Buyers Guide: Energy Metrics for New Injection Moulders

Procurement teams evaluating new injection machines often focus on tonnage, cycle time, and mechanical precision. Energy performance is frequently treated as a secondary consideration, often reduced to a vague annual estimate. This approach leads to poor purchasing decisions. The energy footprint of an injection moulder is determined by specific technical configurations that vary significantly between vendors.

This guide outlines the exact data points to request when evaluating the energy footprint of a new machine. It provides a framework for comparing vendors on equal technical footing. The goal is to move beyond marketing claims and assess the actual energy efficiency of the equipment.

What are the core energy metrics to request?

Vendors often provide general power ratings. These numbers do not tell you how much energy the machine actually consumes during production. You need data that reflects real operating conditions.

Request the following specific metrics from each vendor:

1. Maximum power consumption: The peak electrical demand when all components are active. This determines your site power capacity requirements.
2. Average power consumption per cycle: The energy used during a standard production cycle. This is the most critical metric for long-term cost analysis.
3. No-load power consumption: The energy used when the machine is idle but connected to the power supply. This impacts your energy costs during machine changeovers and downtime.
4. Energy consumption per part: The total energy divided by the number of parts produced. This normalizes the data for different cycle times and part sizes.
5. Power factor: A measure of how effectively the machine converts electrical power into mechanical work. A lower power factor means higher losses and higher utility costs.

These metrics allow you to model the actual energy cost for your specific production profile. You can calculate the annual energy cost based on your planned operating hours and production volume.

How does the hydraulic system affect energy efficiency?

The hydraulic system is the primary energy consumer in most injection moulders. Traditional hydraulic systems use a fixed-speed pump. The pump runs at full capacity constantly. Excess pressure is dissipated as heat through relief valves. This process wastes significant energy.

Servo-hydraulic systems use variable-speed pumps. The pump speed adjusts to match the actual hydraulic demand. This reduces waste. When the system is idle or during low-pressure phases, the pump slows down or stops. Energy is recovered during the injection stroke.

Request the following hydraulic specifications:

Criterion	What to look for	Why it matters
Pump Type	Servo-hydraulic vs. fixed-speed	Servo systems reduce idle energy use and provide better energy recovery.
Motor Control	Direct drive or variable frequency drive	Variable speed control matches output to demand, reducing waste.
Energy Recovery	Presence of regenerative braking or energy storage	Captures kinetic energy during motion phases for reuse.
Hydraulic Oil Temperature	Operating range and control method	Stable temperature reduces pressure losses and improves efficiency.
System Pressure	Maximum and operating pressure settings	Lower pressure settings reduce energy demand per cycle.

Fixed-speed systems are cheaper to buy. They are simpler to maintain. However, they consume significantly more energy over the machine’s lifespan. Servo-hydraulic systems have a higher initial cost. They recover this cost through reduced energy consumption. The choice depends on your production volume and energy costs.

What motor specifications should you verify?

The electric motor drives the machine’s main functions. Motor efficiency is a key factor in the machine’s overall energy performance.

Request the following motor data:

• Motor type: Induction, synchronous, or permanent magnet.
• Efficiency class: The rated efficiency percentage.
• Speed control method: Direct drive or belt drive.
• Power rating: The continuous power output in kilowatts.

High-efficiency motors convert more electrical energy into mechanical work. They produce less waste heat. This reduces the load on the machine’s cooling system. It also lowers your electricity bill.

Variable speed drives allow the motor to match its speed to the machine’s demand. This is similar to the hydraulic system. A motor running at full speed when only partial power is needed wastes energy.

Ask the vendor for the motor efficiency rating at different load levels. Motors are most efficient at their rated load. They are less efficient at partial loads. If your production involves frequent partial loading, this data is critical.

How do cooling loops impact energy consumption?

The cooling loop maintains the mold temperature and the hydraulic oil temperature. It is a significant energy consumer. The cooling cost depends on the design of the loop and the efficiency of the chiller.

Request the following cooling data:

• Cooling power consumption: The energy used by the chiller per hour.
• Cooling capacity: The heat removal capacity in kilowatts.
• Chiller type: Compressor, absorption, or heat recovery.
• Recovery system: Whether the chiller has a heat recovery unit.

Heat recovery systems capture waste heat from the chiller. They can use this heat for space heating, water heating, or pre-heating the hydraulic oil. This reduces the net energy consumption of the machine.

The cooling loop design affects the efficiency of the chiller. A poorly designed loop requires the chiller to work harder. It consumes more energy. Ask the vendor for the loop design details. Look for insulated piping and proper flow rates.

How to calculate the total energy cost?

Energy cost is not just the price of electricity. It includes the cost of the machine’s energy consumption over its lifespan.

Use the following formula to calculate the annual energy cost:

1. Determine the annual production volume in parts.
2. Multiply the energy consumption per part by the annual production volume.
3. Multiply the total energy by the cost of electricity per kilowatt-hour.
4. Add the cost of any heat recovery savings.

This gives you the annual energy cost. Compare this cost for each vendor’s machine. A machine with a higher initial price may have a lower energy cost. Over time, the energy savings can offset the higher purchase price.

Consider the machine’s expected lifespan. Calculate the total energy cost over the machine’s life. This gives you a more accurate picture of the total cost of ownership.

How to standardize vendor comparisons?

Vendors provide data in different formats. Some use annual estimates. Others use per-cycle data. You need to standardize this data to make fair comparisons.

Create a comparison sheet with the following columns:

• Vendor and machine model
• Tonnage and stroke
• Maximum power consumption
• Average power per cycle
• No-load power consumption
• Energy per part
• Power factor
• Hydraulic system type
• Motor efficiency class
• Cooling system type
• Heat recovery system
• Annual energy cost (your calculation)
• Total cost of ownership (over machine life)

Request the same data points from all vendors. Do not accept general estimates. Ask for test data or simulation results. If a vendor cannot provide specific data, this is a red flag.

Use the comparison sheet to rank the machines. The best machine is not always the cheapest. It is the one that offers the best balance of performance, reliability, and energy efficiency for your specific application.

Decision checklist for energy efficient machine selection

Use this checklist to evaluate your shortlist of machines:

1. Data completeness: Have you received all the energy metrics listed in this guide?
2. Hydraulic system: Is the hydraulic system appropriate for your production volume?
3. Motor efficiency: Is the motor efficiency class acceptable for your energy costs?
4. Cooling system: Does the cooling system include heat recovery?
5. Energy cost: Have you calculated the annual energy cost for each machine?
6. Total cost of ownership: Have you calculated the total cost of ownership over the machine’s life?
7. Vendor support: Does the vendor provide real-time energy monitoring?
8. Maintenance: Are the energy-efficient components easy to maintain?

If you cannot answer “yes” to all these questions, request more information. Do not proceed with a purchase until you have a clear understanding of the machine’s energy footprint.

Final thoughts

Energy efficient injection molding machine selection requires specific data. It is not about choosing the machine with the lowest price. It is about choosing the machine that offers the best long-term value.

Focus on the technical details. Request the specific energy metrics. Calculate the energy cost for your production profile. Compare the total cost of ownership. Make an informed decision based on data, not marketing claims.

The energy footprint of your machine will impact your operating costs for many years. Invest time in evaluating the energy efficiency of your equipment. It will pay off in the long run.