3D Printing Jump Start: complete notes

Not Extruding at Start of Print

Printer doesn't extrude at the beginning. Very common for new owners. Four possible causes:

1. Extruder not primed: nozzles leak (ooze) when sitting idle hot, both while preheating and while cooling, leaving a void, so extrusion is delayed. Fix: prime before printing with a skirt (add more skirt outlines on the Additions tab if needed) or extrude manually with the Jog Controls.
2. Nozzle starts too close to the bed: no room for plastic to exit. Symptom: nothing for the first 1–2 layers, normal from about the 3rd–4th as the bed lowers. Fix: Z-axis G-code offset (G-Code tab), e.g. +0.05 mm moves the nozzle further away. Increase in small steps.
3. Filament stripped against the drive gear: shavings or a missing section of filament. See Grinding Filament.
4. Extruder clogged: from debris in the nozzle, hot plastic sitting too long, or insufficient thermal cooling so the filament softens outside the melt zone. May need disassembly. Ask the manufacturer; the “E” string of a guitar fed into the nozzle tip works well.

Not Sticking to the Bed

The first layer must bond strongly to the platform.

• Bed not level: one side too close, the other too far. Use the Bed Leveling Wizard (Tools menu).
• Nozzle too far from the bed: you want the filament slightly squished onto the plate. Z-axis G-code offset −0.05 mm = 0.05 mm closer. Small changes only (layers are ~0.2 mm).
• First layer too fast: use “First Layer Speed”, e.g. 50% = the first layer prints 50% slower.
• Temperature/cooling: plastic shrinks as it cools. An ABS part 100 mm wide printed at 230 °C and cooled to 30 °C shrinks almost 1.5 mm, but the bed doesn't, so the part separates. Heated bed (e.g. 110 °C for ABS): PLA 60–70 °C, ABS 100–120 °C. Disable the fan for the first layers (e.g. layer 1 at 0%, layer 5 at 100%). For ABS the fan is often off for the whole print. Keep drafts away.
• Build surface: BuildTak sticks well to PLA; heated borosilicate glass works for ABS. Keep it free of dust, grease and oils; clean with water or isopropyl alcohol. Tapes: PLA → blue painter’s tape; ABS → Kapton tape (polyimide film). Glue stick, hair spray.
• When all else fails: brims and rafts. A brim adds rings around the part (like a hat brim); a raft goes underneath. Both give more surface area for small parts.

Under-Extrusion

The printer gives no feedback on how much plastic actually leaves the nozzle, so less can come out than the software expects. This causes gaps between adjacent extrusions.

• Test: print a 20 mm tall cube with at least 3 perimeters. At the top, gaps between the 3 perimeters = under-extruding.
• Incorrect filament diameter setting (Other tab). Measure with calipers. Common: 1.75 mm and 2.85 mm.
• Increase the extrusion multiplier (flow rate; Extruder tab, per extruder): 1.0 → 1.05 = 5% more. PLA ~0.9, ABS ~1.0. Increase 5% and reprint the cube.

Over-Extrusion

Too much plastic, messy prints, ruined outer dimensions. Adjust the same settings as for under-extrusion in the opposite direction: decrease the extrusion multiplier.

Gaps in Top Layers

Parts have a solid shell around a partly hollow interior (e.g. 30% infill = 30% plastic, the rest air). Example: 5 top and bottom solid layers on a cube.

• Not enough top solid layers: solid extrusions sag into the infill air pockets. Rule: the top solid section should be ≥0.5 mm: 0.25 mm layer → 2 layers; 0.1 mm → 5 layers. Try 3 → 5. Extra layers go inside the part dimensions.
• Infill percentage too low: 10% infill = 90% air, with big gaps to bridge. Try 30% → 50%.
• Under-extrusion: if the two above don't help.

Stringing or Oozing

Also called whiskers or “hairy” prints. Plastic oozes out of the nozzle while it travels. Main countermeasure: retraction (filament pulled back into the nozzle before travel, pushed back in before printing resumes).

