Vacuum thermoforming process

Thermoforming is a plastic tranformation process. At first sight thermoforming seems to be simpler than injection moulding technology because it matches no problems related to plastic resins compounding.

However akwardness comes precisely from the heat shaping of a resin already manufactured thanks to various transformations such as extrusion, calendering or casting to convert plastic into a film or sheet.

The plastic memory of the material caused by tensions from inside, coming from the previous transformation process, involves non-uniform forming and film thickness out of control. The complexity in thermoforming process,  as mentioned above, consists in standardisation of features and technical performances of the final product.
Accuracy in equipment design, vast experience in mold construction, manufacturing process and high quality control, allows to reach the fixed goal.

Thermoforming process

Thermoforming is a hot-deformation process that molds thermoplastic film or sheets on a mold. The shape of the mold is faithfully copied by suctioning out the air that remains between the film and the surface of the mold under low levels of vacuum (~0.5 mbar of final pressure).

In some vacuum machines, compressed air (at a pressure of up to 10 bar) is injected into a bell closed on the other side of the film to achieve greater fidelity of minute details and more uniform stretching. One of the intrinsic characteristics of the thermoforming process is that new material is never added; the quantity of material is predetermined and only deformed.

To obtain the most uniform stretching possible, suitably shaped counter-molds are often used to improve results at the most difficult points.

Thermoforming operations

Molding by thermoforming is only the first step in making the final product. Starting from a film or sheet with defined physical dimensions, the thermoformed piece must be separated from the scrap, i.e., the excess material that is not part of the shape of the piece to be obtained.

In the case of the thin materials used to make light packaging, we proceed to punching using American type dies and presses.

For thick materials, on the other hand, we use milling cutters. Currently, we, almost exclusively, use numerical-control centers that are capable of performing complex cutting and drilling to meet the customer’s needs.

For the production of objects that must be robust and highly precise (such as pallets for robotized handling), we glue and weld 2 or more shells (i.e., single thermoformed pieces) specifically designed for the production of articles with box elements that significantly increase their strength.

We can perform any other work necessary to obtain the required product.

Le materie plastiche

Only some thermoplastic materials can be transformed into films and sheets suitable for thermoforming.

  • PS: polystyrene (and its derivatives EPS, BOPS and ABS)
  • PVC: polyvinyl chloride
  • PET: polyethylene terephthalate (in its various formulations: PET-A, PET-G, PET-C)
  • PP: polypropylene
  • PC: polycarbonate
  • Mixed compounds (Koblend, Gerpack, etc.)

Depending on the application and the cost, different materials can be used that determine the characteristics of the thermoformed product and the processes needed to make it.

Polyethylene terephthalate

This a thermoplastic made through the polymerization of ethylene with terephthalate acid in the presence of oxygen. It can become a synthetic fiber or a audiocassette tape, it is increasingly used in packaging for its brilliant transparency but its best known use is in bottles for mineral water and beverages

High Density Polyethylene

High Density Polyethylene is mainly found in beverage and detergent bottles, pipes, industrial crates and chests, fuel tanks, tubing for transporting gas and water under pressure and toys.

Vinil or Polyvinil Chloride

This is a thermoplastic material made from ethylene and table salt. Industrially produced since 1930, thanks to its versatility, resistance to wear, chemicals and the weather, PVC is used in the most varied applications. It is used in the kitchen for food containers or in the walls, doors, windows and tiles of our homes as well as in credit cards; food and pharmaceutical packaging (food trays, blister packs, etc.) cables, transport, sports and leisure, furniture, clothing, household items and medical products (blood plasma bags, oxygen tents, etc.) are examples of the countless uses.

Low Density Polyethylene

It was discovered by Gibson and Fawcett in 1935 and is made through the polymerization of ethylene. By modifying the polymerization process, it can take the form of: LDPE (Low Density PolyEthylene), in the form of bags and film, housewares, toys, containers and pipes.

Polypropylene

This is a thermoplastic obtained through the polymerization of propylene. It is one of the most widely-used plastics in the world and is easily transformed into any object: from food containers, furnishings, bottles for detergents and personal hygiene product bottles to toys, carpeting and garden furniture. Furniture, clothing, housewares and medical products (blood plasma bags, oxygen tents, etc.) are examples of countless uses.

Polystryrene

This is a thermoplastic made by polymerizing styrene. It is made into food trays, tableware, plates and caps. It is also know in its expanded form (EPS), when it is completely white and light with sound-absorption properties: it is also used to carry ice cream home from the store on hot summer nights thanks to comfortable double-tray packaging: expanded polystyrene on the outside and thin, shockproof polystyrene on the inside.

All other resins: Multi-layered plastic

All other plastics that do not fall within any of the above-listed categories. Independently of their characteristics, there are still recyclable with the standard procedures used for plastic.

ESD

Thermoplastics suitable for ESD applications (ESD = Electro Static Dissipation), which can therefore dissipate electrostatic charges in a controlled and lasting way. Used in various sectors, such as the electronics and semiconductor industries, the construction of ventilation systems, medical technology, the chemical and pharmaceutical industries. In other industries where the inert material generates dust during treatment or in the presence of flammable liquids and gases, in the paper industry, in the manufacture of fabrics or films or in the mining industry.