This page explains the functions, features, and pitfalls when working with the extrusion screw. These essentials are to help you understand how best to use the machine to your specifications.
The Filament Maker extrudes with a collection of features and components working together efficiently. It is up to the user to utilize these tools and ensure that the machine works well.
Table of Contents
FunctionFeatures
Things to Watch Out For
Machine Settings
Safety / Error Messages
Further Information
Function
The core of the extrusion system is an extruder screw inside a barrel. This is being rotated by a motor with a gearbox. After the material is fed into the Hopper, the particles are pushed forward further into the barrel by the screw threads. The screw (along with other features) is responsible for the flow.
The most important thing to remember about the screw is that its efficiency is directly related to the material’s state in the barrel.
If the particles are not melting and are solid throughout the barrel, the screw will struggle to turn, causing Error Messages, high motor current, and maybe even a blockage. If the particles melt too early and are liquid throughout the barrel, the screw will have no issue turning but there will be almost no output.
Material is too solid throughout = low flow/extrusion, potential clogging
Material is too liquid throughout = low flow/extrusion, potential material degradation
It's all about finding the balance!
Features
There are two available screws for the Filament Maker.
Both screws are made from hardened nitride steel and are 335mm in length. Furthermore, both screws have a compression zone towards the end, meaning the space in which the material flows is greatly reduced, adding more friction and pressure, allowing for a homogenous output.
The High-Flow Screw is ideal for stability and speed. Its simple and efficient design ensures a continuous and consistent extrusion flow.
The Material Mixing Screw is for advanced compounding as it features a built in mixing section at the tip of the screw. This section is sometimes referred to as the pineapple section due to its criss-crossing lattice design, perfect for ensuring a homogeneous output.
The screw’s rotation is measured by RPMs, and can be set from 2 up to 15 RPMs. There are many uses for both high and low RPMs, but in general the screw speed should be between 3-7 RPMs when extruding filament.
Things to Watch Out For
RPM
The screw RPM is recorded by DevoVision. The datalog records the set RPM and the actual RPM, as well.
For example:
We set the screw speed to 3.5RPMs, but the graph shows small dips where the RPM slows down from the set speed. This is not good. Perhaps there are some larger un-melted particles which causes the screw to not rotate as smoothly. Therefore based on the datalog evidence we can adjust the Heaters to make sure we melt all the material sufficiently and not put extra effort on the screw.
This example of a DevoVision graph shows the set 3.5 RPM (first graph, yellow line, 350), whereas the actual RPM is moving up and down a lot more (first graph, blue line, 310-390). There is a close relationship between the RPM and the Motor Current (second graph).
Motor Current
The motor current is directly linked to the screw speed and is also recorded by DevoVision. As with the screw RPM, the motor current should be smooth and consistent, staying in the same value for a long time, without any sudden spikes or dips.
A consistent motor current means there is good pressure and good flow happening inside the machine, and that the screw is no "struggling" to turn. However, if the motor current dips over time, it might mean that there is no more pressure in the barrel at all, and it is time to adjust the heaters or the feeding.
Once again, it’s about finding the right balance between having enough pressure to extrude, but not too much pressure to cause clogging or issues. Nuance!
Machine Settings
Settings > Extrusion screw RPM 2.0 – 15.0
Safety / Error Messages
Safety Warnings
There are no safety measures related to the screw, other than what is already covered in Hopper Essentials.
Error Messages
"Extruder motor too hot."
This occurs when the extruder motor has run too hot due to too much friction generated by the screw or extruding for a very long period with high RPM settings.
"Extruder motor current limit reached."
This occurs due to too much friction generated by the screw. The temperature settings might not be correct.
Troubleshooting
Additional related guides can be found in the Filament Maker troubleshooting category.
Further Information
Faster production rate
Read the article on increased throughput and faster production rates.
Purging
Read the 'Purging your Filament Maker' article.
Additionally, learn how to disco purge the Filament Maker.
Troubleshooting
The Filament Maker has some errors that can be easily solved:
Next essential: The Heaters