UConduit H-Bot 3D Printer / Reprap

by iquizzle, published

UConduit H-Bot 3D Printer / Reprap by iquizzle Jun 13, 2013
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The UConduit 3D printer is an h-bot 3D printer, with a frame built from electrical conduit (steel conduit that you can find at the hardware store). The source files are hosted on github at https://github.com/iquizzle/uconduit. All printed parts are designed using OpenSCAD so that parts can be freely compiled and modified. Conduit was chosen as a frame material for its low cost ($3.50/5ft), stiffness and hardware store availability. Standard build volume is approx 250mm in each dimension.

The printer is held together using o-rings and compression flanges. Each end has two rubber o-rings. There is a hard clamp and a soft clamp. The hard clamped o-ring creates a pivot point and firmly holds the conduit in place. By adding a second soft clamped o-ring on each end, vibrations are very effectively damped. As a result, the printer is not only fast, but also super quiet! Additionally, wiring can be neatly routed from the top to the bottom of the printer (using the conduit for its intended purpose!).

I'm not listing this 'thing' as a work in progress. All parts have already been revised a minimum of 3 times, and have been under development since last September -- I will continue to upgrade and support this design until it is safely in the hands of the hacker community. :)

I've created a google group for this printer and general hbot/corexy discussion and support:

A video of the UConduit in action can be viewed here:

Special thanks to Free from http://www.terawattindustries.com for support and helping with the build and supplying parts. Also thanks to ckaos for publishing his h-bot (thing:27202), which I analyzed several times during this build.


  • Download the (beta) BOM (on github) and STL files.
  • Print 4 top vertexes and 4 bottom vertexes, 2 x-ends, 2 z-ends, 2 leadscrew couplers, and 4 bottom plugs
  • All other prints are supplied in the appropriate quantity in the STLs
  • Build the frame by clamping the o-rings between the beveled cutouts and the compression flanges (detailed build guide to follow)
  • Install the linear rods during frame build, x-rods are press fit and should be installed during frame assembly
  • Assemble and install one x-end and then y-rods in that xend, slide the carriage onto the y-rods
  • Install the other x-end and clamp the other end of the y-rods within
  • Tap the j-head mount with 1/8" NPT and screw in the push-to-fit (but not all the way in)
  • Screw the j-head mount onto the carriage (4 M4 screws)
  • Install the stepper motors
  • Assemble the z-ends, and loosely assemble the leadscrew couplers
  • Thread the leadscrew through the z-end and push though the linear rod
  • Install the assembly on the frame (press fit on top, clamp on bottom)
  • Screw the idler into the mount
  • Wrap the gt2 belt

Instructions are limited at this point, but build guides should be available in the near future. If you'd like to start a build and run into problems, post to the google group and I can offer help.

I highly recommend buying a 3mm ball end hex key for the M4 screws on the frame. The first time I built the frame, I only had a straight end and realized that I could have saved hours of struggle if I had a ball end hex!

  • cat not included

con u duit? yes, yes u con -- the only printer repeatedly endorsed by Rob Schneider. http://www.youtube.com/watch?v=VZ2HcRl4wSk

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Hi iquizzle,
Thanks for making this available. I've built one and I have been able to get pretty decent prints so far. (excusing the usual failed prints for numerous reasons) I would like to make some design changes and hope you might have the part files in a format that I can load into Solidworks. Right now I have to do a lot of rework to import it and then actually recreate each part.

I'm on the final stretch with my build of the Unconduit. I actually reversed the z axis so I didn't have to worry about the acme rods falling off. Will post photos of the build soon.

iquizzle - I really like your idea of using conduit to build the frame and I have been thinking about building a variant with the main change to use CoreXY instead of H-Bot. Do you know if anyone has already done this and has completed the design changes? Also, do you think the print results of the CoreXY redesign would be worth the time invested when compared to prints from the existing design?

Thanks! I thought I had heard of someone working on a corexy version a while ago. I'm not sure if it ever materialized. I think it would be an excellent upgrade. I'm still using mine in H-bot form almost 3 years later! I've mostly overcome the racking issues by using some LM8LUU bearings in a few places... still, a corexy version would be superior.

If you have a good idea for how to convert this design to corexy, I think it would be great. If not, I'd recommend getting 3x LM8LUU bearings to mostly eliminate the racking. If you plan ahead, you could also extend the axes ~10mm without having to modify any of the printed parts. That way you won't lose any of the print space with the longer bearings.

See this "thing" for the longer bearing holders: http://www.thingiverse.com/thing:560217

I might also have the mods I made to the gantry somewhere on my computer to accommodate LM8LUU. I'll dig around for the STLs.

LM8LUU bearing holders for UConduit X-Ends

I would really like to build this printer as well. I would like to make it for a 300mm bed as someone else seems to have done and an ultimaker gantry if possible. Is there any draw back in a conduit frame vs aluminum. If not why spend the extra money?

All of the parts seem to be like 1mm small. I printed out all of the parts, but the conduit does not fit in the parts. UGH. This might be my own fault though, not sure.

@CarbonAtom6 I was successful by scaling the parts. I scaled PLA to 102% and ABS to 103%. If you scall one you'll have to scall all or they won't line up right.

Perhaps it's because PLA shrinks?

Yes, I think so, in addition to not using Polyholes (See Nophead's post here: http://hydraraptor.blogspot.com/2011/02/polyholes.html). I ended up using the Slic3r 1.6 advanced feature which allows you to set an XY Size Compensation to compensate in addition to changing over to polyholes in the source files.

What steps_per_mm do you use for the all the axes?

the firmware Support the printrboard rev-d

hi can i just ask what diameter tube you are using ??

