A mid-sized injection molding company producing automotive interior parts decided to replace a 150-ton legacy hydraulic press with a modern, all-electric one. The goal was simple: reduce energy bills, lower peak demand electricity charges, lower maintenance costs, and improve production consistency. We tracked the hydraulic press’s installation and operation for 12 months and compared the results with the previous 12 months. The results showed significant and repeatable savings in energy, demand electricity charges, maintenance, and productivity.
Injection Molding Machine Benchmark: Measuring Traditional Hydraulic Press Performance
Before evaluating energy savings, it was necessary to establish a rigorous benchmark for the legacy equipment. We collected 12 months of historical operating data for the legacy hydraulic press: recorded power consumption, production hours, cycle times, peak demand readings, maintenance invoices, and scrap/quality records. To ensure comparability, we standardized production output and adjusted for seasonal demand fluctuations to ensure consistency.
Operational Overview: The hydraulic press operated in two shifts, producing 300 days per year, for a total annual operating time of 4,800 hours. During active production, the measured average instantaneous power consumption (including heaters, hydraulics, auxiliary equipment, and peripherals) was 45 kW. Additionally, the plant pays a monthly demand charge that reflects its peak power consumption. We recorded an average peak demand of 60 kW for the hydraulic press during combined operation. The machine’s historical average cycle time for a representative part series is 30 seconds, producing approximately 1,200 parts per hour in continuous operation. Due to occasional part warpage and inconsistent processing, the scrap rate averages 3.2%.
Injection Molding Machine Retrofit: Specification and Installation of Energy-Saving Devices
To replace the hydraulic press, they selected a modern, all electric injection molding machine with a matching clamping tonnage and shot volume, optimized for energy efficiency and process control. Key technical differences and installation details determine its energy-saving potential, including:
The all-electric unit features direct-drive servo motors for injection, screw retraction, and clamping operations, a high-efficiency heater control system, and an advanced screw/barrel design to minimize backpressure during plasticization. The controller provides finer profile control, enabling optimized acceleration curves and shorter hold times. This all-electric injection molding machine costs more than a traditional hydraulic unit. However, the company qualified for state-level energy efficiency subsidies and utility incentives for demand reduction; the combined incentives offset approximately $5,000 in incremental investment. We conservatively treated the subsidy revenue as a one-time credit in the project’s cash flow model.
Energy, Demand, and Maintenance Calculations
After the new unit went online, the customer observed significant changes in energy consumption and operating costs. The average load measured during production for the all electric injection molding machine (including heaters, servo drives, and auxiliary equipment) remained stable at 20 kW. Therefore, the average load reduction per machine was 25 kW.
Demand charges were reduced. The plant’s demand charge is $15 per kW per month. A typical demand charge for a hydraulic press is 60 kW. Furthermore, under a comparable production schedule, the new machine’s peak demand charge is 30 kW. The replacement machine reduced monthly demand power bills by 30 kilowatts, resulting in over $400 in monthly demand power savings.
Productivity, Quality, and Environmental Impact
In addition to measurable energy and maintenance cost savings, the replacement also delivered several high-value secondary benefits, enhancing total lifecycle value. These soft benefits are often overlooked but can significantly improve business performance and should be factored into any investment case.
Cycle Time and Output. The injection molding machine boasts faster, more repeatable motion profiles, along with quicker injection and clamping sequence response, resulting in a 10% reduction in average cycle time for the target part family. This improvement increased output from 1,200 parts per hour to 1,333 parts per hour, equivalent to an approximately 11% increase in output. For production planners, this translates to higher capacity utilization and reduced pressure to add shifts during peak demand periods. While maintaining the same utilization rate, approximately 55,200 more parts were produced over the course of a year. In effect, the company redeployed excess capacity to new customers rather than relying on additional overtime, thereby increasing revenue without a corresponding increase in labor costs.
Ultimately
This case study demonstrates that the economic and operational case for energy-efficient injection molding machines is both reliable and repeatable when rigorously implemented. Replacing a hydraulic press resulted in a simple payback period of approximately 1.68 years, direct annual operating cost savings of roughly $23,800, and significant improvements in output, quality, and environmental performance. These results are not isolated cases; similar outcomes have been achieved across many industries when professionally measured and commissioned.
