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Scrap Rate & First Pass Yield (FPY) Calculator
Calculate scrap percentage, first pass yield (FPY), and multi-stage rolled throughput yield (RTY). Uncover the hidden factory and quantify the true financial cost of material waste and rework labour.
Quality & Waste Optimisation
Scrap Rate & First Pass Yield (FPY) Calculator
Measure First Pass Yield, scrap percentage, and multi-stage Rolled Throughput Yield (RTY). Quantify the true financial cost of scrap and hidden rework labour.
1. Batch Volume & Quality Inspection Counts228 Good First Pass
Gross parts initiated into the production run
units
Parts discarded due to dimensional defects or material damage
scrap
0 (Zero scrap)Scrap Rate: 3.2%Max: 63
Parts requiring deburring, re-machining, re-soldering, or adjustment
rework
0 (100% First Pass)Rework Rate: 5.6%Max: 88
2. Financial & Labour Cost Drivers£42/hr Shop Rate
Raw stock and prior operations cost lost per scrapped unit
£/ unit
25 mins
£42 / hr
3. Multi-Stage Routing & Annual Capacity Model5 Stages Routing
Used for Rolled Throughput Yield (RTY = FPY₁ × FPY₂ × ... × FPYₙ)
stages
1 Stage3 Stages (Fab → Weld → Paint)6 Stages (Full Line)10 Stages
Total units scheduled across all shifts per year
units/yr
Quality & Yield BenchmarkStandard Production
First Pass Yield (FPY)
91.2%First Time Right
Acceptable baseline yield, but rework creates a hidden factory that steals available capacity.
Scrap Rate
3.2%
8 parts lost
Rework Rate
5.6%
14 reworked
Final Yield
96.8%
242 usable
Rolled Throughput Yield (5 Stages)63.1% RTY
If each operation achieves 91.2% FPY, the probability of a part passing all 5 stages without any rework or scrap drops to 63.1%.
Stage 1 Cumulative Yield91.2%
Stage 2 Cumulative Yield83.2%
Stage 3 Cumulative Yield75.9%
Stage 4 Cumulative Yield69.2%
Stage 5 Cumulative Yield63.1%
Financial Defect Impact£925 / batch
Material Scrap Waste£680.00
Rework Labour Loss (5.8h)£245.00
Annual Waste Projection£44,400 / yr
Eliminate the hidden factory with live work order tracking
Synctile identifies quality bottlenecks at individual work centres, tracks rework routing in real time, and prevents scrap from propagating downstream.
Immediate visibility. Visual scheduling for discrete manufacturing.
Production Batch Yield Breakdown & Opportunity Loss
Six Sigma DPMO: 88,000 defects/million
First Pass Right (228 units • 91.2%)
Reworked (14 units • 5.6%)
Scrapped (8 units • 3.2%)
First Pass Yield (FPY)
Measures the percentage of parts completing an operation with zero rework and zero defects. The true indicator of process health.
The Hidden Factory
Rework masks defective processes by making final yield look acceptable, while quietly consuming 15% to 30% of shop floor labour and machine capacity.
Rolled Yield (RTY)
Multi-stage routing compounds defect probability. A 95% FPY across 5 sequential operations results in a Rolled Throughput Yield of only 77.4%.
Quality Metrics Demystified
Understanding First Pass Yield (FPY) vs Scrap Rate vs Final Yield
In high-precision manufacturing, tracking only the final scrap rate creates a dangerous illusion of quality. A shop floor might report an impressive 98% final yield, yet 20% of those finished parts required extensive manual rework, secondary machining, or weld repairs before passing quality control.
First Pass Yield (FPY), also known as First Time Right (FTR), measures the percentage of units that pass inspection on their initial run with zero rework and zero adjustments. It is the purest reflection of true operational stability and machine capability.
Core Mathematical Formulations
SR
1. Scrap Rate
Percentage of total units produced that cannot be salvaged and must be discarded.
Scrap Rate = (Scrapped ÷ Total Units) × 100
FPY
2. First Pass Yield
Percentage of parts that pass inspection without any rework or scrap.
FPY = ((Total - Scrap - Rework) ÷ Total) × 100
RTY
3. Rolled Throughput Yield
Cumulative probability of a part passing all N sequential process stages defect-free.
RTY = FPY₁ × FPY₂ × ... × FPYₙ
The Hidden Factory and Multi-Stage Rolled Throughput Yield
The concept of the Hidden Factory was introduced to describe the hidden capacity absorbed by fixing operational errors. When parts require rework, they consume machine hours, skilled technician time, and floor space that could otherwise produce revenue-generating orders.
Capacity Cannibalisation Rework Steals Machine Hours
When a CNC mill or welding cell re-machines a defective batch, scheduled jobs are pushed back, increasing customer lead times and causing delivery delays.
