APP – Finetuning

Melting all the plastic 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.

Experimenting in a structured way, following a certain methodology, is the best approach to find the optimal settings for your material. In this part, keeping an eye on the datalog is very important, because the diameter fluctuation will be the quality criteria.

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

3. Concretely, in terms of settings ?

If you have not faced any “obvious” extrusion issues during the previous step, then your thermal profile is probably a straight line (all heaters on the same temperature, 5RPM, 50% fancooling).

If you have already adjusted the settings, you probably already have a thermal framework.
For example you know that a lot of cooling is required, and the temperatures should be below 240°C, overall.

Following the experimental loop from section 2:

  • First it is good to focus on the temperatures – all of them at once. You should start by decreasing all the temperatures by 5°C, wait, look at the tolerance, repeat. In most cases, the final temperatures end up being lower than the starting ones. The idea is to quickly explore the entire thermal window, by discovering the extremes.
  • Then, looking at the log and the output, you should be able to tell what seemed to be the best thermal range.
  • Once you have a good baseline, start adjusting each heater individually. In general, H4 and H3 influence the pressure, while H2 and H1 determine the texture of the output. In a lot of cases, the final temperatures are quite close to each other (spread out over a range of 20°C), and H2 is the hottest, followed by H3 or H1. Not always.
  • Once you feel like you have experimented enough with the temperatures, you can choose the best profile and change the speed by steps of 0.5RPM. Usually between 3.0 and 8.0RPM.
  • The fancooling is a special parameter: feel free to change it anytime. A good way is to go for 50 – 100 – 75 – … or 50 – 0 – 25 -…  Remember that the filament should end up round and solid.

4. One example

Still with the standard PLA from 3devo.

In the last step, we found out that:

  • PLA can melt easily around 180°C. This is a good baseline
  • The difficult step is cooling down the filament enough so that it remains round through the puller. To obtain the perfect roundness, it is necessary to:
    • Decrease the screw speed
    • Decrease the temperatures (especially H1)
    • Increase the fancooling

Here are a few options to make the flow as stable as possible, and really optimize the process:

  • 100% fancooling is not ideal, because you will not be able to increase that when the air in the room becomes warmer. Let’s choose 70-80% and change the other settings accordingly.
  • The RPM does not seem to have a major influence on the stability of the flow. But speeds above 5.0RPM require more cooling. 3.5RPM is a very good choice, because less cooling is required, but the filament still comes out quite fast.
  • The flow of PLA is already good with 180°C set on all heaters.
    • To limit the need for cooling, let’s decrease H1 to 170°C.
    • To increase the pressure inside the barrel, a good strategy often consists in lowering H4. Let’s decrease H4 to 170°C.

That’s it.

You would obtain great results with 170 180 180 170, 3.5RPM, 80%.
We spent more time studying every combination afterwards, which is why the presets are slightly different.

Of course, that worked well for our standard PLA, here at 3devo. Each PLA is unique.