Regrind is material you’ve already paid for. Start-up scrap, trimmings and rejects go through the granulator and back into the next run, often at a fraction of the cost of virgin compound. Yet on most small extrusion lines it’s the least-tracked material in the building: a few bags by the granulator, and a best guess at how much went back in.
That guess is where money disappears, where colour and quality problems start, and where traceability quietly breaks.
Why it’s worth tracking
- Cost. Every kilo of regrind used is a kilo of virgin compound you didn’t buy. If you don’t know how much you’re reusing, you don’t know what it’s saving you, or what losing it costs.
- Quality. Too much regrind, or the wrong colour or grade, shows up as surface defects, dimensional drift or poor impact performance. Usually after the customer has it.
- Traceability. When a complaint comes in, you need to know which runs fed the regrind that went into that batch. Without records, you can’t.
Treat regrind as its own stock
The single biggest improvement is to stop treating regrind as “the bags by the granulator” and start treating it as a material in its own right.
- Give every bag or octabin an identity when it’s made: a lot number, the grade, and the weight.
- Record where it came from: the job or product it was reground from, and the date.
- Keep grades and colours apart. White rigid, grey rigid and flexible should never share a bag. Anything unknown is quarantined, not mixed in.
- Label it so anyone picking it up knows what it is without asking.
Set a regrind limit in every recipe
Each product should have a maximum regrind percentage, agreed with whoever signs off quality, and some products (often those made to a customer spec) will be zero. Then record what each run actually used, so you can see it was within the limit.
Example. A glazing bead recipe allows up to 18% regrind.
The job needs 489 kg of material in total, of which 88 kg is regrind.
88 ÷ 489 = 18.0%, so the run is right at its limit, and within spec.
Issue it by lot, oldest first
When regrind goes into a run, note which lot it came from. Use the oldest stock first, so nothing sits long enough to pick up moisture or contamination. This is the step that makes traceability work: complaint, to batch, to run, to regrind lot, to the runs that made it.
Reconcile it regularly
Once a week, weigh what’s actually there and compare it with what the records say should be there. The difference is your losses: floor sweepings, contaminated bags thrown away, or regrind used without being recorded. Small, regular checks catch problems while they’re still small.
Start with a spreadsheet
You don’t need a system to start. Our free Regrind and recipe tracker records each run’s regrind use, checks it against the recipe’s limit automatically, keeps a running regrind stock by grade, and shows what reusing regrind is saving you in virgin material.
When the spreadsheet stops being enough
Mannin Systems does all of this as part of the day’s work: booked at the station, checked against the recipe, and traceable from supplier to customer. See regrind stock by lot in the working demo.