KEVOS® MAKEOS · Manufacturing
Injection Moulded Part Cost (Clamp, Cycle, Machine, Material, Mould)
Will my moulding machine run this mould, how many parts an hour will it make, and what does each part cost in machine time, plastic and mould against my target price?
Cost check for an injection moulded part: clamp force from the projected area and cavity pressure, shot size against the barrel, cooling time from the wall thickness, cycle time and parts per hour (as the injection moulding estimate tool), then per good part the machine cost at your hourly rate, the plastic including runner and scrap, and the mould amortised over its life quantity, against the target price.
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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 | Area of one part projected on the parting plane. |
| Cavities | Number of cavities. | |
| Runner projected area | cm² | Projected area of the runner system. |
| Cavity pressure | MPa | Average cavity pressure for the material and flow length. |
| Clamp margin | % | Extra clamp force allowance. |
| Part volume | cm³ | Volume of one part. |
| Runner volume | cm³ | Volume of the runner per shot. |
| Melt density | g/cm³ | Density of the melt. |
| Cooling | ||
| Wall thickness | mm | Thickest main wall of the part. |
| Thermal diffusivity of the plastic | mm²/s | Thermal diffusivity of the plastic. |
| 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 | Fill, hold, mould open, eject and close time. |
| Machine and costs | ||
| Machine clamp force | kN | Rated clamp force of the machine. |
| Machine shot capacity | cm³ | Shot capacity of the machine. |
| Machine rate with operator share | $/h | Hourly rate of the machine with its share of an operator (from the machine hour rate tool). |
| Plastic price | $/kg | Price of the plastic. |
| Scrap rate | % | Share of parts rejected. |
| Mould cost | $ | Cost of the mould charged to this part. |
| Parts over the mould’s charged life | Number of parts over which the mould cost is spread. | |
| Target cost per part | $ | Cost per part you need to reach. |
Method and formulas
- Clamp force = projected area × cavity pressure × (1 + margin); shot = cavities × part + runner; cooling time t = s² ÷ (π² a) × ln[4 ÷ π × (T_m − T_w) ÷ (T_e − T_w)]; parts per hour = cavities × 3600 ÷ cycle (as the injection moulding estimate tool).
- Machine cost per good part = rate ÷ [parts per hour × (1 − scrap)]; plastic per good part = shot mass ÷ cavities × price ÷ (1 − scrap).
- Mould per part = mould cost ÷ life quantity; total against target.
- Example: 754.2 parts an hour; each good part costs 0.36159 $ (machine 0.082015, plastic 0.079575, mould 0.2).
Limitations
- Plate cooling estimate for the thickest wall; ribs and bosses can control the cycle.
- Runner material assumed not reground.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Quote a moulded part
- Compare cavity numbers
- Check a mould suits a machine before a trial
Who it is for
- Moulding estimators
- Product designers
- Production managers
What you get
- Clamp force, shot and barrel use
- Cooling time, cycle and parts per hour
- Machine, plastic and mould cost per good part
Interpreting the result
- More cavities cut the machine cost per part but raise the mould cost and clamp force.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 584–592, 134–146. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Injection Moulded Part Cost (Clamp, Cycle, Machine, Material, Mould) calculator
