Filament
The usual home printer.
Science desk · A beginner’s introduction · Printers and plastics
3D printing makes a solid object by adding material, usually one thin layer at a time, from a file on a computer. People also call the whole family additive manufacturing. This page is the short tour: the three machines a beginner will actually meet, the plastics those machines eat, and how to pick a first one.
A mill cuts material away. A printer adds it only where the object should be. Software slices the shape into layers, thin horizontal slices. The machine builds one, steps up by the layer height (how thick that slice is), and repeats. Thinner layers look smoother and take longer.
Workshops first met this in the 1980s, when light hardened a liquid plastic one layer at a time. That process is stereolithography. Chuck Hull applied for the patent in 1984; it was granted in 1986. The same decade brought a laser that sticks powder together, and a hot tip that melts a plastic wire. Standards writers now sort every machine into seven families.
The usual home printer.
Fine detail, messy liquid.
Mostly a shop machine.
Filament is the solid plastic wire on a spool. A motor pushes it into the nozzle, the small hot metal tip that melts it, which lays a bead — a thin line of melted plastic — onto the bed, the flat plate the object sticks to, then steps up one layer height for the next slice. The beads grip each other, but not perfectly, so a part often splits between layers before the plastic itself snaps.
An overhang is a bit of the shape that would be printed in mid-air. Supports are extra plastic the software adds to prop it up. You snap them off, or dissolve a second material printed only for that job. The everyday name is fused filament fabrication, or FFF. Material extrusion is the wider name, and it also covers machines that melt pellets (small plastic grains) instead of a spool. As of 2023, FFF was the most widely used method.
The head can move a few ways — a sliding bed (a bed-slinger), belts with the motors fixed (CoreXY), three arms (a delta), or a conveyor belt — and any of them can print the same plastic. For a first printer, the plastic and the fresh air matter more than which of those you bought.
A resin printer uses a liquid, not a spool. Resin here means a liquid plastic that stays liquid until light hardens it, sitting in a vat (the tank). Stereolithography draws each layer with a laser. A projector can flash the whole layer at once; people abbreviate that DLP. A screen in front of an ultraviolet lamp can be the mask instead; people abbreviate that MSLA, for masked stereolithography. The platform lifts one layer height, and the next layer hardens.
You then wash off spare liquid and usually finish under a lamp. That last step is a cure. Detail comes from a tiny spot or a pixel (one little square of the picture), not from a squeezed bead, which is why small letters look clean. Standard resin is brittle next to a decent filament print, and the liquid irritates skin until it is cured. Supports are still required and leave small marks. Desks use these for miniatures, jewelry patterns, and dental models.
Powder bed fusion spreads a thin layer of dry powder, fuses the slice that belongs to the object, then spreads another layer. The loose powder holds up overhangs, so you often need few printed supports, and the surface looks slightly sandy. To sinter a powder means to heat the grains until they stick, without necessarily melting them into a puddle.
For plastics, the common version is selective laser sintering, or SLS: a laser sinters the powder, often a nylon. Developed in the mid-1980s, it suits hinges, ducts, and hole-filled shapes, and it is usually a shop machine. A cousin skips the laser: an inkjet lays a fusing agent (an ink that makes powder absorb heat) where the part should be, then a heater sweeps the bed. Metal versions melt powder with a laser or an electron beam (a tight stream of the tiny particles inside atoms), and they are factory tools.
Standards list four more families. Skip them until a job needs one.
Material jetting squirts droplets of the build material, like an ink printer that stacks. Droplets may be wax, or a resin cured by ultraviolet light as they land. A second material can be a support that washes away. There is no tank.
Binder jetting prints glue into a layer of powder: metal, sand, ceramic, or plastic. The fresh part is weak until an oven heats it solid, or the tiny holes are filled with wax or another material. Sand printers make molds for casting metal.
Directed energy deposition feeds metal wire or powder into a small molten pool on the part, using a laser, an electron beam, or a welding arc. Shops repair a worn surface or add metal onto a piece that already exists. Detail is coarser than a powder-bed part.
Sheet lamination cuts each layer’s outline from paper, plastic, or metal foil and sticks the stack together. Paper versions can look a little like wood, and they are not strong parts. You will not meet this often.
Filament melts when hot and freezes when it cools. Resin, once light has tied its molecules into a permanent network, generally does not melt back. A spool and a bottle are not interchangeable. A glass transition is the temperature where a solid plastic starts to soften. Numbers below are typical public ranges, not a promise for one spool.
Polylactic acid, PLA, is the teaching plastic. It is easy and brittle, and it softens around 60–65 °C, so a hot car can warp it. It comes from plants such as corn and biodegrades only in specific industrial conditions, not a backyard pile. It gives off fewer particles than ABS, but not zero. Lactide, a vapor from the plastic, is one of them. Use it for first prints and cool indoor parts.
PETG is a tougher, slightly bendier cousin of the plastic in drink bottles, and it is medium difficulty. These sources give no single temperature where it always fails, so none is invented here. It is sticky when melted, so strings — thin hairs of plastic — can trail across the print. Reach for it when PLA snaps.
ABS is tougher than PLA and softens near 105 °C. It is medium difficulty and shrinks as it cools, so a draft can split the layers. It wants an enclosure (a box around the printer) kept roughly 40–60 °C, and a real vent, because it releases styrene, a sharp-smelling gas. ASA is the sunlight-resistant version and still wants that box and fresh air. Use ASA outdoors.
