clearance / moving parts -- the magic behind it?

Hello, first time here!

My apologies if this has been asked before, or if there's an easy link to the explanation.

I was browsing through the shop and noticed many printed models that either have interlocking seperate shapes, or even whole mechanical constructions with moving parts, all assembled during printing (or so I assume).

I can't seem to wrap my head around how Shapeways printers would be able to achieve this, if I try and imagine the process in my head, all I seem to be thinking about is that the seperate parts somehow have to be floating mid air throughout the printing process. It's a silly idea, but this brings me to my question:

Is there any information or an explanation available on how the printers manage this (to me) magic feat of production, where it somehow manages to have models suspended in mid air, interlocked and everything, to be printed out in 3D?

Thanks in advance.

A magician never reveals his secrets <grin>

There are a number of videos of the process, including the "How it works" video at the bottom of this page.

The keyword here is "support material". Your model is not "floating in air", but it does have to have something to rest upon.
The magic is also inherent in the fact that the models are produced one layer at a time.

In the case of White,Strong,Flexible, a uniform layer of nylon granules are smoothed out on a surface. The laser then passes by, welding some of the granules together, making the first layer of your item. Then another layer of granules are spread on top of the first layer, and the laser again welds those together - but also it fuses any granules from the 2nd layer that are in direct contact with those from the first layer. If you skip welding for a couple of layers, then there is un-fused material that sits between the parts of your model - acting as a support for the next item to be placed on top of them.

Does that help?

Hi, thanks for the quick reply.

I somehow missed out on the "how it works" video! I went through their whole youtube channel but missed out on this video. Sorry.

I never thought of the support material as a "bucket full of sand" kind of thing, but it makes complete sense now. This will definitely help me in my future printing endeavors.

Thanks!

Another major magic component of design of designs like this is being aware of how the required clearances between parts and process variations in manufacture might interact to affect movement. If your designs rely on very precise fits you can end up with problems. I haven't done too many multiple part designs but when I started I found getting repeatable fits was problematic.

A lot of knowledge can be gained by having some small test pieces printed prior to going gangbusters with a big and expensive design with many moving parts. There are some things that can happen in printing that are not expected, although they should fall within the process variation tolerance for a process. Printing test pieces for joints, clips, snaps, screws, etc. can end up saving you time and money by requiring fewer interations of a larger scale device to get things right.