3D Printing Glossary

ABS (Acrylonitrile Butadiene Styrene)

A petroleum-based thermoplastic commonly used in injection moulding (LEGO bricks, automotive trim) and FDM printing. ABS is stronger and more heat-resistant than PLA (glass transition ~105 °C vs ~60 °C for PLA) but significantly harder to print: it requires an enclosure to prevent warping from thermal gradients, a heated bed at 100 to 110 °C, and good ventilation because its fumes contain styrene. Most beginners are better served by PETG for parts that need temperature or impact resistance. ABS also dissolves in acetone, which can be used for post-processing (acetone smoothing or chemical welding). See the materials comparison for full property table.

Bed adhesion

The ability of the first layer to stick to the build plate during printing. Good bed adhesion prevents the print from lifting or warping mid-print. It depends on three factors: the surface material (glass, PEI spring steel, garolite, BuildTak), the bed temperature, and the Z-offset setting. PLA typically adheres well to PEI at 60 °C. PETG adheres to PEI but can bond so strongly that it tears the PEI coating on removal if the surface is not cooled first. ABS requires a higher temperature and benefits from an enclosure to prevent edge warping (adhesion failure at corners). Applying a thin layer of glue stick or hairspray to glass creates a separation layer that improves PETG adhesion and protects the surface.

Bed temperature

The temperature of the heated build plate, set to keep the first few layers above the material's glass transition temperature so they remain slightly soft and adhere well without warping. Typical values: PLA 50 to 65 °C, PETG 70 to 85 °C, ABS 100 to 110 °C, TPU 40 to 60 °C. A bed that is too cold causes warping and poor adhesion; too hot can cause the bottom layers to spread (elephant foot) or cause PETG to bond permanently to certain surfaces. Bed temperature is distinct from hotend temperature: the bed heats the build plate; the hotend melts the filament.

Bowden extruder

An extruder configuration where the motor that drives the filament is mounted on the frame (remote from the printhead), connected to the hotend by a PTFE tube through which the filament travels. The advantage is a lighter printhead, which allows faster movement with less vibration. The disadvantage is that the long PTFE tube introduces compliance (stretch and flex), making retraction tuning more difficult and flexible filaments nearly impossible to print reliably. Common on Creality Ender 3 and similar printers. Compare with direct drive.

Bridging

Printing a horizontal extrusion spanning a gap between two walls, with no support material underneath. Short bridges (up to about 50 mm in PLA) print cleanly with the right settings: high fan speed to solidify the plastic quickly before it sags, slightly increased print speed, and cooler hotend temperature to reduce droop. Longer spans produce sag and can fail mid-print. The maximum reliable bridge length varies by material (PLA bridges well; PETG and ABS bridge poorly without enclosure and cooling). Bridges are always printed at 90° to the longest unsupported span where the slicer can choose the angle.

Direct drive extruder

An extruder configuration where the filament drive motor is mounted directly on or very close to the printhead, minimising the distance the filament travels before entering the hotend. Benefits: precise retraction control (shorter retraction distances of 0.5 to 2 mm vs 4 to 8 mm for Bowden), reliable printing of flexible filaments (TPU, TPE), and faster response to extrusion commands. Drawback: the added weight of the motor on the moving gantry can introduce ringing artifacts at high speeds, requiring input shaping or lower acceleration settings. Common on Prusa MK4, Bambu Lab printers and many modern designs.

E-steps (extruder steps per millimetre)

The number of stepper motor steps required to advance the filament exactly 1 mm through the extruder. It is a fundamental calibration value in Marlin and similar firmware, stored as steps/mm for the E axis. If E-steps are too low, the printer under-extrudes (not enough filament); too high and it over-extrudes (too much filament). Calibrate by commanding 100 mm of extrusion, measuring how much actually moved, then adjusting: new E-steps = current E-steps × 100 / actual distance moved. E-steps must be calibrated once for each extruder setup; they do not need to change with material or print settings (slicer flow rate handles those adjustments).

