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Part 1: About ABS

What is ABS?

Introduction

ABS is a type of thermoplastic. It is noteworthy for its wide use in manufacturing, as it offers acceptable to excellent performance across a broad range at a low material cost.

The name "acrylonitrile butadiene styrene" is an ingredient list: ABS is made by polymerizing, or chemically joining into long chains, these three materials, called monomers. Varying the ratio of each monomer modifies the resulting material (for this reason, properties of ABS and other polymers are often given within a range). In addition, other polymers can be added to further tweak the final product's properties.

Because ABS is an amorphous polymer, when heated it can be extruded and molded like glass. It is machinable at room temperature and is chemically weldable with common solvents like acetone. Combining these techniques allows manufacturers multiple ways to fabricate parts with ABS and contributes its popularity in manufacturing.

Manufacturing ABS

a hand holding plastic resin

A bag of resin pellets. Source: SuSanA Secretariat

ABS and other thermoplastics are distributed as pellets of plastic resin commonly called nurdles. Manufacturers melt this base resin, adding colorants or other additives to modify the appearance and properties of the final product. From there, the molten ABS is formed into shape and cooled.

For FDM filament manufacturers, the molten ABS is stretched into long, thin cylinders of a uniform diameter called filament and rolled on to spools.

a roll of Orange Prusament filament

A spool roll of Orange Prusament filament. Filament is normally available in 1.75mm and 2.85mm diameters.
Source: Prusa Research

General Properties

ABS is widely used in injection molding. Injection molding allows mass production at low per-unit costs with a high up-front cost for the molds and prototype(s).5

Prototyping ABS parts for injection molding was one of the first commercial uses of FDM 3D printing. 3D printed parts can be nearly as strong as their injection molded equivalents; this allows cheap prototypes before committing to an expensive mold.

Below are some general properties of ABS plastic. We'll get into more detail in Part 2 about how ABS behaves when printed.

Pros

  • Thermoplastic (can be heated repeatedly without damage)
  • Affordable and easily sourced
  • Rigid & impact resistant
  • High continuous use temperature
  • Can be machined
  • Can be painted
  • Can be chemically glued
  • Good heat insulator
  • Excellent electrical insulator
  • Some resins can be sterilized for medical use
  • Easily recycled in industrial conditions

Cons

  • Not UV-stable (degrades in sunlight)
  • Fair chemical resistance
  • Poor solvent resistance
  • Most resins are not food safe
  • Combustible under open flame
  • Not consumer recycleable

ABS has numerous useful properties, particularly how easily it can be shaped and machined. ABS tolerates most everyday temperatures, though food safety and burning when exposed to open flame are both concerns.

Because solvents are a problem, ABS is generally kept away from garages and kitchens.

ABS is not UV-stable and yellows and cracks over time when left in sunlight. A UV-stable and weather-resistant substitute, ASA, is discussed in more detail in Part 3 under Alternatives.

Pre-consumer ABS recycling is performed, but ABS recycling is not available to consumers (post-consumer recycling).

Material Categories

ABS is not the only FDM-printable plastic. For purposes of this article, we will discuss three different categories of 3D-printable plastics.

  • Entry-level plastics:
    • PLA (polylactic acid)
    • PETG (polyethylene terephthalate glycol)
    • TPU (thermoelastic polyurethane)1
  • Engineering plastics:
    • ABS (acrylonitrile butadiene styrene)
    • ASA (acrylonitrile budadient acrylate)
    • PA (Nylon, polyamide)
    • PC (polycarbonate)
    • PP (polypropylene)
  • High-end plastics:
    • PTFE (polytetraflouroethylene)
    • PEEK (polyether ether ketone)
    • PEI (Ultem, polyetherimide)
    • PMMA (Acrlic, poly(methyl methacrylate))

This list is for the purposes of discussion only; it is not a standard. Some materials, like PC, qualify as engineering or high-end depending on the formulation used.

Entry-Level Plastics

Entry-level materials are printable by nearly any off-the-shelf FDM printer2. They are low cost, easily obtained, printable in open air, and relatively forgiving for novices. Air filtration with these plastics is recommended indoors3 but is not absolutely necessary.

The requirements for printing entry-level plastics are very basic:

  1. Nozzle temperatures up to 245°C (473°F);
  2. Heated bed temperatures up to 80°C (176°F); and
  3. Air temperatures should be within 15°C (59°F) and 30°C (86°F).

Entry-level plastics have wide melt ranges and not all require a heated bed.

Engineering Plastics

Engineering plastics, including ABS, have widespread use in other manufacturing industries. Engineering plastics print at higher temperatures and require more environmental control than entry-level materials:

  1. Nozzle temperatures up to 285°C (545°F);
  2. Heated bed temperatures up to 110°C (248°F);
  3. Air temperatures 40°C (104°F) or higher;
  4. Air filtration or venting; and
  5. Benefit from uniform air temperature.

Of the list above, #4 and #5 require an enclosure and #3 typically needs one.

Note that the last item, uniform air temperature, is not related to using a part cooling fan; instead, it refers to using fans to evenly distribute heat around the print environment. This is largely beneficial when printing larger parts that may otherwise cool unevenly.

The specific requirements for printing ABS are on the next page.

High-End Plastics

Lastly, there are high-end plastics. Materials in this category are often used in manufacturing for aerospace, medical, and other industries. Printing these plastics requires the use of materials that can tolerate extreme temperatures. FDM printing high-end plastics requires a carefully insulated and well-protected build environment.4 These are typically commercial printers or bespoke hobbyist machines.

As a rough cutoff, engineering plastics end and high-end plastics begin when a material requires any one of the the following:

  • Nozzle temperatures over 280°C (536°F);
  • Heated bed temperature over 120°C (248°F); and/or
  • Air temperatures over 60°C (140°F).

This article does not delve into high-end plastics, as they are outside the capabilities of all but the most expensive FDM printers.

  1. TPU is a large family of polymers that are flexible. Most TPU sold as filament has a Shore A hardness of 90-95 and feels like soft rubber. Flexibile filament imposes unique requirements that are outside the scope of this article. ↩

  2. Without significant modification. ↩

  3. During the extrusion process, all plastics off-gas VOCs and microparticles of plastic. Some plastics are typically printed in open air, but lack of unpleasant odor does not equal safety. An activated carbon/HEPA filter combination in the same room as a 3D printer (preferably near the build area) is considered sufficient for open-air printing, but research is ongoing. ↩

  4. For example, PEI is used to coat 3D printer heated beds, which can reach 125°C or more. Considerations for high-temperature enclosures are discussed in Part 2. ↩

  5. A familiar use of injection-molded ABS is in the manufacture of LEGO bricks. ↩