Temperature, speed & what to change when it goes wrong

Fine strings of plastic left behind whenever the nozzle travels over open space.

• Dry the filament.Moisture boiling inside the nozzle is the single most common stringing cause on PETG, Nylon, and TPU — test this before touching any slicer setting.
• Reduce nozzle temperature in 5°C steps.Too hot makes the filament runnier and more prone to ooze during travel.
• Increase retraction distance slightly (0.5–1mm on direct drive, 1–2mm on Bowden).Pulls the molten tip back far enough that it doesn't drool out during travel.
• Increase retraction speed.A faster retraction clears the nozzle tip before pressure has a chance to push more filament out.
• Enable/increase “wipe on retract” and coasting.Wipe moves the nozzle a short distance before lifting, dragging the string back onto the part instead of leaving it hanging in the air.
• Increase travel speed.Less time in the air over the gap means less time for ooze to stretch into a visible string.

Drooping, rough, or stringy undersides on angled surfaces and unsupported spans.

• Increase part cooling fan on the overhang region specifically.Cooling the plastic faster lets each layer support the next one instead of sagging under its own weight before it sets.
• Slow down the outer wall and overhang speed.Gives the fan more time to cool each bit of plastic before the next layer lands on top of it.
• Lower the layer height.Thinner layers bridge and cool more reliably, and each one has less weight for the layer below to support.
• Reduce nozzle temperature slightly.Cooler, stiffer plastic holds its shape on an overhang instead of drooping while still soft.
• Add supports below ~40–45° from vertical.Some geometry is unprintable bridge-free regardless of tuning — supports are the honest fix past a certain angle.
• For ABS/ASA/Nylon/PC specifically: don't over-cool.These materials rely on some retained heat for layer bonding; excess fan trades away strength to fix an overhang — reduce speed/temperature first instead.

Prints fine at low speed, but walls thin out, gaps appear, or layers sound "starved" once speed goes up.

• Increase nozzle temperature in 5–10°C steps toward the top of the material's range.Hotter plastic flows more easily, raising how much the nozzle can push through per second.
• Raise the max volumetric flow limit in the slicer if it's currently capping speed.Slicers automatically slow down when a move would exceed this number — if it's set too conservatively, you're leaving speed on the table or, if set too high, forcing an unachievable flow rate.
• Reduce print speed for that feature (usually thin walls or small text) back to where flow can keep up.Sometimes the honest fix is that the hotend simply can't melt plastic fast enough at that speed — slower is the reliable answer.
• Check for partial nozzle clogs or wear.A partially blocked or worn (oversized/undersized) nozzle opening reduces real flow capacity below what the slicer assumes.
• Increase hotend heater power / check thermistor calibration if using a high-flow nozzle.Some upgraded hotends need more sustained wattage than stock to hold temperature under high flow — temperature can sag mid-print without you seeing it on the display.

Visible gaps between extrusion lines, weak layer bonding, or walls that look thinner than specified, independent of speed.

• Check filament diameter consistency and E-steps calibration.If the extruder isn't feeding the amount of filament it thinks it is, every other setting is compensating for the wrong problem.
• Increase flow rate / extrusion multiplier by 2–5%.Corrects for filament that's slightly undersized or a hotend that melts less efficiently than assumed.
• Increase nozzle temperature slightly.Under-melted plastic is more viscous and harder to push through consistently.
• Check the extruder gear tension and for grinding.Too loose slips on the filament; too tight can crush it — both reduce how much actually reaches the nozzle.
• Inspect for a partially clogged nozzle.Debris or carbonized residue narrows the opening without fully blocking it, which looks exactly like under-extrusion.

Parts print slightly oversized, surfaces look lumpy, or corners/seams bulge outward.

• Reduce flow rate / extrusion multiplier by 2–5%.Most direct fix — too much plastic is being pushed out relative to how far the nozzle travels.
• Re-check filament diameter and E-steps calibration.A miscalibrated extruder or oversized filament feeds more material than the slicer assumes, independent of the flow setting.
• Lower nozzle temperature slightly.Overly hot, runny plastic tends to ooze extra volume out at corners and seams.
• Reduce line width if it's set above the nozzle diameter by a large margin.An overly wide line width setting tells the slicer to push out more plastic per pass than the geometry needs.

