Material change and purge

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

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 before dropping temp
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 the manual extrude on the display to push out 50–100 mm³ before starting

Tip

Tip from Davide: “The material might purge itself” — especially if switching between batches of the same base. Run some purge lines before judging the output.

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 output is consistent. Extrude 100–200 mm³ manually. The output should be clean, consistent, and free of the old material’s color/texture.
3. Step 3 — Lower to new material temperature. Now reduce to the target material’s temperatures.
4. Step 4 — Prime before printing. Run another 50 mm³ purge at the new temperature before starting the actual print.

Caution

Never drop temperature with old material still in the barrel if the old material has a higher melt point than the new material — it can solidify partially and create a clog.

Using purge compound (optional)

Commercial purge compounds (e.g. Dyna-Purge, Slide) are 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.

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 (use the hopper knobs or the vacuum reverse)
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:

• Start with a small amount — 0.5–1% solid masterbatch by weight
• Minimum 2% of solid masterbatch for homogeneous color output
• 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