Max Volumetric Speed (MVS)

The maximum rate, in cubic millimeters per second (mm³/s), at which the G1 pellet extruder can melt and push out plastic. With Klipper-driven pellet printers like the G1, MVS — not motion speed — is usually the limiting factor for print speed.

Why MVS matters

Set too high, the screw can’t push enough material against the back-pressure. The extruder stepper draws maximum torque, can’t deliver, and starts skipping steps. You’ll hear the characteristic “tak-tak-tak” and see the screw coupler jerk instead of rotating smoothly.

The G1’s mechanical kinematic limit is about 300 mm/s. You’ll rarely reach that — extrusion is what slows things down. Recommended print move speeds:

Normal printing moves: 120–150 mm/s
Travel moves: up to 300 mm/s

Reference values

Material	Safe MVS
Virgin PLA	~250 mm³/s
Virgin PLA + SmoothFlow	~300 mm³/s
Recycled PLA + SmoothFlow	~300 mm³/s
PETG	~250 mm³/s
PETG + SmoothFlow	up to ~400–500 mm³/s
With Liquid Masterbatch	reduce — masterbatch lowers screw grip

MVS vs. nozzle diameter

Smaller nozzles increase back-pressure and reduce achievable MVS:

Nozzle	Max MVS (mm³/s)	Example layer	Print speed
8 mm	~500	10 mm × 5 mm	~10 mm/s
3 mm	~300	4 mm × 1.5 mm	~50 mm/s
1 mm	~150	1.2 mm × 0.6 mm	~208 mm/s

Symptoms of MVS too high

Stepper motor “clicks” or “tak-tak-taks” — see Extruder motor skipping
Screw coupler visibly jerks (look from the right side of the extruder)
Under-extrusion at high-flow regions (infill, large features)
Audible torque struggle from the motor

Fixing high-MVS issues

When the motor skips:

Reduce print speed in real time from the display or Mainsail until smooth
Stop the print and lower MVS in Ginger Slicer before restarting

To recover lost speed without lowering MVS:

Raise the temperature by 5–10°C (more flow without lower speed)
Add SmoothFlow (reduces friction so the screw can push faster)
Combine both — usually the most effective

Switching to a larger nozzle without increasing MVS

A common mistake: switching from a 3 mm to 8 mm nozzle but keeping the same MVS (e.g. 250 mm³/s). The larger nozzle can theoretically flow much more, but the slicer is still capped at the old value → the print takes longer, not shorter.

Fix: when switching to a larger nozzle, increase MVS in the material profile to the new nozzle’s safe limit (see table above). For an 8 mm nozzle with PLA, 400–500 mm³/s is achievable.

Special considerations

Liquid Masterbatch + high MVS

Masterbatch reduces the friction between pellets and screw. At high MVS, the screw stops “biting” and you get under-extrusion. Lower MVS or reduce masterbatch percentage to restore grip.

Insufficient layer cooling

If small parts deform, layers haven’t cooled in time. Don’t fix with MVS — increase Min Layer Time in the slicer’s cooling section.

Where to set MVS

In Ginger Slicer:

Open the material profile
Find Max Volumetric Speed (under speed/cooling settings)
Set the value
Save the profile and re-slice

Tuning workflow

Start at the safe value for your material
Slice and print a test cube
Listen — any “tak-tak”? Any irregular extrusion?
Yes → lower MVS by 25 mm³/s, retest
No, smooth print → optionally try increasing temperature or adding SmoothFlow to push higher
Save the final value in your material profile

Sources

Ginger Academy — Ginger Slicer