• Retraction distance (the most important setting): direct drive 0.5–2.0 mm; Bowden up to 15 mm. Try +1 mm.
• Retraction speed: too slow still oozes; too fast separates the filament from the hot plastic or grinds it. Sweet spot 1200–6000 mm/min (20–100 mm/s).
• Temperature too high: less viscous, leaks more easily. Lower by 5–10 °C (too low and it won't extrude).
• Long movements over open spaces: enable “Avoid crossing outline for travel movement”.
• Movement speed: a higher X/Y travel speed means less time to ooze.

Overheating

Plastic exits at 190–310 °C. You need a balance between flowing freely and solidifying quickly. Example: the tip of a pyramid deforms.

• Insufficient cooling (most common): increase fan power, or add an aftermarket or handheld fan.
• Too high temperature: lower by 5–10 °C (not too far).
• Printing too fast: small layers don't get time to cool. Use speed overrides to slow down layers that take less than e.g. 15 s.
• When all else fails: print multiple parts at once, so the nozzle leaves each part and gives it time to cool.

Layer Shifting

Most printers use open-loop control: no feedback about the actual toolhead position, so the printer can't detect or correct a shift (e.g. if you bump it).

• Toolhead moving too fast: the motors can't keep up and you hear clicking. Reduce the Default Printing Speed and X/Y Axis Movement Speed by 50%. Lower firmware acceleration.
• Mechanical: belts (rubber, fibre-reinforced) stretch over time. Too loose → the belt slips on the drive pulley; too tight → excess friction in the bearings. The belt should be somewhat tight, but not so tight the system can't rotate. A loose set screw (grub screw) on a motor pulley means the motor turns but the pulley doesn't.
• Electrical: not enough current to the motors, or overheating motor drivers stopping the motors until they cool.

Layer Separation and Splitting

• Layer height too large: nozzles are 0.3–0.5 mm. Each new layer must be pressed onto the one below. Rule: layer height 20% smaller than the nozzle diameter (0.4 mm nozzle → max ~0.32 mm).
• Print temperature too low: warm plastic bonds better. ABS at 190 °C breaks apart easily; it needs 220–235 °C. Try +10 °C.

Grinding Filament

The drive gear (sharp teeth pressing the filament against a bearing) keeps spinning while the filament can't move, and grinds it away until nothing is left to grip (“stripped”). Signs: lots of small plastic shavings; the motor spins but the filament doesn't move.

• Aggressive retraction (too fast or too much): try 50% lower retraction speed.
• Increase extruder temperature by 5–10 °C: plastic always flows easier when hotter.
• Printing too fast: the motor spins slower if you print slower (e.g. 3600 mm/min = 60 mm/s → −50%).
• Check for a nozzle clog.

Clogged Extruder

Kilograms of plastic pass through a hole “only as big as a single grain of sand”. Clogs are usually something inside the nozzle blocking the flow.

1. Manually push the filament: heat up, jog-extrude e.g. 10 mm while pushing lightly by hand.
2. Reload the filament: retract it out (hot), cut away the melted/damaged part with scissors, reload.
3. Clean out the nozzle: heat to 100 °C and pull the filament out manually (hopefully with the debris), or push a guitar E string back through the tip. Follow the manufacturer's instructions.

Stops Extruding Mid Print

• Out of filament: load a new spool.
• Filament stripped against the drive gear (printing too fast or extruding too much): motor spinning, filament not moving.
• Extruder clogged: check the filament is clean with no dust on the spool (dust builds up in the nozzle).
• Overheated extruder motor driver: drivers have a thermal cutoff. X and Y keep moving but the extruder doesn't. Turn the printer off, let the electronics cool, add a cooling fan.

Weak Infill

Infill connects the outer shells and supports the upper surfaces.

