Section Overviews
Overview
This is where you will come if you want to either build a Tommelise or get information that be of use to you in making your own design ideas a reality. There is a lot of content that will eventually show up in here that I haven't managed to get written down yet. The good news is that I have finished building Tommelise and I have all of the systems running and for now there do not seem to be any major design errors in the Tommelise concept. Mind, getting Tommelise to make useful things is still likely to take a long time.
What that means is that I am feeling pretty confident of the basic design concept and detailing of Tommelise. I already know that there are a lot of things that could be improved. Fortunately for you I am not a perfectionist. If it gets near to doing what I want, I will be very happy indeed.
Do keep in mind that the latest stuff that I'm doing is always posted in the blogs. I will often post an extensive blog entry that is really a first draft of what turns into a documentation section.
CAD
If you are going to design something for a 3D printer to make you need a 3D CAD package of some sort. I have used and endorse, after a fashion, the Art of Illusion 3D modeling software. It is pretty easy to use, especially if you have no prior experience with such software. It is also free and easy to install.
Positioning System
There is nothing in this section at the moment. The positioning system of Tommelise is the wooden gantry structure that you can see in the Gallery pictures.
Tommelise positions the work surface on which it builds objects via threaded rods of the sort that you can buy in any good hardware store. I turn these threaded rods with small, cheap plastic gearboxed gearmotors. This rotational motion is turned into pretty accurate linear motion by the simple expedient of screwing a coupling nut onto the rod and then securing that to the working surface that you want to move. In practice, it is a little more complicated than that, but not much.
I use three of these gearmotor/threaded rod/coupling nut assemblies to provide accurate positioning in the x, y and z (vertical) directions.
Extruder
The thing that makes Tommelise possible is the Mk 2 Extruder developed by Dr. Adrian Bowyer of the RepRap Project of which I am a member. While I like to think that I've made improvements to the Mk 2 I had something very good to improve on, a situation that would have been impossible without Dr. Bowyer's design genius.
The Mk 2 uses a technique called Fused Deposition Modelling (FDM) developed under NASA contract during the 1980's. A good way to think of how it works is to think of a cake decorating syringe full of icing. With such a syringe a chef can create icing fantasies on a cake. With the Mk 2 you can make your own fantasies real in any of a variety of plastics.
The Mk 2 functionally works a bit like a hot glue gun. A hot glue gun uses a cylindrical slug of plastic which the trigger forces into a heated cylinder. The heated cylinder melts the plastic which is then extruded from the end of the glue gun. The Mk 2 works in a very similar manner. Instead of a hand-powered trigger a gear motor pushes a filament of plastic into the Mk 2's heated extruder barrel. The thrust of the filament being forced into the barrel pressurises the molten plastic which then emerges from an 0.5 mm orifice at the end of the barrel. The plastic swells on leaving the extruder barrel to 0.8 mm. That molten thread is what you make objects with.
The positioning system takes the function of the chef and moves the Mk 2 around in three dimensional space to make your design ideas real.
Power
Tommelise uses 12 volt direct current power, about 40-45 watts of it. It uses 12 volt direct current mostly because it is very hard to hurt yourself with 12 volts. I want children to be able to use Tommelise safely.
Controls
Tommelise is controlled by a software application running on your PC which communicates with a small microprocessor-driven controller board. I have made a point of making the controller board design very simple and keep the complexity of the system in the software, which is called firmware in such controller boards.
Tommelise is a Wintel application written in Visual Studio .NET 2005's Visual Basic language. unless you want to write a Linux compatable software app in something like Java or Python. If I get enough interest and demand I will use a code translator to do that for you since there are a number of good.
The controller board firmware was written in the Oshonsoft IDE and used their BASIC compiler for the Microchip PIC 18 family of microcontrollers.
I will be posting schematics and tips on how to make up this board as well as source and hex code for programming it.
Tools
I've recently created a stripboard design app for people needing such a facility.
Parts
I typically give a parts price for Tommelise of $150-175. There are a few things to remember. The parts price does not include the cost of the hand tools that you need to build it. You can easily spend several hundred dollars on those alone if you are not careful. If, however, you already have a modest workshop set up to do basic woodwork and electronics soldering you are probably pretty much good to go.
As well, the biggest mistake that you can make, I certainly did it at first, is to shop around looking for the absolute best price that you can find for each component. The problem with that strategy is that it ignores the cold, hard fact that in many cases you will be paying as much or more for shipping the components as you will for the components themselves. This shipping surcharge goes down as you order more and more parts at once from a single vendor. Thus it is best to look at the price of a market basket of components rather than individual prices.