What are temperature sensors in the hot runner industry

In the hot runner industry, temperature sensors are mostly used to keep an eye on and control the temperature of the hot runner system during injection molding. This makes sure that the molten plastic flows evenly and steadily through the runner, which stops temperature changes from causing product defects. These sensors need to be very accurate, respond quickly, be able to handle high temperatures, and be stable for a long time. Common types are thermocouples and resistance temperature detectors (RTDs). K-type, E-type, and T-type thermocouples, as well as small thermocouples made just for hot runners, are the most popular choices.

I. Common types of temperature sensors and where they are used


1. Thermocouples Thermocouples are the most frequent temperature sensors in hot runner systems. They are popular because they are small, respond quickly, and can handle high temperatures. Thermocouples are largely classified into the following sorts based on how they work and what they're made of:

K-type thermocouple (NiCr-NiSilicon)

Temperature range: -200 to1300°C is the most typical range, however it can go up to 1200°C.

Features: inexpensive, good linearity, great resistance to oxidation, and works with most standard injection molding methods.

Uses: controlling the temperature of hot runners in general, but especially good for processing common plastics like PE, PP, and ABS.

E-type thermocouple (NiCr-Constantan)

Temperature range: -200 to 0 degrees Celsius900 degrees Celsius

Characteristics: excellent thermoelectric potential, excellent sensitivity, and facile signal collection.

Uses: Keeping an eye on changes in temperature. Sensitive precision injection molding situations, like making medical devices and electronic cases:

Thermocouple T-type (copper-constantan)

The temperature range is from -200 to 350 degrees Celsius.

Features: Good stability at low temperatures, good for processing plastic at low temperatures

Uses: controlling PVC and some biodegradable materials in low-temperature injection molding

Miniature thermocouples made just for hot runners

Suzhou Jingmin Sensors' "hot runner thermocouples," for example, have a small-diameter probe (as small as 0.5mm) and an armored structure design that gives them great mechanical strength and the ability to block interference. They can also be put in tight spaces to get accurate point temperature measurements.

2. Resistance Temperature Detectors (RTDs) are mostly platinum resistance thermometers, such the PT100 and PT1000. They can measure temperatures from -200 to 600 degrees Celsius and are accurate to Class A (±(0.15+0.002|t|)℃).

Features: Very stable and easy to repeat, however they respond a little more slowly than thermocouples.

Uses: Mostly used to keep an eye on the temperature of the outside world or the extra heating zones of hot runner systems. They can also be used with thermocouples to make temperature control more accurate overall.

II. High-End Integrated Sensor Solutions

Some manufacturers have started making composite sensors that sense both pressure and temperature as intelligent manufacturing has grown. For instance, Kistler's 4004A piezoresistive melt pressure sensor can measure temperatures up to 350°C and keep an eye on melt pressure in the hot runner at the same time. This lets you analyze and improve flow behavior in real time. This sensor has a front-end diameter of only 3 mm, so it can be immediately put in injection nozzles or small extruders. This makes it perfect for high-precision injection molding and 3D printing.

These digital sensors can be connected to process monitoring systems like ComoNeo through an RS232 interface or an analog output. They support TEDS (Electronic Data Sheet for Sensors) functionality and can be used for data collection, visualization, and intelligent early warning. This helps to create a "digital twin" injection molding production line.

III. Important Things to Think About When Choosing

When choosing a hot runner temperature sensor, you should think about these things:

Temperature Range: This is the same as the melting point of the plastic being worked on (for example, PC needs to be above 300°C).

Response Speed: The faster, the better, so that changes in temperature are reported right away.

Space for installation: A smaller shape makes it easier to integrate

Recommended protection rating: IP65 and higher to work in complicated industrial settings

Long-Term Stability: Lowers the need for calibration and maintenance expenditures

Compatibility: Works perfectly with current PLC systems and temperature controls