The Backbrace project

I started out my printing adventure with an AO-100. Basically a lulzbot edition narrower mendelmax 1.0 with motors on the bottom instead of the top. At the time it was pretty much the best thing out there, even used as mine was, aside from the slightly newer AO-101. Compared to the prints I can put out today, what it produced in the stock configuration wasn’t exactly ideal, but even before i started doing my usual slightly over the top modification efforts to it, one of the things I always really liked about it was the super solid a-frame construction. I can’t emphasize enough how sturdy that frame is. You can literally stand on it and use it as a stool if you want.

The Taz is arguably a better printer in almost every respect, except probably the stiffness of the frame. Most people would make the argument that as the bed is moving back and forth in the Y axis, you don’t reeeeely need reinforcement in the Y axis for the upper gantry. And if you aren’t printing at super high speeds they would most likely be correct. But the fact of the matter is, I can use my little pinky finger, push on the upper top corner of the gantry and have it flex ever so slightly (under 1mm) without too much effort, even with the custom solid billet aluminum bed to frame mounts I have. So, I want to eliminate that. And conveniently, I happen to have 3 spare Taz 500mm Aluminum extrusions with which I plan to do exactly that.

So, the theory here is that a mount attaches to the upper corners, a 500mm stick with printed endcaps bolts onto that mount on either side, and then bolts onto the third stick, which eventually gets bolted up just outside the back of the Y motor plate. I might cut up two shorter sticks or something to complete the triangle later, but thats the general layout.

That gives me two things. additional stiffness from those elements alone, but also a place to mount my soon to exist clear acrylic windows (the ones that go with the soon to exist top plate with a slot in it) and extend my Z openbuilds mid span braces. That will in turn give me the start of a box. I plan on mounting a solid-ish removable rear enclosure box that will open up and fold away against these back braces when not in use, and eventually someday a front enclosure of some sort, possibly a more fancy variant of my taped on turkey bags, rigged like a tent with spars and reinforcements and whatnot. I don’t really need one for my printing, but it would be nice to have the option for really delicate prints like giant Eiffel towers or the like. It also ties the bed to frame in one more location. I’m toying with the idea of also attaching a partial bottom plate to close the plenum.

This will also give me additional mounting points when operation “securely bolt your taz to a very solid heavy machine base to run it really fast without it shaking to pieces” gets underway at some point. At this point i’m not intending to fit front braces since they would be in the way of part removal more than rear ones will be. I rarely try and remove a part from the back.

Thats the theory anyways. Any ideas or thoughts are appreciated!

I’ll release the parts once i’m sure they are solid enough. the spar mount looks like I may want to bump it out a mm or two.


This is all the required plastic parts. There will be two or 3 more optional parts, but this will allow you to build the frame. Pictures and whatnot forthcoming. You will need 3 500mm Taz extrusions (20mm x 20mm) 2 stick on rubber feet, some 50mm-ish M5 bolts, some M5 nuts, some t-nuts and a bunch of 10mm m5 nuts and washers.

There will also be an optional “second spool” arm for mounting on the back diagonal, which will allow you to theoretically have two 5lb spools mounted at once. (and also move that arm so i can run the openbuilds crossbrace for the Z axis all the way across) . There will also be a pair of printed corner bracket brace things to go from the corner of the diagonal to the lower corner of the taz stock frame Since the other braces tie in at the back of the Y axis, those probably aren’t required, but if you are doing this you are looking to beef your frame up anyways, so why not?
Taz_Zbrace_Arm2.stl (169 KB)
Taz_Zbrace_Blocks.stl (349 KB)
mountszbrace.stl (150 KB)
Taz_Zbracelower2.stl (73.1 KB)
Taz_Zbracelower.stl (72.9 KB)

Sneaky peak at the printed parts in place:

It’s just loosely bolted up, and the back bed mount isn’t printed yet. But the geometry works and you don’t have to cut the rail!

Got all the main parts installed, so far it seems to be working well, though I do need to create an alternate upper left (control box side) frame mount. The existing design will interfere with a full Z travel move due to the cable chain on my machine. There are a couple of potential options, the easy one interferes with another later plan I have, but may be the ultimately easiest solution. I also discovered that the lower end of the diagonal 500mm rails are either going to need to be filed down on one corner to not drag on the table, or I need to take 2mm from the upper mount which cuts into the strength area for the bolt mount itself. I may try 1mm first and see if I can get away with that.

One side effect of this project so far that I hadn’t anticipated. it makes the entire machine much quieter in X and Z moves. It’s actually becoming a bit of a problem because I can’t hear it downstairs anymore unless its doing a retraction. So there is that as a bonus!

