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Openbuilds v-slot X axis for Lulzbot TAZ 4 or 5 printers or the AO-10X ballscrew modification

by piercet Jun 5, 2015
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Love these mods! Thinking of converting the X and Y axes of my Taz 5, but wondering how it compares to using 12mm hardened shafts and linear bearings. I have been reading the old Lulzbot forum threads...which approach do you think is more difficult and which one do you think gives better results?

Thank you! There are pros and cons. The major negative on the openbuilds vs 12mm hardened rods is cost. The rod route is cheaper by quite a bit. The major upside is the openbuilds mods do give you better dimensional accuracy. Much better than 10mm rods, slightly better than 12mm. I actually have a 12mm y axis rod project somewhere in there for a 6 bed. The amount of weight you can have on the taz openbuilds bed is significantly higher than what you could have on the 12mm rods, but unless you are printing very large metal fill objects that's not a concern for most people. The boxed structure does serve to entirely eliminate side sway caused by the slight offset in the bed belt anchor positions, the 12mm rods might not. If you took a page from the mini 2 and added endpoint compression bolts to compress the rods that would likely have the same effect. If you go 12mm rods dont go with the ball bearing slides, they chew things up a terrible amount even on hardened shafts. Bottom line i would go with the openbuilds mods over the 12mm rods, and have with all four of my taz units. I dont think thats just creator bias on my part. Even the hardened rods are still unsupported in the middle. The bed is more important to consider the rails over the rods if you were only considering one axis if we are talking 12mm rods vs openbuilds. If we are comparing the stock 10mm rods the x axis becomes much more important to retrofit. The main differences you would see are in the consistency of the layer thickness in Z and y axis definition. As to which is more difficult, probably the openbuilds one unless you buy a predrilled bolt on kit from someone like me, in which case it's easier. Drilling the bed is the only tricky part above adding rails, assuming you would have to cut rods to final length and or design parts that don't yet exist to accommodate them. Hope that helps!

Thanks for the detailed response! That is very helpful. I think I will go the Open Builds route in that case. I am putting everything together in a SolidWorks assembly, would you be willing to share the latest versions of the STEP files? Looks like the STL files have been updated but the STEP files have not.

I'll upload them sometime this weekend.

You now could get these parts really really cheap in the Banggood Anniversary Sale with up to 11% Discount:


I will say that having tried both approaches, I highly recommend going the metal plate route. Fits a lot better and a lot stiffer...

Just for clarification, the printed parts with the higher value first number are the more recent revision correct? For example the XMotor Endcap 9 0 A is the newer version of 8 4 C? I am looking to install the new MAX Endstop with this awesome upgrade!

That is correct. The older ones use a slightly different geometry, so I have left them in place in case anyone ever has to reprint an older part for some reason. They are mostly interchangeable, the alignment of the endstops is the main change.

Would it work on Taz 6?

The Taz6 X to Z axis geometry is slightly different. It lacks the X end plates, and moves the bearing guide rod closer to the leadscrew. There is a taz 6 specific end piece, but it is currently undergoing revision and doesn't fit without modification. I'm working on it, but its been a lower priority than some of the other projects https://forum.lulzbot.com/viewtopic.php?f=16&t=4908

The PDF instructions sizes for M5 Bolts seems to be in error generally.
There are a few places where it lists a size ending in a 2 (ie 32) when I believe they were meant to in a 5 (ie 35); but it was done several times.
And there were a lot of 10mm M5 listed but in most cases these are not long enough to fit through the part and provide enough threads to grip (or in most cases they just were flush with the other side). When replaced with a 15mm M5 it would function. This was annoying since I ordered 10mm in quantity and end up only uses one or two and didn't order enough 15mm. There were a few others that were also short but I happened to have some of them and they were just one or two of those.

The small spacer hole size was WAY to small to fit a M4 let alone the called for M5 requiring drilling.

Now just waiting for bolt orders as metric are hard to come by locally (USA can be so annoying when it comes to metric).

BUT, that rail is ROCK SOLID! The stock unit had a little rotational play; this doesn't. Can't wait to see how it performs.

Also since you seem to be in Washington according to your profile, Ace Hardware has metric bolts of most lengths in stock locally. I get most of mine from the parkrose Ace Hardware down in Vancouver, WA but I know there are similar stores up north as well that will have everything except possibly the M2 bolts, T nuts and heat set inserts.

All the Ace Hardware stores closed around me; even the Grainger closed so the closest is Seattle. Sigh.

