Prusa i3 Improved for laser cut

by twelvepro, published

Prusa i3 Improved for laser cut by twelvepro Jan 1, 2013
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Prusa i3 Improved for laser cut by twelvepro is licensed under the GNU - GPL license.

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We found latest Prusa i3 printer design, the one Josef Prusa showed at Makerfaire this year in New York, for its elegant simplicity, but hinge like connection between Y axis assembly and frame needed improvement, in our opinion.
Using CAD software we reworked Prusa i3 design:


You will need (for now we using mixed SAE and metric parts):
Smoth Rods (8mm)
X-Axis: 2 x 15"
Y-Axis: 2 x 16"
Z-Axis: 2 x 12.5"

  • If you purchase 36" (1M) smoth rods, you will need 3 of them
    Threded Rods:
    3 x 8.5"
    1 x 12"
    2 x 17.5" (18")
  • it will take total 2 x 36" (1m)
    5 mm for Z- Axis: 2 x 12"
    We stil working on instructions and complete BOM.
    Kit available for purchase.
    Happy New Year to all!!!

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bonjour, je voudrais savoir a quoi sert la pièce : buddasch_i3. Merci d'avance

For future changings, the y carryage bed has three holes, but the y belt clamp has only two mounting holes...

where to order steel parts?

how do you mount a heatbed to it?

and sorry for asking but I don't find an assembly instruction

where do I install the unthreaded spacer

hi, the parts you used are fully compatibles with the prusa i3 rework? the suppoonly diference is the wood motor support?Smooth and threaded rods are the same from the rework?

We published our design about 6 month before Prusa i3 Rework came out.
I would ask them about compatibility :0)

What is the minimum size of laser cutter required to cut this frame?

thanks for sharing he design.

Do you have the OpenScad file for the Xcarriage?

Sorry, no SCAD files

thanks for the reply, do you have any source file so that I can tweak the stl for my printer? It would really help me a lot. Also the source for the Y belt clamp would be an help.

What is the difference between Laser Cut Parts and Laser Cut Layout DXFs? Which one should we send to be cut?

i just got my set delivered from snijlab.nl
and i used Prusa_i3_Frame_V2_Laser_Cut_Parts.dxf and it's spot on so far

Thanks for the answer. I will probably use this file then although the Layout DXF seems to waste less material, the parts are better arranged on the sheet

Feb 27, 2015 - Modified Feb 27, 2015

I thank you for this nice design.
i think i have spend 3 days figuring out the best laser cut design until i stumbled upon yours.
Can't wait till my parts arrive, this build will cost me 200 euro which isn't that bad.
I have spend a week sourcing parts to get the best deals possible.

I tip my hat to you.
Thanks and greetings from Holland..

Thank you, please upload some pictures of your build.

What is the quantity and length of screws required to assemble the frame? Thanks!

One of the files for download is a BOM (Bill Of Material) should have all information needed.

Will the laser cutt able files need to be scaled or altered to be cut?

No scale needed.

Also, is this for a 6" or 8" prusa?

8", MK1- MK2 heated bed.

Also, is this for a 6" or 8" prusa?

What type of J-head extruder holder is compatible with the X-carriage?

I can't find any use for Prusa_i3_Z_Shaft_Cup and Prusa_i3_X_Carriage_Belt_Clamp. Could you provide closer explanation of theirs use? Thanks!

The shaft is used on top of the z axis and z threaded rod, but I think it is useless. The other one I don't know...

In Prusa_i3_Frame_V2_Laser_Cut_Layout WRONG size, please correct it.

Could you please be more specific what sizes are wrong?
It was designed based on original Prusa i3 design, all plastic parts are still compatible.

I am wondering, why does the lasercut plan have 3 holes for the y-belt clamp, but the included part only has 2 holes?

New .DXF file was uploaded

Thank you for a new drawing. On the new drawing dimensions are normal.

Is this made for m8 or m10 rods?

The threaded rods are 8mm

Yes you can use plastic parts from Prusa i3 design

Doesn't the Prusa i3 design use M10 rods instead?

Would it be possible to use regular Prusa I3 printed parts with this?

The .dxf file seems to be scaled 2:1. Pay attention, it may need some work before ordering it from a laser/water cutting company

Any recommendation for an extruder? I got all files waterjet cut and parts ready to go, I am just not sure which extruder to attach

Prusa i3 mini X-carriage for GT2 belts with 30mm spacing
Greg's Wade extruder for Prusa i3
by misan

BOM seems to be not ready yet?

