Jonas Kühling

As already mentioned next door we finally got things wired up and successfully finished our first test prints resulting in even better quality than expected (for the fifth or sixth run at all..). Since our RepStrap was meant to initially start another Family tree of RepRaps – at least one original Mendel Prusa RepRap 3D printer as the nearest milestone – Simon yet got busy in printing a set of Prusa parts from the latest iteration 2 while he is still tweaking settings for enhanced build quality. No major modifications were necessary to the raw build at all, the whole assembly largely works as intended. It does print!

This is part 1 of our documentation and I will have a closer look on used materials, tools and the frame. We will have one post for each detail like the three axes, linear bearings etc. the following weeks while RepStrap’s first child is being completed gradually.

Tools and Materials

Most of the work was done by hand, except the use of a power drill and cutting the main frame parts with a jig saw. For achieving reasonably rectangular holes the drill was backed by a fairly cheap but on the whole practicable drill stand. Not the best choice for precise drilling at all, but it fitted our needs. It’s that kind of manual, dirt emitting operations that should become rare in future projects using one of our to-be 3D printers… But none the less, here’s a quick summary of all used tools:

• power drill with drill rig
• jig saw
• hacksaw
• several files, pliers, screwdrivers
• set of wrenches
• ruler, pencil…

As a RepRap is aimed to be made of easy to purchase materials, most of the feedstock could be found at the next hardware store. We needed to call on a more specific hardware dealer to get the aluminium U-profile of the desired dimensions, but it took us only one additional attempt as well. To have it as a cute list either:

• one board of 15mm thick wood laminate, 50x100cm
• about 2 meters of 20mm squared wood strip
• about 4 meters of M8 threaded rod
• pack of M8 nuts an washers (at least about 60)
• pack of 40mm M8 bolts (about 30)
• set of 15mm M3 bolts and washers (at least 12)
• aluminium L-profile, 15x30mm
• aluminium U-profile, 15x40mm
• about 3 meters of 8mm smooth rod
• M3 threaded rod, nuts and washers, micro bearings (were used, but not recommended in retrospect)
• bunch of 608 ball bearings (at least 30)
• some sort of 20x20cm plane wood/plastics/… for the y carriage

During the build process we made several changes to our plans, that’s why the implementation of the y carriage’s linear bearing design differs from x and z, as we first finished the y axis and revised the build plan afterwards, since the results didn’t sufficiently fit our requirements. We’d better made it the way we used to do later, where we got along without M3 threaded rods an bearings different to standard 608 ones at all.

The Frame

The frame was designed with few major goals in mind: to have it quite similar to the basic RepRap Mendel design as it is heavily community tested and easy to set up, to minimize parts that have to be cut and assembled and to only have to drill holes rectangular to the surface of any part that needs to be drilled. Some inspiration came from RepStraps like the 1X2, Adesina and other bootstrapped RepRap inspired 3D printers documented in the reprap.org wiki.

While an original Mendel is designed for being printed, it is not recommended to imitate the entire design by simply making the parts from wood. And well, I must admit that our design still is some kind of the hard way, too, but we made our choice… If you plan to build your own RepStrap I strongly recommend to follow the guide for a WolfStrap Wooden RepStrap – I guess it’s the most comfortable way to get to your own working printer and reasonable results for printing a first set of e.g. Mendel Prusa parts in the least amount of time.

However, sometimes you just need a little challenge. We replaced both Mendel-characteristic triangular frame sides by parts cut from a wooden plate, so that the count of required individual 90 degree rod connectors is reduced to 8 for attaching the smooth rods of y and z axis to the frame. Drilled six times each, the two wooden frame parts were connected using threaded rods, nuts and washers. The eight rod connector blocks were made of squared wood strip, drilled twice in each nonaxial direction with both holes gently “touching” in the middle of the block, as shown in the thumbsketches and pictures below.

RepStrap BuildLog Summary:

1. Part 1: The Frame

Tagged: buildlog, frame, open hardware, open source, reprap, repstrap