Hitting the Powder- 3d Printing 101
I thought Jtravis's post on vacuum forming was pretty interesting so I'm going to run through the same description for 3d printing. Along with the CNC mill and vacuum former the 3d printer is one of the major modeling devices here.
It begins with a digital model in Rhino. Since Rhino is a surface modeler, a major chore is to thicken the model considering the final scale. Typically printing below a 1/16" thickness is a roll of the dice (unless your Austrian). If a double surface isn't modeled then it will read as one solid object as oppose to a hollow object which is usually more efficient. Thickening the model must also consider leaving openings to let powder inside the model out
Once thickened it has to be closed in to one enclosed surface. This is then converted from a Nurbs surface to a mesh and exported as a .STL file.
The model can be checked pretty thoroughly in Rhino as far as looking for gaps or holes but if it is really sloppy, alot of people bring it in to a notorious little program called Magics which can stitch and fill all seams.
The final program is 3d Printcorp where the object is positioned in the print bed. The max area of our printer is 8x10x8. Positioning involves an understanding of the machine's operation both to save yourself time and money.
3d Printers are powder based and operate off of two bins one for building and for supplying powder. It prints from the bottom up. Translated in to a a series of horizontal sections the printer heads (basically binding agent injectors) sweep over the build tray building one layer at a time. With each successive pass, the build tray descends until the full model is built. Typically height is the major factor in printing time. Printing times vary from one hour to 8 hours with the general rule of thumb being one vertical inch per hour. Cost at the school is now calculated based on overall time and not volume of powder or binding agent. Hopefully this doesn't lead to flatter models at UCLA.
Next is the fun part. Since the part is encased in a bed of powder it must be excavated like a a fragile fossil. When exposed to air the models tend to harden with time but the first handling is the most dangerous.
Pieces are usually cured with ultra-toxic zap glue (pink bottle) which hardens them to a safe state. From here they can be sanded and painted. -Aaron T(A)DS