APP – Pre-heating and transition

An extrusion experiment starts with choosing a good starting point.

Choosing inappropriate starting temperatures for your material, might result in the irreversible clogging of the Filament Maker.

Once the correct settings have been determined, it might be necessary to use transition materials before starting the experiment.

1. Determining a good starting temperature

The concept is simple: before feeding your material in the hopper of the Filament Maker, you must be 100% sure that it will melt. With this in mind, the starting temperature should be high enough for the material to melt.

  • If your polymer is semi-crystalline, it has a melting point. In that case, it is recommended to start the experiment 10-20% above the melting point (in °C). For example, if the melting point of PA6 is 220°C (approx), then you can start the test at 260°C.
  • If your polymer is amorphous, then you can start experimenting 150°C above the glass transition temperature.

In general, you can also set the 3D printing temperature, which is usually high enough.

2. How about the other settings ?

It is always a good choice to start with:

  • Screw speed = 5RPM. The flow is often the most stable between 3.0 and 7.0RPM.
  • Fancooling = 50%. This parameter does not really matter at this stage. An average value is a good start.

Tip : Make sure that the  fans are pointing as downard as possible ; not horizontally nor straight up toward the nozzle.

Tip : Make sure the magnetic plate is covering the hole around the nozzle.

3. Before pressing “Start extrusion”: Transition

Choosing an appropriate starting temperature which will ensure the full melting of your material, is a good first step. But this temperature must also be able to melt the material that is currently inside the barrel when you start the experiment.

The barrel of the extruder never runs empty. Let’s say A has been left inside the Filament Maker at the end of your last session. You want to process B, starting at temperature T.

The only way to get an output, is to push it with an input. In other words: to push out A by feeding B, the settings you choose must melt both A and B at the same time.

  • If the starting temperature T that you have chosen for B, is included in the thermal window of A, then you can immediately launch the process at T: wait for the machine to reach T, remove A from the hopper, start feeding B.
  • If T is too high or too low for A, then you need a transition material.

4. Transition materials

According to our purging guide (at the end of the extrusion process), three materials can be safely left inside the Filament Maker during shutdown:

  • virgin PLA (no additives nor colorants)
  • HDPE
  • Devoclean MidTemp EZ

Their thermal windows are (respectively):

  • 170-230°C
  • 180-280°C (up to 300°C but not for long)
  • 180-320°C

There is one more transition material: Devoclean HighTemp (280-420°C).

That gives you 4 options to cover 170-420°C. The vast majority of polymers must be processed somewhere between 200-300°C. This is covered by HDPE and Devoclean MidTemp EZ.

5. One practical example

Problem:

PLA is in the machine. You want to process PolyCarbonate (PC).

PC is amorphous ; its glass transition temperature is 150°C approximately –> you need to start feeding PC at 300°C.

Solution:

  • Set 200°C on all heaters
  • Press “Start extrusion” –> “Automatically”
  • Transition PLA –> Devoclean MidTemp EZ
    • Remove PLA from the hopper or let it run empty
    • Feed Devoclean MidTemp EZ (start with 200g, be ready keep feeding)
    • Wait until the output is pure Devoclean MidTemp EZ
  • Set 300°C on all heaters
  • Wait until all heaters have reached 300°C (keep feeding Devoclean MidTemp EZ)
  • Transition Devoclean MidTemp EZ –> PC
    • Remove Devoclean MidTemp EZ from the hopper or let it run empty
    • Feed PC (start with 200g and keep feeding as much as you need)