Cheapest 3D Printer

My latest obsession is trying to build a 3D printer for as cheap as possible.

Partly it's because I believe 3D printing is a disruptive technology. The lower the cost for making a 3D printer, the more people will have access to the technology, and sooner the disruption will take place.

And partly, it's because I'm just really really cheap.

Low Cost

What does low cost really mean? One obvious way is to look at the price of something if we were to buy it new in a shop. If we only source new parts and new materials, we're going to have a difficult time creating something truly low cost.

My strategy is different. I'm going to try and get as many of the source materials as possible for "zero dollars."

Consider old car tyres. Any time you can recycle the rubber from an old car tyre into a seesaw or a swing, or into building materials or to protect a wharf, then the cost of that rubber is effectively "zero dollars."

That's why the core design elements of my 3D printer are going to be fishing line and lego. Two very cheap substances if you source them the right way.

Fishing Line

Nylon fishing line is an amazing substance. It's strong. Durable. Inexpensive. It's readily available everywhere around the globe. And if you need small quantities, you can often obtain it for "zero dollars". You probably already have some.

Lego

Lego is an amazing substance. It's available everywhere. It's manufactured to extremely high tolerances. It's consistent across time and place. It comes in a variety of colors. It's durable.
While lego might not be cheap, you can often *borrow* lego for "zero dollars" by using the magic words "I'm trying to make a 3D printer out of lego."
Once your print run is complete, you can simply disassemble the lego and return it to it's previous state.

Calibration Problem

When I look at the designs for existing 3D printers, one of the biggest design considerations seems to be finding out where the extrusion point is in relation to the "bed". Existing designs carefully measure the motion of the motors, try really hard to make the frame rigid, and then have lots of complicated software to try and calculate where exactly the filament is being deposited.

Ack, too difficult.

Why go through all the calculation, when you can measure directly?

My plan is to use the camera on an Android tablet to see where the bed is, and, at the same time, to see where the print head is. If it needs to move to the left, well, the tablet will keep the motors spinning until it lines up. Too far to the right? no problem, spin the motors the other way until it matches. Checkmate calibration problem!

OpenCV

Oh, and remember our lego? We know exactly how large a block is in the real world, so we can measure off distance in our 2D camera space by placing a known lego calibration object made with a few different known colors.

This way it doesn't matter if our fishing line stretches during the course of the print, or our lego gets bumped half way through, or the ambient temperature changes which make the layers a tiny bit thinner.. no problem, the camera on the android tablet sees all.

And how much does it cost for an Android tablet? "zero dollars." You just have to use the magic words: "Can I borrow your Android tablet to make a 3D printer?"

Next Steps

I've already starting on version 1 of the prototype. Watch this space.