Mini-mendel built and working!

I went to the USA to visit Zach and Bre and the others from Makerbot and to give a talk at MIT for an innovation lab. I proposed to give a demo, but didn’t dare bring one of my Darwin RepRaps on an airplane. They are very heavy and fragile, unlike the Mini-Mendel, which is quite sturdy compact and lightweight and can fit in a smaller, strong box. I had brought the printed parts (blog post about ordering, printing and preparations here) with me to the US and worked on them at New York Resistor. Besides having a really great time there, I also made a lot of progress. I barely got it running in time for the demo, I had done a proof of concept extrusion with X-Y movement, but it wasn’t exactly what you would call 3D printing yet, let alone reliable printing.
In the day after the presentation I fixed the most important problems (belt tension, belts running off the pulleys, writing firmware bug workarounds, etc.). The fact that I didn’t have a unix based toolchain for compiling the PIC32 code of the BitsFromBytes board, did make matters really complicated.

Overly ambitious I had been trying to get multi-material working on their v3.1 board. I actually did a short amount of multi-material extrusion but couldn’t repeat the same with different g-code (after deleting the file that worked from the SD card).

The parts for the Mini-Mendel were printed with both the Darwin from the Q1 2008 cast parts from BitsFromBytes and the Darwin offspring machine that I’ve printed with the former machine. So it’s at least in part a third generation machine, but the majority of the parts came from my older machine (I’m so used to the process).

Anyway, a picture says a thousand words, so here’s a moving picture (and no more talking):

(BTW: if you didn’t pay attention to the song’s lyrics, you should listen to it again!)

The machine is considerably smaller than the Darwin (or regular Mendel), as you can see from the following picture:

From RepRap Dev

I’m driving the extruder with my ‘remote’ drive mechanism:

From RepRap Dev

You can put a beefy NEMA23 on it to have a lot of torque and without much complexity (just the part, a motor, a bearing and a pinch wheel).

It is pushed into a Bowden cable (a PTFE tube). At the hot end, I’m using my new coupling to keep the Bowden cable attached to it:

From RepRap Dev

There’s documentation available for it on Thingiverse, as are the models to download and print this add on. The parts/suppliers that I used for this can also be found at Thingiverse.