Interactive guide

How an FDM 3D printer works

It's a hot glue gun on a robot arm. A computer-controlled nozzle melts plastic and draws a part one thin slice at a time, from the bottom up. FDM stands for Fused Deposition Modeling: fused plastic, deposited layer by layer.

01From idea to plastic

The printer never sees a 3D shape. It only follows a long list of simple commands. Click through the four steps to see how a model becomes that list.

02Watch it print

A side view of a simple gantry printer building a vase. Change the layer height and see the trade-off: thinner layers look smoother but take far more passes.

  1. Heat upNozzle ~210 °C, bed ~60 °C
  2. Feed & meltGears push filament into the hotend
  3. Draw the layerNozzle sweeps, plastic sticks to the layer below
  4. Rise & repeatMove up one layer height, go again
Layer0 / 0
Height0.00 mm
Nozzle25 °C
Bed25 °C

    

  







  
03Inside the hotend

  
Follow the filament from top to bottom. Colour shows temperature: blue is cold and stiff, orange is molten. Click any part (or press the button) to learn what it does.

  

    
      
        
          
          
        
        
      

      
      SOLIDpushable
      SOFT
      MOLTEN~210 °C

      
      
        
        
      

      
      
        
        
        
        
        
        
        EXTRUDER
        
        
      

      
      
        
        
          
          
          
        
        
        
        
        
        
        FAN
      

      
      
        
        
        HEAT BREAK
      

      
      
        
        
        
        
        HEATER
      
      
        
        
        SENSOR
      

      
      
        
        
        NOZZLE0.4 mm hole
      

      
      
        
        
        
        COOLING
      

      
      
        
        
        
        
        
        HEATED BED
      
    

    

      

      

      

      

        
Think of it as

        
When it goes wrong

      

      

        
        

      

    

  







  
04Words you'll hear

  
Once these click, slicer settings stop looking like a cockpit.

  

    
Layer height
Thickness of each slice. 0.2 mm is a normal balance of speed and finish.

    
Perimeter / wall
The outline traced on each layer. More walls means a stronger part.

    
Infill
The hidden interior pattern (often 10–20 %). Mostly air, so it saves time and plastic.

    
Support
Throwaway scaffolding printed under overhangs, since plastic can't be laid on thin air.

    
Retraction
The extruder pulls filament back briefly before travel moves, to stop oozing and stringing.

    
Bed adhesion
How well layer one sticks. If it doesn't stick, the whole print fails.