Idling may feel harmless, but it isn’t free. In fact, it can waste a significant amount of energy, thereby raising production costs. Depending on the machine type, age, and drive system, an idling injection molding machine can consume between 52% and 97.5% of the energy it uses during full production. In other words, a machine that isn’t molding parts may be burning nearly the same amount of electricity as one running at full speed.
That’s a huge price to pay—especially for plastics processing plants with dozens of machines, tight margins, and rising energy bills.
When it pays to switch off
For idle periods longer than 20 to 45 minutes, it’s often more economical to shut a machine down completely and restart it when needed. Modern machines warm up quickly, and the energy saved during downtime usually outweighs the cost of reheating barrel zones or re‑pressurising hydraulics.
At the very least, setting machines to enter a defined idling mode reduces unnecessary consumption:
- Lowering heater temperatures
- Switching off hydraulic pumps
- Turning off compressed air supply
- Stopping cooling water circulation
If your machines don’t have an automated idle mode, it’s worth creating a standard operating procedure so operators know exactly what to shut down and when. Some tips for reduce idling costs:
1. Match the job to the right machine
Running a small mold on a large machine is one of the fastest ways to waste energy. Larger machines have higher base loads, so even when they’re idling, they consume significantly more power. Therefore, use the smallest machine that can safely and reliably run the job.
2. Control your start‑up sequence
When multiple machines start up at once, a plant’s maximum demand can spike, resulting in penalties from your energy supplier. Plan start‑ups better to shave costs:
- Stagger machine warm‑ups
- Start high‑load equipment at different intervals
- Use automated scheduling where possible
3. Measure everything
You can’t improve what you don’t measure. Once you know the relative costs, you can make informed decisions about when to shut down, when to idle, and how to schedule production more efficiently. Track:
- Start‑up energy
- Idling energy
- Full‑operation energy
4. Define a clear idling mode
Every machine should have a documented idling procedure. This might include:
- Reducing barrel heater temperatures
- Switching off hydraulic motors
- Turning off compressed air
- Stopping cooling water flow
- Shutting down auxiliary equipment
5. Make handling systems smarter
Conveyors, robots, dryers, granulators, and cooling systems often run continuously even when the machine they support is idle. Designing these systems to operate on demand only can eliminate hours of unnecessary energy use.
Idling is one of the most overlooked sources of energy loss, but it’s also one of the easiest to fix. Improved planning, machine allocation, and clear idling procedures can all help plants reduce costs. And improving overall operational efficiency ultimately lowers the environmental impact of injection molding.