It is vital to purge your Filament Maker after each extrusion session, before stopping the flow of plastic.
1. What does “purging” mean ?
Purging means flushing a material out of the barrel of the Filament Maker, by pushing it out with a purging material.
2. Is it really necessary to purge the Filament Maker after each use ?
Even if you plan on processing the same material several times in a row.
The one exception is when processing virgin PLA.
Only 3 materials can be left inside the machine during shutdown:
- virgin PLA
- DevoClean MidTemp EZ
Fortunately, the purging process is quite simple, and often quite fast.
3. Why do I need to purge my Filament Maker ?
To avoid irreversible clogging of the barrel and degradation of the material.
After every session of extrusion, the Filament Maker must be purged thoroughly : all the material which was being processed and that still remains inside the barrel, must be flushed out with a purging material.
Skipping the purging step can have terrible consequences for the equipment:
- the material left inside the barrel degrades. This starts as soon as the flow stops, knowing that the machine remains hot for 2h, and that plastics are degraded by heat. The plastic molecules start breaking, the structure changes, the plastic loses its properties and burns.
- the material crystallizes/solidifies irreversibly. It will take a bit of time until all the plastic inside the barrel becomes solid, but this process starts as soon as the flow stops. In some cases, it will still be possible to get some flow back
- the screw becomes stuck irreversibly. This is a more severe variant of the previous point. Good examples are PEEK and PVA: after being left for 5-10min inside the barrel without flowing, these can clog the machine entirely and irreversibly.
4. What purging material can I use ?
A purging material is defined by:
- its capacity to remove impurities from the barrel (abrasive additives can help)
- its thermal range. This window of temperatures must match the process temperature of the material you wish to purge out.
At 3devo we use the 3 following options. Other purging materials exist on the market. We know these 3 very well, and their combined thermal range covers almost all existing plastics.
|Purging Material||Purging Capacity||Thermal Range (°C)||Can I leave it inside the machine safely during shutdown ?||When to use it ?|
|HDPE||medium||180-280||Yes||To purge virgin plastics in the thermal range.|
|Devoclean MidTemp EZ||high||170-320||Yes||To purge any material in the range, including composites.
Use it if anything goes wrong during the extrusion (impurity coming out, flow stopping).
|Devoclean HighTemp||very high||280-420||NO||After Devoclean MidTemp at 295°C to reach high temperatures.|
To purge high temperature materials (PEEK,…).
Purge it with Devoclean MidTemp at 295°C after use.
5. What settings do I use to purge ?
There are no purging presets.
You should use the same temperatures you were using to process the material you are about to purge (because it, too, must melt). Those temperatures must also be included in the thermal range of the purging material (see table above).
Screw speed :
You can use the two following methods:
- High speed purging: 15RPM
- Disco purging: randomly change the speed every minute to create turbulence in the flow
You must keep purging until you get a pure output of purging material, free of any other material or impurity.
This usually takes about 15min, under normal circumstances, but it can take a lot more time
- when two purging materials are involved (Devoclean HighTemp and MidTemp EZ)
- if the material is very persistent (colorants, additives)
- if the screw is partially stuck, the flow is weak, and you are trying to get a good flow back
Amount of purging material :
It depends, just like the duration.
Often, 150-200g is the minimal amount required, but some processes involving multiple transitions or persistent substances can consume more than 400g.
The objective is to ensure that none of the previous material has been left inside the barrel. You will need to keep feeding the hopper until this condition is met.
6. Want to know more ?
Please make sure you read our Full Guide and become an expert of purging and maintaining your Filament Maker in good condition.
It contains more information, pictures, instructions, examples…
If you still have questions, please feel free to ask us at firstname.lastname@example.org. It will be a pleasure helping you avoid problems.