Thermoforming

Thermoforming is a process for forming thermoplastic materials. Earlier, it was referred to as thermoforming, thermoforming or vacuum forming.

One differentiates the thermoforming process after each set semis: Thinner shapes are called sheets, thicker (from about 1.5 mm) plates. Foil semifinished products can on large ( up to Ø 1.8 m) rolls are fed thermoforming machines.

In addition, the thermoforming of the tools for thermoforming.

Thermoforming " on a roll "

Article from thin films ( 0.2 to 1 mm) such as chocolate box inserts, foam kisses packaging, game box inserts, folding blister for all kinds of small articles on breadboard walls in retail, yogurt or margarine tubs are widely used. Schiebekartenblister, seal caps and hard -to-open clamshell, where often small items to be sold and which are welded by high frequency RF electrodes are, also.

The procedure

From large roles, the film is out on the sheet edges in so-called Stachelketten. The still hard cold foil is fed to the forming machines first and then cyclically passed. In a warm-up station heaters are driven by industrial heating controls and the film heated so one or both sides. The warm, now softer film is easily drawn into the sting guides it apart, so they do not so much slack. In the tool station, the film is held in place by clamping frame, pre-stretch and the thermoforming mold drive through the plane of the film through and give the finished contour before been rough. Then compressed air comes from one side and vacuum from the other side to bring the film rapidly and strongly to the water-cooled wall ( contour ) of the aluminum mold. By 0.5 to 0.8 mm, small holes and / or 0.2 to 0.3 mm wide slots, the air escapes between the film and aluminum tool. The cooled, solid film is then separated from the mold and applied to the next working cycle of the Ausstanzstation. Where the external dimensions or holes are punched in the finished workpiece by means of die-cutting.

In the next cycle, the article is manually removed from the thermoforming machine or automated using stacked pile shaft, Clipboard, lifter and knife. The finished film products are then removed manually in batches, often packaged in poly bag and placed in boxes.

There are other, here only very briefly mentioned types of thermoforming:

  • High-performance machines work with hardened steel tools and punch the foil products from the same moment shaping.
  • Medium series machines are operated partly with vacuum or compressed air.
  • Small series are occasionally produced by a small roll of film or plates in semi-automatic machines and the parts then separated by rolling punch and die-cutting.

With sliders, top and side hung cores may also realize complex designs. Can be punched in more than one plane only. Previously packaging were cuboidal; today they are almost always adapted to the often complex geometries of the articles to be packaged or only reason provided with curved faces and edges to obtain individual "modern" packaging.

Thermoforming sheet goods

Plates between 1 to 2 mm thickness were processed for sorting trays, transport trays, KLT deposits, simple technical parts and esp. m. Material thickness from 2 to 10 mm are used for refrigerator walls, bathtubs, dashboards, lights etc. This method works similarly to that described above, with the restriction that can not be produced so efficiently, using sheets ( wastage). Plastic sheets can be processed in a size of 2,200 x 3,300 mm. The height of the parts can be up to 1,500 mm. For special applications, the shape size may even be bigger. However, there are in larger dimensions only a few semi-finished products, ie plates, which can then be processed. Remarks to the manufacture of thermoforming parts is always the stretch of the material, ie how much to stretch the material and how much is thereby reduced the wall thickness of the deformed part. Also note at the geometries and the rear section. This is material-dependent limits or necessitates elaborate mechanisms.

The materials

Mono films were once made ​​of PVC, are now predominantly made from PET, PS and PP. Multilayered films ( PSEVOHPE / PPEVOHPE ... ) with better heat seal properties or vapor barriers for better shelf life of food, etc. are often used. Flocked films: Circuit box inserts, cutlery drawer inserts, inter alia,.

Basically, however, can be processed in this method, all thermoplastics. For each application there is a suitable plastic. From talc -reinforced PE oversized fenders can be made. ABS with acrylic top coat is used for cladding, exposed to severe weather conditions or come into contact with chemicals. A certain electrical conductivity of small load carriers (because of " fatal " static electricity in electronics be processed area) is effected by the addition of carbon black particles. Also the deformation of high-performance plastics such as PEEK is now possible.

Applications

In addition to the classical application in packaging, thermoforming has increasingly found applications in the industrial sector. As an alternative to injection molding, it is characterized by convenient tool costs and is particularly economical, especially with small and medium series. Examples of thermoformed parts are hoods and panels of all types for machine and plant construction, for agricultural and construction equipment, trucks and commercial vehicles. Furthermore fenders are manufactured, fittings and much more. In particular, the combination of shape, color and function, in which industrial designers increase the use of this procedure.

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