Hey, will an E3D hotend work instead of a JHead? I think the groove mount is slightly different.

The groove mount might need to be modified slightly if it's a little different.. Unless it could be shimmed. Probably a 10 minute scad rework if you had the dimensions handy.

This may or may not be a silly question, but can this be extended to accommodate a bigger build area?

It's not a silly question! It's also been done! Check out this monster: http://www.thingiverse.com/make:41570

One suggestion I would make is that if you go bigger, plan to swap out the LM8UU y-axis bearings for the longer version. LM8LUU. This helps nullify any h-bot twist and prevents distortion on things like interior circles. In my current bot (which is standard size), I use 1xLM8LUU and 1xLM8UU on each side for this reason. I'll try to remember to post the bearing holders for the LM8LUU this weekend.

UConduit H-Bot 3D Printer / Reprap

omg it IS adam savage xD

Is there anyway I could get access to all the parts like motors and wires for a hobbie printer, ive been looking and I need help starting out. I have access to a 3d printer and will be able to make some parts

Is anyone selling or would sell a set of the printed part to get me started?

Thank you.

I just printed all the parts and getting ready to put it together. If you pay for the shipping and cost of filament and time I can send you all the pieces. maybe $40? I can run the printer at night and it won't affect my printing time so I will do it cheap. I just ask that you complete the project and send me pictures!

Have you thought about using an E2D-v6 hotend?

I have -- but my jhead has been really solid with bowden & PLA. As much as I like to tinker... for hotends, I'm definitely an "if it ain't broke, don't fix it" kind of guy.

Hi, this is very nice and intuitive design. May I ask which firmware you are using, can you share any special settings? thanks!

Myself and the owner of the 3d printer store "terawatt industries" worked on corexy(and therefore also h-bot since the kinematics are identical) support for Marlin firmware last winter/spring. Corexy functionality is now included in the marlin firmware since June(?) of last year. All you have to do is uncomment the corexy definition in the configuration: https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/Configuration.h#L254https://github.com/ErikZalm/Ma...

I'm having a chicken-or-the-egg problem -- I need to print parts in order to put this printer together ... but I don't have a 3D printer. Is there anyone who would be willing to print these parts for me, and if so how much would make it worth your while?

makexyz is a website where folks with 3d printers will print stuff for you.
check it out. all over the country.

what country are you from?

United States. I'm near Rochester, NY.

how stiff is the frame using this method? does the frame need to sit still or can you move it about without worring about frame moving out of alignment?

Since everything is connected to the top square, that's really the only part of the printer that needs any "stiffness". The top square uses a double o-ring grip on each vertex, which is pretty solid. I've moved my printer all over my apartment and taken it in my car to various places. It's been fine. Once the orings are well tightened, you'd have to really yank on it to get it to slip.

I typically print around 100mm/s and it handles that easily. I've printed at 3 times that speed with really high accelerations, and it's still fine (not that I would recommend doing that). On a machine like this, you'll spend probably zero time worrying about the frame, and more time worrying about the gantry torsion inherent in h-bots. I've mostly gotten rid of that with a few modifications which are discussed on the hbot google group.

Hello, Mr. magic

Your printer is making too great. I wish I could have one wish this amazing machine. But I do not know want to build this amazing machine which need specific accessories. It makes me feel very confused.

Dear Sir, can you give me a list of specific items yet?

Thank you, I wish you a Merry Christmas.

My email address is: [email protected]

Thanks again

Thank's for your kind words. The bill of materials is on the github page here: https://github.com/iquizzle/uconduithttps://github.com/iquizzle/uc...


Hello.Very impressed with your printer.I very much want to repeat it.I need your help.You can make the models under 12 shafts and bearings?Best regards.

I'll start a build thread. my 8mm smooth rods havent arrived yet. thanks

how much are the tubes inches and in cm?

You will need 8x375mm tubes and 4x415mm tubes. Check out the bill of materials (UCON_BOM.pdf) on the github: https://github.com/iquizzle/uconduithttps://github.com/iquizzle/uc...

is M4 Nuts 150 or 155¿

The BOM leaves you with a few extra of each screw -- so the number of nuts doesn't match up perfectly.

I've printed all parts and now starting to acquire all needed hardware. I'm going to need help putting together.
I'd pay for build instructions

I'll help you with your build if you want to start a build thread on the google groups: https://groups.google.com/forum/#!forum/h-bot-and-corexy-3d-printershttps://groups.google.com/foru...

Also, if I have time this week, maybe I can do a teardown and rebuild of my printer with pictures.

The cat print is amazingly life-like.

Originally I just printed this model: http://www.thingiverse.com/thing:62536http://www.thingiverse.com/thi...

Then I attached strings to it and made it dance around... but I really wished it was a real cat. Next thing I know, he's sitting under my printer purrrring and life is grand, apart from the cricket infestation.

2-color standing cat

Do you think is possible to use DryLin ® R - Solid polymer bearing RJM-01 (igus) in place of LM8UU? http://www.igus.com.br/wpck/default.aspx?pagename=drylin_r_rjm_01http://www.igus.com.br/wpck/de...

I believe it is possible, but you will have to modify some parts (which might not be too difficult). If I remember, those bearings are 16mm OD, whereas LM8UU are 15mm.

Nice work! You have any high res photos of some of your prints?

Thanks! I'd upload some, but they aren't that good yet. The positional accuracy looks great so far, but I need to optimize retraction settings because there is still some blobbing from the bowden backlash.

This is a great idea! What sort of lead screw did you use?

Thanks! I'm using 3/8"-12 ACME thread leadscrews. It would be very easy to modify parts for different leadscrews. I just used those because they were available at my local hardware store and are super cheap online as well.