Saturday 31 March 2007

Chicken and Egg

The problem with making machines that make themselves is how to make the first one! A bootstrap machine has to be made by hand first. This has come to be known as a RepStrap machine in the RepRap community. Lots of people are trying different approaches using whatever materials are easy to come by locally. Wood, Lego, Meccano, copper pipe and drawer slides have all been used by different RepStrappers. The machine needs three axes of motion and an extruder head to extrude molten plastic filament. Most RepStrap machines use threaded rod as a means of creating accurate linear motion from a stepper motor for the axes.

This was the approach I was planning to take when I started looking at this in mid January. I had a look at how professional CNC machines are put together and saw that the prices are a lot more than I wanted to pay but the accuracy and speed was a lot better than I could hope to achieve with drawer slides, etc. I had a quick look around to see if I could get anything second hand or from the surplus market. To my surprise I found an XY table on ebay for $400 which has a super small step size of 6 um but is able to move quickly and has very high stiffness.

This gave me the idea that I could make a very accurate machine that is also stiff enough to do milling. I found a Z axis on CNCzone for $150 and the project was born.


My friend Wes pointed me to and I immediately decided it was what I going to do with part two of my life. I have been collecting motors and other "useful" junk for years and have at last found something interesting to do with them. My hobby, starting as a child, used to be electronics but it is increasingly hard to find something to make that you can't buy cheaper and better. Consequently I haven't built anything at home recently. My skills lie in electronics and software and I can get by in woodwork and metalwork which I learnt from my father who was a patternmaker by trade. This project involves all these disciplines plus material science and chemistry which I know virtually nothing about but am interested to learn more.

In short, making machines that make other machines is the perfect hobby for me. Hopefully my experiences along the way may be interesting to others so I decided to start this blog.