Dual extruder mechanical issue

My brand new Dual extruder after just a few prints has a warped Flex plate (ironic isn’t it). It’s warped so much the two large gear nuts were rubbing together.

This plate either has to be stiffened up or made out of something like PC.

Does anyone have the solid model of the flex plate from the dual extruder? I can only find the stl

Is Lulzbot aware of this issue? Bottom line is the flex point is too stiff in comparison to the rest of the flex plate. So when I leveled the two nozzles, the wrong part of the flex plate bent. It’s either this or it warped from the heat.

Ok I found the solid model. Had to download freecad and convert it to my cad software format.

I’ve made a quick stab at what I think the dual flex mount has to look like. Let me know what you think.

Attached is an stl (zip) and a step file.
flexplatedual_bill.zip (980 KB)
flexplatedual_bill.stp (242 KB)

I guess no one else has had this problem.

Well here’s the final design of the fixed flexplate for the dual extruder if your stock one gets warped.

I printed this and it’s a huge improvement. Now the flex plate bends at the hinge like it’s supposed to instead of between the extruders (like mine did).
flexplatedual_bill_revb.zip (1.07 MB)
flexplatedual_bill_revb.stp (253 KB)

I will continue the conversation with myself, I imagine eventually others will run into this issue.

Anyway the new print of flexplate has also warped after a few hours of printing. It is clear that ABS is inadequate for this part. I am beginning to think that part of the flex plate will have to be made out of aluminum (the part that the two extruders connect directly to. We could still make the rest ABS. I am thinking a playing card size plate of aluminum captured inside or on top of the ABS flex print. Or perhaps screwed to it. Not sure yet. Or make the flex plate stronger and out of PC.

I had been running a Lulz dual extruder for quite a long time, had no issues with the flex plate warping.

I did, however, have issues with the design as a whole (that thing is HEAVY and puts a lot of wobble everywhere!) so I ended up moving to an E3D Chimera. For a short while I was running it as a bowden, but now my fancy-shmancy Servo extruder has arrived, and it looks like this:

Getting it running smoothly was… not easy. Lots of firmware hacking, running some extra cables, a step down voltage convertor, etc etc. But, I can run two extruders with a single stepper motor! The servo acts kind of like a car transmission, shifting the motor between two gears. The mount I designed is also rigid as hell, and since everything is very, very close to the smooth rods there’s not much flex (if any).

The extruder is the HPX2-MAX by Dglass3d. For the moment, I can’t really recommend it unless you like a challenge - there’s almost no documentation on it at all yet, and the modified firmware they use is either much older, or much newer than the TAZ firmware - I had to tweak a LOT of stuff to get it running nicely. The Dglass guys are relatively good with information, but all my communications with them suffered a lot of delays. Basically, very nice product, but they need a lot of work on the support side.

Very nice. I will keep an eye out for it, once they’ve got it a little better documented.

Well I can’t understand it my flex plate keeps warping. What temps did you run with the dual? ABS needs at least 230. Even at 230 it warps after a long print.

IMO the flex plate needs to be made from aluminum or PC. Aluminum would be ideal, but then you’d have to come up with a hinge.

Do you have a picture of your warped flex plate? I’ve taken mine apart (needed parts from it for the Chimera) but here’s a picture of the dually mount I’ve been using for the past 3-4 months.

Did you print your dually yourself, or order it from Lulz? I made my own, so I’m not sure exactly how they make theirs, but mine was made with ABS, at either .3 or .5mm (can’t remember, probably .3mm) layer height, 100% infill. I usually run ABS at 245 through my E3D hotends.

I used the stock one until it warped. Then I printed another at 75% infill, and then another with the modified design I attached in this thread. All out of ABS.

They’ve all warped at 235°C after just a few hours of printing.

I’ll try it at 100% but I don’t know if that will matter. Not sure why mine is warping and no one else’s is.

Is it all the same brand of ABS? Maybe it’s just not a very good batch? I don’t know why yours is warping either, a picture would be helpful.

I’ve been lurking on this thread off and on…

billyd - could it be that you’re flexing the plate too much to get both nozzles level? Maybe instead of relying on the screw, you can pre-shim the toolhead on the x-carriage. Maybe a few washers (or print a M3 sized cylinder) for the top mount screw to create a tilt down for the second extruder?

BTW - That servo dual extruder sounds interesting… So the servo gets PWM from the Rambo board and marlin somehow. Maybe a dedicated thread for discussion would be more appropriate.

BTW - That servo dual extruder sounds interesting… So the servo gets PWM from the Rambo board and marlin somehow. Maybe a dedicated thread for discussion would be more appropriate.

Yeah - at some point I’ll probably make a thread about it if anyone is interested. It was a PITA to set up - LOTS of firmware hacking, and basically no documentation (yet). Nevertheless, now that it’s working it’s pretty great. Only major drawbacks is that it really can’t push 1.75mm ‘soft’ materials (even Soft PLA, which is stiff compared to Ninjaflex), and the filament idler arms are VERY springloaded - it hurts my fingers to drop in new filament. They’ve told me they’re working on that, however.

So for now, I keep a Flexystruder on-hand for when I need to do squishy prints.

I’d be interested in a dedicated thread with your notes and possibly conf.h… don’t want to flood this thread with questions. :slight_smile:

Alright, I’ll try and toss up a postmortem in a few days. And it’s a lot more than just conf.h - or conf. and confadv.h. It’s all over the place (pins.h!)

I’ve managed to successfully print the flexplate from Polycarbonate, so I think my warping issues will be gone for good now!


You are not alone. I just ran into this issue with a 4hr build. Granted, I was running hot, I just didn’t realize it till now. 240C head temp and just started experimenting with an enclosure. (Corrugate!) The high temp is part of my attempts to get ABS/HIPS to print together. Maybe it was a bad idea…

How is the PC flex plate performing?


That flexplate sounds like it should be machined from aluminum…

Haven’t been around in awhile. I ended up making both the flexplate and the mounting plate out of polycarbonate and they are holding up well after many prints.

billyd, I have been dealing with this issue since I unboxed my duallie as-well! I have been thinking PC for mine aswell, but I am going to try to milll one first!

I am also going to try a simple laser-cut approach, using 3 ply furniture grade.

I would be interested to hear your results from extended use with the PC flex-plate.


Still going well but one of my extruder assemblies came loose. Nozzle clogged and I can’t get it unclogged. Just ordered new nozzles.

Lulzbot needs to use all metal locknuts in the dual extruder assembly so they don’t loosen up over time as you print. The first sign was the dual calibration was off (because the nozzle moved). A second sign was they were out of alignment in Z too.

Actually the tool heads need to be all aluminum with all metal locknuts and hexagon heads. Enough with the printed parts. Even PC will move over time if you print with a hot extruder in an enclosure.

Also the flex plate is a problem because there is nothing holding the nozzles down. As the print is made, the dormant extruder can drag over parts of the print causing the nozzles to move up in response (because the flex plate is not restrained from going up). I wrapped a rubber band around the nose of the flex plate to restrain it. This helps a lot. But the flex plate should be designed with a captured screw so it holds its z position both up and down.