Tuesday, April 28, 2009


2 turntable designs for a 3d scanner

There has been plenty of talk in the forums over the need for a 3d scanner. One major method that has been used is to build a turntable to rest you object on. Then with simply a webcam, laser and wineglass you can rotate the object slowly and get a full scan of it.

The method is pretty well described both at

sjbaker wiki

The only question is where to get the turntable?

Well, in the space of 3 hours, two seperate designs for turntables have been posted online. Myself and Simon Kirkyby have both designed turntables that work on essentually the same principal, but taking some different routes in the actual design. I was going to be posting about my own design but simon's appeared as well so I though I'd put them both up here to make sure everyone knows about them both and can use different ideas from both. I'm pretty sure there is some wierd 1000 monkey thing going on though, because Simon and I live within 10km of each other and have met together on the reprap project before.

Both designs have the following advantages:
1. Every part is less than 10cm by 10cm. Meaning they can be printed in a cupcake printer.
2. Both are based on a simple dc motor
3. Both can be pretty easily run based on a DC driver circuit and a very simple arduino program

So, onto the designs. Apologies for the quality of my pictures.

The design needs some improvement, It was designed for printing, but when it come to milling that stand is very wasteful (thanks to forrest for pointing this out). But can probably be improved, I personally am a little bit dodgy when it comes to the gears themselves, so someone might want to have a look at them before printing. The Stl files can be found attached to this post I made in the forums yesterday. While a more detailed look at the design can be found on the perth reprap blog at Free As In Steins

The second design was done by Simon Kirkby. His includes a spot to place your camera and laser. It uses a different design and isn't quite as angular as mine. His looks to possibly use less material, but not be millable.

The stl files can be found on thingiverse.

Odds are one of the turntable designs can be perfected to form a big part of a 3d scanner.

There is a post on the forums with some images of reduction gears (I had the same issue):

I saw that post. The reduction of gears works on two principals by how I understand them. Decreasing angular velocity and increasing torque at a certain spot in the centre of the circle.

The reason I arranged the gears this way was not to increase torque, but rather so that all the weight of the object would be adsorbed by the central bolt and bearing, instead of by the motor. It would slow down the rotation somewhat, but it mainly was done so that I could put a large weight on the main tray and not worry about damaging the motor.
This may be of no interest, but it could one day negate the need for a line laser. It could possibly remove the need for anything other than an object and a camera.
Photosynth is able to build impressive 3d models using normal photos of an object:
(plugin required, press p to view point cloud)

It's not open source, and you can't get hold of the 3d models. There is an opensource equivalent (although it doesn't do automated image matching):
Sorry, this is more relevant to what I was talking about:

If you are going to use turntables, you might as well use DAVID laser scanner software. It seems to be the most versatile program out there, and if you can get over the fact you have to pay for it, it really gives you am amazing level of detail. http://www.david-laserscanner.com/
3d scanning from Surfdev, a specialist scanning service performed by a reverse engineering company.
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