1Resin Loss never happens only at part injection
Tracking only post-startup rejects hides color-change, plastic-type-change, trial-shot, screw-purge scrap and hopper-held material from reports. The straight method is Mass Balance from warehouse resin entry to good parts
Visible losses
Rejects, specks, color contamination, short shots, flash and weighable trial-shot parts
Hidden losses
Machine stoppage time, purge material, in-system held pellets, contingency production and sorting labor
2Pie chart: scrap starts before the mold
Sample analysis of 103 scrap samples in the source splits process-level causes into 3 big groups. The point: Prep work 46% Outweighs direct injection. Never start fixes with machine-parameter tuning alone.
Scrap causes by step
n = 103 · FY1998Material bags 22% plus incomplete purging 24%46%
Heat-burnt and degraded resin24%
Molds 20% plus dust and others 10%30%
Check 4 easily missed contamination sources
3Why burn residue and specks return
Molten resin grips barrel and screw metal surfaces. Longer hot holds with oxygen exposure degrade it, stickier to metal, slowly becoming carbon flaking into parts. End-only fixes let specks return.
Sealing
Sealing. Never leave barrels empty during stops. Plan system sealing on long stops to cut degradation-accelerating air.
Routine Cleaning
Routine Cleaning. Purge on schedule before budding residue hardens into screw-pull carbon.
Read deeper at Carbon and Black Specks article And prevention at Routine Purging & Sealing
4Bar chart: compare total cost, not per-kilo price
The source case runs a 125-ton machine switching black ABS to white PP, comparing ASACLEAN purging compound against white-PP material chasing. Figures below hold for those terms only.
Black-ABS to white-PP case
Illustrative case, not a guarantee| Item | With compound | PP-chased | Case difference |
|---|---|---|---|
| Asaclean | 0.6 kg | 0 kg | — |
| White PP | 0.4 kg | 10 kg | 9.6 kg less PP |
| Total time | 7 min | 35 min | 28 min shorter |
| Direct cost per original assumptions (THB) | About THB 169 | About THB 445 | About THB 276 less per round |
Converted from source figures for Thai-context cost reading, using the 100 JPY = 29.6498 THB midpoint of the Bank of Thailand 31 Jul 2026, rounded to nearest baht
What Thai plants should do: Substitute real pellet costs, per-minute machine cost, labor, reject and waste-disposal costs, logging from last good part to first good part under identical gates
55 repeatable scrap-cutting steps
Make loss visible in kilos, minutes and baht
Split rejects, purge scrap, trial shots, runners, held material and downtime by machine, job and shift
Find true causes
Separate old color, old resin, burn residue, paper, thread, metal, grease and dust so no problem defaults to bad machine settings
Kill causes, stop repeats
Fix bag-opening methods, switch air-blowing to vacuum dust collection, cover grinders, and match purging compound to resin type and temperature range
Confirm with Controlled Trial
Same machine, job, color, amounts and good-part gates, comparing baseline vs new method over at least several rounds
Standardize what works
Log SOPs naming purging-compound amounts, temperature, screw cycles, Back Pressure, shot order, end gates and owners
6How to pick injection purging compound for real loss cuts
Never judge on high cleaning power or per-kilo price alone. Fitting compound must carry old residue out, chase quickly with job pellets, leave no residue, and run inside the process temperature range.
Still unsure? Use Smart Grade Selector For preliminary screening, then have technicians confirm against real machine terms before trials
7FAQ
Where to start cutting injection-process loss?
Start from mass balance splitting received material, good parts, rejects, color-change scrap, trial-shot jobs and held material. Then fix the heaviest cost or time point.
How does injection purging compound differ from job-pellet purging?
Compound is built to carry residue, color and old resin out of screws and barrels. Job pellets serve as part-production material. Effectiveness needs machine and real-change trials to confirm.
Can the 94%, 6%, 46-24-30% figures benchmark today?
No. Figures come from ASACLEAN FY1998 training-data cases explaining loss structures only. Plants should use their own current baselines.
Will purging compound end specks forever?
No single method guarantees every case. Jointly control hold time, temperature, air, sealing, hopper, grinder and mold cleanliness and purge steps.
Where is your machine loss?
Send resin, color, machine size, changeover time and scrap amounts for technician-planned Controlled Trials