KEVOS® MAKEOS · Manufacturing
Injection Moulding Clamp, Shot, Cooling and Cycle Estimate
What clamp force and shot size does this mould need, how long will it take to cool, and how many parts per hour will it make?
First estimate for an injection moulding job: clamp force from projected area of the cavities and runner and the cavity pressure with a margin, shot volume and mass against the barrel capacity, cooling time for the wall thickness from the plastic’s thermal diffusivity and the melt, mould and ejection temperatures, cycle time and output per hour.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Mould | ||
| Projected area per part | cm² | Projected area of one part in the direction of mould opening. |
| Cavities | Number of cavities. | |
| Runner projected area | cm² | Projected area of the runner system. |
| Cavity pressure | MPa | Mean pressure in the cavity (about 20–40 MPa for easy-flow materials and thick walls, 40–80 for thin walls and stiff materials). |
| Clamp margin | % | Margin on clamp force. |
| Part volume | cm³ | Volume of one part. |
| Runner volume | cm³ | Volume of the runner (0 for a hot runner). |
| Melt density | g/cm³ | Density of the melt. |
| Cooling | ||
| Wall thickness | mm | Largest wall thickness of the part. |
| Thermal diffusivity of the plastic | mm²/s | Thermal diffusivity of the plastic (about 0.07–0.12 mm²/s). |
| Melt temperature | °C | Melt temperature. |
| Mould temperature | °C | Mould surface temperature. |
| Ejection temperature | °C | Temperature at which the part can be ejected. |
| Other cycle time (fill, hold, open, eject, close) | s | Time for filling, holding, mould movements and ejection. |
| Machine | ||
| Machine clamp force | kN | Clamp force of the machine considered. |
| Machine shot capacity | cm³ | Maximum shot volume of the machine. |
Method and formulas
- Clamp force = (cavities × A_part + A_runner) × cavity pressure × (1 + margin).
- Shot = cavities × V_part + V_runner; barrel use = shot ÷ capacity (20–80% preferred).
- Cooling time t = s² ÷ (π² a) × ln[(4 ÷ π)(T_m − T_w) ÷ (T_e − T_w)] (plate cooling to ejection at the mid-plane).
- Cycle = cooling + other times; output = cavities × 3600 ÷ cycle.
- Example: 4 cavities need 968 kN of clamp and cool in 11.093 s, giving 754.2 parts per hour.
Limitations
- Estimates only; mould flow simulation gives cavity pressure and fill time properly.
- Cooling time assumes a flat wall cooled from both sides.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a moulding machine for a new mould
- Estimate cycle time and output for a quote
- See how wall thickness drives cycle time
Who it is for
- Moulding engineers
- Estimators
- Product engineers
What you get
- Clamp force against the machine
- Shot volume and barrel use
- Cooling time, cycle and output
Interpreting the result
- Cooling time rises with the square of wall thickness: thinner, even walls pay back on every shot.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 584–592. Topic reference; no source tables or recommended settings are reproduced.
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