Also called right first time, rolled throughput yield, RTY
What is first pass yield?
The proportion of parts that come out right the first time, with no rework.
What else it is called
- Other names
- right first time, rolled throughput yield, RTY
- In French
- rendement au premier passage
Related entries
Understanding first pass yield
The proportion of parts that pass every operation the first time, counted before any correction. That last clause is what makes the number honest. A part that failed inspection, went back for rework and then passed is not a first-time pass. Counting it as one turns a cost you could have measured into one you cannot see.
The compounding is the part that surprises people. Five operations each running at 95 per cent sound healthy and together deliver 77 per cent, so rework rates that look tolerable station by station add up to a margin problem at the end of the line. Worse, rework is usually performed by the most experienced people available, which means the cost lands on exactly the labour you can least spare.
This is the measure that explains the common and baffling situation of a plant with excellent customer quality scores and disappointing profit. The quality is being achieved by inspection and correction rather than by the process, and the customer never sees what it cost.
How it is calculated
First pass yield = parts completed with no rework ÷ parts started
For a line, multiply the stations’ individual yields rather than averaging them. The compound figure is called rolled throughput yield and it is always worse than people expect.
In practice
If the shipped quality is excellent and the margin is thin, this is usually the number that explains it.
Frequently asked
Does scrap count against first pass yield?
Yes. Anything that did not come out right the first time counts against it, whether it was scrapped or recovered. Scrap and rework are different costs and both are first-pass failures.
What is the difference between first pass yield and the quality factor in overall equipment effectiveness?
They measure the same idea at different scopes. The quality factor applies to one machine in one run. First pass yield is usually stated for a whole process or product, and when it is compounded across operations it is called rolled throughput yield.