Material change and purge

How to switch from one material (or color) to another on the G1, and when a purge is actually necessary.

Use the guided macro

The printer has a CHANGE_MATERIAL macro that walks the whole thing in five prompted steps. Use it rather than doing this by hand — it sequences the parts people get wrong.

1. Open Macros in the interface and find CHANGE_MATERIAL
2. Enter the temperature first. Open the dropdown to the right of the button and set CHANGE_MATERIAL_TEMPERATURE. Without it the macro stops and tells you to
3. Press the button and follow the prompts

Two things it does that are worth knowing. It sets the Feeding Zone 15°C below the other two zones, for the same reason the inlet plugs when it runs hot. And at step 2 of 5 it stops and asks you to empty the hopper and the pipe — which is the step that gets skipped.

The rest of this note is what those prompts are asking for, and what to do when the change is not routine.

Always purge at the hotter material’s temperature

Whichever way you are switching, run the purge at the temperature of the higher-melting of the two materials — never at the lower one.

Going from PETG to PLA, that means purging hot before dropping the temperature. Drop it first and the PETG still in the barrel stiffens instead of leaving, and you have made a clog out of a material change.

When do you need to purge?

Situation	Action needed
Same material, same color, new bag	No purge — just reload
Same material, color change	Light purge — let material self-flush
Same material family (e.g. PLA → rPLA)	Light purge usually enough
PLA → PETG (different temperature)	Full purge at PETG temperature
PETG → PLA (lower temperature)	Full purge at PETG temperature, then drop
Contamination or degraded material in barrel	Full purge or Barrel clog purging procedure
End of print, same material tomorrow	No purge — just let the machine cool

After a print ends: what to do

Nothing special. When a print finishes, the G1 cools down normally. The material left in the barrel solidifies safely and is ready to melt again at the next print.

• Do not try to empty the barrel after every print
• Do not run manual extrude to “clean” after a session
• Just start the next print as normal — the purge line at the start will prime the nozzle

Light purge (same material, color change)

1. Load the new material into the hopper (remove the old pellets or add new on top)
2. Heat the printer to normal print temperature
3. Run a long purge line (300–400 mm) by starting a print with a large brim or skirt
4. The old color will appear first, then gradually transition to the new color
5. Alternatively, use manual extrude on the display before starting

Often it purges itself

Between batches of the same base material the changeover usually clears on its own. Run a few purge lines before deciding the output is wrong.

Full purge (different material or temperature)

When switching between incompatible materials (e.g. PLA to PETG):

1. Step 1 — At higher temperature. Heat to the higher of the two materials’ temperatures. Run the purge at the higher temp so the old material is fully molten and can be pushed out.
2. Step 2 — Purge until the output is consistent. Judge it by what comes out, not by a quantity: clean, even, no trace of the old colour or texture. For a sense of scale, Ginger Slicer’s own start-of-print purge pushes 10 000 mm³ along a 500 mm line — and that is only priming a barrel that already holds the right material.
3. Step 3 — Lower to new material temperature. Now reduce to the target material’s temperatures.
4. Step 4 — Prime before printing. Run a purge at the new temperature before starting the real print.

Using purge compound (optional)

A purge medium — commodity injection-grade PP as the cheap option, or a purpose-made compound (what to purge with) — is useful for:

• Severe contamination (degraded/burnt material)
• Switching from colored to natural/clear material where perfect color purity is needed
• After a Nozzle and barrel clog that left residue

For normal material changes between compatible materials, purge compound is not required. The base material itself (clean, without pigment) can serve as a purge medium.

Do not purge with fibre-filled material

PETG GF and PETG CF do not scrub the screw, and they cost considerably more than what you would purge with on purpose. See Extruder screw.

Critical: empty the corrugated tube too

When switching materials, a common mistake is cleaning only the hopper and forgetting the corrugated tube. Pellets remain inside the tube and fall into the hopper once printing starts, contaminating the new material.

Complete feeding system flush:

1. Turn on the vacuum manually
2. Let it suck all remaining pellets from the tube into the hopper
3. Then empty the hopper — remove the two knobs at E04 and let everything out
4. Visually check the tube — there should be no remaining pellets visible
5. Even 1 pellet of old material will cause contamination in the first layers

Note

Confirmed issue with PLA → PETG switch (a customer in Ireland): the hopper was cleaned but the tube still had PLA pellets → the first prints were milky/mixed.

When contamination is in the feeding system

If the hopper and corrugated tube contain residue of the previous material:

1. Remove the tube and shake out pellet dust and fines
2. Wipe the inside of the hopper with a dry cloth
3. Load the new material and run a purge before printing

See also Hopper suction problems if the feeding system is clogged.

Mixing materials with masterbatch or powder pigment

If you mix dry powder pigment or solid masterbatch into pellets:

• Solid masterbatch needs about 2% by weight to come out evenly coloured. Below that the colour streaks
• If the first batches are uneven, run purge lines until the mix is consistent
• Avoid over-diluting — too much masterbatch increases viscosity and can cause under-extrusion
• Prefer Liquid Masterbatch for more consistent, less viscosity-affecting coloring

Related notes

• Barrel clog purging procedure — for stubborn clogs after material change
• Nozzle and barrel clog — troubleshooting extruder clogs
• Liquid Masterbatch — preferred coloring method
• Hopper suction problems — cleaning the feeding system
• Multi-Heating Zones — temperature settings per zone