Elephant foot

A first-layer defect where the bottom of a print spreads wider than intended, producing a flared base that looks like an elephant's foot. Caused by the first layer being squished too flat against the bed (Z-offset too low), bed temperature too high, or hotend temperature too high for the first layer. The excess pressure pushes melted filament outward beyond the intended outline. Fix in order of priority: (1) raise Z-offset slightly so the nozzle is fractionally farther from the bed; (2) reduce bed temperature by 5 °C; (3) use a first-layer horizontal expansion setting in the slicer (negative value trims the first layer outline). A small amount of elephant foot is normal and can be tolerated; severe elephant foot prevents parts from fitting into assemblies.

Extrusion

The process of pushing molten filament through the nozzle to deposit material on the build surface. The extruder motor drives the filament into the hotend, where it melts, and the nozzle shapes and places it. The volume of plastic deposited per unit time is the volumetric flow rate. Extrusion is distinct from the extruder (the mechanism) and the hotend (the heater assembly). Under-extrusion produces gaps and weak parts; over-extrusion causes blobs, rough surfaces and dimensional inaccuracy. The slicer controls extrusion volume through the combination of layer height, line width, print speed and flow rate multiplier.

FDM (Fused Deposition Modeling)

The most common desktop 3D printing technology, in which a spool of thermoplastic filament is melted and deposited layer by layer to build a part. Also called FFF (Fused Filament Fabrication), which is the open-source term. FDM printers are widely available, inexpensive to run, and support many materials. Their limitations are visible layer lines, anisotropic mechanical properties (parts are weaker in the Z direction than XY), and the need for support structures on steep overhangs. Alternatives include resin (SLA/MSLA, higher resolution, photopolymer), SLS (powder sintering, no supports needed) and SLA (used for dental and jewellery). Most tools and guides on this site target FDM.

G-code

A text-based numerical control language that instructs the printer's firmware where to move, how fast, and when to extrude. A slicer converts a 3D model into a G-code file. Key commands: G0/G1 (move), G28 (home axes), M104/M109 (set/wait for hotend temperature), M140/M190 (set/wait for bed temperature), M82/M83 (absolute/relative extrusion mode), M92 (set steps per mm). G-code is largely standardised across FDM printers running Marlin, Klipper or RepRap firmware, though some commands vary by firmware. You can inspect and edit G-code in a text editor to understand or fix print behaviour.

Hotend

The heated assembly at the end of the printhead that melts the filament for deposition. It consists of: a heater block (aluminium, holds the heater cartridge and thermistor), a heat break (thin tube that creates a thermal gradient to prevent heat creep), a heatsink (dissipates heat above the heat break), and the nozzle. The hotend temperature is set in the slicer and controlled by PID feedback. A clog (jam) in the hotend is the most common hardware failure in FDM printing: usually caused by printing too cold, retraction pulling molten filament above the melt zone, or contaminated filament. All-metal hotends (no PTFE in the heat break) can print above 240 °C for engineering materials; PTFE-lined hotends are limited to about 240 °C and should not be used with ABS or Nylon at full temperatures.

Infill

The internal structure printed inside a solid-looking part. Infill percentage describes the density: 0% = completely hollow, 100% = completely solid. Most functional parts use 15 to 40% infill. The infill pattern also matters: grid and lines are fast; gyroid and honeycomb are isotropic (equal strength in all directions); triangle and cubic are stronger in Z. Higher infill increases strength and weight linearly but takes much longer to print. Wall count (perimeters) has more impact on part strength than infill percentage for typical loads: a part with 4 walls and 20% infill is usually stronger than 2 walls and 40% infill. Use the Print Time Estimator to compare print durations at different infill percentages.

Jerk (and junction deviation)

In Marlin firmware, jerk is the maximum instantaneous velocity change the printer allows at a direction change, measured in mm/s. A high jerk value allows the printer to change direction sharply without slowing down, enabling faster printing but risking missed steps and ringing artifacts (ghosting). A low jerk value forces the printer to decelerate more before corners, reducing ringing at the cost of print time. Junction deviation is the equivalent setting in newer Marlin versions and Klipper: it controls the same behaviour using a different (more physically correct) model. Typical jerk values: 5 to 20 mm/s for XY; junction deviation 0.01 to 0.08 mm. Ringing (ripple patterns near sharp corners) is a sign that jerk or acceleration is set too high for the frame's stiffness.

