How do you calculate plastic housing scrap rate?

Divide scrapped housings by total housings molded, then multiply by 100. With 8 scrapped out of 250 molded, scrap rate is 8 ÷ 250 × 100 = 3.2%.

What is a good scrap rate for injection-molded IoT enclosures?

Stable molding processes on consumer enclosures often run scrap below 1–2%. A 3.2% rate is above that band and worth a process or tooling review.

What is the difference between scrap rate and yield?

Scrap rate is the percentage rejected; yield is the percentage good. At 3.2% scrap, molding yield is 96.8% — the two always add to 100%.

Why is my scrap gap to target negative?

The gap subtracts target from scrap rate. Here 3.2% − 95% gives −91.8 points, which shows the target was likely entered as a yield goal rather than a low scrap ceiling.

Should I count start-up shots as scrap?

Count purge and start-up shots consistently with your policy. Mixing them in or out between runs makes scrap-rate comparisons meaningless.

How do I bring housing scrap down?

Attack the top defect first — tune pack and hold for sinks, raise clamp or fix vents for flash, and lift melt temp or injection speed for short shots. Each recovers part of the scrapped material.

Smart Home & Consumer IoT Hardware calculator

Plastic Housing Scrap Calculator

Plastic housing scrap rate is the share of injection-molded enclosures rejected for defects like sink marks, short shots, flash, or weld lines out of the total molded. For smart home and consumer IoT hardware, the housing is the part customers see and touch, so cosmetic and dimensional scrap directly hits material cost and delivery. Tooling engineers and molding technicians track it per run to catch process drift, mold wear, and resin lot problems before a whole build is compromised. High scrap quietly burns resin, cycle time, and machine hours that never become sellable product.

What this calculator does

Estimate plastic housing scrap for smart home and consumer IoT hardware using production-ready inputs so teams can track KPI performance and decide whether corrective action is needed.
Use it when plastic housing scrap in smart home and consumer iot hardware needs a clean rate and gap-to-target you can put on a tier board.
It computes the percentage of molded housings scrapped, then the point gap between that scrap rate and your target.

Formula used

Plastic housing scrap rate = plastic housing scrap count ÷ total plastic housing scrap population × 100
Plastic housing scrap gap to target = plastic housing scrap rate - target plastic housing scrap rate

Inputs explained

Molded housings scrapped for defects:
Total housings molded in the run:
Target scrap rate for the mold:

How to use the result

Use it after a molding run or shift to grade tool and process health and decide whether parameters or the mold need attention.
Scrap rate tells you how much you lost, not why — sink, flash, and short shots each point to different fixes, so pair it with a defect Pareto.

Current U.S. benchmarks

Global copper trades at $13,484 per tonne (IMF via FRED, May 2026), up 41.5% in a year, and U.S. industrial electricity averages 8.66 cents per kWh. Both feed electrified-hardware unit economics.
Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate plastic housing scrap rate? Divide scrapped housings by total housings molded, then multiply by 100. With 8 scrapped out of 250 molded, scrap rate is 8 ÷ 250 × 100 = 3.2%.
What is a good scrap rate for injection-molded IoT enclosures? Stable molding processes on consumer enclosures often run scrap below 1–2%. A 3.2% rate is above that band and worth a process or tooling review.
What is the difference between scrap rate and yield? Scrap rate is the percentage rejected; yield is the percentage good. At 3.2% scrap, molding yield is 96.8% — the two always add to 100%.
Why is my scrap gap to target negative? The gap subtracts target from scrap rate. Here 3.2% − 95% gives −91.8 points, which shows the target was likely entered as a yield goal rather than a low scrap ceiling.
Should I count start-up shots as scrap? Count purge and start-up shots consistently with your policy. Mixing them in or out between runs makes scrap-rate comparisons meaningless.

Last reviewed 2026-05-12.