Ask General Plastics Machines why they use Raytek noncontact IR temperature measurement technology in their thermoforming machines, and they’ll tell you it comes down to the bottom-line benefits: higher product quality, less scrap, fewer rejects, lower energy costs, and higher yields.
In the thermoforming industry, precise temperature control is key to the production of high-quality products. Thermoplastic materials are heated in a thermoforming oven until they achieve the correct softness or "sag," and then molded into the desired shape. Ideally, the thermoplastic sheet should be heated uniformly to its appropriate forming temperature.
Traditionally, thermoformers relied upon specialized manual techniques for sheet temperature control. Operators tried to minimize the difference between the sheet's core and surface temperatures, while ensuring both areas stayed within the material's minimum and maximum forming temperatures. It’s a difficult balancing act, as low heating temperatures can produce stresses in thermoformed parts, and high heating temperatures cause problems such as blistering and loss of color or gloss.
For General Plastics Machines, Inc., a leading Original Equipment Manufacturer (OEM) of single-ended, double-ended and rotary thermoforming machines, infrared (IR) sensor technology provided an automated temperature control solution improving sheet temperature monitoring and cycle control. General Plastics Machines’ custom thermoforming machines are utilized in vacuum, pressure, stretch and drape forming applications.
“With infrared temperature measurement technology, our customers see an improvement in production—and they don’t have as much scrap,” said General Plastics Machines’ President Bob Elder. “They make better quality parts because they get uniform thickness coming out of their thermoforming machine.”
General Plastics Machines selected Raytek to supply its advanced GP Series temperature monitoring system to handle multi-zone sheet temperature control. The Raytek equipment monitors the temperature of plastic sheets passing through the thermoforming machine, allowing the cycle to be set by the surface temperature of the sheet. The machine’s controllability helps to properly heat sheets of varying thicknesses and material types.
Using the Raytek controls, thermoforming machine operators can set a high alarm providing an output signal that goes to the processor and sets the time accordingly. When the process hits the set point temperature, a relay in the GP monitor closes and the alarm sounds.
“I had a customer tell me, ‘When we run the infrared scope, we don’t reject parts. When we don’t run the scope, we do,’” said Elder.
General Plastics Machines’ thermoforming systems also use IR sensor technology to optimize the thermoplastic de-molding process. Thanks to the Raytek Thermalert TX Series infrared sensing head and a GPC panel-mount temperature monitor, operators can maintain consistent cooling temperatures across molds—increasing production throughput and allowing parts to be removed without significant losses due to sticking or deformation.
Elder noted, “Operators sometimes run their ovens too hot, or leave parts in the mold too long. By using our system with the infrared scope, they save 30-40 seconds or more on a four-minute cycle. That makes a real difference in production.”
The Raytek GP Series is a versatile, noncontact temperature measurement system combining a compact, value-priced monitor and an infrared sensing head with coolable housing. The GP Series provides a robust solution for measuring thermoplastic sheet temperatures prior to parts forming.
The heart of the GP system is a 1/8 DIN digital monitor providing advanced infrared processing capabilities, including Peak and Valley Hold, Averaging, and a User-adjustable Offset. The rugged Thermalert GPR sensor is available with standard or close-focus optics, and provides temperature readings with 1% accuracy.
The GPC temperature monitor includes a compact, easy-to-use interface and display for process instruments. This economical, digital panel meter with built-in mechanical relays displays temperature for IR sensing heads and outputs alarm signals when set point temperature is reached. The GPC monitor accepts inputs from any 0–5 V sensor, 4–20 mA sensor, or compatible thermocouple. In addition, it can be used with various Raytek noncontact infrared temperature sensors.
Along with its large 4-digit LED display, the GPC monitor provides a user-defined 4-20 mA or thermocouple output. Two adjustable setpoints/deadbands control 5 V alarm outputs or optional 3 A mechanical relays (GPCM). The GPC monitor accepts 110–220 VAC power and provides a 24 VDC/50 mA excitation voltage, capable of providing loop power to external sensors.
The Raytek Thermalert TX temperature sensor combines high performance, noncontact temperature measurement with industry standard two-wire technology. Smart TX sensors provide digital communications, as well as 4-20 mA output, allowing remote configuration and monitoring. Up to 15 sensors can be installed on a single multidrop network.
The smart TX sensors feature remotely adjustable temperature and output subranges, adjustable emissivity, ambient temperature check, and a user-defined alarm output. Averaging and Advanced Peak/Valley Hold algorithms are provided for accurate measurement of complex discrete processes.
Raytek DataTemp Multidrop software serves as an easy-to-use interface for system configuration and monitoring. The software allows operators to set temperature and output ranges, emissivity and alarm points, and then monitor temperature data from single or multiple sensors on a real-time graphical display. Data can be archived or exported to other applications for analysis and process documentation.
“Thermoformers using our system spend less on electricity because their ovens are not putting out junk parts—they’re consistently producing good parts,” Elder concluded. “It’s a win-win situation.”