What does this calculator do?
Spread shared setup over accepted units. Whole-plate time and consumption can differ from a single part multiplied by quantity.
How to use the calculator
- Define the attempted quantity and whether setup applies per plate or per order.
- Assemble a variable cost per attempt without duplicate setup expenses.
- Enter the rejection fraction supported by comparable production records.
- Compare total batch cost, expected accepted quantity and cost per accepted unit together.
How the calculation works
Batch cost = setup + quantity × unit cost; divide by expected accepted units.
Batch cost = setup + attempted quantity × variable unit cost. Expected accepted quantity = attempted quantity × (1 − failure% / 100). Cost per accepted unit = batch cost / expected accepted quantity.
Practical calculation example
Twenty attempts at 3 plus setup 10 cost 70. At 5% rejection, expected accepted quantity is 19, so cost per accepted unit is 70 / 19 = 3.684211.
Understanding the results
Slice the actual plate and check cooling, collision clearance and shared failure risk. Include inspection and packaging of every piece.
Define what a batch quantity means
The quantity input is the number of units attempted in the batch, not a promised number of accepted units after inspection. That distinction drives the denominator of the result. The calculator adds one setup charge to quantity multiplied by the variable cost per attempted unit, then divides by the expected accepted quantity. It therefore answers the cost per acceptable item from a defined production run. It does not automatically add replacement attempts until an order is fulfilled. Use a separate scenario if your actual agreement is to deliver a fixed number of good parts regardless of the number attempted.
Separate setup from repeatable work
Setup includes work that occurs once for the chosen batch boundary: preparing the build arrangement, initial machine preparation, or a shared check whose cost does not grow directly with every attempted unit. Variable unit cost covers the expenses assigned to each attempt. If a plate contains several parts, decide whether setup applies once per plate or once to a larger multi-plate run. A ten-plate order with a setup requirement on every plate cannot be represented by charging only one plate's setup to the whole order. Either sum those setup charges or define the batch as one plate.
Track the yield explicitly
With failure fraction p, expected accepted quantity is attempted quantity multiplied by one minus p. If twenty attempts have a five percent failure probability, the expectation is nineteen accepted units. It is perfectly valid for an expected quantity to be fractional because it represents an average across many comparable runs, not an actual count on one finished plate. The model assumes a stable average rejection fraction and charges variable unit cost to every attempt. It cannot predict exactly which item will fail or whether several parts share a common failure that affects their outcomes together.
Reproduce the default result
Twenty attempted units at 3 each produce 60 variable cost. Adding setup of 10 gives a total batch cost of 70. At five percent rejection, expected accepted quantity is 20 multiplied by 0.95, or 19. The resulting cost per accepted unit is 70 divided by 19, approximately 3.684211. Without rejection it would be 3.50. This example shows both setup dilution and the yield adjustment in one result. The total batch cost remains 70: the calculator divides already incurred cost among expected accepted items rather than increasing spending to purchase unspecified replacement attempts.
Understand economies of batch size
With the same unit cost, setup and yield assumptions, forty attempts cost 130 and yield an expected thirty-eight accepted items. Cost per accepted item is about 3.421053. The improvement comes from distributing the unchanged setup charge over more accepted units; it does not come from reducing the variable cost of each attempt. At very large quantities, the setup share approaches zero and the result approaches unit cost divided by the acceptance fraction. These assumptions fail if larger runs require extra setup, different support layouts, higher reject rates or overtime. Recalculate those inputs instead of extrapolating blindly.
Distinguish shared failures from average yield
Several parts on one build plate may be affected by the same adhesion problem or interruption. The expected accepted quantity can still be represented by a meaningful long-run average yield, but the variability of one batch may be much greater than independent item failures would suggest. This tool does not calculate that variability, a confidence interval or the chance of completing a specific order. Keep production records at a useful boundary: attempted units, accepted units, shared interruptions and their costs. For a new layout, a small trial can inform the yield input better than copying an unrelated machine's historic rejection fraction.
Compare layouts with the same delivered requirement
A denser plate might reduce setup per item but lengthen the job or complicate removal. A sparse layout could have higher setup share yet lower individual finishing effort. Assemble variable unit cost consistently before comparing them. If a support strategy changes mass and removal time, both belong in the updated unit input. Do not compare a layout costed before inspection with one costed through finished delivery and conclude that the first is cheaper. A comparison is only useful when both alternatives cover equivalent quality, finishing and packaging. This calculator's arithmetic cannot repair inconsistent cost boundaries.
Use the estimate to plan, then reconcile
After completing a run, compare the observed total cost and accepted quantity with the inputs. Replacing expected yield with the actual accepted count gives an actual cost per accepted item for that run, provided the cost boundary is unchanged. Keep the expected result for forward planning and the realized result for process improvement; they serve different purposes. If no units are accepted, the actual division is undefined and the loss needs separate reporting. Avoid treating a near-one-hundred-percent rejection scenario as an ordinary quotation. It signals a process that needs correction before reliable pricing or delivery promises can be made.
Advanced tips
- Charge repeated plate preparation at the same boundary used for quantity.
- Revisit unit cost and yield when a denser layout changes supports or finishing.
Common mistakes
- Entering the required good-part order quantity as if it were attempted quantity.
- Adding a second reject allowance to a unit cost already adjusted for yield.
- Assuming a fractional expected quantity is a guaranteed physical output.
Frequently asked questions
Does the tool buy replacement attempts for rejected parts?
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No. It costs the entered run and spreads that cost over its expected accepted items.
Why can accepted quantity have decimals?
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An expectation is a long-run average. A real batch always contains a whole number of accepted items.
Can every part fail together?
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Yes, shared failures are possible. This calculator models average yield but not the distribution of correlated batch outcomes.
Sources & methodology
Mathematical results depend on the supplied inputs. Material properties and machine limits need confirmation for your exact equipment. Editorial specialist approval remains pending.