## Monday, September 17, 2012

### DMLS Wind Tunnel Models

Additive manufacturing, sometimes called direct digital fabrication or rapid prototyping, has been in the news quite a bit lately. I wrote a post recently for Dayton Diode about the many additive manufacturing options available for fabricating functional parts or tooling in response to comments on a piece in the Economist, and commented recently on Armed and Dangerous in a discussion about 3D printed handguns. There are just so many exciting processes and materials available for direct digital parts production today. Some of the work I've been doing recently to qualify one particular additive process for fabricating high-speed wind-tunnel models (abstract) was accepted for presentation at next year's Aerospace Sciences Meeting.

We used Direct Metal Laser Sintering (DMLS) to fabricate some proof-of-concept models in 17-4 stainless steel. DMLS is a trade name for the selective laser melting process developed by EOS. The neat thing about DMLS (and additive processes in general) is that complicated internal features like pressure tap lines can be printed in a single-piece model. Being able to reduce the parts count on a model to one while incorporating 20 or so instrumentation lines (limited only by the base area of our particular model) is really great, because one part is much faster and less expensive to design and fabricate than a multi-component model with complicated internal plumbing. The folks down at AEDC are also exploring the use of DMLS to fabricate tunnel force and moment balances for much the same reason we like it for models and others like it for injection mold tooling: intricate internal passages, in their case, for instrumentation cooling and wiring.

## Monday, September 10, 2012

 UpAerospace 10 inch Payload Can (PTS10)

There seems to be a great deal of difficulty (brlcad, opencascade) in getting any of the open source CAD programs incorporated into the Linux distributions that maintain high standards on acceptable license terms and packaging guidelines (Fedora). Luckily, for a pragmatic guy like me I can now install FreeCAD from the RPMFusion non-free repos.

yum install freecad

I'm excited to see if I can get better Boolean operation results (less manual mesh fixing) with FreeCAD for 3D printing than I've had with Blender.

## Saturday, September 8, 2012

### 2011 AIAA Day-Cin AiS Entries

 Stripes
Neither of these pictures won the competition, but the AIAA folks give you a nice print of your picture at the end so it's very worthwhile to enter their Art-in-Science competition.
 Breakdown

## Sunday, September 2, 2012

### Human Powered Helicopter Flight Testing

Flight test is a tough business. Even more so when every second airborne requires near max physical exertion!

I hope these students get their structure fixed and get back in the air soon. This is some really great work. Their vehicle only weighs 71 lbs.

Check out their record setting human-powered helicopter endurance flight.