• Try alternate infill patterns: Grid, Triangular, Solid Honeycomb are strong; Rectilinear, Fast Honeycomb trade strength for speed.
• Lower the print speed: infill is printed fastest, so the extruder can't keep up and under-extrudes. Try −50%.
• Increase infill extrusion width: e.g. 0.4 mm perimeters with 0.8 mm infill = 200%. Thicker, stronger infill walls. To keep the same %, lines are spaced further apart, so many users also raise the infill %.

Blobs and Zits

Marks where the extruder starts/stops a perimeter. Watch whether the defect appears at the start or the end of a loop.

• At the start → priming too much. Use a negative Extra Restart Distance: e.g. retraction 1.0 mm with −0.2 mm → retracts 1.0 mm, primes only 0.8 mm.
• At the end → Coasting: turn off the extruder shortly before the end to relieve nozzle pressure. Typically 0.2–0.5 mm.
• Avoid unnecessary retractions (especially with Bowden extruders): “Only retract when crossing open spaces”, “Avoid crossing outline for travel movement”.
• Non-stationary retractions: enable “Wipe Nozzle” (wipe distance ~5 mm) plus “Perform retraction during wipe movement”, so the nozzle keeps moving while retracting and leaves no stationary blob.
• Choose the start-point location: random, or closest to a specific XY point, e.g. the back of a statue.

Gaps Between Infill and Outline

Perimeters trace the outline; infill uses a fast back-and-forth pattern. The two must bond.

• Not enough outline overlap (Infill tab; % of extrusion width): e.g. 20% → 30%.
• Printing too fast: the infill has no time to bond. E.g. 3600 mm/min (60 mm/s) → −50%, then increase gradually.

Curling or Rough Corners

Curling later in the print → overheating: the plastic doesn't cool fast enough and changes shape. Cool each layer rapidly. Curling at the very beginning → a bed adhesion problem.

Scars on Top Surface

The nozzle drags across previously printed plastic while travelling.

• Extruding too much plastic: check over-extrusion first.
• Vertical lift (Z-hop): “Retraction Vertical Lift”, e.g. 0.5 mm, lifts the nozzle before travel. It only happens during a retraction. To lift on every move, disable “Only retract when crossing open spaces” and “Minimum travel for retraction”.

Gaps in Floor Corners

Weak foundation, most obvious where the size changes (e.g. a 20 mm cube on top of a 40 mm cube).

• Not enough perimeters: e.g. 2 → 4 (the wall thickness matters a lot because the interior is partly hollow).
• Not enough top solid layers: e.g. 2 → 4.
• Infill percentage too low: e.g. 20% → 40%.

Lines on the Side of Print

One bad layer shows as a line or ridge. Often cyclical (e.g. once every 15 layers).

• Inconsistent extrusion, mostly poor filament quality: a 5% diameter variation can change the extrusion width by up to 0.05 mm.
• Temperature variation: a poorly tuned PID controller makes the temperature oscillate (sine-wave pattern). A tuned printer holds ±2 °C; if it varies more, recalibrate the PID.
• Mechanical: bed wobble or vibration; a Z-axis threaded rod not positioned properly (backlash, poor micro-stepping settings).

Vibrations and Ringing

A wavy pattern from vibrations/wobbling, seen at sudden direction changes such as sharp corners (inertia of the extruder), e.g. each face change of a 20 mm cube.

• Printing too fast (most common): lower the Default Printing Speed and X/Y Axis Movement Speed.
• Firmware acceleration: ramps speed up and down gradually. Decreasing it reduces ringing further.
• Mechanical issues: a loose screw or broken bracket.

Gaps in Thin Walls

A fixed nozzle size causes trouble with walls only a few times wider than the nozzle, e.g. a 1.0 mm wall with a 0.4 mm extrusion width.

• Adjust the thin wall behaviour (Advanced tab, Internal Thin Wall Type): default “gap fill” (back-and-forth) or “Allow single extrusion fill” (one dynamic-width pass).
• Change the extrusion width to fit: e.g. a 1.0 mm wall → 0.5 mm extrusion. Best for consistent wall thicknesses.

