Why You Should Insulate Your Injection Molding Machines

APH Team
Dec 29, 2025
3 min read

Insulating the barrel of an injection molding machine is one of the highest ROI (Return on Investment) retrofits you can perform. It typically pays for itself in under a year—often within 6 to 9 months.

Here is a breakdown of why they are used, the available types, and the operational "watch-outs" you need to be aware of.

1. The Business Case (Why do it?)

Energy Savings: The most obvious benefit. Barrels radiate massive amounts of heat. Insulation can reduce the energy consumption of the heater bands by 25% to 40%.
Reduced Load on HVAC: A naked barrel acts like a massive space heater. In the summer, your AC works double-time to fight the heat your machine is generating. Blankets lower the ambient temperature in the plant.
Faster Start-ups: The barrel retains heat during downtime, meaning the machine reaches the set-point temperature faster on Monday mornings or after shift changes.
Heater Band Longevity: By retaining heat, the bands don't have to cycle on and off as frequently (lower duty cycle), which significantly extends their life.
Safety: They prevent operator burns. A naked barrel is 400°F+; an insulated blanket is usually touch-safe.

2. Types of Insulation Blankets

Most blankets are custom-fitted or sold in modular standard sizes.

Standard Fiberglass/Silicone: The most common type. Usually made of a fiberglass liner with a silicone-impregnated outer shell. Good for standard operating temperatures (up to ~500°F).
Ceramic Fiber (High Temp): Used for engineering resins (Peek, Ultem, etc.) that run at very high temperatures. These can withstand continuous usage above 700°F-1000°F.
Aerogel: The "Ferrari" of insulation. It is much thinner than fiberglass but offers superior insulation values. Useful in tight spaces where a thick blanket might interfere with the machine frame or moving parts.
Hard Shells: Instead of soft blankets, these are rigid metal covers lined with insulation. They look cleaner and are more durable against physical abuse, but are harder to remove for maintenance.

3. The "Watch-Outs" (Potential Downsides)

While the benefits are high, insulation blankets can cause process headaches if not managed correctly.

A. Overheating / Shear Heat This is the #1 issue. Injection molding generates heat in two ways: heater bands and shear (friction from the screw turning).

The Problem: If you are running a fast cycle with a high-viscosity material, the screw generates so much shear heat that the barrel naturally overheats. The machine controller tries to cool it down, but the insulation blanket traps that heat inside.
The Result: You lose process control. The material degrades, color shifts, or you get black specks.
The Fix: If you have a zone that consistently overrides its set point due to shear, do not insulate that specific zone (usually the metering zone near the nozzle).

B. Maintenance Access If you have a blow-out or a heater band failure, you now have to unstrap a hot, possibly plastic-coated blanket before you can fix it.

The Fix: Ensure you buy blankets with quick-release buckles or Velcro high-temp closures, not wire ties.

C. Sensor Interference If the blanket covers the thermocouple incorrectly or creates an air gap around the sensor, the machine will read the temperature "under the blanket" rather than the steel barrel temp accurately, leading to wild temperature swings.

The Fix: Ensure the blankets have proper cutouts for thermocouples and junction boxes.

4. Installation Best Practices

Zone by Zone: Do not wrap the entire barrel in one giant sheet. Use separate blankets for each heating zone. This allows you to remove one section for maintenance without exposing the whole barrel.
Nozzle Gap: Leave a small gap near the nozzle. This is a messy area where plastic blow-back is common. If plastic gets inside the insulation, it ruins the blanket and becomes a fire hazard.
Tight Fit: The blanket must fit snugly against the heater bands. Air gaps between the heater and the blanket create a "chimney effect" where hot air rises out the top, sucking cold air in from the bottom, defeating the purpose.

Quick Calculation for ROI

If you want to estimate your savings roughly:

Assume a 1000-ton machine uses ~40kW/h for heating. Insulation saves ~30% = 12kW saved per hour. 12kW x $0.12 (cost per kWh) = $1.44 saved per hour. Running 24/5 (6000 hours/year) = $8,640 savings per year, per machine.

American Process Heat will perform on site measurements and design your insulation to match your machines. Reach out to today to schedule our technical sales representative to visit your facility.