Total project cost so far is the $15 after shipping for the 500mm extrusions, probably 1/2lb plastic all said and done (maybe 1lb), some drop in T slot nuts for $5-ish for 20 of them from makerstoolworks, 2 furnature feet that I had laying around from other projects and a few regular bolts and nuts (m5) 12mm, 6mm, and 55mm long.

It’s just about there! The lower crossmembers get printed tomorrow, along with the openbuiulds Z brace extensions and the new dual extruder rear diagonal arm thing. Probably the modified top brace bits too.

Project is on hold for a little bit due to an unscheduled catestrophic bed corner failure mid print of the lower crossmember. Apparently the bed corner mounting bolt can just strip out and cause that corner to go flying. I don’t feel I had particularly excessive tension on it. but apparently it felt otherwise. So yeah, i’m down until i cut new holes for the new bed.

Got the new bed on the machine, and its all dialed in. Also did my first new print with the new bed, the new squishy silicon fuel line tubing based bed corners, and the first half of the backbrace on. I honestly expected almost no improvement because I already print really nice prints. I’m happy to report that I am literally “floored” at the improvement over where I was. Will post pictures as soon as I bring a cell phone up here or find my @#$%^ camera battery charger in one of these boxes, but quite frankly the layers line up perfectly now. I can’t easily detect the edges with my eye at 0.35mm layers printed at my usual 120mm/s general quality medium speed setting. I can barely even feel them. The only reason i can even see them is the fillament at the edges is round. I’ve been giggling uncontrollibly like a madman watching these prints come off. I don’t know if its the back braces, the bed corners, or something else i inadvertently changed in the rebuild, but these are literally the best prints i’ve ever done and I don’t even have the lower crossmembers or the mid supports printed yet.

Here are the rest of the corner mount parts. more parts still on the way sometime this week, the project will probably get published later in the week officially, also more pictures to come.

The alternate corner mount is only if you are someone like me who has cable chain running in the exact area you would otherwise want to run a backbrace. Only use that one if the other one conflicts, as the other one is stronger.

I’m really excited about this project now!
Taz_Zbracelower2.stl (73.1 KB)
bottom mountzbrace.stl (448 KB)
mountszbrace.stl (150 KB)
uppercorneralt.stl (150 KB)
Taz_Zbraceupperleft3a.stl (60.7 KB)
Taz_Zbrace_Arm3.stl (84.6 KB)

Eagerly waiting for pics…

Ask and ye shall eventually receive! My cell phone camera, so different quality than normal. Not sure if that’s a good or a bad thing.
lowercrossmember.stl (190 KB)
The new lower crossmember, because my printer doesn’t actually say lulzbot anywhere when its printing. Outage is the lulzbot font by the way. Matches the front blinky light box of doom.

The right side lower crossmember mounts. Ignore the big scrape in the surface, once I finish moving when that happens someday (argh!) I will replace that top with a heavy stone slab of some sort.

The existing Openbuilds Z axis crossmember. This will get extended to the back. A variant for standard Taz’s may also end up existing.

The lower feet. The offset here could be replaced with a more rigid style like on the main frame, I did it this way so you can use an uncut 500mm rail such as surplus from a Taz that Itworks carries for $5. It’s still ridiculously strong. I overbuilt these connections by a considerable amount I think.

Apparently they are all sideways. Huh.

Back rear Y axis to lower main crossmember pieces. These look flimsy but they are really quite sturdy. 2 addition stick on feet go on the bottom of the rail. I suppose i’ll have to make some sort of Taz 6 flex feet mount at some point too.

Inner control box side upper mount. Note the neat stick on measuring tape.

Upper right side backbrace mount.

More pictures, description edits coming soon.

Edit: Why are the edit buttons no longer visible anywhere? they are just dots. is annoying.

Back lower corner mount, just behind the control box. The lower crossmember mounts just forward of that.

Upper left “alternate” style mount. It’s not quite as strong as the other style, but it’s out of the way of the cable chain.

Full control box side view

Very cool!
Thanks for the pictures. Something just wasn’t clicking in my head, but now I understand how it works.
I also have a few spare pieces of extrusion waiting for a new purpose.

The labels disappeared after a recent forum update. Sorry about that. We’re looking into it. As a workaround, hovering over the edit buttons will display the label.

The backbrace looks stout!

Thanks for looking into that!

The whole frame feels like an AO-101 frame now, Which is what I was aiming for. Also, I can use my taz as a stepstool in emergencies now.

Project is published!