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Fiber Optic Solution Will Melt The Heart Of Your Thermocouple!

October 28, 2015

It had to happen sooner or later. We’re talking about fiber optics vs. thermocouples: which sensor is better at monitoring melt-temperature during the injection molding process?

For years, the all-important melt-temperature monitoring process was strictly a thermocouple thing. But leave it to a Chicagoland vendor (Okay, Futaba of Japan … but they’ve been in Schaumburg for years, right?) to provide a new solution to injection molders’ endless quest for more effective melt-temperature monitoring.  And this breakthrough is just part of a host of process-monitoring products being introduced to the U.S. from Futaba.

But we’re getting ahead of ourselves here:  the fiber-optic sensors offered by Futaba can directly sense the temperature of the melt. These sensors come in long knockout-pin type versions or short flush-mount versions for installation in a mold flow path. Unlike thermocouple-type sensors (which, by the way, Futaba also supplies), the IR type is not affected by the surrounding steel temperature of the mold.  What’s more, it can sense the IR emissions of the melt even as the part cools and shrinks away from direct contact with the sensor.

Whys is melt-temperature sensing so critical? Duh! Because it gives molders critical information into the combined effects of barrel heating and shear heating, okay?  The measured cooling rate correlates with the degree of packing of the part. So, let’s review: if you know the actual plastic temperature as the runner and part cool, it allows better decisions on injection speeds, pack pressures, mold temperatures, cooling time, cycle time and more.

Futaba also says melt-temperature sensing is useful for detecting end-of-fill in mold cavities, because of its fast (8 millisec) response rate. The IR melt sensor is already being used in Japan by major customers such as Toyota, Nissan, Panasonic, and Denso.  The rest of the world will undoubtedly follow suit.

The other sensors offered by Futaba are no slouch, either:

Cavity-pressure sensors: Futaba also markets standard strain-gauge sensors of knockout-pin or button type for those “old-school” types.

Process monitors — the best of both worlds: Futaba’s Mold Monitoring System (MMS) is described as a “simple and smart” hybrid solution for cavity-pressure or melt-temperature monitoring. The eight-channel pressure amplifier is as simple as it is effective. It’s easy to set up and operate with minimum training, and reportedly sells for much less than competing systems. It can operate with a PC link or not. Operators can choose from eight parameters to make accept/reject decisions (peak pressure, area under the curve, etc.).

So, can you sense it?  The heart of your plastic injection molding business is melted by all this, right?


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