Very early this year, we got an invitaton to a DIY fair, the MakeMunich.
"We have to take a printer with us", my friend and business partner Domonoky said. "A portable printer?", I asked, "Why not mobile?", he answered. So the idea came up to build a mobile 3D printer.
A look in the worldwideweb showed, that we were not the only ones, who had the idea of a mobile 3D printer:
Images of mobile ultimakers at the dutch week and the picnic festival.
But this ultimaker seemed to be a bit large for carrying around. We wanted to make it smaller. The first project name was BonsaiMobile, but unfortunately a japanese company named Bonsai 3D printer was founded in february this year, so the name had to be changed. It's a Prototype, it's mobile and it's Beta: BetaProtoMobile.
First of all, we looked for a suitable power supply. Many searches and many results later we found a suitable Li/FeS battery and a ATX-power-supply:
20 aH Li/FeS Battery automotive ATX PSU
We also looked for LiPoly and other battery packs, but most are too weak or - if they have enough power - too dangerous. The choosen Li/FeS battery has the advantage that it doesn't burst spontaneously, like LiPolys do sometimes.
The next thing was the frame. We'd need a frame not made of round rods but light and stiff aluminium profiles. Solution: Makerbeams.
Then we went on with an openSCAD model of the printer to get an idea of the real print-size left after adding battery, ATX PSU and reprap electonics. It should be a compact and light printer and we wanted to eliminate the z-wobble resulting of bad centered x-end-rods or the nut moving in the threads tolerances. We took the idea of the delta bots like the rostock to move up and down with a simple carriage between a timing belt. To not power the z-motor all of the time and to get enough resolution we decided to take a worm-driven z-axis.
Soon it turned out that it makes no sense to move the whole z-axis up and down with only one belt and two smooth rods.The Prusa design has 2 linear bearings on top of each other. Installing this into the small frame would turn out into a print height of only 5 cm, which is too small, even for a mobile printer.
After playing around with some different types of z-carriages, we found a design with two instead of one smooth rod on each side and four parallel linear bearings driven by two belts. The x-carriage is wide, so the weight of the extruder is balanced well. The extruder can move out of the top of the frame, so more printing height is available.
Also we tried to tension the z-axis belt with greg frosts Prusa x-carriage belt clamps, which work with a set-screw at the carriage. Unfortunately the screw needs 1cm of our valuable printing height, so an alternative to this mechanism had to be found. Solution: We tend the belt on the top with wingnuts.
The last step to get enough printing height was to take an extra short J-head hotend. These new hotends have an advanced design and are 1cm shorter than the old ones.
Step by step we built up the printer, changed some plastic parts, inserted the endstops and wired it up for a first real movement and working test.
Here are some images of the prototype:
The z-axis worm drive: Casted parts. The original was made with 4 and 5mm bore.
Top of the z-axis: A pulley - also casted- on two 6mm/9.5mm (ID/OD) bearings. The T5-Pulley is only for fixing.
Image of the real printer vs. digital openSCAD model.
The test setup with our printer prototype (with the wooden test printbed), the Echinus electonics, the ATX PSU and the Li/FeS battery.
Only the entrails: the Echinus electonics, the ATX PSU and the Li/FeS battery.
We also made a video about this very first test:
The plans are to complete this prototype, add a polycarbonate printbed and a cover and walk around with it on the MakeMunich on april the 20./21. 2013
See you there
BonsaiBrain
