RepRapOneDarwin
Contents
RepRap 1.0 "Darwin"
These pages are under construction.
This page, and those to which it links, are a comprehensive guide to making the first release of the RepRap machine: RepRap 1.0 "Darwin". However since Darwin is not yet complete, neither are these instructions :)
Overview
RepRap 1.0 "Darwin" is a rapid prototyping machine that is capable of making the majority of its own component parts. Instructions and all necessary data are available completely free under the GNU General Public Licence from this website to everyone.
As RepRap 1.0 "Darwin" can copy itself, once you have one you can make others for your friends; or if they have one you can ask them to make one for you. Of course, you can also make as many as you want for yourself; the more you have, the faster you will be able to make other items. RepRap etiquette asks that you use your machine to make the parts for at least two more Darwins for other people at cost, as well as using it to make whatever you or anyone else on the internet can think up...
Darwin consists of a frame made from rods and printed parts. A flat build platform moves vertically in that frame, driven on screw threads by a stepper motor. At the top of the frame there are two write heads that move horizontally (driven by toothed belts and two more steppers) extruding a thin stream of molten plastic to form new layers on the build base. The machine prints layer by layer to form a solid object. The build base then moves one increment down, the second layer is extruded, and so on. There are two heads to allow a filler material to be laid down as well as the plastic. This filler is used to support overhanging parts of the objects being built, and is removed when the process is finished.
Specification
The RepRap 1.0 "Darwin" machine has the following characteristics:
- Working volume: adjustable, but nominally a 300 mm cube
- Working materials: Polycaprolactone and a filler/support
- Configuration: 3-axis Cartesian drive using stepper motors
- Computer interface: RS232 (or USB -> RS232) at 19200 baud
- Two fixed material deposition heads, user exchangeable (two heads are better than one...)
- Power supply needed: 8A at 12V DC
- Driving computer and operating system needed: Microsoft Windows, Linux, Unix, or Mac.
What order to do things
The first thing to do is to get the software you will need working. It will run without a RepRap machine attached, and - as you start to build hardware - you can connect it up in a partly-finished state to your computer for testing.
After installing the software, you should start to build the six circuit boards for the electronics of the RepRap machine. The first (and simplest) controls the communications, the next three control the X, Y, and Z axes of the machine, and the final two control the machine's write heads. Note that it says "start to build". With the exception of the communications board, the boards are all based on the PIC 16F628 microcontroller, and each board will work with just that chip and its power supply. You build the boards with just those components on plus an indicator LED each. Then you connect them all up (first individually, then together) via the communications board to your computer and check that everything is talking to everything else.
Then you put the driver electronics on each of the last five boards to connect to the motors, heaters, and sensors of the RepRap machine. Once more you can test without the rest of the machine - just plug in the stepper motors, for example, and the software will cause them to rotate on your workbench.
Finally, you build the hardware of the write heads and the Cartesian robot that carries them. The order here is not so important, but probably a good way to progress is to make one write head, then make the robot, then get those working together. Finally you add the last head, and your RepRap machine is complete.
Software
These instructions assume that you will be working with the source code of the RepRap software. A little after the first release we will also be putting out binaries for people who do not wish to get into the details of the code.
Installation
Note that all the electronic information needed to build a RepRap machine (that is, the circuit diagrams and mechanical designs, as well as the software for your main computer and the firmware for the RepRap machine's microcontrollers) is available from the RepRap Subversion repository at Sourceforge. In the sections below you will be instructed on how to download all this; not just the software for your main computer.
Follow the link that is appropriate to your computer platform:
- Downloading and installing the RepRap software under Linux or Unix (most reliable)
- Downloading and installing the RepRap software under Microsoft Windows (probably works)
- Downloading and installing the RepRap software on a Mac (no Java3D = no RepRap control software.)
Electronics
Wires and Connectors
Electronics are no good on their own, they need to be connected together in order to do something really useful. Obviously you're going to want to use some sort of wire, but which one and how will you connect it?? Dont worry, because in this guide we will attempt to simplify it for you.
Power Supply
The RepRap machine needs a regulated power supply giving at least 8 amps at 12 volts. The easiest way to do this is to convert a normal PC power supply into a RepRap power supply.
PowerComms Card
The Power / Communications card is the link between the computer and the RepRap printer. It uses RS232 to communicate over a serial port. If you do not have access to a serial port on your computer, there are widely available USB -> RS232 converters available. It also distributes the 12v power via connectors for all the other boards.
