Modding the Lulzbot Mini

So recently i’ve finally gotten my homemade / homebuilt Lulzbot mini working. And it’s working pretty good. The most critical problem i was facing was that my 3d printer would start printing either too close to the heat bed (or if i added extra bed leveling washers) it would print too far away. This was a critical problem as the first few layers are the most important and if you can’t get you prints to stick to your print bed then the rest of the print will usually unstick and fail. Thanks to some helpful people on the Lulzbot forum i was able to adjust my z-offset to the correct height that worked for me.

The second issue is that recently i’ve noticed my large and tall prints failing miserably at a certain height and the filament not coming out thick enough and the top gets all cob-weby like a spider web, but worse. Apparently this is called “Heat Creep”. The problem in part may be caused by the tiny blower fan on the Lulzbot mini not providing enough cooling and heat slowly rising in the hot end until the filament actually melts too soon and cannot be extruded properly. This makes sense as the problem only occurs after a long time printing. So the logical step was to replace the tiny blower fan (or squirrel fan) with a larger fan that will do the job. The new Taz 6 has obviously taken that tiny fan into consideration and has changed it to a large 40mm fan.

EDIT: The failing on large prints may be due to me using a half-size stepper instead of a full size stepper motor for the extruder. This means too much voltage is being applied to the motor and it is getting super hot. Over time this means the motor looses steps and probably causes my printing problems.

Unfortunately the Taz 6 x-carriage and modifications are not a drop in replacement for the Lulzbot Mini i decided to make my own. This is what i came up with and it seems to work beautifully. http://www.thingiverse.com/thing:1587110

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I have only tested this on HIPS so far, but it has eliminated the heat creep i was getting with HIPS. PLA apparently suffers more from heat creep problems than other filaments, but this mod will likely help with PLA heat creep issues as well.

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Progress on my Homebuilt Lulzbot Mini

Today i made significant progress on building my own Lulzbot Mini 3D printer from scratch. Technically i now have two 3d printers i’m building from scratch, but the other one is bigger and one i’m designing myself. Just like me to not finish one project before starting another. At least i’m going to work on this one and finish it before continuing on my other one (which might be converted into a homemade CNC mill).

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Today was a major milestone because most of the components are put together and i finally was able to test part of the electronics i wired up myself. I was able to test the Y-axis motor and limit switches as well as the X-axis stepper motor. All seemed to function correctly using Lulzbot’s Cura software. The software did have an unexpected safety feature however, it wouldn’t let me turn any of the motors on without the bed thermistor wired up. So i had to wire up a temporary 10k thermistor for testing purposes. It worked great. I was running the Cura software under Ubuntu Linux. The Cura software gave me an error that it could not autodetect the serial port or something like that, so i ran it as the root super user and that fixed the problems.

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Since i’m building this thing from scratch instead of buying one premade i’m trying to find ways of cutting costs. Although i think i will end up spending more than i hoped. But anyway, part of that is looking into ways that i might be able to replace expensive commercial products like the IGUS bearings and the Leadscrew nut. I’ve already drafted up a 3d printable version of the leadscrew nut and posted it here on Thingiverse. The nut has yet to be tested, but i’ve also had some RJM-01-08 IGUS bearing replica prototypes made in Nylon. The RJM-01-08 IGUS replica bearings turned out to be too tight, but with a drill i was able to make them usable. They are currently being used to remove the wiggle and slop i was experiencing from using the 1mm too small LM8UU ball bearings.

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I originally got the LM8UU bearings as a cheaper alternative to the commercial RJM-01-08 IGUS stock bearings the Lulzbot mini uses thinking they would work. They work, and i am currently using some, but the stock STL files from Lulzbot have holes that are 1mm too big because of the slight size difference between them and the LM8UU. I might try to modify the STL files [i have modified the lulzbot solidworks files] to make LM8UU compatible parts in the near future, but for now i’m happy with my 3d printed nylon ones. I’ve heard PLA might work too, so i will experiment with that in the future as well.

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Here are some more pictures:

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