Injection molding · Materials
Regrind Blend Calculator
Turn an approved regrind percentage into a virgin-and-regrind weighing recipe in kg or lb. See the material weights, blend shares, and both ratio directions in one batch recipe.
Formula and method
Regrind mass = total batch mass × (regrind % ÷ 100)
Virgin mass = total batch mass − regrind mass
The entered percentage is the regrind share of the finished virgin-plus-regrind batch. It is not a percentage added on top of the virgin mass.
Inputs and units
Enter the target finished batch mass and a regrind percentage already approved for the exact job. Choose kg or lb; the selected unit applies to virgin, regrind, and total mass.
Worked example
For a 500 kg batch at 20% regrind, weigh 400 kg virgin resin and 100 kg regrind. The split is 80% virgin / 20% regrind: 4:1 virgin-to-regrind and 1:4 regrind-to-virgin.
Use the result for weighing
Transfer the virgin, regrind, total, unit, and approved percentage to the batch or setup record. Recalculate when the target batch changes.
Checks before blending
Confirm clean and segregated regrind, material identity, drying and contamination controls, scale consistency, lot traceability, and the required production trial.
Important limitation
This calculator never recommends an allowable regrind percentage. Material history, part performance, appearance, customer specifications, and regulatory requirements can change the approved limit.
References: Movacolor MCTC recipe calculations and BASF Ultradur processing notes.
Next calculation
FAQ
Is the 20% default a recommendation?
No. It is an arithmetic example only. Enter a limit approved for the exact material and job.
Why show both ratio directions?
An 80% / 20% blend is 4:1 virgin-to-regrind and 1:4 regrind-to-virgin. Showing both labels prevents an unlabeled ratio from being read backwards; the 0% and 100% boundaries are written as material-only states.