Additional Manufacturing Reporting Concepts

Throughput Yield

While overall yield is simply P/(P+F), we can consider the "throughput yield" of our process by multiplying the FPY of each stage:

FPY(overall) = FPY(test1) x ... x FPY(testN)

This overall throughput yield gives us the probability that any unit will make it through the entire process without failing.

Note that the more steps you have will result in a lower probability of a unit escaping the line. Every decrease in FPY along the way compounds further down the line.

Units-per-hour (UPH)

UPH is a measure of the total number of units produced in a given hour of production time.

Cycle Time

Cycle time is a metric for how long a process takes. Cycle time can be evaluated for each individual step or for the overall process.

Cycle time is usually reported for each test step. If UPH requirements increase, additional stations for high cycle time tests are required (or test methodology must be improved).

You can track the overall cycletime for a unit through the production line (from start of input to packout). Note that each unit's cycle time can vary depending on any number of reasons:

  • Repairs
  • line down to adjust a station
  • Lunch break
  • Shift change

As such, I recommend tracking an average of each unit's overall cycle time.

Work in Progress (WIP)

Units that have not cleared a test stage or cleared the test line can be considered WIP. Tracking WIP gives you a better idea of what is actually being included in your overall output and yield.

In Repair

I like to have my CMs add two stations to their process flow:

  • FA Checkin
  • FA Checkout

This allows the CM to generate reports indicating how many units are in repair at any given time. The CM can also report how many units have returned to the line but not yet started testing.

Test in Progress

This is a subcategory of failing units.

"Test in progress" tracks units that are currently marked as "fail" but have not fullfilled the retest policy. Since the retest policy is not fulfilled, they are not yet "true failures".

Fail on Line

This is a subcategory of failing units.

"Fail on line" tracks units that have failed beyond the retest policy but haven’t checked into repair.

Loopers

Loopers are units that enter into your repair / return cycle repeatedly. This can simply be 1-2 loops, or like the Hotel California: you can checkin, but you can never leave...