3D printing offers the opportunity to create many things not practical with other methods because of cost or the nature of the shapes involved. The medium used in 3D printers is called PLA. Typically this is available as 1 kg of a 1.75mm filament wound on a spool ready to load into the 3D printer. The 3D printer heats the PLA and ejects it as a thin film in the desired pattern. It's similar to a glue gun but under computer control.

PLA, also known as polylactic acid, or polyactide is obtained from renewable and natural raw materials such as corn. The starch (glucose) is extracted from the plants and converted into dextrose by the addition of enzymes. The result is a durable plastic utilized by 3D printers in the part making process.

PLA is somewhat like the plastic used in common injection molded models. Similarly it does not respond well to high speed machining. However compared to styrene it is a harder and more durable material. This characteristic permits some finer detailed structures. One drawback is the surface texture created by 3D printers. However this can be easily dealt with in the finishing process.

Many common solvents have different effects on PLA. Off-the-shelf solvents from the hardware store will not dissolve PLA. They might make a mess of the finish or destroy the shape. Only Ethyl Acetate, the solvent used in women's nail polish remover, will actually destroy it by dissolving it.

Two cements that have shown excellent bonding characteristics with PLA are ACC (Krazy Glue) and clear adhesives like E6000 or Quik Grip. ACC works very quick and provides a hard, secure joint. E6000 is a good space filler and after setting and been allowed to completely harden, it is a very permanent bond. Quik Grip has a lot of the same features but is highly recommended if you face the possibility of having to disassemble the item.

I'm using Ace Hardware's version of Rustoleum. It is thicker than common model paints but works well if thinned in the region of 4:1; the exception being White, Yellow and Reds, 2:1 may be a better place to start.

3D printers offer the option of determining the density of infill. A 3D part is typically a shell filled to a selected density. The lesser the density of the infill, the faster the part may be completed. However, a shell of .4mm and a 10% infill still yields an extremely durable part.

Tapping threads into PLA is very much like working with steel. Typically turn in 1/2 a turn then back off to allow the chips to clear. In actuality it only allows the the tap to remain cool. All cutting actions result in the energy to be dissipated as heat. Power tapping my be counter-productive.

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