Hello fellows,

I'm planning to use this model to build my Prusa i3.
I just need to be sure about the size of the rods:

Smooth Rods (8mm)
X-Axis: 2 x 381mm
Y-Axis: 2 x 406mm
Z-Axis: 2 x 318mm

Threded Rods:
5 x 406mm
3 x 216mm
1 x 305mm
2 x 445mm or 457mm (?)
5 mm for Z- Axis: 2 x 305mm

Can someone please help me?
I just need this measurements in millimeters.

Thanks so much!

I used X:385 / Y:405 / Z:320 for the smooths and they are only a few mm in excess (6mm for Z, 5mm for X and doesn't matter for Y). There is no problem exceeding a few mm from the exact length so I rounded up the lengths.

For the threaded I used 3 x 210 / 1 x 280 / 2 x 440 for the Y base (8mm) and 2 x 310 for Z (5mm), but 305mm would do fine. You only need 8 threaded rods to assemble it.

Where is the Bill of materials? Still working on it?

Where can I buy plastic needed?

would this work with 1/4" wood?

Yes, it will work. We use it with no problems.

Where can I buy plastic parts for this model?

Before I built my printer I got my parts printed by BusyBotz at http://www.busybotz.comwww.busybotz.com

So which bed did everyone go with? Has anyone designed a 3 point leveling system for this variant?

Hi. Great design !
I am wondering to do or buy one, but why did you use metric and imperial ? Could we use only metric ?


Yes, you can do it...

Just curious. Has anyone else noticed, or experienced issues with a potential flaw with this, and most i3 variations (seemingly including the original). Where the y-bed attaches to the main frame, there's nothing really holding it in. The bed simply sits in the two grooves for the threaded rods.

If your surface isn't absolutely perfect, you'll never get a flat bed. Really those groves in the frame need changing for simple holes. That way even if one corner wasn't level, it shouldn't cause so much of an issue as right now the bed will just sit slightly higher up thanks to the groove.

You can tighten bolts on either side of the groove as much as you like, however having only been using my new i3 for a few weeks have had to re-tighten them twice, and found minor variations in bed level each time.

Curious to know if anyone else has mentioned this issue, and if there is in face a better way of keeping the bed firmly attached to the main frame. Maybe some sort of extra (printed) mounts that attach under the bed?

I would suggest use nylon luck nut instead of regular nut. When you mount heated bed, you should use springs (1 for each corner). Some heated beds are bended from corners to the center, then best choice would be a glass on top of it.

What thickness material is this designed for?

It was designed for 6mm material thickness.

Thank-you for the fast reply.

What is the size of the table for laser cut?

It is made based on MK2 heated bed sizes and have mounted holes.

WARNING!!! DO NOT BUY FROM TWELVEPRO! I placed an order with twelvepro from Australia. All they sent me was a tracking number for a parcel sent to Switzerland??? They will not reply to any of my emails. Very disreputable company!

Mxdbag said: WARNING!!! DO NOT BUY FROM TWELVEPRO! I placed an order with twelvepro from Australia. All they sent me was a tracking number for a parcel sent to Switzerland??? They will not reply to any of my emails. Very disreputable company!

He place order, we send it out with 2 weeks delay. Ship to Australia.
He changed address and was sending nasty emails...

as thingverse is for things.. and i have ordered many times from them and always received what i ordered and in a timely fashion I'm going to call bullshit. You need to take Ordering/Orders up with them and and leave them off thingiverse.

Hello, what extruder are you using?, Where did you find it?

at this moment is the buddasch and x-carriage compatibles?

Just to help the next guy I am posting here that this latest files X-Carriage and buddasch they are not compatible. Holes do not match, and some other problems. Do not waste your time printing them.

the stl files are missing the extruder/hot end carriage!!

i bought these plastic parts on ebay, but your stl files are missing a part. wheres the hot end/extruder mount to lm8uu printed part?

would it be possible to cut this with a cnc? My friend only has a cnc router.

You can try use our .dxf file or you can order it at:

Are the i2 parts useable to make the i3? i.o. can I upgrade?

You can use electronics, heated bed LM8UUs, extruder, but all plastic parts and frame was changed.

Where are X-carriage file?


These are ALL source files representing current stage of development, which is - without extruder. We were going to complete it with extruder and publish it, but since you demanded it with uppercase - here they are.

For assembly instructions, please consult with https://github.com/josefprusa/Prusa3https://github.com/josefprusa/...
Attached photos and CG images might help as visual clues.

Assembly diagrams and instructions will be published as soon as they are ready.

BOM has all you need, except for extruder parts. All parts numbers are included.
Shaft and threaded rod are given with their exact length in millimetres.

