Théo Lepage-Richer

Fab Academy / Digital Fabrication 2015

An Open-Source Rotational Casting Machine

As I have already mentioned throughout the weeks, I decided to build as my final project a rotational casting machine. Big industrial ones are pricey and those readily available online as DIY versions are quite limited in size, without mentioning that they require constant assistance, as they must be powered by hand. In that sense, I intend to develop a design that could easily and cheaply be used and brought together by any fab lab around the world.

My favorite design so far is industrial designer Annika Frye’s, but it still involves many flaws from a fab lab perspective: the metal frame she uses is an expensive, custom-made one; the speed of the motor can hardly be set with any precision; the actual design and building process behind it is still pretty opaque… but it is still really insightful when it comes to the ‘hacking’ of readily available second-hand components. Studio Myfirst also has developed a great rotocasting machine, but it’s size and hand-power source do not really suit a fab lab environment – that being said, their use of a single plywood board for the design of the whole piece, as well as their great attach-system for the mold are great inspirations in the design of my own version.

At the most pragmatic level, the success of my project will be based on its mechanical properties, i.e. if it can provide a rotational movement on two axes that would make possible the casting of a shallow molded piece. Yet – more generally – I also want to evaluate the success of my project on its potential to be reappropriated and used by various fab lab sites around the world for their own use. My objective would then be to make a piece that can easily be brought together using methods that we have reviewed throughout the term, as well as cheap, second-hand pieces that can be readily found anywhere. The size and characteristics of these last-mentioned pieces might indeed vary depending on where they are brought, but I aim at developing a design that could easily be adapted to these small variations, if someone somewhere was interested in making another iteration of it for its own fab lab.

To start on that track, I spent the week working on my design, i.e. making 2D and 3D drawings of the rotocaster, and making a small-scale version of it. To do so, I reduced and adapted my drawings for a plywood sheet of 3mm and laser-cut it – the proportions were fine, but this first prototype made me realized that I had made some measurement mistakes, so I will be able to resolve these issues before milling the actual thing.

Project 01a

Nota bene: to make the 3D model of my project, I downloaded and used some pre-designed pieces from grabCAS – the chainrings, the wiper motors, the switch and the potentiometer, to be more precise. You can find all these models on grabCAD, or download them here. The model itself can be downloaded here.

See below for all the details/for each step.

Your Name

  • Week: 15
  • Subject: Applications and Implications
  • Tools: Rhino
  • Objective: Propose a final project that integrates the range of units covered
  • Files: Click here
Project 01a
What materials and components will be required, and how much will they cost?

This budget is a bit of a worst-case scenario one. I am confident that I will find the bike parts for cheap at the some second-hand bike store or maybe some nice board of wood at IAAC, but, at least, it’s encouraging to see – even in the worst case – how affordable this project is for any site that might be interested in building their own roto-caster.
Project 01a
What parts and systems will be made, and how?

The bevel pinions will be molded and casted. The two frames will be milled from a plywood board. The motor part will be ‘hacked’ out of a second-hand wiper motor using an electronics board that I will design, mill and solder.
Project 01a Project 01a
What tasks need to be completed?

As I have already made the bevel pinions during the molding and casting week, the frames and motor part will be my main priorities in the first two weeks of development.
Project 01a
What are the remaining questions to be answered?

The main remaining question is to know how I am going to make the whole thing ‘stands’. I might indeed mill two supports out of plywood, but I might also start looking for a metal frame to old everything together.
Project 01a
What are the remaining questions to be answered?

Before modeling all the parts, joins and mechanisms, I would need to have my main pieces at hand. In that sense, in order to start the concrete design process as soon as possible, I would aim at having the motor, the bike parts as well as the plywood board by the 22th of May at the latest.

The mechanical design assignment might indeed be time-consuming so I don’t want to set unrealistic objectives for myself, but I will try to volunteer myself as the designer of the motor apparatus, which would allow me to start working on my new DC motor board – the older ones threatening to overheat and break if I try to connect a more powerful motor to them – and, ideally, have it working by the 29th of may.

Then, the week of the 1st of June would be dedicated to finishing the motor part as well as milling the two frames. From there, the remaining two weeks would be dedicated to the bringing together of all the bits and parts into what will hopefully be a working rotational casting machine. If I do manage to finish in advance, I will cast some simple pot or similar shallow piece, just for the sake of it.