Corners or edges curl up off the bed mid-print, sometimes popping the whole part loose.

• Increase bed temperature toward the top of the material's range.Keeps the bottom layers hot enough that they don't shrink and pull away as they cool.
• Close/add an enclosure and eliminate drafts.A sudden temperature drop across the part — from an AC vent, an open door, or a cooling fan — is the most common trigger for uneven shrinkage.
• Add a brim or increase brim width.Extra anchoring material at the base resists the corner's pull more than the part alone can.
• Reduce or disable the part-cooling fan for the first several layers.Active cooling on a material that needs to cool slowly (ABS/ASA/Nylon/PC) accelerates the uneven shrinkage that causes warping.
• Clean the bed surface and consider glue stick or specialty adhesive.Weak first-layer adhesion gives the corner somewhere to lift to in the first place.
• Reduce chamber-to-room temperature gradient once the print finishes.Opening an enclosure immediately after a print exposes a still-hot part to cold air and can warp it after the fact.

The bottom few layers of a part flare outward slightly wider than the rest, most visible on vertical walls near the bed.

• Lower the bed temperature slightly (or the first-layer bed temp specifically).A too-hot bed keeps the bottom layers soft long enough that the weight of the part above squishes them outward.
• Reduce first-layer squish / Z-offset.Pressing the first layer too flat forces plastic to spread sideways beyond the intended wall line.
• Enable elephant's-foot compensation in the slicer.Purpose-built setting that insets the first few layers slightly to counteract the bulge directly.
• Increase first-layer cooling (where the material tolerates it — PLA/PETG, not ABS/ASA/PC).Sets the bottom layer faster so it holds its shape sooner under the weight above.

The print detaches from the bed early, corners lift immediately, or the first layer looks patchy and translucent in spots.

• Clean the bed with isopropyl alcohol.Skin oils and dust are the single most common cause and the easiest to rule out first.
• Re-level the bed / re-check Z-offset.A nozzle sitting too far from the bed lays plastic down without pressing it into the surface.
• Increase bed temperature for the first layer specifically.A too-cool bed lets the plastic solidify before it bonds to the surface texture.
• Slow down the first layer.More time in contact with the hot bed improves the bond before the nozzle moves on.
• Add a glue stick, hairspray, or specialty adhesive (especially ABS, ASA, Nylon, PC).Some materials don't bond well to bare glass or PEI and need a chemical assist regardless of temperature.
• Increase first-layer line width or add a brim/raft.More surface contact area gives the print more to hold onto for small or oddly-shaped footprints.

Layers split apart cleanly, sometimes audibly, either during printing or when the part is later stressed.

• Increase nozzle temperature.Hotter plastic fuses better to the layer below it — the most common root cause of weak Z-axis bonding.
• Reduce or disable part cooling (for ABS/ASA/Nylon/PC).Cooling the layer too fast prevents it from properly welding to the next one before it's deposited.
• Enclose the printer and raise chamber temperature.A stable warm environment keeps every layer from cooling and contracting unevenly relative to its neighbors.
• Dry the filament.Moisture boiling at the nozzle tip creates weak, bubble-filled layers that separate under far less stress than they should.
• Reduce print speed / increase layer time.Gives each layer more time to bond thermally with the one beneath before the nozzle moves on.
• Reorient the part so the stress it will experience runs parallel to layers, not across them.No amount of tuning fully closes the gap between in-layer and between-layer strength — design around it when possible.

A visible bump or blob running vertically up one side of the print, at the point where each layer starts and stops.

• Enable seam hiding (align to a corner, or use a "scarf"/painted seam) in the slicer.Moves the visible pressure spike from a flat, visible face to a corner or a feathered transition where it's far less noticeable.
• Reduce retraction distance and enable wipe.Excess retraction followed by re-priming at the seam is a common source of the small blob at the start of each loop.
• Enable coasting near the end of each perimeter loop.Stops extrusion slightly early so residual pressure in the nozzle doesn't dump extra plastic exactly at the seam.
• Lower flow rate slightly.If the whole print runs a bit over-extruded, the seam is where that excess becomes most visible.

Faint wave-like ripples on the surface, radiating away from corners, holes, or other abrupt direction changes.

