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| Theller Engineering
707-762-3820 Designers of the
world's most advanced hot tack machines.
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Computer Control | Specifications The model PC2 Heatsealer, with full graphics capability, makes heatseals under conditions simulating vertical form/fill machines. When configured in the alternative analytical mode, it provides accurate heatsealability measurement for comparison of materials at known interface temperatures. When heatseals from the PC2 are tested for strength on its companion machine, Theller's Model D Mini Tensile Tester with optional computer interface, the controller will plot the curve of Heatseal Strength vs. Sealing Temperature | |
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With its computer-based accuracy, the model PC2 makes heatseals under precisely controlled conditions of temperature, dwell time and pressure. For determining the effects of the die-configuration variable, sealing dies are quickly interchangeable to commercial serrated styles, or to custom designs for individual users. |
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APPLICATIONS | The precision and flexibility designed into the PC2 makes it suited for many applications including
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PRINCIPLES OF OPERATION
Heatsealing with a hot-die sealer involves subjecting the material to pressure from a hot die for a period of time. The strength of the resulting heatseal will depend on the conditions existing during the sealing period, including die temperature, dwell time, die pressure, die impact, and die configuration.
Dynisco/Theller sealers control the first four factors to values set by the operator. The fifth factor depends on type and geometry of the dies. |
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FACTORS CONTROLLED |
Temperatures of the two dies are separately controlled and displayed by individual circuits.
Dwell time is measured by the computer, which counts milliseconds between the onset and termination of sealing pressure. Pressure of the dies on the material is generated by an air cylinder and independently measured by an electronic load cell. The load cell puts out dc voltage proportional to force applied by the die. When the operator starts the sealing cycle the controller tracks the load cell analog voltage vs. time. The voltage value is digitized, in most cases a thousand times per second, and the resulting pressure vs. time sealing pulse is displayed on the monitor. Die impact is adjusted by a needle valve in the main air cylinder pneumatic system and observed graphically on the monitor. Die configuration is varied by interchanging dies of various styles. |
AUTOMATIC TEMPERATURE CALIBRATION | ACCURACY AND REPRODUCIBILITY The model PC2 has eliminated most equipment-related variance. Its platinum sensors, together with proprietary electronic circuitry, read the temperature of each die to the closest tenth of a degree at a point within a millimeter of the sealing surfaces, permitting the computer to control within a 0.2° band, with automatic calibration every three minutes. |
AUTOMATIC FORCE CALIBRATION | The PC2 heatsealer also employs a system for measuring true dwell time to ± 2 milliseconds. The system uses an electronic strain gage to detect both the onset and removal of force on the sample under test, while the computer counts the interim milliseconds. The computer calibrates the pressure system automatically at the start of each sealing cycle.
Control and readout are by the controller with data acquisition board and monitor. Operating software provides graphics of the pressure vs. time sealing pulse in addition to digital display of temperature, pressure and dwell time. For routine work the graphics can be bypassed.
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In addition to automatic calibration of the temperature and pressure circuits, the controller enables the use of less-complex electronic circuitry than required by digital machines, due to software control and monitoring rather than by hardware. As a corollary, improvements and upgrades can usually be made via software, which is less expensive and more versatile than hardware circuit modifications. | |
DATA HANDLING | Data are displayed and stored in notebook format, with each test cycle shown on a single line of the notebook. The notebook data files are saved and can be directly exported to spreadsheet programs for further statistical analysis of preparation of presentation tables, graphs, etc. When the Theller model D Mini Tensile Tester (with optional computer interface) is used to measure strength of heatseals made by the PC2 sealer, data on sealing conditions as well as seal strength appear on each line of the notebook. The seal profile is shown as a graphic on the monitor. |
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HEATSEAL CURVE | Usually seal strength measurements are made at a series of sealing temperatures. At any time during testing or later, the operator can display on the monitor a plot of notebook data points showing Seal Strength vs. Sealing Temperature. As testing at each temperature is complete (e.g. triplicate determinations) the controller calculates and enters in the notebook the average and standard deviation for that test group. The plot then displays the data points and their means. Finally, the controller plots a line through mean strength at each sealing temperature, which constitutes the heatseal curve. The plots can then be printed to hard copy. |
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