BOM is not structured by assembly, just raw data exported by CAD software.

Thickness of material for laser cut frame - 0.25" or 6mm. You can probably use 0.22" as well.

Good luck building!

We will publish more as soon as have something else to share.
We are open for questions or suggestions.

I've paid, I've gotten less than what I expected quality laser cut parts and need the DXF files to get the parts re-cut properly. How do I escalate this under the GPL?

Submit your claim in GPL court, I guess. I sent all source files to Twelvepro to publish, it will be done it half an hour. What are your issues with the frame, by the way? I assembled three printers and barely find areas of improvement. I think you just using publicity on Thingiverse to resolve something with Alex which is not related to the printer design. Please, use other means of communications to do it.


It is coming today....
I am glad you are interesting. Your opinion is very important for us.

I'm not kidding around here: where are the laser cut files for the laser cut kit I purchased? Apparently, as with the printed parts I bought, I need to have the parts re-made and need the files to do so. You appear to have alignment issues with your laser cutter as dims don't match from hole to hole and hole placement is off so parts don't fit cleanly.
I like the design but need it cut by someone that has their laser dialed in correctly (MakerFarm).

Alex is out of reach at the moment and I could not take over this thing, however, I posted all necessary STL files here:


Twelvepro will eventually repost STLs here as well as BOM and DXFs. Eventually means - when we feel like we are ready to post them, not when you guys feel like we need to. Don't push.

Prusa i3 - STLs for Improved Laser Cut Frame Design

I used Buy it Now on eBay and thus paid full price for both a laser cut MDF set and a printed parts set. Under the GPL I am entitled to the design files.

I've asked nicely by email and now I am asking publicly.

I want the files for the parts I have. I am over joyed you all are continuing to refine the design but the moment you took my money you hit Rev X. You are supposed to be able to give me Rev X to match the parts I have.

I've printed all posted files and compared them to Twelvepro's parts. Twelvepro really needs to work on dialing in their 3D printer. I hope that doesn't mean I'm going to be working hard to get this Prusa i3 working well after I struggle to finish it. :-(

I would appreciate it if you all would post the rest of the files so I can print them properly as well. (and I get ready to rebuild this baby one more time...)

Pictures are up on Twitter.

Diamond Age calls it Banana, I call it Sunshine! I love this PLA!

Two last feedbacks before bed... the Y belt clamp has some serious bite to it. I'm very convinced one wouldn't even need tie wraps. That said, you can't tension the belt once it's in the clamp. You have to pull the belt back out and force it back in. Maintaining tension whilst forcing the belt sideways into the clamp is, ummm: challenging.

I was hoping to use the third hole in an RRD MK2A hot bed. Have you all thought about moving the horizontal bars out closer to the edge so a "third hole" for a three hole bed level could be popped in? You could still leave in the normal four holes and add the third hole.

Is this your support forum for your purchase?

Almost forgot to mention...

You might want to check the dim's on the 5mm bearing on both of the top laser cut pieces. One 5mm bearing went in nice and snug, the other went in loose, not sloppy loose but not snug either.

And religious holy wars aside: the constrained Z threaded rods work damn well so far. So if I'm going to hell for tying them down I'm going there on biscuit wheels baby!

I would also love to hear about what nuts I need to be using for the Z threaded rods on the X ends... I've cobbled that together for now as well.

Looks great I'm excited. I can't wait for the laser cut files. My laser cutter is begging to get started on building one. I just finished the Prusa Air 2 and I have no problem gutting it for some parts to build this out.

Actually you do have a problem with your Prusa Air 2 printing out the parts: they aren't posted. You can't build one with the parts posted combined with the original Prusa i3 parts. They changed the Y belt clip and haven't posted it yet.

Well good news and bad news on the X end motor. You can see the pictures on my Twitter (scotty1024). Part printed great and bonded very well with Diamond Age Banana on my PrintrBot Jr (my current top dog print quality 3D printer).

Which means the bad news is Alex needs to buy a PrintrBot Jr. :-)

Actually I suspect Alex didn't use the official Prusa i3 parts extrusion settings: .3mm layer height and 220% extrusion width. From my experience those are pretty unusual settings.

The bad news for me? I guess I've gotta rebuild this thing one more time. :-)

I don't know if it was Twelvepro's printing or inherent to the design but the outer side of the diamond pattern, right there at the peak of the diamond broke in the X end motor part Twelvepro sent me. The X carriage parts in general made many creaks and pops when inserting the rods so I'm not 100% convinced they were bonded well.

Now that I have the STL I will have to try printing my own X motor end and see how well my PrintrBot Jr bonds it.