TPU, thermoplastic polyurethane, is rubbery filament for gaskets, cases, and bumpers. Print slowly or the soft wire buckles before the nozzle. TPE (thermoplastic elastomer, the stretchy family TPU belongs to) is slower still. Skip it when the part must stay stiff.
Nylon is a family called polyamides, not one melting point. It is strong, a bit flexible, medium difficulty, and it drinks moisture from the air, so keep the spool dry or the print bubbles and weakens. PA12, the nylon most powder machines use, melts at 178–180 °C. PA11 melts at 180–190 °C. A filament nozzle runs hotter so the melt can pass a small hole.
Ordinary vat resin holds small detail and chips if dropped. Treat the liquid as a skin hazard until cured. Tough, flexible, and castable resins (burned away to cast metal) are different bottles. A dental or skin-contact label applies only to a formula tested for that use.
A few names can wait. Polycarbonate is very tough, softens near 147 °C, and needs a hot enclosed machine. PEEK, PEKK, and PEI are high-temperature engineering plastics (PEEK softens near 143 °C and melts near 343 °C; PEKK near 162 °C; PEI near 215 °C), far past a starter printer. Fiber-filled filament adds short carbon or glass strands and needs a hardened nozzle. PVA dissolves in water and supports PLA. HIPS (high-impact polystyrene) supports ABS and also releases styrene.
Starter set hides the plastics you can skip for now. Temperatures shows nozzle and bed ranges. The ? button explains the rest. A spool’s own label wins when the numbers differ.
11 materials
| PLA | Easy | Brittle. Softens in a hot car, around 60–65 °C. | First prints, models, cool indoor parts | 180–230 °C | None required; 60–80 °C also used |
|---|---|---|---|---|---|
| PETG | Medium | Tougher and a bit bendier than PLA. No single heat limit in these sources. | Parts that should not snap | 220–235 °C | None required |
| ABS | Medium | Tougher. Softens near 105 °C. Wants a warm closed box, and it smells. | Functional parts, if you can vent the room | 210–250 °C | 50–100 °C |
| ASA | Medium | Like ABS, and it holds up better in sunlight. | Outdoor parts, with a box and a vent | 240–260 °C | 100–120 °C |
| TPU | Harder | Rubbery. Not a stiff or high-heat plastic. Print slowly. | Gaskets, cases, bumpers | 225–235 °C | None required |
| Nylon | Medium | Strong and a bit flexible. PA12 melts at 178–180 °C. Must stay dry. | Tough parts. Also the usual powder-bed plastic. | 220–260 °C | 50–100 °C |
| Standard resin | Careful handling | Fine detail, and brittle if dropped. Heat depends on the bottle. | Miniatures, patterns, small precise parts | — | — |
| Polycarbonate | Not a first printer | Very tough. Softens near 147 °C. Needs a hot enclosed machine. | Strong parts that see more heat | 270–310 °C | 90–105 °C |
| PEEK, PEKK, PEI | Not a first printer | Stay solid after ordinary plastics have softened. PEEK melts near 343 °C. | Special factory parts | About 340–450 °C, by plastic | About 100–200 °C, by plastic |
| Fiber-filled | Like the base plastic | Stiffer than the plain plastic. Heat follows that plastic. Wears a soft nozzle. | Stiffer parts, with a hardened nozzle | PLA-filled 195–220 °C; ABS-filled 210–260 °C | PLA-filled: none required. ABS-filled: 50–100 °C |
| PVA and HIPS | Helpers, not the part | PVA dissolves in water. HIPS is the dissolvable support beside ABS. | Holding up overhangs you will remove | PVA 180–230 °C; HIPS 210–250 °C | PVA: none required. HIPS: 50–100 °C |
A running filament printer gives off gases and extremely small dust. Volatile organic compounds, VOCs, are chemicals that evaporate into the air. Ultrafine particles are specks about 1 to 100 nanometers across (a nanometer is a billionth of a meter), small enough to travel deep into the lungs. A 2016 chamber study found about 100 million to about 100 billion of them per minute, mostly by plastic: styrene from ABS and HIPS, caprolactam (a sharp vapor) from nylon, and lactide from PLA. PLA usually makes fewer than ABS. Neither is zero. Print in fresh air, not a bedroom, with a box and a vent.
Liquid resin is a skin problem too. Methacrylates, chemicals common in these resins, have caused allergic rashes in published cases. A sensitizer is a chemical that can train skin to react next time, and a government lab study found more irritants and sensitizers in light-curing resins than the safety sheets listed. Wear gloves and eye protection, cure leftover liquid before throwing it out, and stop if a rash returns. One two-lab pilot measured about 4,100 particles per cubic centimeter beside a resin printer, against about 2,200 beside PLA. Ventilate both.
Powder printers finish as a cake of fine dust. Brushing that dust into the room is how you breathe it, so those machines belong in a closed box with a shop routine for spills.
Match the machine to the shape, the plastic to the job, and both to the room. Start with a filament printer and PLA. Move to PETG when parts snap. Use ASA in the sun, or ABS when you want that tougher heat-tolerant plastic, only with an enclosure and a vent. Use TPU when the part must bend, and expect a slow print. Use nylon for toughness if you will dry the spool. Use a resin printer when tiny detail matters more than strength, and budget gloves, a wash, a cure lamp, and ventilation.
Leave polycarbonate and the high-temperature plastics until the printer was built for those heats. Leave powder and metal to a shop. The way the head moves does not make a smelly plastic safe, and it does not make uncured resin safe on bare skin.
This is an introduction, not medical advice, shop procedure, or a buying list. When a spool label or a room’s ventilation disagrees with a general range, believe the specific one.