I measured all the bolts as I was assembling, the measurements reflect the required bolt thread length, not the overall bolt thread length. The two 32mm long bolts for the idler tensioner are correct. The longer bolts for the backplate with a metal backplate should either be 35mm or 30mm long for the most part. The 10mm long bolts worked fine for the T-nuts and parts as printed on this end, I just pulled one to measure. Maybe they sent you the wrong bolts? I'm sorry that you were annoyed by that, it wasn't my intention to annoy you. The small spacer is designed to be threaded onto the M5 bolt to provide extra support, you can certanly also drill it without affecting it at all, and if a printer is overextruding the hole diameter may quite possibly be too small. They print fine on mine anyways. At any rate, sorry you wncountered difficulties.

I measured them, 10mm was not long enough.

Maybe its the printed parts.

What profile did you print with? Did you scale at all?
I print with a 0.5mm nozzle, used the fast/low quality, used ABS, and didn't scale it (ABS can shrink a little but I expected that you accounted for this).
The dimensions seem spot on when they interact with beam and other parts; just things around the M5 screws seem a little off.

Did I mention that I am excited by this upgrade! ;-)

I print with Repetier host using my own custom slicer ABS profile for a 0.5mm nozzle. No scaling, printed in ABS. Are you getting a raised lip around the holes by any chance? that could account for it. Not sure what to tell you otherwise heh.

The instructions were pretty confusing around the carriage due to the assumptions of a metal plate.

With the printed T Bracket, which way is the flat side oriented in the build, toward the carriage or away?

If you use the printed T Bracket, there are a few things you need to do that are listed in the instructions to make it work.
1) The bolts that hold the belt studs, omit the nut between the bracket and the first carriage washer. The T Bracket is already thick and this extra nut will put the belt studs way offset out of the plane of the belt causing the zip ties on the belt to collide with the end pieces.
2) Due to normal printing tolerances, the inside of the T bracket will need some trimming to reach the full extension on the X axis. This area where the T bracket slides next to the end stops has a very close tolerance. You can test it by just moving the X axis all the way to each end. I had to also make sure the lock nut was aligned so an edge was parallel to the end stop edges, otherwise it would collide.

I also suggest that edge of the printed idler (the piece with bearing) that is flush with the bar be sanded. In my case normal printing tolerance added a minute amount of rough surface which kept the tension screws from aligning well. Just a little sanding fixed it and allowed it to smoothly move when tensioning the belt.

flat side of the printed T bracket goes towards the rail, or towards the front carriage.

The longer m5 heat set inserts are usually narrower than the short ones for some reason. You will need a deeper 0.3mm narrower hole to fully engage. You can try a couple of things. If you mush the last 3mm of the longer insert into the shorter hole, it may melt enough plastic to lock it in place. You can also try printing a thin plastic insert ring and melt locking it in place. Another option would be tape over both ends of the insert, put it in the hole with epoxy, then let 7t cure and remove the upper tape, hopefully preserving the threads. If you go that route you might want to consider gluing it in upside down to lock it into the bore.

I can get the longer M5 inserts to fit by filing them with a metal file and making plastic "rings" to melt them in place with, works great, thanks!

One more question if you don't mind: I'm using the printed backplate, and the instructions manual doesn't cover how to install that. I'm talking about installing the post_spacers for the belt specifically. Do I drill through the holes, insert a nut at the back and then use it like the metal backplate, or do I need heat set inserts here (the holes are a bit small for this though)? Thanks!

I intended the printed backplate to get a bolt through it with a nut securing it in place. I have seen people use the heat set inserts too though. Either way works fine.

Just to be sure - using your intended method means drilling through the holes, right? Cheers, excited to implement this mod

Yeah, in some cases the only way to get a clean hole is to force a bridging operation that needs to get drilled out later. Those are one of those places.

I'm having trouble getting the rail to be square with the endplates. It's as if it's too short in both ends even though the rail is the correct size and the idler endpiece is positioned about 5mm away from the rail. Any ideas? :) Thanks. Also, do you know if the Mcmaster Carr heat set inserts are available somewhere else? Installing these narrower ones the way I've done it is not very stable, but I can't seem to find anything in Europe that will fit.

Appreciate it!

I usually start with the motor side, bottom the rail out in the motor X end, put the plate on, measure for square with a 90 degree block or a t square or something along those lines, then lock it down and tight with the bolts. I then install the assembly and square the other side. One of the Lulzbot forum users was able to find them in Germany using the information in this post https://forum.lulzbot.com/viewtopic.php?f=16&t=2897&p=26813&hilit=heat+set+inserts#p26813

Thanks, I'll try a couple of these and see if they work :)

I have only been able to source 10mm long M5 heat set inserts here. Can I use these in place of the 6.75mm ones somehow? I've ordered some 7mm long ones from China but that usually takes a couple of months to arrive, so if I could use what I have somehow that'd be perfect. Thanks!

Heh, thanks. It's getting there. I still need to finish the carriage bits, but I should have those done in the next weekend or so.

You have come true one of the wettest dream I ever had !!!!!