Case Study | Sprue & Runner Recycling — Injection Molding Plant Making Appliance Parts
For injection molders, sprues and runners are raw material you have already paid for. Grinding them back into clean regrind on site lets you reuse up to 25% of your feed, cut your virgin-material bill, and clear your workshop floor. Here's how one appliance-parts plant did it.
The customer and the site
Products: injection-molded appliance housings, switch panels and internal brackets, mainly in ABS/PP
Scale: 8 injection molding machines (120–250T), two shifts, ≈20 hours of operation per day
Waste source: every shot carries a sprue and runner; operators snap them off with pliers and drop them into bins beside each machine
Waste volume: 1–2 bins per machine per day — ≈250 kg/day across the plant
Waste form: solid sprues and runners (some with residual material), harder and denser than virgin pellets
How it used to be handled
Sprue was stockpiled for 3–5 days and sold to a scrap dealer at scrap price — or shipped out as industrial waste, at the plant's own cost.
The problems before
Price leakage: selling sprue at scrap price instead of reusing it at virgin price loses several thousand RMB per ton
Outsourced grinding didn't pay: processing fees plus freight — and the material left the plant for good
Workshop burden: piles took up floor space and blocked aisles; in peak season, sprue bins spilled into the walkways
The solution
| Step | How it works |
|---|---|
| Crusher placement | Crusher sits in a centralized area at the back of the workshop, right next to the sprue staging point — plug in and run |
| Feeding | At shift end, workers wheel the collection bins over and dump them straight into the large hopper — no pre-cutting |
| Collection | Drawer-style collection box slides out when full and empties directly into regrind bags |
| Reuse | Regrind blended with virgin material at 15–25% (top up color masterbatch to match); dark-colored and interior parts can take a higher ratio, visible parts keep a lower ratio to protect surface quality |
| Surplus | Unused regrind is bagged and sold at regrind prices — more valuable than raw sprue |
Results (example calculation)
| Item | Figure |
|---|---|
| Sprue recovered per month | 6 tons (250 kg/day × 24 working days) |
| Reused in place of virgin material | 3.6 t/month (60% reuse rate) |
| Raw material saved | ≈ RMB 43,000/month (3.6 t × RMB 12,000/t) |
| Disposal / outsourced grinding saved | ≈ RMB 3,000–6,000/month |
| Total material-side savings | ≈ RMB 500,000/year |
Calculation basis: like-for-like substitution (1 t of sprue reused ≈ 1 t less virgin purchased), before electricity and process losses. Actual savings = reused volume × (virgin price − total regrind cost).
One-liner: Turning 250 kg of daily sprues into reusable regrind — this plant cuts its virgin material bill by roughly RMB 43,000 per month.
Get your own numbers (optional CTA): Tell us your machine sizes, materials and daily sprue volume — we'll calculate what in-plant grinding could save your plant.
Note: Figures are example calculations based on assumed parameters (material price, reuse rate, operating days) and will vary with each plant's actual conditions.