The belt clamp is missing for the X carriage and is not compatible with the original Prusa i3 clamp. I purchased and Express Mailed a printed parts kit and didn't get the needed clamp either. :-(

Also, their laser cut Y carriage is incompatible with Prusa i3 Y belt clip. Fortunately they included that part but it is NOT posted here. The Prusa i3 part has 3 screw holes in a T pattern and their new part has two inline holes. Completely incompatible.

I am using #10 x 24 threaded rod. I bought a 24" piece at Home Depot and they sawed it in half for me (they were also sawing up 3 36" rods for a Rostock mini).

However the only #10 nut Home Depot had is not fitting in their nut trap. :-(

I have mine up and moving with X Y and Z calibrated but am puzzling over extruder options. I am sure Prusa is patting himself on the back but as far as I can tell his new removable extruder plate is a complete pain in the ass.

The Z rods are not tightly held in the laser cut frame kit I received Friday. I had to zip tie the rods to keep them from coming out. :-(

My build with Prusa i3 parts I printed (Alex assured me Friday I could use i3 printed parts) and then re-build with the parts I bought is all up on my Twitter: scotty1024.

A promising design but for now it is unbuildable from any publicly posted parts or even from parts bought from them. I hacked around the missing cable clamp but I have limited X range of motion due to zip tying the belt and that kludge running into the X idler bearings. :-(

I wanna show my new baby off locally but she's ugly right now. :-(

Which is frustrating because the laser cut frame makes the Z axis a WOW! (well, once you zip tie the Z rods) I used GT 2 belts and cables (Trinity Labs) and oh baby she moves nice. (until the zip tie his the idler bearing)

Thank you for providing your feedback. As far missing or broken plastic parts - Twelvepro will resolve this issue. You probably get original Prusa X carriage with 2.5mm ratchet by mistake. Regarding design (Work in progress!):

  1. Fixing Z axis shafts on the top - I just used crazy glue and it worked pretty good for me, however, I will post a drawing-template for drilling two holes and STL for printed cap to fix this issue completely. Probably tomorrow.

  2. Missing STLs will be posted soon by twelvepro, but might be changed few times until settled as a stable release.

  3. Posted here is our modified X carriage. It has GT2 2mm ratchet spacing. Alex will post belt clamp for X, it is the same clamp as on original, larger Prusa i3 Carriage. I can explain procedure how to tight X belt, if someone need detailed explanation.

Actually Alex wrote me to say there ain't no belt clamp for X! He says they zip tie like I did, only they only use one zip tie. :-P

I've asked Alex to kindly post pictures of the parts he ships being used to build a working printer??? If you aren't going to have a manual or BOM and just pictures: THEY NEED TO BE OF THE ACTUAL PARTS!

Sorry, I feel better now.

I would be nice if they let you know on eBay that the laser cut and printed parts kits are so volatile and not published publicly so you can print/cut new parts to keep up.

And someone needs to dial in their printing as their parts are debonding when assembled.

The Z rods, Brook just pops in a hole next to the rod and self taps a machine screw into it (see Printrbot Jr.)

Adding a cut out for the microATX power supply would be easy and very very cool. You could even add a hole for a push on/off switch to wire up to the ATX green wire.

If they're debonding when assembled (I assume they're splitting in between layers?), then the parts either need printed slower or at higher temperatures to increase interlayer adhesion. I've printed over a dozen part kits for the i3 and learned a LOT about what it takes to print these well.

The Prusa i3 parts have been coming out rocks for me using the suggested .3mm with 220% extrusion width. I liked the results so much I used them on a set of Rostock mini parts as well.

And yes, the x motor end debonded on a layer boundary, a complete break. The x end idler and x carriage both made creaking and popping sounds as the rods went in. The parts I printed work great.

The x-motor-end.scad/stl in the /jo-final branch is the #1 problem part in this entire project. I had a LOT of cracking/breaking of the vertical support where the motor mounts to the part due to shrinkage stresses from the layers above it. I've successfully solvent-welded the pieces back together with acetone and a clamp but I hate doing that. Since then I've slightly modified the part, making that vertical piece wider + adding support material, which I then cut out after the part has printed and cooled. I also print this part slower and hotter, which helps too. Really, I think the x-motor-end.scad in the /master branch is the better design option but it uses different mounts for the LM8UU's.

Z axis - there are many ways to fix things easily. I suggested my way, you can use another. Alex was correct about carriage, but this smaller carriage without clamp will be used for PG35L extruder. Posted carriage is more useful for larger geared extruders.

