I've been negligent in the posting of new subject material on my web site. In part, because my roommates conspired to involve me in a gigantic time sink, but also because my rapid prototyper arrived [1]. These devices, also known as 3D printers, take a 3D design and quickly generate a facsimile in plastic, resin, or a dozen other possible materials. This allows the designer to quickly test out a design before spending the money on having it manufactured for real.
While a mainstay in mechanical engineering for years, the considerable price of these machines have left them out of the outs of hobbyists (the cheap ones tend to be multiples of $10,000). That is, until a couple years ago when the RepRap project started up. Started by an academic (of course), this project's goal was to design a rapid prototyper that could be manufactured using a rapid prototyper. Once this goal is accomplished, one generation of machines could manufacture the next at low cost.
By virtue of being overly idealistic, there exist a few major problems. The first, most obvious problem is reminiscent of the chicken and the egg: where do the parts for the first generation of machines come from? While some people have access to commercial rapid prototypers, this is an expensive option for the majority of people. To address this problem, several companies started up using more accessible tooling (such as laser cutters) to manufacture machines of similar design which could be used to manufacture a first generation RepRap (or “bootstrap” the process).
This particular construction project has been my third attempt to get a working prototyper, and the first two attempts both illustrated the second problem: a self-replicating machine can be only as sophisticated as its ability to manufacture. Add to this, the limited engineering experience of the project initiators and unique limitations of each manufacturing method, the first generation of these machines were far from optimal. My first attempt came when a friend purchased a laser-cut derivative of a Darwin (version one RepRap). While we got the machine assembled, it had a habit of rattling itself apart and the extruder (the heart of the machine, responsible for laying down the plastic) refused to work but once.
Realizing the goal of a self-replicating rapid prototyper might be a bit overly optimistic, several companies started up product lines which simply sought to make a low-cost rapid prototyper. The ability to replicate itself was simply not a concern; instead, the focus is on optimizing the design for the manufacturing capabilities available to them. The most well-known manufacturer here would be Makerbot Industries, the source of both my second and most current attempts.
Makerbot's first product, the Cupcake, improved upon the performance of other laser-cut RepRaps, but still suffered many of the same problems. Most critically, the extruder, while improved from the original Darwin, still suffered significant reliability problems that prevented me from ever successfully manufacturing an item. Their newest generation of extruder, included with my recently purchased Thing-O-Matic, appears to largely resolved the problem. So, here's my assembled machine:
Thing-O-Matic
by Jonathan McGee
Before people start asking me to make random things, take notice of my choice of words: assembled, not finished. After the device was fully assembled and happily throwing the stage to and fro, extruding plastic and the like, I tried to print a shot glass to celebrate my success...failure. The print can't make it much more than an inch vertically before the extruder head embeds itself into the top of the object and otherwise begins misbehaving.
The instructions from Makerbot have you use a default configuration for skeinforge (the program that converts the 3D drawing into machine commands). What I hoped would be an acceptable starting point turned out to be non-workable. So for now, I need to figure out what combination of settings will resolve my problem.
Given the primary symptom (the print head catching on the building object beyond a certain height), it appears that more plastic is being extruded than the default calibration expects. This is unexpected, given that MakerBot's current extruder runs on a stepper motor, so the extrusion rate should be the same for everyone. So far, I've been able to get a tower to successfully complete by increasing the measured layer height, but not without side effects. I'll follow this post up later once I have a better idea of what's going on and how to resolve it.
Footnotes
- The actual reason would be that my attention span is shorter than the lifespan of a mayfly.