APP – Finetuning (PEEK)

Melting PEEK is a very good first step, but now the melting process has to be very well controlled for the flow to become stable.

This can only be achieved by finetuning the settings.

At this stage, the filament is still not being spooled.

1. The goal

For the flow to be stable, the material must melt at the right moment:

  • not too soon, otherwise not enough pressure will be generated
  • not too late, otherwise unmelted particles can cause RPM fluctuations or even come out unmelted

The objective of the finetuning step is to narrow down the diameter fluctuation, which can be seen on the Filament Thickness graph.

2. The methodology

In order to control the melting process and achieve a tighter tolerance, you must:

  • Change the settings slightly
  • Wait long enough (usually 15min-20min) to be sure that the output really corresponds to the new settings
  • Look at the tolerance on the filament thickness graph, and see if it has become better or worse
    • If the tolerance becomes tighter, it means you have made the right choice, and can keep adjusting the settings in the same direction
    • If not, or if the changes seem to have a negative impact on the results overall, then you should probably try opposite changes
  • Repeat this loop

Luckily, PEEK does not leave a lot of room for experimenting :

  • tempratures must be close to 395°C
  • screw speeed around 4-5RPM
  • fancooling around 50-100%

3. What we did

As a matter of fact, not much had to be done in that part.

The small changes done in the previous steps allowed the filament to become round, smooth, and solid, and also quite consistent in diameter.

For some grades of PEEK, it can be good to decrease H4 and H3 (370°C and 380°C for example), always leaving H1 high enough. That might increase the stability of the flow.

Our final settings were :

  • (H4 –> H1) 390 395 395 395 °C
  • fancooling 80%
  • screw speed 4.5RPM

Again, each grade of PEEK is unique and therefore requires specific settings.