Rotational Molding worked example

Mold Arm Utilization at 68% target arm utilization: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop target arm utilization to 68%, then walk the calculation through step by step. Mold Arm Utilization measures what share of a rotomolding machine's spider arms are actually carrying molds and cycling product versus sitting empty.

The inputs for this scenario

Arms actively molding parts: 8 units (held at the documented default)
Total mold arms on the machine: 250 units (held at the documented default)
Target arm utilization: 68 % (the input this scenario stresses; the baseline uses 95)

Working through the calculation

The calculation starts from the formula this tool documents: Mold Arm Utilization rate = affected amount ÷ total amount.
Rate works out to 3.2 % at these inputs, and this is the headline figure for the scenario.
Gap to target works out to 64.8 points at these inputs.
Affected count works out to 8 count at these inputs.
Total count works out to 250 count at these inputs.

How this compares with the baseline

Against the tool's baseline example, where target arm utilization sits at 95% and the headline result is 3.2 %, this scenario lands almost exactly on the baseline at 3.2 %.
The practical read: the gap between this scenario and the baseline is entirely attributable to target arm utilization, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It counts arm occupancy, not cycle quality — an arm loaded with a slow-curing or oversized mold can hurt throughput even at 100% utilization.

Results at a glance

Rate: 3.2 % (headline result)
Gap to target: 64.8 points
Affected count: 8 count
Total count: 250 count

Run it with your numbers

To rerun this with your own numbers, open the live Mold Arm Utilization calculator, set target arm utilization to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.