Shrinkage Compensation Calculator

What does this calculator do?

Estimate compensation from cooled dimensions. Local elephant foot or hole offsets differ from proportional shrinkage.

How to use the calculator

1. Collect measurements and check units.
2. Measure several sizes and directions. Use hole compensation or CAD clearance for local mating errors.
3. Record assumptions and check the result before applying it.

How the calculation works

Scale = target/measured. Shrinkage = (nominal − measured)/nominal. Compensation for fraction s = 1/(1 − s).

Practical calculation example

Understanding the results

Measure several sizes and directions. Use hole compensation or CAD clearance for local mating errors.

A ratio correction for a repeatable dimensional error

Shrinkage compensation here means multiplying a dimension so that a repeatable proportional printing error is counteracted. Enter the intended nominal dimension and the measured cooled dimension from the same feature. The calculator reports the required scale and the observed linear reduction. It cannot identify the cause of the discrepancy. Material contraction, motion calibration, extrusion, first-layer effects and measurement technique can all affect a dimension. Before applying a global scale, establish that the error is consistent and proportional across representative sizes rather than assuming every undersized feature is caused by shrinkage.

The inverse is not the same percentage

The scale factor is target / measured. The percentage setting is that factor multiplied by 100. Observed shrinkage is (1 − measured / target) × 100. For a 100 mm target measured at 99 mm, observed shrinkage is 1%, but compensating scale is 100 / 99 × 100 = 101.010101%. Adding exactly one percent gives only 99.99 mm under the assumed process. The difference is small in this example but grows with larger errors. Compensation uses the inverse of the retained fraction, not simply the original fraction added back.

An oversized part also has a result

If a 100 mm target measures 101 mm, the observed shrinkage output is −1%, meaning an observed expansion or positive dimensional deviation. Compensation becomes 100 / 101 × 100 = 99.009901%. The calculator permits this case because dimensional correction can require reducing the model. A negative shrinkage number does not establish that the polymer physically expanded after cooling. It describes only the relationship of the two entered dimensions. Document the sign and investigate the process instead of selecting a familiar material shrinkage percentage to override a contradictory measurement.

Measure after a consistent conditioning period

Measure cooled parts under comparable conditions using an appropriate instrument. Hot dimensions can change as the object cools, and flexible walls can be compressed by caliper pressure. Choose a well-defined feature and measure several positions rather than the largest visible bulge. Keep first-layer regions separate when elephant foot is present. For moisture-sensitive materials, conditioning state may affect dimensions and should be recorded. A measurement with uncertain feature boundaries is a weak basis for changing an entire model. Repeated readings and repeat prints reveal whether the apparent error is stable enough to compensate.

Distinguish proportional errors from fixed offsets

Test at more than one nominal size. If 100 mm measures 99 mm and 50 mm measures 49.5 mm, both suggest a 0.99 retained ratio, consistent with a proportional model. If both dimensions are instead 0.5 mm short, their scale ratios differ and a fixed offset is a better description. Small holes can have their own errors from path geometry and material deposition. Enlarging the whole object to correct one hole changes every other dimension. Use CAD clearance or suitable slicer compensation for local fit issues, and reserve global scaling for evidence that supports it.

Different axes may require different treatment

A printed part can behave differently in X, Y and Z because of orientation, layer structure and process conditions. This calculator handles one measured dimension at a time. Repeat it for each axis or feature you are investigating, then compare the factors. A single uniform factor is only justified when the relevant errors are sufficiently similar for the application. Applying different axis scales can distort circles and interfaces, so evaluate the geometry consequences in CAD or the slicer. A correction to one measured axis is not proof that the entire part is now dimensionally accurate.

Do not confuse clearance with shrinkage

A moving or mating assembly needs intentionally designed clearance even if both parts print at their nominal dimensions. The required gap depends on the particular design, surface quality and function; there is no universal value supplied here. If a shaft and hole do not fit, measure both separately and compare their intended dimensions before scaling either model. Compensating an observed error and designing a useful gap are related but distinct operations. Keep the corrected model dimension and the functional clearance calculation traceable so an adjustment is not accidentally applied twice.

Validate using a second printed sample

After selecting a justified factor, apply it once, reslice and print another representative sample under the same conditions. Measure the new cooled result instead of trusting the arithmetic alone. If the correction overshoots or varies between runs, revisit the error model or process stability. Record original target, measured result, selected factor, material, temperature and orientation. Use the model-scaling tool to inspect overall dimensions after a uniform change and the build-volume tool to check fit. The compensation result is a proposed process correction, while an accepted physical sample demonstrates whether it meets your specific dimensional requirement.

Advanced tips

• Measure several sizes and directions. Use hole compensation or CAD clearance for local mating errors.

Common mistakes

• Applying global scaling to a fixed hole offset or first-layer bulge.

Frequently asked questions

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.