What material is best for your product?

Carbon and Glass Fiber "Reinforcement"

Pros

• Makes the material it's added to stiffer
• Often Increases heat resistance
• Adds significant dimensional stability to part, low or insignificant warpage
• can make a hard to print material much easier to print

Cons

• Adds Cost
• The tiny sharp carbon fibers can pose a health hazard by embedding in skin and being breathed into the lungs
• Often lowers the parent material's tensile strength, unless it is a continuous fiber strand

Materials come not just in different colors and types, but also sometimes with fillers. You might hear the term, "carbon fiber reinforce" or "glass fiber reinforced" but these terms are not true. The materials are typically mechanically weaker from the added carbon or glass fibers and the correct term is not "reinforced" but "filled". These fillers do provide other advantages; they make the part more stiff, usually enhance the materials temperature resistance, make the material more dimensionally stable by lowering the material's shrink rate and give the finished product a textured look. As a general rule Carbon Fiber makes the material much stiffer than glass fiber and glass fiber gives the material a bit more heat resistance than Carbon fiber does. Glass fibers seem pretty straight forward but carbon fibers have many variables. For instance Carbon fibers fillers can be anything from a powder to chopped lengths a millimeter long; some manufacturers have figured out how to put a continuous strand of carbon fiber in the material, essentially creating a carbon fiber printed woven product that produces radically strong parts. Both carbon and glass fibers aid greatly in the printability of the material by preventing the parent material from having long continuous extrusions, minimizing the materials shrink when it cools after the hot printing process; this can turn a difficult to print material into a much easier to print material.  Photo From NathanBuildsRobots.com he also has a YouTube channel

Shrink rate 

• All plastics expand when hot and shrink when cooled 
• Shrinking changes the dimensions of the finished part
• Shrinking can be compensated by material fillers, chemical additives and careful design of the part
• The larger the part the more significant shrinking is
• There are materials where shrink is so insignificant it is a non issue

When plastic is heated up and either pushed into a mold or printed, the hot material expands, but once it cools the material shrinks. this is a typical plastic behavior. In severe cases a material can shrink so much that the edges of the material will pull up and put a bow in the entire part. There is a lot of factors that determine how a part shrinks such as, the material used, if it has any fillers negating the shrink rate, the geometry of the part, how well the material adheres to the build plate and even how the heat propagates through the part during the printing process. Here at Deseret Manufacturing we use materials that are modified for use in the 3D printing process. Whether injection molded or 3D printed, part shrinkage is common but falls under 0.3% for most materials we use. For most applications. we have found that shrink rate is an insignificant factor that requires no accounting for. 

Nylon - Easy Nylon, PA612-CF15

Pros

• Flexible 
• Very Slippery 
• Sometimes good heat resistance
• Good chemical resistance

Cons

• Mechanical Properties tend to be lower than half once wet (takes about 30 mins to absorb water from atmosphere)
• Requires more equipment to print and often needs annealing after printing is required (additional manufacturing costs)  
• Once wet it's strength and temperature resistance is typically poor or greatly diminished

Nylon is often touted as the most amazing material; claiming incredible strength, impact resistance and high temperature resistance, but there are many nylons and most of them have very low strength and less heat resistance than one might expect. Nylon has one really bad issue: water makes it much weaker and lowers its heat resistance, also nylon loves to absorb water. Nylon absorbs water so fast that it needs to be dried constantly while printing. Even in the dry state of Utah, if nylon is not being dried while printing you only get about 30 minutes of print time before the water it has absorbs starts steaming while being melted and ruins the prints. Some manufacturers conduct tests for their Technical Data Sheets that show how the material performed after absorbing water from the air often showing the material is exceptionally weak once water logged. There are exceptions to this phenomenon. One thing that nylon has going for it so well is it's slippery nature. If you need some kind or sliding surface nylon is a great choice, as long as it doesn't have any abrasive fillers.   

