Timing Belt X GT2, Printrbot Simple V2

by iamjonlawrence, published

Timing Belt X GT2, Printrbot Simple V2 by iamjonlawrence Dec 2, 2013


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This will work for both V2 designs (with & w/o string tension)

In response to multiple requests I have developed this GT2 timing belt conversion for the X axis of the Printrbot Simple. This thing is similar to my original http://www.thingiverse.com/thing:191706

Differences are:

  • Use GT2 belt & pulley instead of the MXL
  • Use 608 Bearings instead of R2
  • Raises print bed 6.5mm


  • GT2 tooth form
  • Common 608 Bearings


  • Bearing Caps have very thin wall due to limited space.
  • Decreases available Z height by raising print bed.

For anybody having trouble printing these parts I have uploaded a 2014 version to Shapeways if you would like to order them online. http://shpws.me/rbxE

This is marked as a work in progress. If you have a success (or failure) please let me know. Feedback is greatly appreciated.


  • Made plate thinner to allow for some Z calibration error.
  • Raised motor height by 2mm to allow more clearance between belt pulley and lower wood plate.
  • Re-worked belt ends and lower plate orientation to allow for entire 100mm travel.
  • Eliminated need for raising the build plate.


  • Removed excess material inside bearing slot to allow 100mm travel.
  • Removed material to allow clearance for tie wrap end.


  • Updated the right hand belt end file "XBeltEndGT2RevC.stl" to give some clearance for the 2014 fan. This moves the tension mount 15mm further out and gives plenty of room for the fan to clear.


  • Updated the motor mount plate to allow some clearance around the 22mm motor pilot dimension. If the motor plate does not sit flush then when you tighten the motor mounting screws you can warp the plate pulling the bearings out of alignment. "MotorMountXGt2-RevD.stl" will help correct this interference.

For discussion of the evolution of this project please refer to http://www.printrbottalk.com/forum/viewtopic.php?f=106&t=5697

Special thanks goes out to ahaer for all the R&D work!


Just a "head's up"

In order to replace the X axis motor plate, ALL sides of the machine will have to be removed. This includes sliding the Z rods out of the base plate. You don't have to remove them from the top plate, but they will need to come out of the bottom plate.

The dis-assembly is more scary than difficult. Simply be mentally prepared for a complete dis-assembly of all sides and it won't be too bad.

Your efforts WILL be rewarded, and you will not want to return to the string drive.

One tip on threading the belt: Using a 4 inch length of sticky tape cut to the same width as the belt, stick one side to the top of the pulley, and rotate it around until it comes up on the other side. Then stick the smooth side of the belt to the tape and carry on turning it through, pulling gently on the end of the tape.


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Hey guys. I recently added many upgrades to my printer including this...and a heated bed. While this design works great with a cool bed, once I heated it up to print with abs the bearing rods snapped. I now have a dilemma since I can't print a new part. If anyone would be willing to print that center section out of a high temp plastic or cnc mill it, please contact me at [email protected] with a price. Thanks everyone. I will eagerly await the moment I can get my printer working again.

Do you still need help with this?

yes, if you could help that would be fantastic!

Ok, I'll print one this weekend.

Man thank you so much. People like you are what make this community great. If you want to contact me in my email that would be great, that way i can tell you where to send it. :)

I sent you an email yesterday. Need your address.

Hi Jon, just wanted to thank you for your work. I just finished installing the X and Y axis GT2 mods, and it went quite well. i am in the process of recalibrating since the pulleys are bigger than the sanding drums, but the initial test print looks great. Everything fit as expected. If anyone is considering these mods and want to see what's involved in the installation, I have some notes on the process in my project blog at http://shortcircuitsandinfiniteloops.blogspot.com/2015/02/gt2-belt-drive-conversion-of-printrbot.html

This worked out really well for me. The disassembly and reassembly were easy, I did it while watching Rudolph the Red Nosed reindeer. A couple things weren't clear in the instructions here or the guide on instructables; I had problems figuring out what to do with the ends of the belt, so I folded it over and zip tied it, and orienting the bed and the new screw for the x end stop was confusing. I made an adjustable x endstop trigger to replace the screw, so now I'm done and moving on to the y.
The only problem is that the belt ends twist and make the belt walk off the pulley. I haven't found anything that can keep them straight, so I might just drill a second hole.

can you link me the cad drawing im having a friend cnc this out if some aluminum and he said he needs all the measurements

Hello I recently upgraded to the gt2 belt and the belt is continuously slipping off. I haven't been able to print anything because after about 2-5 minutes the belt slips off. Does anyone have any ideas of how to fix this?

