You should systematically log all your extrusion data with DevoVision. Here is what the data can teach you.
1 - Install DevoVision
First things first, please make sure you install DevoVision.
2 - Log your data
You should start a datalog at the very beginning of each extrusion session.
Once your Filament Maker is recognized in the list of ports, simply press "Connect" then "Start logging".
Please DO NOT start a datalog in the middle of an extrusion run.
This would reset the system, causing the material to stagnate and degrade for a moment.
3 - Visualize your log
During the extrusion session, you can visualize your log in the "Live view" tab.
You can also access logs from previous sessions in the archive tab called "Log view".
4 - Analyze your log while experimenting
The experimental methodology consists in adjusting parameters and observing how the process reacts. More detail here.
Data is only one piece of the puzzle.
The second piece is what you see coming out of the machine.
You should interpret the results by combining the two.
4.1 - Temperatures
Each heater gives 3 pieces of data :
- setpoint : target value that you selected in the Settings menu
- temperature : measured temperature.
- duty cycle (dc) : indicates the activity percentage of the heater. The duty cycle percentage decreases when the temperature increases toward the setpoint, thanks to a control loop
After adjusting the setpoint on one heater, please wait for 20min at least before changing the setpoint again.
4.2 - Motor current, or Extruder Current
It gives an indication of the pressure inside the barrel. The more difficult it is for the screw to rotate, the higher the current. However, this does not mean that you want a current as low as possible. Some pressure is needed for good melting and stable pushing. A balance must be found.
Safety trigger : the Filament Maker shuts down when the current reaches 9000mA.
Big sudden spikes in the motor current might indicate inconsistent feeding/melting (premature melting, heterogeneous particle size,...).
4.3 - RPM
3.5-7.0RPM is often the best window.
Fluctuations of +/- 0.1RPM are acceptable.
Big fluctuations do not necessarily indicate that your motor is broken, but that the material flow is inconsistent. It is an indicator of stability which should be linked to the motor current.
You might need to keep adjusting other parameters (feeding and temperatures mainly)
4.4 - Filament thickness
This is the main quality indicator.
The goal is to keep the filament thickness between the tolerance lines (typically +/- 100 micrometers, though each printer has its own range).
Spikes outside the tolerance lines are a tricky topic. Spikes above the lines are generally more problematic than spikes below the lines. Depending on your printer, spikes of 50/100/150 micrometers might be acceptable or not.
You can assume that you have achieved stable results once the filament thickness consistently stays between the lines for 30min+. Only then we recommend you to start spooling.
The sensor is responsible for measuring and ensuring that, on average, as long as the filament does not escape the reading range, the thickness corresponds to the setpoint.
However, the fluctuation around that setpoint - or tolerance -, is not the sensor's fault.
The thickness tolerance is connected to 3 keys.
4.5 - Puller speed
This is connected to the filament thickness.
The sensor measures the thickness and automatically adjusts the puller speed.
Puller speed control loop
- Thickness is measured every second
- Thickness average is calculated over 20s
- If the average differs from the setpoint (eg 1.75mm), the calculator automatically adjusts the puller speed
This system works well if the pressure/flow is stable inside the barrel. In that case, the puller will find a cruising speed after 1-2min, ensuring a tight tolerance.
If the pressure/flow is not consistent (due to melting issues, excessive fluidity,....), the puller will not be able to keep the thickness without a tight tolerance. This does not mean that the sensor is malfunctioning. These could cause problems.