BACK PRESSURELock the screw, build shear
During purging, ASACLEAN travels toward the nozzle while melt pressure tends to push the screw backward.
Back pressure raises compression and surface contact while the screw still rotates at the front-most position.
Right resistancebecomes scrubbing power
When the screw resists retreating, ASACLEAN pellets get squeezed and rotated across barrel walls and flights more — letting residue purging work at full potential.
How Screw Speed affects purging
Back Pressure builds resistance and compression; Screw Speed sets shear rate, material turnover in flights, and how often ASACLEAN meets metal-surface residue.
More contact cycles
Faster screws flip ASACLEAN across flights more often, more mechanical scrubbing.
Spread force in flights
Right speed keeps melt flowing with no dead points, carrying color and carbon out better.
Must pair with Back Pressure
Speed alone with low resistance retreats the screw easily and scrubbing drops; with Back Pressure holding, rotation converts to more in-barrel scrubbing.
Usage principle: Set Back Pressure to control screw retreat, then tune Screw Speed for even rotation and shear to draw ASACLEAN full cleaning power.
Why the screw must sit front-most (Screw Position = 0)
The key ASACLEAN purging technique: push the screw front-most then set Back Pressure high enough to resist and lock the screw in place near the nozzle (Zero position) — no retreat while still rotating material forward.
- When the screw rotates material forward but Back Pressure holds it from retreating resistance and scrubbing build (Scrubbing action) — mechanical friction between ASACLEAN, flights and barrel walls.
- Cleans dead spots Dead spot and check rings more thoroughly.
- On machines with Back Pressure limits where screws self-retreat, order Short shots / high-velocity shot short shots periodically to push the screw forward instead.
Screw locked near the nozzle (barely moving) while rotating material — ASACLEAN squeezed and scrubbed fully in the barrel.
Back Pressure mechanism and direction
Why screws must retreat while conveying material forward, and how Back Pressure helps.
1. Plastic accumulates ahead
Rotating screws convey and press melt continuously into the front-most section (metering zone).
2. Accumulation pressure (melt pressure)
Melt piled in the confined space ahead of the nozzle pushes the whole screw shaft backward.
3. Back Pressure resists
Machine builds reverse pressure at the shaft tail to slow retreat, pack melt tight, expel air and mix better.
Tune Screw Speed and Back Pressure by site symptoms
Screw speed is no fixed value — start from existing conditions, then tune to real machine and grade symptoms.
ASACLEAN pellets will not fully melt
Unmelted particles exit at nozzle and purge pile.
- Cut screw speed by about 15-20 percent
- Hold temperature
- Add slight back pressure if needed
- Avoid instant temperature cuts
Melts fine but residue stays with black specks
Needs more shear and agitation.
- Raise screw speed within safety
- Raise back pressure for agitation
- Short and high-velocity shots purge nozzle and check ring
Residue after purging
Must chase leftover compound clean out.
- High-but-safe screw speed plus back pressure while pushing compound out
- After RX follow with RE or next resin to kill residue. RX is Not yet available in Thailand.
R-Series setting guide (RU / RE / RX). RX is Not yet available in Thailand.
R-Series is rheology-designed for more cleaning power, less residue — no need to change conditions at once Start from current values, fine-tune screw speed and back pressure by symptoms.
| Grade | Replaces | Highlights | Setting guide |
|---|---|---|---|
| RU | U | Balanced cleaning power with low residue | Current conditions OK — if unmelted cut screw speed by about 15-20 percent; if residue stays raise screw speed plus back pressure. |
| RE | NewE | Low residue for transparent and natural jobs | Hold recommended temps, lean on back pressure to purge compound out. |
| RX | Top cleaning | High cleaning power with Glass Fiber | Cylinder only, no sealing, no in-machine residence, usually followed by RE or resin to chase residue. |
Cases differ by site
Real Thai factory cases show fitting values differ by condition, part type, industry and process context — no single formula fits every machine.
Consider with other factors
Fitting screw speed and back pressure must weigh ASACLEAN grade, real running temperature, resin thermal stability and site symptoms.
CSC sets with you
Send machine, resin, temperature and symptoms for CSC technicians to plan screw speed and back pressure logic for your machine and job.
This content is principle-level guidance; real results depend on resin type, machine, production conditions and grade — always verify the Technical Data Sheet and consult ASACLEAN specialists before real use.
Want Back Pressure & and Screw Speed tuned for your machine?
Send machine, resin, temperature, ASACLEAN grade and symptoms for CSC technicians to plan max-efficiency tuning logic.