Troubleshooting: Nozzle build-up

When extruding material on the filament maker a common issue is nozzle build up. This phenomena could limit the flow and quality of the produced filament.

Sometimes the material you’re extruding will stick to the nozzle; this phenomenon is called nozzle build-up. You can see how it can look in the figure 1

Figure 1: Example of nozzle build-up

You’ll notice nozzle build-up occurring if the material solidifies around the nozzle and keeps returning after you’ve removed it; this happens because the nozzle temperature is too low for the material being processed. Build-up can be especially problematic with semi-crystalline polymers. The material will continuously solidify when it gets in contact with the nozzle if it’s below the material’s melting point.

There are multiple ways to prevent nozzle build-up; however, all of the methods aim to keep the temperature in the nozzle high enough, so no material solidifies around it.

1. Insulation

Because the nozzle is not heated directly, the glass wool must fully insulate the nozzle area. Although the insulation limits the heat loss in the area from heater 1 to the nozzle (resulting in a higher nozzle temperature), if you decide to change the nozzle, it is vital that the glass wool fully insulates the new nozzle. It is also essential that the nozzle plate is placed around the nozzle to limit heat loss of the nozzle.

2. Temperature of the material

If we want to reduce the chance of nozzle build-up, we can start by increasing the temperature of Heater 1. By increasing it, Heater 1 will transfer more heat to the nozzle. As a result, the temperature of our material will also increase in temperature. Due to the increase in temperature of the nozzle, the material won’t be cooled down to a temperature where nozzle build-up can occur.

It is also possible to increase the screw speed; this increases the output rate, resulting in the material spending less time in the nozzle. Therefore, less heat is transferred from the material to the nozzle, preventing the build-up.

3. Fan orientation

When using the fans to cool down the filament, they shouldn’t be aimed towards the nozzle. When the fans face the nozzle, they will cool it down, resulting in the build-up. In the figure 2 is the preferred orientation presented.

Figure 2:  Example fan orientation 

3. Chart with causes and actions

Figure 3 shows a summary of the possible causes and the corrective actions that should be taken when material start building up on the nozzle.

Figure 3: Summary of potential causes and corrective actions to prevent nozzle build-up