PLA vs ABS Filament: Which to Print With and When

The two materials ask for different machines before they ask for different settings. Raise3D's Premium PLA sheet recommends 190–220 °C at the nozzle, a 30–60 °C build plate, the model cooling fan on and an environmental temperature from room temperature up to 45 °C. Its Premium ABS sheet recommends 245–265 °C, a 90–105 °C plate, the cooling fan off and a 20–50 °C environment. That last figure is the enclosure: no open room sits at 50 °C, so the sheet is describing the air inside a closed chamber warmed by its own bed. The same ABS sheet lists a raft separation distance among its recommended settings and printed its own test specimens on a 100 °C build plate.

The physics behind the enclosure is the glass transition. ABS stays rubbery until it cools to about 100 °C (UltiMaker measures 100.5 °C, Raise3D 101 °C), so each new layer is laid on a part that is still hot and still shrinking. On an open frame the upper layers cool faster than the lower ones, the part pulls inward, corners lift off the plate and tall walls split along a layer line. PLA's glass transition is 59–62 °C, so it is rigid again a few millimeters below the nozzle and holds its shape with the fan on. UltiMaker describes its ABS as formulated to minimize warping and Raise3D describes its ABS as having great warping resistance, and both still specify the heated plate; the formulation reduces the effect, the chamber removes it.

Heat deflection temperature is the figure to read when a part will run warm, and it is worth reading correctly. Both UltiMaker sheets test to ISO 75-2 method B at 0.455 MPa on printed specimens: 58.8 °C for PLA, 86.6 °C for ABS. Raise3D's ABS sheet reports heat distortion under ISO 75 as 98 °C at 0.45 MPa and 100 °C at 1.8 MPa, as printed on the sheet. ASTM D648 covers the same property, and its Note 3 states that D648 and ISO 75-1/75-2 address the same subject matter but differ in technical content, and that results shall not be compared between the two methods. A D648 figure on one sheet and an ISO 75 figure on another are therefore not the same number, and neither is a service temperature.

The practical line each vendor draws is the service temperature: UltiMaker lists its PLA as not suitable above 59 °C and its ABS above 87 °C, and Raise3D gives its ABS a long-term service range of -20 to 90 °C. A PLA bracket in a vehicle cabin in summer, or a PLA duct on a warm power supply, sits inside the range where the sheet says it will deform; the same part in ABS does not. Note that the Vicat softening points, 64.5 °C for UltiMaker PLA and 93.8 °C for its ABS, sit only a few degrees above the deflection figures, so there is no margin to borrow. Neither material is rated for the outdoors on UltiMaker's sheets: long-term outdoor use is on the non-suitable list for its PLA, and long-term UV exposure is on the same list for its ABS.

PLA is the stronger material in a pull test and the stiffer one under load. On UltiMaker's sheets, printed flat, PLA yields at 52.5 MPa with a tensile modulus of 3,250 MPa; ABS yields at 38.1 MPa with a modulus of 1,962 MPa. Raise3D's figures point the same way: 40 MPa and 2,681 MPa for PLA against 33 MPa and 2,174 MPa for ABS. A gauge, a fixture or a bracket that must not flex is a PLA part on those numbers alone. The trade is in bending: printed flat, UltiMaker's PLA breaks at 4.8% flexural strain while its ABS does not break at all past 10%; upright, both materials break at 2.0% tensile strain, which is why either fails at the layer line when it fails.

Toughness runs the other way. UltiMaker's notched Charpy figures, both on ISO 179-1/1eB printed specimens, are 3.9 kJ/m² for PLA and 14.2 kJ/m² for ABS, about 3.6 times the energy before fracture. UltiMaker records its ABS result as a hinge break, the specimen still holding together at the notch, and its PLA result without that marker; the sheet's own note files PLA among the brittle materials, and its upright PLA specimens show no yield point at all. Two cautions. Raise3D's sheets show the two nearly level, 13.4 against 12.6 kJ/m², on a different specimen and method, so impact figures from different sheets do not compare either. And every figure on both sheets is for a 100% infill specimen; a 20% infill part is weaker in every direction and weakest across its layers, whichever material it is.

PLA finishes by sanding and priming and does not respond to acetone; its strength is what comes off the plate, with sharp detail and a matte or silk surface. ABS sands cleanly and is soluble in acetone, so a part can be vapor-smoothed to a gloss, solvent-welded to another ABS part or touched up with a brush, which is why a printed enclosure meant to pass for a molded one is usually ABS. Acetone is flammable and the vapor needs the same ventilation as the printer, so the finishing step belongs in the shop, not the classroom.

Emissions are the other operating difference. In NIOSH's 2018 field study, run on MakerBot printers with PLA, ABS and Tough PLA filaments, respirable particulate in a conference room with up to twenty printers running was non-detectable (below 0.03 µg/m³) and VOC concentrations were well below occupational exposure limits; the PLA tested produced lower ultrafine-particle emissions than published results from other emission tests. NIOSH's recommended controls are local exhaust ventilation or a snorkel extractor at the printer, an enclosed ventilated rack that exhausts outdoors, or a room air cleaner with HEPA filtration. ABS prints roughly 50 °C hotter than PLA, so it is the material that makes those controls the default rather than the option.

UltiMaker's PLA sheet describes the material as made from organic and renewable sources, and PLA is the filament that carries compostable claims. Read those claims against the standard they are tested to: ASTM D6400 is the Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities, and it applies to municipal and industrial composting facilities, the places that reach the thermophilic conditions it requires. Nothing in that scope describes a landfill, a home compost bin or the ocean, so a PLA print discarded with ordinary waste is not a compostable product in any sense the standard supports. ABS is petroleum-derived and makes no such claim.

On cost the spool is rarely the decision. PLA runs on the least expensive class of printer; ABS spools on the same product lines are often priced close to PLA, so the real premium is the enclosed, heated-bed printer and the exhaust it needs to run indoors. Where a part needs more heat and impact tolerance than PLA but the shop has no enclosed printer, PETG is the usual middle option: it prints between the two in temperature and, on most open-frame machines, without the chamber ABS needs. It is a different material with its own sheet, and it does not change the PLA-versus-ABS answer for the parts at either end.