The thing needs the clamp but I think the single clamp isn't the best approach. You need to be able to anchor one end of the belt and then tension on the other and clamp it down, trying to clamp both at once seems like it would be a circus act to me. Heck I'd pay $5 to watch someone do it. :-)

Right now I have an M3x10 zip tied as an anchor on the left and tucked nicely into the belt slot. But the right hand side has the zip tie off board and keeps hitting the idler before reaching full range of motion.

I don't understand the comments about a smaller carriage. The posted unit achieves full range of motion.

Yes, using tie wrap you can temporary fix one side of X belt, then screw on clamp a little bit. Then I use needle pliers to pull another side (by twisting belt around pliers). It clicks through ratchet in small steps. As soon as you achieve good tension - screw on the clamp completely. It takes about 3-5 minutes to do it. If you master it, which is easy, you can make good money showing the others how to do it for $5.

Laser cut DXF files, all STLs and BOM for this adaptation will be released as soon as we finalize all changes based on feedback from users. We are also working on our adaptation of Joseph Prusa PG35L extruder which will be part of this design. So, as soon as we ready, you guys will get it. Our work was based on open source hardware and it is open source hardware.

the carriage is changed in jo-final ver which is for plate type i3

Small carriage was designed for PG35L extruders, it is difficult to accommodate larger geared extruder on small carriage. Larger carriage (pictured) is easily compatible with many different extruders of your choice. That is why it was used in this particular iteration. There is enough X tarvel despite its larger size.

While not constraining Z axis lead screw certainly makes
sense in many cases, in this particular design it does not introduce any measurable
or noticeable wobbling or undesired shift between layers. Lead screw is
relatively thin and flexible (M5) while Z axis shafts mounted on the frame are
quite rigid. That is why I decided to introduce an option to constraint it on
the top with flanged MF105ZZ ball bearing, which makes, in my opinion, slightly
cleaner design (I am working with twelvero on this Prusa i3 adaptation). Those
of you guys, who does not like constrained Z axis may just not install ball
bearing on the top. Rigidity of the
frame in this particular design
contributes much to the printing quality, and that was determined by our
tests, while Z axis lead screws are not really an issue at all. But like I
said, there is no point for holly war, just don’t install ball bearing on the
top, if that is what you don’t like.

Happy New Year to everybody!

Will you or Twelvepro release the laser cut files? If so, when / where?

just bought this design from you am eager to try it out, will post and let eveyone know how it works

Thank you!

FYI I'm in the last stages of getting my own laser cut files out there for the i3 frame. When complete, I will release them both on Github and Thingiverse. I'm working with the SeeMeCNC guys on it.

Currently I have mods made for 3/8" acrylic and I'll release one for wood like the Twelvepro one soon. My version uses Josef Prusa's exact same frame.dxf and just adds laser cut slots and screw holes and adds two additional triangular braces for rigidity for more flexible material like wood and acrylic which tie into the back y-axis threaded rod (similar to the Twelvepro ones). All existing i3 parts on Prusa's git repository will work just fine with it:



One comment: the z-axis mounting parts were too weak??? I printed mine at 240C, 3 shells, 40% infill in black ABS and they're not weak at all. Color me confused!

Actually, for those of you worried about constrained z screws, you can fix them as long as the captured nuts are not tightly captured. The smooth rods will keep the z axis in place.

So we now need a fix for a "fix" that didn't fix anything, but brings up new problems? Why not leave the Z-leadscrews unconstrained in the first place?

wjsteele - in reply to

Affix is the better word... And it's simply a design decision... Not "fix" as in repair. Having floating nuts is better than having floating z screws which can catch or flex to a great degree, especially when you travel with the machine. Six of one, half a dozen of the other.

Holy crap have you guys learned nothing? Do not constrain the Z threaded rods! They are loose for a reason!

where are lasercut files?

It is still under development, but based on many requests


Thank you all and sorry for delay.

Somehow it reminds me to the Mendel90 ;-)

I still remember Nophead's comments when the Prusa was released! :P Full circle!

And MendelMax 2.0 .. they become all very alike.

Happy new year to you as well!
Please reconsider your fixed Z leadscrews. It may look less nice, but you will get Z-wobble if you over-constrain them like you do. The thing you need to realise is that all leadscrews (and couplers!)are bent slightly. Clamping them at two points leaves room for the leadscrew to move in XY. If you don't, this XY movement will translate in a XY force on the XZ carriage, leaving a small wobble in your prints.

Also: threaded rod is not a good material for leadscrews: it has too little pitch (so fast Z movement becomes impossible) and the nut will fail within a years time.