3-D Printing: Solid Model Fabrication with a Touch of a Button

Article excerpt

"The complexity of the parts that may be made with these printers is impressive."

Most teachers of drafting and design are currently teaching using CAD software. While most teach two-dimensional drawings in the form of orthographic projections, advances in software are making the construction of 3-D models easier and more practical. Solid models can take the form of a wire frame or shading, and materials can be added to give the model a more realistic appearance.

With all these advances in 3-D modeling, most students still cannot touch or hold the object they have designed unless they fabricate the part on a mill or lathe in conjunction with a CAD/CAM program. One may wonder if there are any other options that would give students the ability to fabricate prototypes of designs easily and quickly. The fact is that the technology has been around for several years. It is known as 3-D printing. These printers have the capability to create prototype parts from 3-D solid models, while giving student designers and CAD operators the option of handling the designed part and sharing that part with others.

What is a 3-D printer? It is a system that can produce real prototype parts of solid models drawn through the applications of CAD packages. There are several 3-D printers currently available that use varying technologies. Those described within this article use different technologies to harden powders of different materials. The method of hardening may be with the use of a laser or ink-jet droplets sprayed onto the powders.

The Process

Since there are various machines on the market using different modeling processes, we will first focus on one of the less expensive systems, such as the Z-Corp printers.

The first thing needed is a CAD package that saves in a format that the printer will accept. These may be .ply (popmail), .bid (bloadable picture), .stl (stereo-lithography) or VRML (virtual reality modeling language) formats, and are the save options on many 3-D modeling packages currently used in school-based drafting programs. Once the operator saves the solid model in the appropriate format, he or she must then import the file into the printer software. This normally takes less than two minutes.

Materials used in the process are then loaded into the machine. They include the forming powder and hardener. Once the machine is prepared, the operator then presses PRINT on the printer and the fabrication process begins. Powder is laid down onto a flat surface of the machine at a thickness between .003 and .01 inches. An ink-jet cartridge then passes over the powder, releasing microscopic droplets that glue the powder together in a process called sintering. Sintering is a way of bonding particles together. The process uses existing ink-jet technology to release the hardener. This helps keep costs down and gives the option of purchasing replacement printer heads locally. The process is then repeated as the part begins to take shape from the bottom up, one layer at a time. (Creators of this technology worked closely with Hewlett Packard when designing this aspect of the process.)

The speed at which parts are fabricated depends on the size of the item. These printers can fabricate complicated parts in hours, while smaller parts may take an hour or less. An 8 X 8 X 8 inch block can be made in 5 to 6 hours, depending on the powder used. The complexity of the part does not increase the time of part fabrication. It is more related to the mass of the item. This is considerably faster than a printer that joins powders with a laser. According to Drew Santin, President of Santin Engineering, "the Z-Corp printers produce parts ten times faster and at one tenth the cost" of a laser hardening system. This is currently the fastest way on the market to produce prototype parts.

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Once the part is completed, it is removed from the printer and excess powder is brushed or blown off. …