Quick answer: Capacity is accepted packaged output in a defined period. Start with validated cycle and active cavities, then apply actual availability, speed and quality losses, changeovers, maintenance and downstream constraints; load the time-phased forecast and test peak and recovery scenarios before making a commitment.
Decision Inputs
| Capacity layer | Calculation input | Typical error |
|---|---|---|
| Ideal | Scheduled seconds, cycle and active cavities | Using a trial-best cycle or disabled cavity |
| Demonstrated | Availability, performance and quality loss | One plant-average OEE for every mold |
| System | Drying, robot, inspection, assembly and packaging | Counting press output when downstream is constrained |
| Committed | Forecast timing, maintenance, changeover and recovery | Promising monthly averages through peak conflicts |
Define the Capacity Unit
State accepted parts, sets or packages and the period. Clarify active cavities, parts per cavity, pack quantity and whether service stock is included. Use a validated quality cycle, not theoretical machine minimum.
Separate calendar, scheduled and productive time. Record shifts, holidays and planned maintenance. A percentage without its time base is difficult to audit.
Calculate the Ideal Ceiling
Divide scheduled seconds by validated cycle and multiply by active cavities. Adjust for family-mold ratios or insert-loading patterns. This ceiling is a reference for loss analysis, not a customer promise.
Confirm screw recovery, mold thermal state and robot motion remain inside the cycle. A short run may not reveal heat or material constraints that appear over a shift.
Apply Demonstrated Losses
Use mold- and cell-specific downtime, minor stops, slow cycles, startup and reject history when available. OEE can organize availability, performance and quality, but retain the underlying causes. New programs should use justified analogues and visible uncertainty.
Track cavity-level reject and disabled-cavity history. A multi-cavity mold with one chronic cavity should not be modeled at nominal count.
Find the System Constraint
Check resin supply, drying, color change, loaders, temperature controllers, robots, labor, gauges, inspection, assembly, printing, packaging, warehouse and utilities. Accepted output increases only when the limiting operation improves.
Map buffers and warm-part limitations. Faster press output can create deformation or queue without increasing shipped product.
Load the Forecast by Time
Convert demand into required accepted hours by part, mold, machine, material and week. Include changeovers, trials, preventive maintenance, tool moves and qualification. Sequence colors and resins realistically.
Review peaks and simultaneous demand, not only annual average. Identify machines that are truly interchangeable and the approvals required to move a mold.
Commit With Recovery Logic
State normal, surge and contingency capacity separately. Model a press outage, mold repair, material delay and demand increase. Define backup machine, spares, labor, supplier and recovery lead time.
Review actual cycle, yield and loading regularly. Update customers when assumptions change. A reliable commitment explains its boundaries and trigger actions instead of hiding all risk in unused percentage.
Illustrative Capacity Model
Illustrative engineering example—not a claimed CKMOLD customer result: An eight-cavity tool runs a 24-second validated cycle. One cavity is disabled, startup yield is lower after color changes and packaging handles fewer parts per hour than the press. The committed capacity uses seven cavities and the packaging constraint while a repair and downstream improvement are tracked separately.
Buyer Questions
What is the basic injection molding capacity formula?
Ideal output equals scheduled seconds divided by validated cycle multiplied by active parts per cycle.
Why is ideal capacity not committed capacity?
Downtime, speed loss, rejects, changeovers, maintenance, downstream limits and forecast timing reduce deliverable output.
Should one OEE be used for all molds?
No. Use specific history where possible because tools, materials, automation and maintenance losses differ.
What is contingency capacity?
It is recoverable output supported by a defined backup machine, tool, labor, material, approval and lead-time plan.
Buyer Decision Checklist
- Define accepted output, time base, cavities and package unit.
- Use a validated stable cycle and actual active cavities.
- Apply mold-specific availability, speed and quality losses.
- Include startup, changeover, maintenance and trial time.
- Audit material, robot, labor, inspection and downstream constraints.
- Load forecast by mold, machine, resin and week.
- Model peak, outage, repair, material and demand scenarios.
- Separate normal, surge and contingency commitments.
Resources for the Commercial Review
- production injection molding
- multi-cavity injection molds
- mold testing and validation
- injection molding services
Apply the Injection Molding Capacity Planning for Mass Production review to your released design. Share the function, exact resin, annual volume, CTQs, cosmetic limits and launch timing through the CKMOLD project form. If CAD is relevant, send it directly to jerry@ckmold.com; the form does not require an upload.