Layer height

The thickness of each deposited layer, measured in mm. It is the primary control for surface quality vs print speed: a lower layer height (0.1 to 0.15 mm) produces smoother surfaces and finer detail but multiplies print time proportionally; a higher layer height (0.25 to 0.35 mm) prints faster but shows visible layer lines. A practical rule: maximum layer height should not exceed about 75% of the nozzle diameter (0.3 mm for a 0.4 mm nozzle) to ensure proper adhesion between layers. Variable layer height (adaptive layers in slicers) uses a finer layer on curved surfaces and coarser layers on flat walls. Layer height has no meaningful effect on part strength in XY; it reduces Z-direction strength as it increases because layers bond less effectively. See the Print Time Estimator to compare times at different layer heights.

Nozzle

The threaded brass (or hardened steel) tip at the bottom of the hotend through which molten filament is extruded. The nozzle orifice diameter determines the minimum feature size and volumetric flow capacity: a 0.4 mm nozzle is the standard for balanced speed and detail; 0.2 mm is used for fine detail; 0.6 to 1.0 mm nozzles print much faster and stronger but with less detail. Brass nozzles are suitable for PLA, PETG and ABS. Carbon fibre, glow-in-the-dark, metal-filled and similar abrasive filaments require hardened steel, ruby-tipped or tungsten nozzles because they wear brass rapidly. A clogged nozzle is a leading cause of under-extrusion. See the Nozzle Size Chart for diameter comparison and Volumetric Flow Calculator for flow rate at various nozzle sizes.

Overhang

A portion of a print that extends horizontally beyond the layer below it, measured as an angle from vertical. At 0° the feature is vertical (no overhang); at 90° it is horizontal (a bridge over air). Most FDM printers handle overhangs up to about 45 to 50° without support material, though the quality degrades progressively. Above 60 to 70°, most materials require support. Overhang performance depends on cooling (PLA prints overhangs cleanly with full fan speed; ABS struggles without an enclosure), print speed (slower = more cooling time per layer), and layer height (thinner = less material drooping per layer). Orienting a model in the slicer to minimise steep overhangs reduces support material and post-processing time.

PETG (Polyethylene Terephthalate Glycol)

A co-polyester filament that combines the ease of PLA printing with better mechanical and thermal properties: tougher, more flexible, chemical-resistant, food-safe certified grades available, and heat-resistant to about 80 °C under load. PETG is glycol-modified PET (the same plastic as water bottles), which reduces brittleness. It prints at 230 to 250 °C hotend / 70 to 85 °C bed, and is more prone to stringing than PLA because of its higher melt viscosity and ooze. It adheres aggressively to PEI and glass at high temperature; let the bed cool to 40 °C before removing prints. PETG is the recommended upgrade from PLA for functional parts needing moderate heat resistance or impact toughness. See the material comparison.

PLA (Polylactic Acid)

The most common FDM filament, made from fermented plant starch (typically corn or sugarcane). PLA is easy to print (190 to 220 °C hotend, 50 to 65 °C bed, or unheated), produces minimal warping, and smells mild. Its weaknesses are low heat resistance (glass transition ~60 °C, meaning it softens in a hot car) and brittleness under impact. PLA is biodegradable under industrial composting conditions but not in a home compost bin or landfill. It is available in hundreds of colours and composites (wood-fill, metal-fill, glow, silk). For most visual models, prototypes and household items that do not encounter heat or impact, PLA is the correct choice. See the material comparison and the filament density chart.

Print speed (mm/s)

The velocity at which the printhead moves while depositing material, measured in mm/s. Higher print speed reduces print time but can exceed the hotend's volumetric flow limit, causing under-extrusion and weak layers. It also increases ringing artifacts if the printer frame is not stiff enough. Practical ranges: 40 to 80 mm/s for PLA on an Ender-class printer; 80 to 200 mm/s for modern direct-drive printers with input shaping. Perimeter (outer wall) speed is typically set to 50 to 70% of infill speed to improve surface quality. Print speed and layer height together determine volumetric flow: Flow = nozzle diameter × layer height × speed (mm³/s). Use the Volumetric Flow Calculator to check that your speed settings stay within your hotend's capacity.

