Rapid Prototyping – Mechanical Iris Diaphragm

Shapeways had a little Halloween special last month where they offered 66% off on their new black detail material.  Always wanting to try out some 3D printing for myself, this offer reeled me in!

So I set out to design something in the shortest amount of time and yet would still give me a good ‘feel’ of what 3D printing is capable of today.  The time constraint was probably also due to the fact I read about the offer at midnight and wanted to send it to print before I sleep 🙂  Result? Concept, Design, Upload, Ordered all within 2 hours!

The concept is a mechanical iris diaphragm, similar to those in cameras but on a much larger scale.  If you’re a Stargate fan, you would have think this is a much SMALLER scale version of the Stargate iris, then I would say that only has 20 blades…mine has 24!

There’s not much design detail out on the web, or at least no design drawings to plagiarise but I’ve seen enough stargate to try design something up myself…

I used Alibre Design Xpress which is a free 3D Parametric Modeler program.  One of the great things about it is that it is not feature stripped as most ‘free’ versions of commercial programs are.  With a very easy to use sketcher, and the parametric nature of the program, the entire iris design was completed in less than an hour.  Most of that time was probably spent tweaking the parameters to make it look good 🙂  One of the design constraints I placed upon myself was to make it a low volume design to minimise the 3D printing costs, hence the odd size.

The mechanical iris diaphragm will ‘open’ or ‘close’ as the outer ring is rotated around the inner ring depending on the direction of travel.  The dynamics of the design was helped by the assembly module of Alibre Design Xpress.  By constraining the pins of the blades to the holes and slots of the rings, I could simply move the ring in the model and watch the blades all move in unison as they are meant to.

Since this is just a proof of concept and I wanted to sleep (~1am by now), I didn’t bother with niceties such as putting covers on the rings to make them look nicer.  The reverse side is going to be ugly…and it’ll show later on.

Before anyone critiques me on the ‘too long blades’,  I did intend them to be that way.  I’ve always thought the Stargate iris looks cool and wondered if it’ll actually fully close.

Shapeways accept files in STL format a defacto standing in 3D printing, and luckily Alibre Design Xpress exports in STL!  Unfortunately the validator at Shapeways didn’t like the STL Alibre exports in… wasted a fair bit of time googling for a solution…

Meshlab to the rescue!  An open source processing and editing program for STL files, where all it took was simply opening the Alibre STL file, answering the ‘do you want to fix  ***’ prompt, then saving.  The resultant STLs was was much smaller than the original and upload to Shapeways validated!

Payment was easy with Paypal and major credit cards as options.  Another fantastic thing about Shapeways is that you don’t have to worry too much about ridiculous shipping costs.  All pricing includes worldwide shipping – a good change since I’m used to seeing $10 bargains with $195 shipping costs attached (Australia…on the fringe of civilisation… [Yes it’s still part of civilisation]).

Ended up ordering 2 sets of blades at slightly different thicknesses, but woohoo…order complete in under 2 hours!

Delivery took a bit longer but that’s probably because Shapeways would have been snowed under with such a great deal, but true to form it did come before Halloween.

Assembly was simply a matter of popping each blade into position, stacking them ontop of each another.  The last couple were the only tricky bit.

This is the iris assembled in the almost fully open position…