FDM filament and material options are growing every day. There are a vast amount of companies that now supply standard PLA and ABS, but there are now also those that produce material options with varying properties.
1.75mm vs 3mm
FDM extruders are built for either 1.75mm or 3mm diameter filaments. There is debate on which is preferred.
The extruder for 3mm filament will have to turn its stepper motor less to extrude the same amount of material, due to the thicker diameter. This can lead to less grinding of the filament which will lead to less likelihood that the filament will be grinded to the point of breaking. 1.75mm, on the other hand, is more flexible while on the spool and is easier to feed. 3mm also has a smaller tolerance percentage ranging from 2.8mm – 2.9mm (1.8%) vs 1.75mm of 1.7mm – 1.8mm(2.9%)
PLA and ABS
The 2 main types of materials used today are PLA (polylactic acid) and ABS (Acrylonitrile butadiene styrene). With very minimal shrinkage rates and a cheap price tag, PLA is the go to for parts that do not require stress. Since the shrinkage rate is so low, parts do not warp while printing PLA. This makes PLA easier to print than other filaments since it’s not required to be in an enclosed environment for large parts. While PLA boasts a high tensile strength, it is also more brittle than most other materials we use with a very low impact resistance. It can crack or break when dropped and does not have many mechanical uses.
ABS has a very high glass transition temperature (105°C) which means that it requires a heated build plate for bed adhesion and to prevent warping and layer delamination. Due to the high shrinkage rates, larger prints also require an enclosed or controled environment with ambient temperatures of around 55°C. ABS is great for mechanical parts and has the ability to be acetone vapor finished.
Selective Laser Sintering (SLS) is a very exciting technology which directly fuses particles together layer by layer, through a high energy pulse laser.
Similar to SLA, this process starts with a tank full of bulk material, but this time in powder form. As the print continues, the bed lowers itself for each new layer as done in the SLS process. Overhangs are naturally supported by the excess bulk powder material making those features much more simple to print than using FDM. The bulk material is typically heated to just under its transition temperature to allow for faster particle fusion and print moves. SLS is the preferred rapid-prototyping method of metals and exotic materials, however, there are additional costs in energy used for fabricating with this method which may reverse any savings realized in the material cost.