Retraction

A brief reverse movement of the filament in the extruder when the printhead travels over a gap, intended to relieve pressure in the nozzle and prevent oozing (stringing). Retraction is characterised by two settings: distance (how far the filament is pulled back, typically 0.5 to 2 mm for direct drive or 4 to 8 mm for Bowden) and speed (how fast it is pulled, typically 20 to 60 mm/s). Too little retraction leaves strings; too much retraction pulls molten filament above the melt zone and causes jams (heat creep) or "blobs" where material leaks out before extrusion resumes. For flexible filaments (TPU), retraction is often disabled or minimised because the material compresses rather than retracting cleanly.

Slicer

Software that converts a 3D model file (STL, 3MF, OBJ) into a printer-specific G-code file by "slicing" it into horizontal layers and generating toolpaths. The slicer is where all print settings are configured: layer height, infill, speed, temperatures, supports, retraction and more. Common slicers: Bambu Studio (Bambu Lab printers), PrusaSlicer (Prusa and many others, open source), Cura (open source, wide hardware support), OrcaSlicer (open source fork of Bambu Studio with advanced tuning). The slicer estimate of print time and filament usage is usually accurate to within 10 to 15% for standard prints, though complex supports and many retractions can throw it off. See the Print Time Estimator for a quick calculation.

Stringing

Thin threads or hairs of plastic left between sections of a print when the nozzle travels over open air, caused by molten plastic oozing out of the nozzle during travel moves. The primary fix is increasing retraction. Secondary fixes: lower hotend temperature (reduces viscosity and ooze), higher travel speed (less time for ooze during the move), and enabling combing (routing travel moves over already-printed areas rather than open air). PETG and flexible materials string more than PLA due to higher viscosity and ooze. Minor stringing can be removed post-print with a heat gun (briefly) or by picking off individual strands; severe stringing usually means the retraction settings are fundamentally wrong for the material-extruder combination.

Support structures

Automatically generated temporary material printed beneath overhangs steeper than the printable limit (usually beyond 45 to 50° from vertical). Supports enable complex geometries to print, but add print time, filament, and post-processing work (removal and surface cleanup). Support types: normal (touching build plate), tree (minimises contact points, easier to remove), and interface layers (dense top layer of support for a smoother overhang surface). Soluble supports (PVA dissolved in water, HIPS dissolved in limonene) produce the cleanest overhangs but require a dual-extrusion printer. Avoiding supports by reorienting the model or splitting it into parts is always preferable to generating them.

Volumetric flow rate (mm³/s)

The volume of plastic extruded per second, calculated as: Flow = nozzle diameter × layer height × print speed. For a 0.4 mm nozzle at 0.2 mm layer height and 60 mm/s: 0.4 × 0.2 × 60 = 4.8 mm³/s. Every hotend has a maximum volumetric flow limit set by its heater power and thermal mass: standard hotends (MK8, E3D V6) typically max out at 10 to 15 mm³/s; high-flow hotends (Volcano, Revo, Dragon HF) reach 20 to 40 mm³/s. Exceeding the limit causes under-extrusion regardless of other settings because the filament cannot melt fast enough. The limit also varies by material: PETG melts more slowly than PLA at the same temperature, so its practical flow limit is lower. Use the Volumetric Flow Calculator to check your current settings against common printer limits.

Z-offset

The distance between the nozzle tip and the bed surface when the printer reports Z=0 (home position). A correctly set Z-offset ensures the first layer is squished slightly into the bed for good adhesion without being so flat that it produces elephant foot or blocks the nozzle. Z-offset is adjusted during bed levelling or via the printer's "live adjust Z" function during the first layer. A first layer that looks like a round noodle sitting on top of the bed means the nozzle is too high (Z-offset too large, or bed too low); a first layer that is invisible or has a rough texture means the nozzle is too close. Automatic bed levelling (ABL) systems using a probe (BLTouch, CR Touch, inductive probes) measure and compensate for bed tilt automatically, but the Z-offset still needs to be set once to establish the correct nozzle-to-bed distance at the probe trigger point.

Frequently Asked Questions