Théo Lepage-Richer

Fab Academy / Digital Fabrication 2015

Make Something Big, to Carry Other Big Things

After two weeks of working at a micro scale with electronics, this week’s assignment – Fab Academy’s now well known “make something big” – arrived as a quite refreshing change. As stipulated by this assignment’s official name – computer-controlled machining – this week is dedicated to large-scale milling/drilling machines such Shopbot and Precix.

For this week, I decided to exploit the specificity of this technics and imagined a design that could be assembled without any additional tool, i.e. only with joints already included in the milling of the board. After hearing some people wondering how they will be able to bring their “make something big” project back home, I took this rhetorical question as a challenge and drew a wheelbarrow that could be easily assembled. To develop my design, I review the differences among the various types of wheelbarrows (the Chinese wheelbarrows, the European wheelbarrow… I have way too many wheelbarrow-related websites in my browser’s bookmarks now) but ended up opting for a fairly classical design – for the others could be made at a satisfying size with the 2500 by 1250 mm OSB board (even though I did have a strong soft spot for the Chinese wheelbarrow

While I didn’t want to use any other additional piece/tool, I had to give up a bit and bought a second-hand wheel hub from a bike shop (as the clerk offered it to me in exchange of 6 beers, it was hard to say no to such a bargain), which allowed me to simplify drastically the overall design of my piece. The milling went smoothly. Within the g-code script generated by RhinoCAM, there were some absurdities that couldn’t be explained – the mill going all the way down into the board, to then do the same thing gradually, and very slowly, in the newly formed whole – but they could easily be rewritten by hand in the .txt document directly, which made me realized how surprisingly straightforward a g-code script is – in the future, if I do happen to have a very simple design in mind, I might attempt at writing some parts of the script by hand.

In the end, the whole workflow went quite well. I made a fair amount of mistakes – my first joints were too short to support the whole structure, I had poorly evaluated the volume of an angled piece and had to cut it at a 45-degree angle, &c. – but managed to correct them with subsequent drafts and/or while assembling the piece. I could finally achieve the objective that I set for myself – building something that was strong enough to carry somebody (ok, I might have cheated a bit by making my test with Josefina, Fab Lab Barcelona’s lightest member, but, hey, a person is a person). Here’s the proof, supported by my euphoric expression of success (and fear that the whole thing could break at any moment):

Make a big Wheelbarrow - Test from Theo L. Richer on Vimeo.

See below for all the details/for each step.

Your Name

  • Week: 08
  • Subject: Computer-Controlled Machining
  • Tools: Rhino, RhinoCAM, Precix 11100
  • Objective: Make Something Big
  • Files: Click here

Project 01a
To start with, I used the Topological Optimization Research Group’s online app to find some inspiration for an optimal design of the piece. The app basically invites the user to put/situate various weights, supports and zones without any material to then calculate in real time the optimal formation of such a topological arrangement.
Project 01a
I then sketched a similar design with Rhino. I took me quite a while before finding a satisfying version – the first ones all had long handle pieces which made it impossible to make a wheelbarrow of a decent size with the board I had – but I ended up stumbling upon the Fab Barrow, which showed me how to exploit the specificity of the milling machine and our material. The only subsequent problem I had was, as pointed out by Ferdi, that my first joints were too small – only 2cm in thickness – and I had to spend a fair amount of time redoing them (that’s the price of putting absolutely no intelligence in one’s sketch I guess).
Project 01a
To translate my plan into a script for the machine, I used RhinoCAM, which I found highly intuitive and easy to use. I started by making a script for the drill – it is essential to firmly fix one’s board – then another one for the inside pieces – those for which the lines are supposed to be drilled from within – and finally for the outside pieces – those needing to be drilled from outside.
Project 01a
The milling itself went smoothly. Ferdi introduced me to the machine’s software and I could initiate the milling after having simply set the 0s. I first ran each script 5cm too high to make sure that the mill wouldn’t run into the nails, nor do anything unexpected, but it did nothing of the sort, and I therefore could send the script at the proper height.
Project 01a
All the pieces came out cleanly, but I realized when I tried to assemble them that I had made two (major) mistakes. The first one was that – as I don’t seem to understand space in general – I hadn’t considered that the angled piece would be lower than in my plan, because of its thickness. I therefore cut it at a 45-degree angle, which made it fit in place nicely.
Project 01a
My second error was that, when I was measuring the necessary space for the wheel hub to fit, I had completely forgotten that the piece holding the hub would have a thickness (duh). To arrange this, I use a drill with a 1.5cm mill to reduce the thickness of the piece at the level of the hub’s bolt – that way, I could maintain the hub in place, even though it ended up bending the holding pieces and reducing the overall strength of the wheelbarrow.
Project 01a
After these two tune-ups, I could finally assemble the wheelbarrow and start carrying people’s stuff around.