Small Features Not Printed

The nozzle size sets the XY resolution (popular sizes 0.4 or 0.5 mm). A 0.2 mm wall with a 0.4 mm nozzle may not even show in the preview.

• Enable single extrusion walls (External Thin Wall Type → “Allow single extrusion walls”).
• Redesign the part with features thicker than the nozzle (in CAD).
• Install a smaller nozzle, e.g. 0.3 mm (many users own a 0.3 and a 0.5).

Inconsistent Extrusion

Identify by watching, e.g. a straight 20 mm line looks bumpy or varies in size.

• Filament stuck or tangled: the spool must rotate freely; check Bowden tube resistance (clean or lubricate).
• Clogged extruder: extrude manually and watch for an even flow.
• Very low layer height, e.g. 0.01 mm: no room for plastic to exit.
• Incorrect extrusion width: keep it within 100–150% of the nozzle diameter. A 0.2 mm width with a 0.4 mm nozzle gives inconsistent flow.
• Poor-quality filament: additives, inconsistent diameter, moisture (PLA absorbs it over time, hence the desiccant). Try a new high-quality spool.
• Mechanical: drive-gear tension too loose, so the teeth don't bite far enough.

Warping

Large or long parts, especially high-temperature materials like ABS. The first layers stick, then the part curls and can separate. Cause: plastic shrinks as it cools. ABS printed at 230 °C shrinks almost 1.5% at room temperature, which can be several mm.

• Heated bed: ABS 100–120 °C.
• Disable fan cooling (common for ABS).
• Heated enclosure: keeps the upper layers warm on tall prints. Keep the doors closed.
• Brims and rafts: hold the edges down.

Poor Surface Above Supports

• Lower your layer height: 0.2 → 0.1 mm = twice as many layers and smaller overhang steps. Supports needed above 45° at 0.2 mm, ~60° at 0.1 mm. Less support needed and a smoother underside.
• Support infill percentage: commonly 20–40%. Or use dense support structures (dense only near the top).
• Upper vertical separation layers: empty layers between support and part. Same material: use at least 1–2; with 0 the supports bond and are hard to remove.
• Horizontal offset from the part: 0.2–0.4 mm.
• Second extruder: a different support material, e.g. PLA with water-dissolvable PVA. Then separation layers can be 0 and the offset ~0.1 mm.

Dimensional Accuracy

Factors: under/over-extrusion, thermal contraction, filament quality, first-layer nozzle alignment.

• First layer impact: a nozzle too high or low affects the next 10–20 layers (e.g. a 0.2 mm layer with the nozzle only 0.1 mm from the bed = oversized bottom). Print 50–100 layers and measure only the top ~20.
• Extrusion multiplier: too low = gaps, holes on top, parts too small. Too high = bulging tops, parts too large.
• Constant error (e.g. always 0.1 mm too big, whether 20 or 100 mm wide) → Horizontal size compensation −0.1 mm (Other tab; shrinks X and Y).
• Increasing error (0.1 mm too small at 20 mm, 0.5 mm at 100 mm) → thermal contraction (common for ABS). Shrinkage = 0.1/20 = 0.5% → scale 100.5%. Can be automated with an Import Action.

Poor Bridging

Bridging = extruding between two points with no support below. Short bridges need no supports (saving material and time); large ones may. Symptoms: sagging, drooping, gaps.

• Verify bridging settings are used: preview in “Feature Type” colouring, where bridges are yellow. If not, check the “Unsupported area threshold” (the region must be larger) and “Apply bridging settings to perimeters”.
• Bridging infill angle: calculated automatically so the infill runs along the bridge (e.g. pillars on X → infill along X). Or use a fixed bridging angle.
• Optimise settings: bridging extrusion multiplier 100% or more. Bridging speed multiplier: experiment (some printers do better slow, others fast). Bridging fan speed override high to cool quickly.
• Use supports for longer bridges.