Signals are passed from the RS232 around the communications ring until they arrive at the device to which they are addressed, which then acts upon them. Thus the RS232 Transmit from the Communications board goes to the Receive on the first controller; that board's Transmit goes to the next board's Receive, and so on, just like the diagram on the right.
There is an extra single-wire synchronization link from the X axis controller to the other two axes. This allows all the steppers to move together in any straight line without their needing to transmit data round the ring for each step.
Stepper Controller Card
The stepper controller card drives a stepper motor. You need three of these boards for a fully functioning RepRap. Each board controls the position of one axis. Together, they position the print head anywhere in the 3 dimensional build area.
Extruder Controller Card
The extruder controller card drives an extruder (print head). You need two of these boards for a fully-functioning RepRap. Each board controls one print head. The board controls the temperature and heating coils needed to melt the plastic. It also powers and runs a motor that feeds plastic into the extruder which is then melted and extruded. One board controls the printing of the plastic that forms the object being built; the other controls the extrusion of a disposable support material for where there are overhangs. Together, these extruders physically do the printing of the objects being made.
Motion System
Z Stage (Vertical)
The Z Stage (or axis) is the vertical component of the mechanics. It either moves the build platform up and down (vertically). Unlike the X and Y stages, the Z stage is used less frequently as it is only active between layers or between sections of the build in each layer. Thus it can move more slowly that the X and Y axes, and so can be drivin via screw threads. This gives slow speed, but precision, and also allows the Z motor to be turned off when there is no vertical motion without the build platform moving.
X and Y Stage (Horizontal)
The Y stage (or axis) is used in combination with the X stage to move the print head horizontally across the build platform. In Darwin, Y is attached to the X stage and the whole X stage moves along with the Y stage as it prints; Y is the stage that carries the X axis and therefore has a heavier load. These two axes are so closely linked that they should be built together.
These stages require specific gears to drive the axes. Here's how to do it at home.
Toolheads
Thermoplast Extruder
This is the hot center of the machine. It can melt a variety of plastics and extrude them out in a thin stream to form a line. Put enough of these lines side-by-side end-to-end and you get a layer in a shape. Stack those up and you have an object. That's additive manufacturing, and it's the whole principle of RepRap.
Construction
Tools
| Stuff You'll Need |
| A computer with a serial port (or USB + serial converter) |
| Power Drill |
| Screwdriver |
| Pliers |
| Scissors |
| Spanners or more pliers |
| Digital calipers |
| Carpenter's Square |
| Craft knife with extendable blade |
RepRap parts
| Quantity | Item |
| 1 | Power Supply |
| 1 | Communications Board |
| 3 | Stepper Controller Boards |
| 2 | Extruder Controller Boards |
| 3 | Stepper Motors |
| 1 | DC Gear Motor |
| 1 | X axis |
| 1 | Y axis |
| 1 | Z axis |
| ? | ground rods |
| ? | timing belts |
| ? | threaded rods |
| ? | limit sensors |
| - | Wires to connect boards |
| - | Reprapped Parts |
| - | misc screws / bolts |
| - | zip ties
|
Construction Process
Printing in 3D
First Printing - Cheers!
If you've successfully assembled everything and are ready to take the plunge, load up this file into the RepRap build area and start the job. After X minutes a few small cylinders suitable for drinking should appear. Gather your friends and fill them with your age-appropriate celebratory substance of choice. Say a cheesy line, and drink. This will demonstrate some excellent properties of your new machine: that the axes work, your extruder works, and the plastic seal is watertight. Welcome to The Future.
Spare Parts and Replication
Now that you have a working machine, make one each of all the component parts of your machine and put them in a cardboard box on a shelf in a cool dry place. In the future if anything breaks, you'll then have the right spare part. If that happens, replace the part, make another, and put that back in the box. In addition to making copies of itself, RepRap can, of course, repair itself...
Also, don't forget to make two machines for friends or colleagues. It's by no means required, but it is definitely in the spirit of the project. The project is free (as in speech), but unfortunately real stuff costs money, so the common etiquette is to pay for raw materials / shipping / construction time.
Supply
In fact, since its in the group's best interest, we will probably be doing group buys in the future. The more people we get, the better prices we can negotiate. Additionally, since it is often easiest to buy as an individual, we will also be listing suppliers where you can get parts. This is a good thing since with this shared knowledge, we'll be able to compare prices as an internet community and if someone finds a supplier with the lowest cost with a compatible part, then we can highlight that source and everyone will benefit from the savings. Economics dictates that the larger this project gets, the cheaper its components will be.
-- Main.ZachSmith - 01 Feb 2007