Impact: Schedule Slippage
Cumulative Multi-Stage Risk Compounding Defect Probabilities (RTY)
If a 6-stage production line maintains 94% FPY at each workstation, the final Rolled Throughput Yield is (0.94)⁶ = 68.9%. More than 31% of all products require rework or scrap before dispatch.
Impact: Margin Erosion
Cost of Poor Quality (COPQ) Sunk Cost Escalation Downstream
Scrapping a raw billet costs only the billet price. Scrapping a machined part after surface treatment, heat treatment, and finish grinding loses all accumulated labour and machine overheads.
Impact: Direct Financial Loss
Six Sigma DMAIC Framework for Scrap Reduction
To systematically eliminate scrap and elevate First Pass Yield towards Six Sigma standards (3.4 defects per million opportunities), top engineering organisations apply the DMAIC methodology:
1. Define
Identify Quality Critical Points
Pinpoint the specific part numbers, work centres, and defect codes driving 80% of scrap costs using Pareto analysis.
2. Measure
Record First-Piece and In-Process FPY
Capture scrap counts and rework labour hours directly at machine terminals to remove reporting lag and human estimation error.
3. Analyse
Root Cause Fishbone Diagrams
Investigate whether defects stem from tool wear, thermal expansion, incorrect clamping pressure, or raw material batch variations.
4. Improve & Control
Poka-Yoke and Visual Buffers
Implement physical error-proofing fixtures, digital tool setting verification, and live work order tracking to sustain high yield.
Concrete Numerical Example of Scrap & Yield Calculations
Consider a batch of 500 precision aerospace brackets processed across a 4-stage machining routing:
- Batch Output: 500 units initiated.
- Inspection Results: 15 units scrapped due to dimensional errors; 35 units required manual deburring rework.
- First Pass Right: 500 - 15 - 35 = 450 units passed first time.
- Scrap Rate: (15 ÷ 500) × 100 = 3.00%.
- First Pass Yield (FPY): (450 ÷ 500) × 100 = 90.00%.
- Final Usable Yield: (485 ÷ 500) × 100 = 97.00% (masking the 35 reworked units).
- Rolled Throughput Yield (4 stages): (0.90)⁴ = 65.61% RTY.
- Financial Impact: At £50 material cost and £40/hr labour with 20 mins rework per part:
Scrap Material Loss = 15 units × £50 = £750.00
Rework Labour Loss = 35 units × (20/60 hrs) × £40 = £466.67
Total Defect Cost per Batch = £1,216.67 (£2.51 added penalty per good unit)
Synctile Shop Floor Control
Prevent scrap cascades with live visual scheduling and rework routing.
When defective parts enter the queue, Synctile isolates rework batches instantly, prevents defective stock from moving downstream, and ensures machine operators always build to the correct revision.
Frequently Asked Questions About Scrap Rate & First Pass Yield
What is the difference between Scrap Rate and First Pass Yield (FPY)?
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Scrap Rate measures only the units that are completely discarded and irrecoverable as a percentage of total output. First Pass Yield (FPY) measures the percentage of units that complete an operation correctly on the first attempt without needing any rework, re-machining, or scrapping. While final scrap rate might appear low (e.g. 2%), FPY exposes hidden defects where 15% of parts required expensive secondary rework.
What is Rolled Throughput Yield (RTY) and why is it important?
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Rolled Throughput Yield (RTY) is the probability that a unit will pass through a multi-stage manufacturing routing with zero defects and zero rework across all sequential operations. It is calculated by multiplying the First Pass Yield of each individual stage (RTY = FPY1 * FPY2 * ... * FPYn). In a 5-stage line where every station has an apparently high 95% FPY, the overall RTY is only 77.4%, meaning nearly a quarter of all finished assemblies incurred rework or scrap along the way.
What is the Hidden Factory in discrete manufacturing?
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The Hidden Factory refers to the undocumented portion of factory capacity, labour hours, and machine time consumed by fixing mistakes, re-machining out-of-spec dimensions, deburring poor laser cuts, and sorting defective batches. Because these parts are eventually salvaged and counted in final yield, standard ERP systems often fail to record the massive capacity drain.
How is the true financial cost of scrap calculated?
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The true financial cost of scrap includes not only the raw material cost of the discarded stock, but also all sunk labour, machine run time, tooling wear, and energy invested up to the point of rejection. If a component is scrapped at the final fifth operation, 100% of the preceding four operations' costs are permanently lost.
How does visual scheduling software help reduce scrap and rework?
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Visual scheduling software like Synctile prevents scrap by ensuring operators work from the latest revision drawings, standardising first-off inspection milestones before running full batches, and routing rework jobs through dedicated queue buffers so standard production flows are not disrupted.