Ive printed all the parts and assembled them, what do i have to do to the software to extend the x axis?

You can go to the support fourm on Printrbot.com and there are plenty of people who know the answer. (I think its something like X____<insert millimeters).

How does this work if you have a heated bed? Can the parts stand up to the heat? I plan on printing this in PLA. Should I print it in ABS or should the PLA be able to withstand the heat from the heated bed?

This re-uses the original wood bed. I am using a heated bed on top of the wood and it holds up fantastic. May be different with an aluminum heated bed because of the heat transfer. Shouldn't be much because the only contact points are the sprung mounting posts, but I can't say for certain how it will behave.
If you are really concerned, I have a hollowed out version available on Shapeways. You can always order it in stainless steel. Then again maybe a new printer would be cheaper...
Sorry not much help here.

Hi all. I'm sorry for my maybe to simple question but I fear to command the wrong mechanical parts on McMaster... ^^. Well in fact it's about the A,B and C parts... could anyone help me ?

A&C - You can find these from Printrbot: https://printrbot.com/shop/gt2-kit/https://printrbot.com/shop/gt2...
B - Is a standard roller skate bearing. You should be able to find these many places really cheap, but here is a McMaster number if you prefer: http://www.mcmaster.com/#5972k501http://www.mcmaster.com/#5972k...

thx a lot ! I appreciate. thank you also for your shared designs. it is so important for the community. pierre from france.

Just uploaded a version for the 2014 Simple to Shapeways if you are really struggling in getting it printed. Not the most economical option, but I thought I would put out a last resort for those who are interested. The parts have been modified to be printed efficiently on the SLS machines over there. Below is a link.

In each attempt of printing the motor plate, my prints always come out as skewed in the x-axis.

If you need a plate let me know I'll print one and send it to you.

I'm trying to see if printing it in a different orientation will get me a straighter print

Try moving the part as far left on your printbed as possible. I have to do this with many flat/wide parts as I have the same issue in the middle of the printbed as you. That is why I am looking into THIS modification - to stop x skewing. .

wow i have the same problem i just did the y mod and now the parts are 8mm to small the y seems to be off for some reason

Sounds like you need to calibrate your Y after changing it to the belt. Printrbot has a document on how to do that here: http://printrbot.com/wp-content/uploads/2012/04/Printrbot-Getting-Started-Guide2.pdfhttp://printrbot.com/wp-conten...

Today I did the install of the X and Y GT belt upgrade. First, the parts are amazing, very nicely designed. I do like the organic and rounded nature of the design. For me the install was a PITA. This is nothing against the design. It was just a royal pain and took me many more hours than I anticipated. I had to tweek so much in order to get everything to fit right. It's amazing it worked! I love the replacement X motor plate. But I had to do things like grind the over-all length of a GT bolt down and add spacers to some parts to get everything to work and provide clearance between the pulleys and bearings and etc. I think I spent about 4 hours with it. But its printing fine now. A worthy upgrade but best assume its going to be a pain and that you will need to tweek things to make it all fit right.

My apologies that your install did not go as smoothly as anticipated. Is there anything that I can address on the design side that may have made your install smoother?
I have not personally installed this design (hence the "work in progress") flag. However, I am using my MXL version upon which this design was strongly based. Soon I will be upgrading my X travel, and at that time I will install this GT2 motor plate & bearings. If you have any suggestions, I can implement/debug them at that time.
Thank you for your feedback.

No apology necessary - there is nothing I would change with your design. My issues are related to using these printed Y bearing stiffeners which move the bearing away from the base a bit more. This required me to raise the bearing block in the GT upgrade out a bit more. I used 2 M3 washers under each corner. I could have printed a spacer but I was feeling lazy. Also the time was related to my Simple being a mix of different parts for a reason thats a long story. So its not an off the shelf release.

If anything you can bring the height of the bearings down so that the bolt heads will clear the bottom of the lower bed. I had this same clearance problem as plexus did and I forgot what my remedy was. I think I ended up removing the bearing caps and used a flat washer instead to bring the bolt head closer in and away from the lower bed.

how are you guys changing the stl files

I am in the process of installing this, but it looks like I need to flip around the bottom half of the bed, so the front is back, and the back is front. But then the x-axis limit switch rubs against the bottom of the wooden plate (just barely, but it rubs). Are we supposed to trim the wood so it won't rub, or do I just have a slightly different version of printer? I bought mine in October of 13. I guess I am going to try and nudge the limit switch over or trim the wood.

