It uses LM8UU bearings. The base that holds the bearings for the Y-rods is a bit weak around the bearings and needs a redesign. But I lost the source file and haven't had time to fix it yet. Will do if there is demand.

The rack-gear made using http://www.thingiverse.com/thing:3575. Note that this library is LGPL, but I have taken the liberty of posting the part here. Consider it distributed under LGPL.

As a coupling for the z-axis I'm using http://www.thingiverse.com/thing:11220 without any changes. I also use it on my prusa, and it works great, reducing z-wobble.

One possible improvement to this design is to not print the full height of plastic for the z-height, allowing the x-end to go a bit further down (it's being stopped when the nut-holder hits the coupling).

I've made various other test designs, including one without the alu sheet that uses plastic instead: http://www.thingiverse.com/image:95169 . I have also made one with two bars on each side of the z-stepper instead of on the outside, but dropped that idea. http://www.thingiverse.com/image:98180 (I don't really need two bars on each end. One should have been enough.)

I'm looking at it now and think I could add another 2 cm build area (1 cm each side) by doing this. The reason I didn't was I then had to design the top parts myself instead of using the printrbot variant.

There is a video of it moving at: http://youtu.be/IaLl8jtqlT8

You can of course use other things than an aluminium sheet. Other metals, but you can probably use a wooden structure also. The printrbot concept seems ok for making a repstrap without many plastic parts, if you don't have a friend who can help you with printing the plastic.


I haven't yet provided the plans for the aluminium, but it's easy to make based on the below instructions. Get hold of a sheet of aluminium (1-2 mm thick) that is about 250 mm wide and 200 mm long. If you use a wider aluminium sheet, you get a wider printer ;-)

Then bend it twice, so that it's a square shape as seen on the photo, with a 60mm top (measured inside). It should fit the alu-reprap-base in each side. You can then put the alu-reprap-base on top of the aluminium shape and mark where you want to drill the holes. I use a 4 mm drill for the screw holes and 8 mm holes for the bars. Print the alu-reprap-y-stepper-holder also and make holes for it. Then drill holes on the side for the Y-rod and make a slot for the Y-rack, as seen on the picture. I made the slot using a dremel, but I guess you can saw it somehow also.

Most of the screws need a nut on the other side. The 8mm smooth rod just slots in through the aluminium and into the plastic base. I don't have any screws etc holding it.

You need to print two of the makerbottable rack and fasten them using a 6mm threaded rod with nuts on both sides. Then fasten this rod below the base by using the alu-reprap-y-rod-holder.

Refer to the printrbot variant page for instructions on the top part. I have to make some changes to it though, to get a larger print area.

Screw everything together...

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Very nice! I am in the process of designing a Y-axis utilizing a rack/pinion system as well. How is the precision along that axis?

:) I haven't tested it a lot, but it seems OK. It might bump the platform upwards a bit as it moves, so it's probably not as smooth as being moved by a belt only. But I think I need to test some prints to see if it works well. I have no slack on it, and even the 0.1 mm seems to move the platform. I was also considering a rubber wheel instead of the rack/pinion, which might be a comparable option.

It might be smoother with some spring mechanism. The rod I used should really be springy, but then I put a beam under it so it's really straight against the above platform. That might not be optimal. Someone said one could put some cloth in-between the gears to make them smoother, and that may also be an option.

This purports to be distributed under the CC-BY-SA license, but is a derivative of several GPL works -- did you get permission to do that license change from the original authors? or are you failing to comply with the GPL, by not publishing the SCAD source for your derived work (as well as changing the license of course)?

You are correct. I have removed the components that are GPL. The RACK is in fact not a real derivative. I made it in Moi3d.

I think I've fixed it now. The printrbot variant files were GPL and are now under a derivative based on this part, with the source files. The gear may still be an issue, as it's LGPL and I've got it on this page, but I've noted in the description that this part is LGPL, and I've given the code to generate it here. As to my files, I'm planning to release them, but I unfortunately lost some of them due to a bug in Moi3D, so I have to recreate them. But these aren't openscad and are not parametric unfortunately. Thanks for reminding me of the licensing issue.

np -- glad to be of service :-)

Sorry to hear that you've lost work -- you might want to look at using some form of version control system to ensure that doesn't happen again.

As a free software person, I'd suggest git (http://git-scm.com/)http://git-scm.com/) but it's perhaps a lot to learn if you're not from a software background already. If y
ou do put the effort in to learn it though, it will almost certainly repay the effort.

Thanks. The problem this time was that Moi3D said it had saved the file, but the save failed (silently) because the same file was open in another program. But yes, I should use GIT as well. Wouldn't have solved this problem, but many other potential ones.

Thanks for sharing!

IMO, some value of 125 up to 150mm should be ok for the Y axis. X can be wider.

I see you are not using foots to stabilize with the shaking on the Y axis moving, it is need since my experience (although I used Nema14 for Z axis, they are smaller and have less weight).

"smooth rod has been changed to be on the outside" ---
gt; could you explain your motivation?

Why did you choose Nema17 for the Z axis? I used Nema14 and they seem to be ok. Also Nema14 is ok for X and Y. Even for extruder Nema14 is ok with Wade and printing at 50mm/s and 0.3mm layer.

Here is my shared pictures and videos: http://reprap.org/wiki/Printf.bothttp://reprap.org/wiki/Printf....

Yes, I should probably use feet. It's quite heavy now and seems stable, but I expect that once I start printing I need feet. I like the feet design of the printrbot variant. I have some rubber feet on it that are screwed on, but they don't help stability.

I changed the smooth rod position in an effort to see if this could increase print area for a given width. It doesn't make a big difference, but does help. The position of the inner rod limits the movement of the X-axis. But it probably requires more plastic when printing the parts. I also did it
to try to make it a bit different from the original design :) and to try something different. I also made one version with two smooth rods on each side of the stepper. I actually printed it, but reverted back to just one smooth rod for this published printer, really because I could use the printrbo
t variant files for the top parts. It was very stable though.

Regarding the NEAM17 vs 14. I think as you say that NEMA14 works fine. Long story why I ended up with this, but it was basically because I originally wanted to test both types of z-motors on the same printer. If 14 worked ok, I was thin
king of making a new one which only could use 14 later. I've made a NEMA14 gregs extruder also, but haven't tested it. Glad to hear that it works. Mine was getting a bit hot when I tested it, so I didn't dare running it properly. But maybe I should have tried.

It's all a learning experience :)

I'm not seeing the X carriage, did you use mine for that too?

Yes, it is yours also. I didn't post it here, as it has no modifications from your design. I might try to make one where I can mount the extruder differently, unless you come up with something clever that takes less space :-)