Using 3D Printer Technologies for Fast Economical Modeling

 Until recently, if a manufacturer, researcher or inventor wanted to test a part for something or visualize an object in solid, 3 dimensional form, they sent a CAD drawing off to a modeling shop where the item was milled from wood, clay, plastic or metal.  This generally took a considerable amount of time and skilled labor, meaning that such ‘prototyping’ was reserved for large companies with equally large budgets.

Small scale businesses and hobbyists had to cobble together mock-ups from wood, cardboard and clay, and these often were not “working” models.

However, that has all changed since the invention of 3D Printers.  As the name implies, a 3D printer is capable of “printing” 3 dimensional objects, building them up a layer at a time rather than carving them from a solid block of material like a CNC carving machine does.  The advantage is that far more complex shapes, even hollow objects can be built with very little fuss and bother.

There are actually many different ways to construct a 3D model using a 3D printer. All of them take a C.A.D. drawing or 3d digital scan of the object to be produced, slice the drawing into thin layers and use each successive layer of the drawing as a road map of where material must be deposited on each layer to build the object.

One method uses an inkjet style printer that deposits a layer of powder – plaster or resin – then the print head “prints” each slice layer with a special binder ink. Another layer of powder is laid down and the next slice is printed. When the run is completed, the unbound powder is removed, leaving the completed model. This method has the advantage of being very fast – Z Corporation claims their printers are 5 to 10 times faster than any other technology currently available, building models in hours not days -- and capable of building full 24 bit color replicas of the original CAD drawing.

A similar method uses a tank of liquid polymer is used and the print head uses a Digital Light Projector.  The liquid polymer hardens where the DLP light strikes it.  The model is built layer by layer just as before and when it is complete the liquid polymer is drained off to leave the completed model.  Z Corporation’s Z Builder Ultra is a popular model for prototyping.

Another similar method is SLS or Selective Laser Sintering which uses a bed of fine granules and a printer head that uses a laser to fuse granules into sold shapes.  This method has the advantage of allowing the unfused granules to support delicate shapes with long arms or thin walls during the build.  In other methods, such shapes would require temporary bracing to maintain the shape during the build.

For very small models or models with ultra fine details, 3D Microfabrication is used. This method uses a block of photopolymerizing gel and a focused laser beam. The gel cures to a solid only where the beam is focused and when the model is complete uncured gel is washed away. Using this method, features under 100 nm are possible as well as extremely complex shapes or interlocking parts.

Fused Deposit Modeling

And finally, Fused Deposition Modeling (FDM) uses a print head with a nozzle that deposits small drops of a liquefied polymer (typically ABS) onto a build bed and builds up from there in a free-standing form. Stratasys developed this technology and is now part of the Z Corp family. Modeling in this manner is inexpensive and can be done in machines small enough for desk-top use.

For the past couple of years, DIYers have thrilled friends and neighbors by building complex models in their desktop 3D printers. But now we have one more addition to the collection: The MakerLegoBot. This 3D printer not only builds things out of Legos, but is itself built of Legos!

Will Gorman, software engineer and confessed Lego maniac has created the MakerLegoBot, a machine that can take a virtual 3-D model and assemble it using Lego bricks.

A stack feed system holding about 35 bricks connects to the LegoBot. The model that the MakerLegoBot is to assemble is designed in MLCad, a modeling program. A Java application that runs on a PC takes the MLCad file determines the print instructions and sends those instructions over a USB cable to the LegoBot.

The LegoBot pulls a brick from the feed system, positions the brick then uses an axle-based release mechanism to leave the brick in place.

Currently LegoBot works with 1×2, 2×2, 3×2, 4×2 and 8×2 Lego bricks. For now, it can not make use of the fancy blocks or motors and the system can build objects that are up to only 12 bricks tall.

If you’d like to try your hand at building your own LegoBot, Gorman has posted instructions on how to build the MakerLegoBot on his site.