Dead spots
Direction-change corners and areas around plugs or valve pins can trap old resin.
HOT RUNNER PURGING
Purge Hot Runner
Purge Hot Runner
More Than Just Non-GF
Glass-fiber-free is the first condition — but resin, manifold and nozzle temperature, gate, valve pin and mold maker advice must still be checked before purging compound enters the system.
Current Product Lineup reference No glass-fiber grades recommended Mold manual takes priority
WHY HOT RUNNERS ARE DIFFERENT
Color out of the barrel does not mean a clean manifold
Judge purging by parts from every cavity — each branch differs in residence time and gate opening.
Thermal history
Long-held resin in hot zones may degrade and shed black specks later.
Flow imbalance
Each drop replaces old color at a different pace, so record results per cavity.
Gate restriction
Small gates and nozzles make purging-compound limits and steps matter more.
THREE GATES BEFORE A TRIAL
Clear these 3 gates before purging compound enters the mold
Must be glass-fiber-free
Glass-fiber grades such as NewEX, RX and PX2 must never pass Hot Runner; gates and fine flow parts are at risk. RX is Not yet available in Thailand.
Inside the temperature range
Check barrel, nozzle and manifold, not one setpoint, plus the next resin temperature.
System permits through-purging
Check the Hot Runner and mold maker manual, gate opening method and specific bans before every start.
Non-GF does not mean automatic Hot Runner approval: Some glass-fiber-free formulas still lack direct Hot Runner listing — verify the latest documents and the real system.
CURRENT PRODUCT LINEUP
4 maker-listed Hot Runner grades
Pick by cleaning goal, old and new resin, temperature and residue needs — never by grade name alone.
Verify the Asahi Kasei product lineupRU
Balanced cleaning power and residue
The maker lists RU as the all-purpose grade balancing cleaning power and residue, for sealing and Hot Runner.
RE
Transparent and free-flowing resins
For low residue including some low-temp engineering plastics; maker-listed for Hot Runner.
SL
Rinsing and sealing
Focused on system rinse-out and low-residue jobs; maker lists sealing and Hot Runner use.
PF
High-temp resins 280-420°C
Glass-fiber-free formula with high thermal stability and less fuming; maker-listed for sealing and high-temp Hot Runner.
Property summaries above come from the Asahi Kasei Product Lineup page as reviewed — not a confirmation that any grade fits every mold.
VALIDATED WORKFLOW
Plan trials from barrel to every cavity
Pressure, speed, shot and gate-opening details must follow machine, mold and grade documents — never fixed web values.
Confirm permission
Check the Hot Runner manual and mold bans before passing foreign material through the manifold.
Record the baseline
Time, material and shots until every cavity passes, before ASACLEAN.
Purge the machine section first
Ready the barrel, screw and nozzle before judging the Hot Runner section.
Controlled system pass
Use confirmed grade and parameters with gates and valves verified working.
Rinse and check every cavity
Displace with next resin, record per-cavity results, stop at defined pass criteria.
Scope:
This content screens and prepares trial plans, not a running SOP — operators must follow machine, Hot Runner mold, product documents and plant safety measures.
FAQ
Key questions before purging Hot Runner
Can every ASACLEAN grade run Hot Runner?
No — pick glass-fiber-free formulas the maker lists as supported, and verify resin, manifold and nozzle temperature and mold terms. Glass-fiber grades such as NewEX, RX and PX2 must never pass the system. RX is Not yet available in Thailand.
Can PX2 run Hot Runner?
No — PX2 is a glass-fiber grade for high temperatures, so Hot Runner is barred. For a glass-fiber-free high-temp grade the maker lists for Hot Runner, consider PF per resin, temperature and system terms.
Why does old color persist in some cavities?
Flow imbalance, uneven valve and gate opening, uneven temperature, or branch holdup. Record per-cavity results and inspect the system — do not add purging compound without analysis.
Is purging barrel and nozzle alone enough?
Only when the manifold holds no problem. If parts still show old color or specks from some cavities, assess the Hot Runner section separately from the barrel.
What data sharpens grade choice?
Old and new resin, color, all-zone temperatures, gate and valve type, cavity count, system brand, machine size, observed symptoms and mold-maker bans.
SYSTEM SCREENING
Send Hot Runner data
Send Hot Runner data
before trial planning
Technicians use this data to screen grades and verification items — never one formula for every system.
Old to new resin and color
Barrel, nozzle and manifold temperatures
Open gate / valve gate and cavity count
Hot Runner brand and manual bans