Factory Digitalization_Ver04. _ Why Sand-Casting Output Never Matches the “Theoretical” Count
- shigenoritanaka3
- 3月12日
- 読了時間: 3分
Mar 12, 2026
Hello everyone,
Today I'd like to talk about a common issue in sand casting: the gap between the “theoretical production quantity” and the actual number of castings produced.
In sand casting, it is common practice to calculate production quantity using:
Number of molds × Cavities per mold × Number of pours
However, this theoretical value never matches the actual number of castings produced.
This discrepancy distorts everything that depends on accurate production numbers:
Defect rate
Cost accounting
Production control
In this article, I explain the most practical and reproducible method to determine the true production quantity in sand casting.
1. Why the Theoretical Quantity Is Always Higher Than the Actual Output
In real casting operations, various in-process losses inevitably occur:
Misruns
Poor filling
Empty molds
Breakage during handling
Therefore,
(Molds × Cavities × Pours) = Theoretical Quantity
represents only the maximum possible output and never equals the actual number of castings produced.
Despite this, many foundries still use this theoretical value to calculate defect rates - which naturally leads to incorrect results and misguided improvement activities.
2. What Goes Wrong When Theoretical Quantity Is Used as “Production Quantity”
Using theoretical quantity as the production quantity causes:
Incorrect defect rates
Distorted cost accounting
Misleading gross margin analysis
Inaccurate productivity evaluation
Wrong prioritization of improvement actions
In short, the entire decision-making process of the factory becomes misaligned.
3. The Most Accurate Method Is “Total Inspection Count” - But It Comes Too Late
The total number of inspected castings is the most accurate measure. However, in sand casting:
Inspection often occurs several days after production
Cost accounting deadlines cannot wait
Production control requires same-day data
This means inspection data lacks real-time availability, which is a critical weakness.
4. The Best Solution: Measuring Actual Output Using a Scale After Shot Blasting
The most practical and accurate method is:
Measure the total weight of castings immediately after shot blasting as the last production process.
Here is the workflow:
Step 1: Install a Barcode Reader on the Scale PC
The operator first scans the production batch ID, which is generated at the time of pouring.
This identifies which batch the castings belong to.
Step 2: Link Required Information to the Batch ID
Pallet weight (fixed value)
Single-piece weight (master data)
Total measured weight (real-time)
All of these are linked to the batch ID.
Step 3: Automatic Calculation by the System:
Actual Quantity = (Total Weight – Pallet Weight) / Single-piece Weight
Step 4: The Correct Production Quantity Is Determined Immediately
This enables accurate data for:
Cost accounting
Defect rate calculation
Production control
Traceability
DX data infrastructure
Everything starts running on correct numbers.
5. Benefits of This Method
Accurate cost accounting
Correct defect rates
Improved productivity evaluation
Visibility of hidden losses
Higher precision in improvement activities
Easy integration with IoT, barcode systems, and MES
Strong foundation for digital transformation
In other words, this method finally establishes a reliable numerical foundation for sand casting operations.
Summary
In sand casting, using theoretical production quantity as the actual production quantity is a fundamental mistake.
The correct production quantity can only be obtained through:
Weight measurement after shot blasting × Batch ID linkage × Digital integration
This approach provides real-time accuracy and directly improves both cost accounting and production control.
If you'd like to discuss this topic or explore improvement opportunities, feel free to contact me. 60-minute free consultation: info@metricjapan.com
I am here to support your improvement activities.
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