Why your 3D printer is not printing anything (and how to fix it)

Two different problems wear the same name. The first is when the printer heats up, accepts the file, and goes through the motions, but no plastic comes out of the nozzle. The second is when the job will not start at all: the screen sits idle, the SD card reads nothing, or the printer refuses to home.

We will cover both. Start by working out which one you have.

The printer moves but nothing comes out

This is the more common version. The nozzle is travelling, the bed is hot, but the print stays as a thin scratch on the build plate, or there is nothing on the plate at all.

Nine times out of ten it is one of four things.

1. The nozzle is clogged

A blocked nozzle is the first thing to suspect, especially if the last print finished fine but the next one will not extrude. Filament carbonises inside the hotend over time, and small bits of debris in cheap rolls get stuck at the tip.

Heat the nozzle to printing temperature for your material and try to push filament through by hand. If it will not move, or it curls out to one side as a thin thread, the nozzle is partly blocked. A cold pull (sometimes called an atomic pull) clears most soft clogs. For stubborn blockages you swap the nozzle out. They cost very little and are worth keeping a couple of spares for.

2. The extruder is not gripping the filament

Look at the extruder gear. If it is shiny and packed with filament shavings, the gear has been spinning while the filament stays still. That happens when something downstream is blocking flow, or the idler tension is too loose.

Clean the gear with a small brush, tighten the idler arm, and push fresh filament through. If the gear keeps stripping the filament smooth, the blockage is further down. Move on to the next two causes.

3. The PTFE tube is damaged or misseated

On Bowden printers (most Creality Ender and CR series), the white PTFE tube runs from the extruder down into the hotend. If the tube has burned at the hot end, or the coupler has lost its grip, filament gets pushed into the gap and jams there instead of feeding into the nozzle.

Pull the tube out at the hotend. If the end is black, melted, or coned out, trim it square with a sharp blade and reseat it firmly. If the coupler does not bite the tube anymore, replace the coupler. This is a five-minute job once you have done it once.

4. The first layer is set too close to the bed

If the nozzle is scraping the build plate, plastic has nowhere to go. The extruder pushes, the filament has nowhere to escape, and you get a dry scratch instead of a line. The print looks like nothing came out at all.

Raise the nozzle a touch (roughly the thickness of a sheet of printer paper above the bed) and run a first-layer test. If the line is now visible, the Z offset was the problem.

The printer will not start the job

This is the second flavour. You hit Print and nothing happens. Or the screen reads the SD card but the file is missing, or shown as garbled characters.

Check the file and the card

Re-export the G-code from your slicer onto the SD card. Use a card the printer has worked with before. Some printers are fussy about cards above 8GB or 32GB. Avoid file names with spaces or special characters, because some older firmware truncates them.

Pull the card out, blow the slot clean, and reinsert it. If the file shows up but the printer freezes when you select it, the G-code itself may be corrupt. Re-slice and try again.

Check the heaters and thermistors

If the printer shows a temperature error (often "MINTEMP", "MAXTEMP", or "HEATING FAILED"), the hotend or bed thermistor has a problem. The printer will refuse to start a print to protect itself, which is the correct behaviour.

You can sometimes spot a loose thermistor wire near the hotend. If the reading on the screen is wildly wrong (-15 deg C, or +280 deg C while the printer is cold to the touch), the sensor or its wiring is faulty. Do not bypass the error. The safety check is there to stop a fire.

Check the firmware

Rarely, a firmware update goes bad and the printer boots but never moves. If you flashed firmware recently and things stopped working straight after, that is your cause. Reflash to a known-good version for your specific board revision.

Can you fix this yourself?

Most of the causes above are DIY-friendly if you have basic tools: hex keys, a sharp blade, fresh nozzles, and a spare PTFE tube. A clogged nozzle, a stripped extruder gear, or a Z-offset problem are all jobs you can do at the kitchen table in under an hour.

Where we draw the line is anything electrical. A shorted thermistor, a damaged heater cartridge, a burnt mainboard, or a failed stepper driver are not kitchen-table jobs. If you have already smelled hot plastic on the board, or seen a brown patch near a connector, stop and unplug the printer at the wall.

Is it worth repairing?

A nozzle, a length of PTFE, and a coupler together cost less than a takeaway. If that fixes it, fix it.

The judgement call comes if the mainboard is dead or the hotend assembly has cooked. A new mainboard for a budget printer can be a meaningful slice of what you paid for the whole machine. On older Ender 3 v1 boards a full replacement plus your time can be hard to justify. On a Bambu, a Prusa, or a higher-end Creality, the board is worth repairing because the rest of the machine has plenty of life in it.

We will tell you straight if a printer is not economic to repair. There is no point posting a £150 printer to us if the fix is going to cost more than a fresh one off the shelf.

What it costs and how long it takes

We do not quote without seeing the printer. A clogged nozzle is a quick job. A fried mainboard with collateral damage to the wiring loom is not. Once we have it on the bench we will email you a fixed price before doing the work, so there are no surprises.

Turnaround is usually within a few working days from when the printer arrives. Parts that have to come from outside the UK can add time, and we will tell you up front if that applies to yours.

When to mail it in

If you have worked through the obvious things (cleaned the nozzle, checked the extruder gear, reseated the PTFE tube, levelled the bed) and the printer still will not lay down plastic, that is the point to send it over. Same goes for any temperature error you cannot clear, anything that smells of burnt electronics, or a screen that has gone dead.

Get in touch through /contact.html with the model of printer, a short description of what it does and does not do, and a photo of the hotend area if you can manage one. We will tell you whether it is worth posting in, what to pack with it, and where to send it.