High Frequency Induction Cap Sealing With IGBT heating units
Objective To heat an aluminum foil inside a plastic shampoo cap forย sealing
Material 2.0โ diameter, plastic flip top cap, with a 0.9โ diameterย aluminum foil seal
Temperature 250 – 300 ยบF (120 โ 150 ยฐC)
Frequency 225 kHz
Equipment DW-UHF-7.5 kW, induction heating system, equipped with aย remote heat station containing two 1.5 ฮผF capacitors (totalย capacitance 0.75 ฮผF).
An induction heating coil designed and developed specificallyย for this application.
Process A three-turn two-position helical coil is used to heat theย aluminum foil in a tunnel style assembly. Product (containers)
passes easily under the induction coil. The assembly is locatedย such that the entire perimeter of the aluminum foil is heated
uniformly. The container and cap is placed under the coil andย RF power delivered for 0.12 seconds. The aluminum foil heats
and seals to the plastic of the cap.
Results/Benefits This induction heating configuration fulfills the process
requirements and:
โข uses a simple, economical coil design
โข increases throughput with a dual-position coil
โข delivers quality, consistent seals
โข offers a repeatable process, well-suited for automation
Inductionย Heating Aluminum Foil For Cap Sealing with IGBT inductive heater
Objective An induction heater is used to heat a polymer laminatedย aluminum foil in 0.5 to 2.0 seconds. The heat produced in theย aluminum foil melts the polymer that bonds to the neck of aย plastic container.
Material Aluminum foil, polyethylene, polypropylene, polyvinylchloride,ย polystyrene, polyethylene terephthalate, styrene acrylonitrile
Temperature 300 – 400 (ยบF), 149 – 204 (ยบC)
Frequency 50 to 200 kHz
Equipment DAWEIย solid-state induction powerย supplies operating between 1 & 10 kW at frequencies of 50-ย 200 kHz. These units operate with remote sealing heads whichย allows the main power cabinet of the equipment to be locatedย away from the immediate production area. Distances of up toย 100 meters are possible. The microprocessor is used to control
and protect the system and ensures that the optimal operatingย frequency is maintained at all times and that each container
receives the same amount of heat energy from cycle to cycle.
Process Two different types of aluminum foil laminates are available forย this application. The first assembly includes backing
board/reseal, a wax layer, aluminum foil, and a heatseal filmย for supported systems (Figure 1). The second assemblyย includes a high temperature film, aluminum foil, and a heatsealย film for unsupported systems (Figure 2). The procedure is to fitย the foil membrane into the cap and to fit the cap to theย container after the product is filled.
Results For the aluminum foil assembly as shown in Figure 1, heatย induced in the metallic foil by the induction coil almost
instantaneously melts the polymer coating and the neck of theย container forming a hermetic seal between the heat seal film
and the rim of the container. The heat also melts the waxย between the aluminum foil and the back board. The wax is
absorbed into the back board. This results in an air tight bondย between the aluminum foil/membrane and the rim of the
container, the back board is released and remains in the cap.
Process (contโd) In the case of unsupported membranes in Figure 2, one side ofย the aluminum foil is coated with a heat sealable polymer filmย and this face that will be in contact with and sealed to theย container. The other side of the foil that will be in contact withย the cap has a higher melting-point film that prevents adhesionย of the aluminum to the cap allowing the end user to unscrewย the cap. Unsupported membranes are typically used where theย end user pierces the tamper evident membrane prior toย dispensing the product.ย The aluminum foil acts as a vapor barrier preserving theย freshness of the product and prevents it from drying.
