Extruder screw

The extruder screw (auger) is the core component of the G1 pellet extruder. It sits inside the barrel, driven by the Main extruder motor, and compresses pellets from the hopper downward through the three Multi-Heating Zones to the nozzle.

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Function

1. Pellets fall from the hopper into the top of the barrel
2. The rotating screw grips and compresses the pellets
3. As pellets travel down through the heating zones, they melt progressively
4. Molten material is pushed through the nozzle at controlled pressure

The screw has a 2:1 compression ratio between the feeding end and the nozzle end.

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New machine — first use

New machines may have machining oil residue and machining debris on the screw from manufacturing, which can end up in the material during the first extrusions. This is normal:

• The first extrusions may appear slightly discolored or smell different
• Purge with the first material at normal printing temperature until output is clean and consistent
• No special action needed beyond this initial purge

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Signs of screw / barrel problems

Symptom	Likely cause
Dark or black particles in extrusion	Degraded or burnt material stuck in barrel
Material melted at screw entrance (visible from top)	Feeding Zone (T0) too hot, or printing at low flow rate
Motor clicks / skips steps	Material too viscous, clog forming, or temperature wrong
Output suddenly becomes more fluid then drops	Backpressure fluctuation from partial clog

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Clearing a clog at the screw entrance (feeding zone)

This is the most common extruder problem. The machine suddenly stops extruding material and the cause isn’t obvious. Opening the hopper (piece E04, the one with the two black knobs) reveals a piece of fused plastic at the entrance of the screw.

1. Make sure the extruder is stopped (not rotating)
2. Open the hopper (E04 — loosen the two black knobs)
3. Remove the fused plastic with a long screwdriver or pliers — it comes out easily
4. Close the hopper and resume printing
5. To prevent recurrence, lower the Feeding Zone temperature (T0) by 10–20°C

Why it happens: when printing at a low flow rate (e.g. 50–100 mm³/s), the plastic travels slowly through the extruder and can stick to the screw, forming the plug at the screw entrance.

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Deep cleaning (barrel flush)

For stubborn contamination (black specks in output, degraded material smell):

1. Set the zone temperatures according to the material being purged out — there is no single figure, it depends on what is currently in the barrel
2. Purge at high flow rate (250+ mm³/s) to mechanically push out contaminated material
3. If needed, run something through the barrel to scrub it — see below

What to purge with

	What it is	Temperature
Injection-grade PP	The cheap option: a commodity polypropylene of the kind used for injection moulding. Flows easily and pushes the old material out mechanically	Its own, low
Dyna-Purge F	Purpose-made, non-abrasive, for extrusion and injection	160–302°C — covers PLA and PETG
Airtech Dahlpram SP209	Purpose-made, non-abrasive, designed for pellet-fed additive machines	Dahlpram range published as 254–410°C

Not the printing PP

The cheap purge is a commodity injection-moulding polypropylene, not the PP sold as a printing material. The printing grades — Formfutura’s among them — are premium compounds, and buying one to flush a barrel with is an expensive way to do a cheap job.

Check the compound reaches a temperature this machine has

The G1’s extruder tops out at 280°C. A compound whose range starts above the temperature you can actually reach will not do its job — Dahlpram’s published floor of 254°C leaves a narrow window at the top of the machine, while Dyna-Purge F’s 160°C floor sits comfortably inside the range PLA and PETG already print at.

Read the datasheet for the grade you buy before running it.

Fibre-filled grades are not a purging medium

PETG GF and PETG CF do not scrub the screw. Fibre-filled material is also expensive, so purging with it costs real money and leaves the contamination where it was. Use PP or a purging compound.

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Technical specifications

Parameter	Value
Screw compression ratio	2:1
Extruder assembly weight	11 kg
Drive	NEMA 34 stepper + 5:1 gearbox, screw coupled to the gearbox output
Motor driver	DM860T (see Main extruder motor)
Operating voltage	55V via step-up converter

The weight is relevant for robotic arm integration or remote head mounting setups.

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Removing the screw for deep cleaning

The motor, gearbox and screw form a single body — the screw is held to the gearbox by a coupler. To pull the screw you extract that whole assembly upward. The extruder itself stays mounted on the carriage.

1. Bring the extruder up to printing temperature and keep it hot — the screw will not come out of the barrel cold
2. Remove the 4 vertical screws connecting the gearbox to the 3D-printed part E01
3. Lift the motor + gearbox + screw assembly out through the top, turning it by hand as you pull to walk the screw out of the barrel
4. Clean the screw and the barrel bore
5. Reassemble in reverse order

Keep the screw locked to the motor

Before pulling, command a minimal extrusion from the display — a value of about 10 is enough. This puts the motor in holding torque, so the screw stays locked to it and turns together with the assembly instead of spinning freely inside the barrel.

Caution

Do not detach the extruder from the carriage for this. The 8 M5×18 CIL screws + 8 M5 washers (assembly manual step 2.1, parts V04 and R01) secure the whole print head to the gantry plate — that is a separate operation and is not needed for cleaning the screw.

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Preventing screw clogging

• Keep Feeding Zone (T0) at the recommended temperature for the material — too hot causes pellets to melt before they enter the compression zone, forming plugs
• Use SmoothFlow — it stops PETG from sticking to the steel of the screw in the Feeding Zone. Without it the material cakes onto the screw and the stepper starts losing steps
• Do not leave the machine at printing temperature for extended periods without extruding — material degrades and can burn onto the screw

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Related notes

• Main extruder motor
• Multi-Heating Zones
• Nozzle and barrel clog
• Extruder motor skipping
• SmoothFlow
• Barrel clog purging procedure