• Reduce acceleration and jerk/junction deviation.Ringing comes from the print head vibrating after a sudden direction change — slowing that change down directly reduces the vibration.
• Reduce print speed, especially outer wall speed.Less momentum at each direction change means less energy available to shake the frame.
• Tighten belts and check for loose frame components.A loose belt or wobbly gantry amplifies vibration that tuned acceleration alone can't fully cancel.
• Run input shaping calibration if the printer/firmware supports it.Purpose-built feature that measures the frame's resonant frequency and compensates for it directly, often solving ringing without sacrificing speed.

Everything above a certain layer suddenly shifts sideways and stays shifted for the rest of the print.

• Reduce acceleration and print/travel speed.The stepper motor is losing steps because it's being asked to move faster than it (or the belt) can reliably keep up with.
• Tighten belts and check pulley set screws.A slipping belt or a pulley spinning loose on its shaft causes the exact same symptom as a lost step.
• Check for physical obstructions (a cable snagging, a knocked-loose part) along the axis that shifted.Something physically blocking the head momentarily has the same effect as a motor skipping.
• Lower stepper current if it's running hot, or increase it if it's undersized for the load.A motor running too hot loses torque and skips; one set too low for the axis load does too, from the opposite direction.

Extrusion gradually weakens over a long print, or the extruder starts clicking/skipping as it tries to push filament that won't come out.

• Dry the filament.Trapped moisture vaporizing inside the nozzle is a very common, easily overlooked clog contributor.
• Check heatbreak cooling (fan and airflow).Heat creeping up past the heatbreak softens filament higher up than intended, where it can jam against the cold end.
• Avoid long pauses mid-print at high nozzle temperature.Stationary hot filament degrades and can carbonize, narrowing or blocking the nozzle opening.
• Run a cold pull / nozzle cleaning routine.Physically removes carbonized residue or debris that's already accumulated, rather than just preventing more.
• Check for a worn or partially blocked nozzle orifice, especially after printing abrasive (CF/glass/metal-filled) filament through a brass nozzle.Abrasive fills erode brass quickly; a worn nozzle behaves unpredictably even with fresh, dry filament.

The top layer looks bubbly, has small gaps, or doesn't fully close over the infill below.

• Increase top layer count.More solid layers give the top surface more material to bridge the infill gaps with before it needs to look fully solid.
• Increase infill percentage or switch to a supportive infill pattern (e.g. grid, gyroid) near the top.Denser or better-spaced infill gives the top layers shorter unsupported spans to bridge.
• Increase part cooling on top layers.Faster-setting plastic sags less into the gaps between infill lines.
• Reduce top layer print speed.Slower top-surface printing gives each pass more time to bond and settle flat before the next one.

Audible popping, crackling, or fine spitting sounds coming from the nozzle, often paired with a rough, bubbly surface finish.

• Dry the filament at the material's recommended drying temperature and duration.This sound is almost always trapped moisture boiling and escaping explosively as steam — it's close to a diagnostic sound on its own.
• Store the spool in a sealed container with desiccant going forward.Prevents the problem from recurring rather than just fixing the current spool.
• Use a filament dryer that runs during printing for chronically humid environments or very hygroscopic materials (Nylon, PVA).Some climates re-absorb moisture faster than a one-time dry-out can outpace over a long print.

A functional part fails suddenly along a layer line under stress, well below where the material's bulk properties suggest it should.

• Increase nozzle and chamber temperature toward the top of the range.Better inter-layer fusion is the biggest lever for real-world strength in these materials — most failures are layer-bond failures, not bulk material failures.
• Reorient the part so the load runs parallel to the layers rather than across them.No FDM part is as strong across layers as it is within one — design/orientation matters as much as settings here.
• Increase wall count rather than relying on infill for strength.Continuous perimeter walls carry load more reliably than infill patterns, which have their own internal weak points.
• Dry the filament before printing the part.Moisture-weakened layers are a common hidden cause of a part that "should" have been strong enough on paper.
• Anneal the finished part (oven or dedicated annealing box, material-dependent temperature) if maximum strength matters.Controlled reheating relieves internal stress and can meaningfully improve layer bonding after the fact for materials like Nylon and PC.