Chapter 2 · Basic Properties of Raw Materials
Common upstream materials for filament include plastics such as PLA, PETG, ABS, and TPU. Many plastics can also be injection molded, but a grade suited to injection molding is not necessarily suitable for making FDM filament or printing consistently.
The underlying reason is that the processes have different requirements. Injection molding shapes material within a mold; FDM first needs filament that feeds consistently, then builds it layer by layer without the constraints of a complete mold. Shrinkage, melt behavior, interlayer bonding, moisture absorption, and feeding characteristics can all become limiting factors.
The following table compares common applications of these materials in the two processes. It presents general patterns to build understanding, rather than measured rankings of brands or specific grades.
| Material | Common Forming Applications | FDM Characteristics and Precautions |
|---|---|---|
| PLA | Packaging, everyday products, printing, and more | A common introductory material with varied colors and finishes; standard grades have limited heat resistance and can also warp. |
| PETG | Transparent or toughness-related products, and printing | Useful for many everyday objects and accessories; check filament condition, stringing, and build-plate compatibility. |
| ABS | Housings, parts, and other molded products | Consider shrinkage, the thermal environment, equipment, and ventilation. |
| TPU | Flexible protection, seals, and more | Flexible feeding must suit hardness, the feed path, and equipment; rigid-filament settings alone are insufficient. |
| PP | Containers and many industrial products | Printing products exist, but adhesion and shrinkage need suitable conditions; do not treat the process as ordinary PLA printing. |
| PE | Packaging, containers, and industrial uses | Some grades are challenging to print; consider adhesion, shrinkage, and processing conditions. |
| PS and related materials | Packaging, housings, and more | Do not treat standard PS and modified categories as interchangeable; applications depend on grade and process. |
| PC | Transparent and technical products, and more | Check the specific grade’s temperature, drying, bed, and equipment requirements. |
| PA | Technical parts, and more | Consider moisture absorption and drying; grades and filled versions can differ considerably. |
| PVA | Specific processing and water-soluble applications | Can serve as water-soluble support; check drying, compatibility, and dissolution conditions. |
PLA deserves a specific clarification: it can be made from renewable feedstocks such as corn starch. However, “bio-based,” “biodegradable,” and “actual environmental impact” are different concepts. This does not mean a printed part will quickly disappear in an ordinary natural environment. Follow local requirements when disposing of it.
The comparison above supports three main points:
Process Requirements Shape Material Choice: Injection molding and FDM emphasize different material properties, so their suitable material ranges differ substantially.
Common Materials Involve Different Trade-offs: PLA, PETG, ABS, and TPU offer different combinations of appearance, stiffness, toughness, heat resistance, and flexibility. A material name alone cannot identify an all-purpose solution.
Opportunities and Limits of Material Modification
Modifications such as adding fiber or changing the formulation can improve a particular processing or service property. An improvement in one property may bring other changes, so consult the specific product information and test with the intended model.
There are also printing products and exploratory applications involving PP, PE, and other materials. However, bed adhesion, shrinkage, and equipment compatibility limit some uses. Being difficult to print on an ordinary desktop machine does not mean a material cannot be printed under any conditions.
The key lesson is that the base material and the process must suit each other. Next, we will look at what you need to understand when buying and using filament made from these materials.
