Page 190 - Robot Builder's Bonanza

PRODUCING “QUICK- TURN” METAL AND PLASTIC PROTOTYPES 159

Not all services cut every material. Most will accept cardboard, plywood, acrylic plastic,
polystyrene, and polycarbonate plastic. Laser cutters generally won’t accept jobs involving
aluminum or expanded PVC, as working with these materials can damage their machines.
Custom laser- cutting services can be found locally as well as online. Do a Web search for
laser cutting. If you’re only interested in local services, online business directories (Yellow
Pages, Yellow Book, and so on) will help you narrow your search to those near you.
Some tips:
• Be sure to read and understand the instructions for submitting files. Most laser cutters pre-
fer files using the DXF format (these have a .dxf extension). Any self- respecting CAD or
vector graphics program can save files in this format.
• Use just one line thickness. Don’t use a “fill” on any of the shapes. Holes should be circles;
the hole will be the diameter of the circle.
• The lower left of your drawing should start at 0,0. No part of your drawing should go below
the 0 marks, or it may not be cut.
• In all CAD and vector graphics programs, the shapes (objects) of the drawing are stacked
one on top of the other on the canvas workplane. The stacking order of these objects mat-
ters: the cutter will start with the objects at the bottom and finish with those on the top.
When cutting out a base, you want the outline of the base to be cut last. See the manual
for your CAD/vector program to learn how to manipulate the order of objects on the
workplane.

Producing “Quick- Turn” Metal and Plastic
Prototypes

Thanks to computer automation, you can now quickly and affordably design and produce
parts for your robot out of metal or plastic. The concept is called quick- turn prototyping, and
it takes the idea of laser cutting to the next level. Using approved CAD software, or a graphics
program that the prototyping service provides, you design your part, then submit it to them
for manufacture. They then produce the part— usually within a few days— on their automated
equipment.
Common parts for quick- turn prototyping include your own motor or servo brackets, cus-
tom gripper components, and even complete robot bodies. Aluminum is widely used in
quick- turn manufacturing, because it can be machined, cut, and bent on automated (and partly
automated) machinery.
A variation on the theme is using 3D printers, where liquid ABS, acrylic, or polycarbonate
plastic is squirted in precise, measured amounts as a “print head” zigzags back and forth. On
each zig and zag, a 3D shape is formed bottom to top. 3D printing is also known as additive
manufacturing, RepRap (after a popular open- source project by that name), and FDM,
which stands for Fused Deposition Modeling.
To turn your ideas into 3D shapes, you need to start with 3D CAD software (SolidWorks
is popular with many quick- turn manufacturers) or some other mainstream program. Or you
may be expected to use the proprietary modeling software provided by the quick- turn service
shop.

15-chapter-15.indd 159 4/21/11 11:48 AM