Calculator Inputs
The page stays single-column overall, while the calculator fields shift to 3, 2, and 1 columns across screen sizes.
Formula Used
1) Total shot volume
Total Shot Volume = (Part Volume per Cavity × Cavities) + Runner Volume + Cushion Volume
2) Shot mass
Shot Mass = Total Shot Volume × Material Density
3) Fill time
Fill Time = Total Shot Volume ÷ (Injection Flow Rate × Fill Efficiency)
4) Automatic cooling estimate
Cooling Time = [t² ÷ (π² × α)] × ln[(8 ÷ π²) × ((Tm - Tmold) ÷ (Teject - Tmold))] × (1 + Safety Factor)
5) Total cycle time
Total Cycle Time = Fill + Pack/Hold + max(Cooling, Screw Recovery) + Mold Open + Ejection + Mold Close + Misc Delay
6) Hourly output and machine cost
Shots per Hour = 3600 ÷ Total Cycle Time
Good Parts per Hour = Shots per Hour × Cavities × (1 - Scrap Rate) × Utilization
Machine Cost per Good Part = Machine Hourly Rate ÷ Good Parts per Hour
Use consistent units. Temperatures only affect the automatic cooling estimate. Manual mode bypasses the thermal equation entirely.
How to Use This Calculator
- Enter cavity count, part volume, runner volume, and cushion volume.
- Add density, injection flow rate, and fill efficiency.
- Enter pack time and choose automatic or manual cooling.
- For automatic cooling, enter thickness, diffusivity, and temperatures.
- Add recovery, mold movement, ejection, delays, scrap, utilization, and hourly rate.
- Click Calculate Cycle to display results above the form.
- Use the CSV button for spreadsheet export.
- Use the PDF button for a clean downloadable report.
Example Data Table
| Scenario | Cavities | Shot Volume (cm³) | Fill Time (s) | Cooling Time (s) | Total Cycle (s) | Shots/hr | Good Parts/hr | Cost/Good Part |
|---|---|---|---|---|---|---|---|---|
| Sample engineering setup | 2 | 91.00 | 2.36 | 9.33 | 22.29 | 161.53 | 275.76 | 0.1632 |
FAQs
1) What does this calculator estimate?
It estimates shot volume, shot mass, fill time, cooling time, total cycle time, hourly output, and machine cost per part from molding process inputs.
2) When should I use automatic cooling?
Use automatic cooling when wall thickness, thermal diffusivity, melt temperature, mold temperature, and ejection temperature are known with reasonable confidence.
3) When is manual cooling better?
Manual cooling is better when you already have validated cycle studies, machine logs, or shop-floor observations and want the calculator to follow them directly.
4) Why does screw recovery use max(cooling, recovery)?
Recovery often overlaps with cooling. The slower stage controls the waiting portion of the cycle, so the model uses the larger value.
5) Does this include clamp tonnage?
No. This page focuses on timing, throughput, and machine-hour cost. Clamp force checks should be validated separately during process setup.
6) How does scrap affect output?
Scrap reduces good parts per shot. Higher scrap lowers effective hourly output and increases machine cost per acceptable part.
7) What units should I use?
Use cm³ for volumes, g/cm³ for density, seconds for times, mm for thickness, mm²/s for thermal diffusivity, and °C for temperatures.
8) Can I use this for quoting?
Yes, for fast screening. For final quotes, combine these cycle results with resin cost, labor, packaging, tooling amortization, and overhead.