WHAT IS THERMOFORMING ?

Thermoforming is a manufacturing process in which flat films or sheets are preliminarily heated to the temperature specific to a given type of plastic and then formed into a product of a specific shape. Relatively cheap and highly effective processing results in thermoforming being commonly used for production of both packaging and large-dimensioned products. The offered solutions take into account many different variants: from production of individual items and prototypes to large-scale industry mass production.

thermoforming machine 4000 x 2000

Thermoforming involves two basic processes: heating of the semi-finished product and shaping (forming). The formed material is fixed around the edges by means of clamps. Electric heating is provided by radiators located on one or both sides of the formed material. Heating time required to obtain an appropriately soft semi-finished product depends on the type of polymer, thickness, and colour. The type of polymer and the filler, if any, are related to the different thermal conductivity of the material being subject to heat treatment. White sheets absorb thermal IR radiation with greater difficulty and require longer heating time than dark-tinged elements. The superiority of thermoforming over the injection moulding technology is clear. Thermoforming uses relatively cheap equipment and forms in relatively low processing temperature and low pressure.

For the purposes of vacuum forming the following are used:

Thermoplastic sheets for thermoforming. Depending on the demands made on the products (mechanical strength, chemical durability, resistance to weather, transparency, stamping depth, acceptable price), sheets of semi-finished products made of various thermoplastics are used. Table 1 (p. 30) contains characteristics of selected plastics which are most commonly used in thermoforming processes. Some thermoplastics require preliminary drying before processing. They include the following: ABS, ASA, PMMA, PA, PC, PSU, PES, and PET. Temperature and time of drying depend on the type and thickness of the plastic.

The following sheets are used with increasing frequency:

FAIR

For the purposes of thermoforming large-dimensioned products, rigid films 2÷4 mm thick or sheets 3÷15 mm sheet are used.

Heating panels are equipped with electric ceramic radiators. They have a  sandwich-type construction which allows simultaneous heating of material from top and bottom. Ceramic radiators are characterized by simple construction, high mechanical strength, chemical durability, low price, easy adjustment, and long life.

Forming is done by applying vacuum on the bottom plane of the semi-finished product. An appropriately selected shape of the stamp allows forming asymmetric oval parts of the product.

Cooling. Cooling of the product in a mould occurs as the heat radiates out into the environment, cold air is blown through jet nozzle fans, and heat is absorbed by the mould. Sometimes, water mist is sprayed over the hot product surface. Cooling time, similarly to heating time, depends on the type of plastic, specifically on thermal conductivity. If thermal conductivity of polystyrene (PS) is assumed to be 1, then PVC and PET would be similar, ABS and PP would have smaller values (0.67), and those of PE-LD and PE-HD would be significantly higher (>2.2).

    

AUTOMATIC SHEET LOADER

New version of automatic sheet loader – version 2017. Automatic material feeder + centering platen + pusher  The movable parts […]

AUTOMATIC ROLL FEEDER

Thermoforming machine with automatic roll feeder with direct laminating function.