I had this same issue. I think it has to do with the way the lower bed is cut on the later versions of the Simple & the volume upgrade. I ended up removing both M2 bolts that hold down the X limit switch and "Kragled" it in place.

The plate should clear over top of the switch no matter which way it is rotated. If it is rubbing, I would guess either your plate is a little warped / bowed or your rod slots are a little wider than average making the plate sit a bit lower. You can always try upside down AND backwards, may clear if it is a warped lower plate. Either way, sounds like you just have a plate just outside the average dimensions.

Your mod is great John. The Y-axis took hardly any effort to implement. The x-axis however, on my printrbot simple XL ordered fall 2013 gives me the same problems decribed here. The top of the bolt holding the x-stopper scrapes along the base of the bed. It took a bit of Dremeling of the bed to overcome that problem. Second, the zip ties holding the rods and bed hit the sides of the printer, thus preventing full movement in the x direction. It seems that either the holes in the plate holding the bearing are a bit wider than in other versions, lowering the axis or that the slots in the bed. This however must have existed before and have passed unnoticed. Anyhow, my solution will be to lasercut a piece to highten the axes or tho dremel out the sides of the printer.

I have the head of the m3 screw closest to the printer on the x endstop switch rubbing on my lower bed frame as well, when the lower bed frame is inserted bacckwards. I tested it on my stock bed and the xl/tower bed. Both of them rub on that screw and prevent it from strapping down the zipgties completely/or moving the bed if you do. I was able to remove that screw with the allen key hole and replaced it with a flatghead philips m3 machine screw. That little bit of a difference gives it the room it needs to move freely. It still looks like it is touching, but is not restricting any movement now.
One other note for anyone using the tower/volume upgrade, there is an extra 6mm wooden plate added to the left side of the stock printrbot simple to make the tower. The left belt arm will not clear this wall and will not allow the bed to hit the x-endstop switch. The fix is as sime as filing about 1/8th of an inch off the arm right at the 45 degree bend. Just takes a couple minutes to give clearance.

What I did was unscrew the one screw that was barely rubbing, and twist the switch to move the screw hole forward a tiny bit. I just need to drill a new hole for the screw I removed from the limit switch, and also drill a hole for the screw that engages the limit switch when the limit is reached, and I should be ready to start printing again.

Have you considered putting up a design for the Printrbot Simple WITH the string tensioner? If you don't have that particular model, I'm happy to provide measurements with my digital calipers. My GT2 kit is ordered (hopefully shipping soon-ish, Printrbot orders seem to be really backed up). I could take a stab at modifying it myself after my stuff arrives, but with my limited experience in SketchUp, who knows how well that will go, haha! Either way, I really appreciate you putting these designs together in the first place!

I have reviewed the X baseplate for the string tensioner, and because the baseplate is flipped around this assembly should work "as is". The rod slot for the new baseplate is 1.5mm longer than the previous version, but the tie wrap locations match up and there shouldn't be a problem. Please let me know if you encounter any issues.

Will do. UPS is supposed to deliver everything on Monday, so hopefully I can get it all put together next week some time. Thanks for the update!

I just looked up to see that Brook has released a DXF of the new version. I will update or remix for the post 10/23/2013 version as time permits. Thank you for the offer to supply measurements.

Awesome! Looking forward to the updated design.

I would be happy to modify to fit the new model WITH the string tensioner, but as you guessed I do not have that version. If you could send measurements, I can certainly alter the design to accommodate.

this design restrict y-axis movement from 100mm down to 70mm when the belt support hits the bearings. If you rotate the y-axis bearing support plate 180 degrees and make new belt supports the bed will be moved in front of the bearings and belt. This means that you will not have to raise the bed (less parts/use original screws), and you will not lose any print area in either Z or X axis. There is no loss in the X because the bed is wider than the x-axis travel...

I'll ask this here, since others may wish to know:
Does the new motor plate lower the motor a bit? I might never have thought of doing that, were I designing this conversion. Well done.

Yes, the new plate drops the motor a bit. This is actually a carryover from the MXL (http://www.thingiverse.com/thing:191706)http://www.thingiverse.com/thi... motor plate. There it was necessary to lower the motor so the pulley was below the stock height of the print platform.

Timing Belt X MXL, Printrbot Simple V2

I just get my Y axis conversion working, and now I have to take my Simple apart again after I print the parts for this!
Great work. I will definitely be testing this!