Thermoforming is a method of manufacturing offering many advantages for small, medium and large series production.
The design and production of the tools required for its implementation are simpler and faster than for other technologies such as injection for example, This technique makes it very competitive, especially in the production of small series.
The principle of thermoforming
Thermoforming leads to the glass transition of thermoplastic materials by heating them above the glass transition temperature [Tg] of the materials to be thermoformed. Once this stage has been completed, the materials enter the rubbery state, which allows the desired shape to be obtained with millimetre precision.
To optimise production quality, ovens are used (drying, post-forming annealing) to prepare the thermoplastics for the various stages of thermoforming.
Carried out in a vacuum or under pressure, thermoforming allows complex shapes and thicker parts to be produced, even in large dimensions, with controlled tooling costs.
The stages of thermoforming
- A mould is positioned inside the machine box on a tray that can move vertically inside the box.
- A thermoplastic sheet is clamped on a frame (reducible format) which also ensures the sealing of the box.
- The material is heated to the forming temperature (infrared sensor) by means of electric infrared panels (halogen, quartz or ceramics).
- Once the optimum temperature has been reached (depending on the thickness of the sheet or the type of material), the heating panels are removed and the softened sheet is then pre-stretched by air injection (bubbling).
- The mould moves to the upper position to shape the part: a vacuum pump then sucks in the air so that the sheet fits the mould perfectly, with mechanical assistance if necessary.
- The part is then cooled while remaining on the mould until it can be removed (demoulding) without adhesion or deformation.
Thermoforming applications are numerous in various sectors of industry requiring the manufacture of moulds and parts with the most perfect surface possible, such as:
- Aeronautics with the manufacture of aircraft seats (plastic parts, synthetic resins and foams),
- SIGN, PLV, communication with the thermoforming of outdoor signs,
- Land transport with the moulding and manufacture of seats in the railway industry (trains, trams, subways, etc.).
CNC thermoforming machines
With the MECAFORM range, MECANUMERIC, manufacturer of industrial tools, offers high-speed CNC thermoforming machines. These are semi-automatic presses for vacuum processing of thermoplastic materials, where the power of each radiating element can be adjusted individually.
NORMAPROFIL T series: 5-axis CNC milling machine with a fixed table, a mobile gantry, 4 Cartesian axes, 2 polar axes optimised for the machining of large parts made by thermoforming process. It is possible to use plastic, foam or resin materials to create the finished products.
NORMAPROFIL M series: 5-axis milling machine for the production of models and moulds or 5-axis machining of thermoformed or rotomoulded shaped parts. Raw materials such as aluminium, wood and its derivatives, brass and alloys can be machined with this type of CNC machine.
NORMAPROFIL WINNER series: allows 5-axis machining for large 3D precision machining applications. Numerous choices of electrospindles allow the machining of plastics, composites or aluminium alloys.