Material Cost: $16-$80 / LBS                                                                                                                                                       Temperature Heat resistance: 140F - 440F

Easy Nylon TDS

PA612-CF15 TDS

PETG

Pros

• Very dense
• Decently strong
• Decent Temperature resistance (154F)
• Somewhat slippery
• Somewhat impact resistant
• Some What Flexible when designed for it
• Decent for mechanical applications
• Water tight

Cons

• Very Dense (if you want something lighter)
• When this material is melted it is closer to a liquid than a solid, as such some geometries can be challenging to print

This is the same material that disposable water bottles and other water tight containers are often made of, except it has a Glycol additive, the last letter of PETG stands for Glycol, which aids significantly in reducing PET's shrink rate. PETG's slippery nature make it a great choice for sliding components and the material is very scratch resistant. Deseret Manufacturing makes many of our products out of PETG; it is a great intersection of strength, temperature resistance and price. 

Material Cost: $5-$13 / LBS                                                                                                                                                              Temperature Heat resistance: up to154F

PETG TDS

ASA

Pros

• Better than ABS in perhaps every way
• excellent UV resistance 
• Good chemical resistance

Cons

• unless you are putting this part outside or somewhere decently hot, use another material

ABS's younger stronger brother, mostly it is chemical and UV resistant by comparison. It produces parts that are less dense. 

Material Cost: $5-$20 / LBS                                                                                                                                                              Temperature Heat resistance: up to 212f

ASA TDS

ABS

Pros

• It probably wont melt in the sun 
• maybe slightly above average impact strength

Cons

• mechanically is weak, low tensile strength
• not flexible at all, turns white where bent
• UV rays hurt ABS easily
• Chemical resistance is very weak
• people think it's awesome but it's basically hot garbage

Patented in 1948, this is a very ancient plastic that usually holds very weak characteristics. Some variants do exhibit good impact strength, but for the most part ABS is not very flexible, becomes white and exceptionally weaker where bent, has very little elasticity, has almost no chemical resistance and releases a lot of toxins when melted.

Material Cost: $5-$20 / LBS                                                                                                                                                          Temperature Heat resistance: up to 136f

ABS TDS

PLA

Pros

• Can produce some pretty great geometries 
• The most color and esthetic choices of all the materials
• Very high tensile strength
• Great for artsy farts stuff

Cons

• Very brittle, easily shatters, chips and cracks 
• Creeps under load, not good for mechanical parts
• Temperature resistance is low (up to 130f heat resistance)
• Low abrasion resistance
• Often makes squeaky sounds when being manipulated under load

PLA has so many color and aesthetic choices because for the longest time it was about the only thing made that a consumer grade 3d printer could easily print. PLA has been in use for a long time as a material for packaging, mostly vacuum forming and padding. When placed under a load, the material tends to conform to the load over the long term, making it a bad choice for demanding mechanical applications. It is common for PLA under no load to sag in the presence of the sun on a hot day.  There are so many cool fillers that manufacturers may add to PLA such as wood (allowing the product to be treated with wood stain) Stone and marble powders for interesting aesthetics and even flexible additives that make PLA bouncy enough to use as a ball. As far as bog standard stuff is concerned, If all the thing needs to do is look pretty, and it's not to be outside, then PLA might be the right choice. 

Material Cost: $5-$30 / LBS                                                                                                                                                         Temperature Heat resistance: up to 130f

PLA TDS

Poly Carbonate

Pros

• high heat resistance (290f)
• Strong in all directions
• can spring back from high loads

Cons

• Difficult to print without fiber fillers making it stiffer and abrasive

Material Cost: $17 - $40 / LBS                                                                                                                                                    Temperature Heat resistance: up to 290F

PC TDS

Thermal Plastic Urethane (TPU)

Pros

• many different durometers to choose from
• depending on the durometer and print thickness, can produce nearly indestructible parts
• excellent chemical resistance
• Leveraging 3D printing flexibility in one part is highly modular by adjusting thicknesses and internal structures

Cons

• a high print failure rate and surface artifacts is usual

Material Cost: $8-$15 / LBS                                                                                                                                                         Temperature Heat resistance: Unknown

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