Heavy Purge

Heavy purging is used when a high temperature engineering polymer (above 290°C) has been extruded by your Filament Maker and it has to be removed from the machine. Below are the details for the purging material, preparations, and step by step guide.

Article Overview

DevoClean HT

Preparation

Warning

Step by step

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DevoClean HT

(High-Temperature, or HighTemp, or HT)

Heavy purge is done with DevoClean High-Temperature (290-420°C), which is the most powerful high temperature grade for hard-to-clean materials. 

The good

Devoclean HT is a purging material built up in basically the same manner as DevoClean MidTemp, but based on different materials and with the additive of glass fiber to enhance stresses and cleaning ability.

DevoClean HT be used for any situation and material as long as it stays within its temperature range of 290-420°C.

The limit

It may not stay in a hot extruder for longer than half an hour (30 minutes), and cannot be left in your Filament Maker after shutdown.

The solution

This automatically requires DevoClean High-Temperature to be purged out of the machine using DevoClean Mid-Temperature. The figure below is an illustration that helps visualize the whole process of transitioning up to +300℃ temperatures, extruding the high temperature processing material, and back down to the safe zone. 

Figure 1. 

step 1: safe transition from MT to HT to be able to extrude at +300℃ temperatures

step 2: introduce the high temp processing material

step 3: when finished with processing material, purge it out with HT

step 4: transition down to MT to be able to safely switch off FM

This is also why, when transitioning in the safe window, we must make sure that the transition is complete! This means that we wait for at least 10 minutes, and confirm visually that only one material is remaining in the barrel. 

To sum up

Warning!

Preparation

Before purging your extruder, there are a few preparation steps that should be taken for safety. This is the same for both a Standard and Heavy purge.

1. Gathering
   The first step is gathering all the necessary tools, materials and information for the purging process. These are:
   • at least 350 grams of purging material, however this will depend on:
     • which level of purging you are using
     • the type of material that needs to be purged out of the machine
     • and the machine’s state
   • a piece of paper or cardboard
   • tape
   • multitool (or a side cutter and pincers)
2. Ventilation
   Make sure that the area is properly ventilated. A fume hood is also highly recommended to guarantee your safety, especially with Heavy purges. Wearing a gas mask is also a good option.
3. Sensors
   Turn off the hopper sensor in the "Settings" menu, so the hopper can be run completely empty before putting in the purging material. Do this by setting "off" under "Hopper empty check".
4. Fans
   Turn off the filament fans by setting the "Filament fan speed" to 0% in the "Settings" menu, and point them as in the picture below.
5. Cardboard
   Cover the filament sensor with the piece of paper or cardboard and hold it in place with a piece of tape.

Setup of the filament maker for a purging run.

Step by step

After preparations are complete, the purging process can begin.

If you're familiar with Disco Purging, go ahead and introduce it to your regular practice of purging. We recommend you perfect the Standard Purging process first, before adding this method. 

The first steps (Steps 1-6) are identical between Standard and Heavy purge with different purging materials.

Steps Overview Step 1: Almost empty hopper Step 2: Small amount of purging material Step 3: Purging Step 4: Large amount of purging material Step 5: Evidence of purging Step 6: Purge HighTemp with MidTemp and Finish purging

Step 1: Almost empty hopper

Let the hopper run empty, until there is few to no granulate of the previous material inside the hopper.

Almost empty hopper: the moment to put in the purging material.

Step 2: Small amount of purging material

Put in a small portion around 60 grams of purging material, so more of the previous material can be flushed out of the hopper and the feeding section of the screw.

Temperature settings don’t need to be changed as long as it is within the range of your purging material’s extruding temperature.

First (small) portion of purging material.

Step 3: Purging

Wait for the small portion of purging material to be flushed away by the extruder. This might take around 15 minutes, but can be more or less. 

Step 4: Large amount of purging material

When few to no granulate is left, put in the next portion of purging material, around 200 grams.

Second, larger, portion of cleaning material.

Step 5: Evidence of purging

Remember, the point of purging is to get rid of the material that was previously used. This can be visibly seen in the extrusion.

When the purging material is coming out of the extruder, usually mixed with the previous material, proceed to the next step. This is usually clearly visible as the structure, color, and surface smoothness of the filament changes.

First signs of cleaning material coming out of the extruder.

Adjustments:

• if the change in the extrusion is still not visible after 15-20 minutes (from the moment the first small portion was put in the hopper) increase the temperatures of all heaters with 20°C.
• If this still doesn’t work, increase the screw speed to 10 RPM to give the flow a boost. As soon as the flow is back, decrease to the original RPM.

Step 6: Purge DevoClean HT with DevoClean MT and Finish purging

After 10 minutes, see if the extruded purging material still contains old material or other contamination.

The first picture below shows an example where the machine is clean as there is only pure purging material (in this case: HDPE) is coming out of the extruder. 

The second picture shows the opposite and requires longer cleaning. 

To do this:

1. set all heaters to 300°C
2. wait until the hopper is completely empty just as in Step 1
3. follow the steps of the purging process again starting at Step 2 with DevoClean Mid-Temperature

After around 25 minutes and 250 grams of DevoClean Mid-Temperature, this process should be completed and the DevoClean High-Temperature will probably be fully removed from the machine. 

Your Filament Maker should now be completely clean again and ready for the next extrusion run.

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To understand how Disco Purge fits into all this, head to its dedicated article. 

Know the practice, but not the theory? Have a look at What is Purging? .