DIY Selective Laser Sintering FAQ

Introduction

Some time ago I started research on feasibility of building a DIY Selective Laser Sintering rapid prototyping machine to work with thermoplastics. It quickly turned out that a there are quite a few enthusiasts who are already doing something in this area, as well as wealth of helpful information. However, what I found, it is very time consuming to gather enough background information to actually be able to design and build an SLS machine. So, I've started this FAQ with the aim to build easily accessible all-in-one collection of common answers to common questions so that other enthusiasts like me could save time looking for the same information. Hopefully this becomes a living document as knowledge of the community grows.

--Igor Lobanov 20:08, 27 June 2013 (UTC)

General Information

What is Selective Laser Sintering?

From Wikipedia[1]:

Selective laser sintering (SLS) is an additive manufacturing technique used for the low volume production of prototype models and functional components (...) An additive manufacturing layer technology, SLS involves the use of a high power laser (for example, a carbon dioxide laser) to fuse small particles of plastic, metal (direct metal laser sintering), ceramic, or glass powders into a mass that has a desired three-dimensional shape. The laser selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.

Lasers

Where can I learn more about lasers?

Some exceptionally good resources are openly available:

• Sam's Laser FAQ: A Practical Guide to Lasers for Experimenters and Hobbyists -- Vast collection of practical and theoretical knowledge on safety, drives, construction, and application of various types of lasers. Maintained by Samuel M. Goldwasser

Are there any viable alternatives to lasers for a DIY SLS machine?

Technically speaking it wouldn't be SLS without a laser, but there are approaches which are generally agreed to be viable.

Light from a powerful halogen or incandescent lamp could be focused by a lens into a tight beam. The drawback of this method is that it is very difficult to construct very narrow beam of light, so it will considerably limit the precision of the parts produced.

An inkjet print head could be used to print a shape over a layer of powder using black ink to improve heat absorption. The layer is subsequently heated by an infrared heating element.

Materials

How to produce PLA powder?

Some people report limited success in mechanically grinding PLA in pellets or filament form to fine powder.

Alternative approach is to dissolve PLA in dichloromethane and then spraying it into water medium mixed with polyvinyl alcohol surfactant to facilitate the dispersion of the PLA solution droplets. The powder precipitant was then filtered and dried [2].

Can I use metal in a DIY SLS machine?

In theory, yes. SLS for metal is called Direct Metal Laser Sintering (DMLS). However, there are practical considerations which perhaps make it less viable option for a DIY SLS machine:

• Most metals have higher melting point compared to thermoplastics, which means the machine has to maintain high temperature for a long period of time without breaking down.
• DMLS requires inert atmosphere, as heated fine metal powder can quickly oxidize in an uncontrolled manner, i.e. explode. This implies more or less airtight enclosure and a steady supply of an inert gas like argon.