Machine Hour Rate Calculator
How to Calculate Injection Moulding Machine Hour Rate
Calculating the Machine Hour Rate (MHR) is one of the most critical financial exercises for injection moulding manufacturers. It represents the total cost incurred to run a specific moulding machine for one hour. Accurate calculation is essential for quoting profitable part prices, budgeting for new equipment, and identifying inefficiencies in your production floor.
Unlike simple loan calculations, determining the MHR requires integrating capital depreciation, variable energy consumption, labor allocation, and maintenance overheads. Below is a detailed breakdown of the components used in our calculator.
1. Capital Recovery (Depreciation)
The machine purchase price is not a one-time expense; it is an investment that must be recovered over its useful life. The calculation typically follows this logic:
- Machine Cost: The total landed cost of the machine, including shipping and installation.
- Amortization Period: The number of years you expect to run the machine before replacement (often 5 to 10 years).
- Annual Operating Hours: The theoretical maximum hours minus downtime. For a 3-shift operation running 5 days a week, this is often around 6,000 hours/year.
Formula: Machine Cost / (Years × Annual Hours)
2. Energy Consumption
Injection moulding machines are energy-intensive. While servo-hydraulic and all-electric machines have reduced consumption, it remains a major cost driver. To calculate this accurately:
- Determine the Average Power Consumption (kW). Note: Do not use the "Connected Load" rating on the nameplate, as the machine does not draw max power continuously. Use an average (often 40-60% of the motor rating) or measured values.
- Multiply by your local Electricity Rate ($/kWh).
3. Labor Allocation
Labor costs in injection moulding are rarely 1:1. Often, a single operator tends to multiple machines, or automated cells may run unattended.
- Operator Wage: The fully burdened hourly cost of the employee (wages + benefits).
- Machine Ratio: If one operator manages 4 machines, the labor cost applied to the MHR is only 25% of the operator's hourly wage.
4. Maintenance and Overheads
Machines require hydraulic fluid changes, screw cleaning, and spare parts. Additionally, the factory floor space (rent/heating) costs money. A standard industry practice is to estimate annual maintenance and overhead as a percentage of the machine's initial value (typically 3-10%) and spread this cost over the annual operating hours.
Optimizing Your MHR
Once you have calculated your rate, you can lower it by:
- Increasing Utilization: Running more hours per year dilutes the fixed depreciation costs.
- Improving Cycle Time: Faster cycles mean more parts per hour, effectively reducing the machine cost per part.
- Energy Efficiency: Upgrading to barrel insulation blankets or servo-drives to lower kW consumption.