Tuesday, January 13, 2009

#3 - Choosing a RepRap Design

Reprap vs Repstrap

So you've looked at some of the pictures over @ http://www.reprap.org/ and decided that you are going to make a reprap. Fantastic!

Now just go down to your local hardware store and buy these parts:

Hmmm. The store manager might have trouble finding them. These parts are designed to be printed out on a RepRap machine, but the problem is that you don't have a RepRap to print them out! It's a bit of a chicken and the egg problem. So you can either:
1. Find someone willing to print out all the parts for you or
2. Build a machine that is capable of printing out those parts.

Any machine built with parts that itself cannot create is called a Repstrap. It is bootstrapping the process of building a reprap. There are currently 2 options for repstrap machine designs:

1. The McWire (based on the design by Tom Mcwire) is a Repstrap whose structure is composed of common pipe components.
2. The Acrylic Repstrap's structure is made from pieces of custom cut acrylic. These custom cuts could come from an online acrylic cutting service like Ponoko.
The acrylic repstrap is also known as a rep(st)rap. The reason for the parenthesis, is that one day we hope to be able to strap a laser to a reprap so that it can cut acrylic. When that day comes, the acrylic repstrap will be an acrylic reprap because it can then manufacture its own parts. Thus the "st" is in parenthesis in anticipation that it will be dropped.

As an aside, I would like to be one of the first ones to strap a laser to this sucker. I've already bought a fire extinguisher for experimentation ;-)

Differences in Repstraps
Since I am not the most social person in the world, and don't feel like meeting someone craigslist style at a mall to get reprap parts, I decided to build a repstrap. But which one?

Remember the components of a cnc?
Power supply
Stepper Motors

It turns out that the electronics (and the power supply), the motors, and the head can be used in all three styles of reprap. The only difference between reprap, repstrap and rep(st)rap is the structure. Hazaa! I like simplicity. So the cost difference between repraps is the structure.

Looks like i'll need to break down the Bill of Materials (BOM) for the McWire, and the Acrylic designs to see which one is cheaper. Though I must admit, the Acrylic one looks very sexy!

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