Vacuum thermoforming is a relatively common form of plastic thermoforming, in which a sheet of plastic is heated to its thermoforming temperature (the temperature where it becomes flexible and ductile, before its melting point). The plastic is then stretched over a mould by a vacuum acting from below, pulling it down and creating a near-perfect fit onto the mould.
If the plastic is stretched prior to vacuum thermoforming, it is possible to form deep drafts, and processes like this are used to create the linings for the inside of refrigerators or chest freezers in one solid piece. However, there are both advantages and disadvantages to vacuum thermoforming, which are covered below.
The Advantages of Vacuum Thermoforming
One of the primary advantages held by vacuum thermoforming is its versatility and adaptability. The most common mould used for vacuum thermoforming is made from a soft wood, which makes the moulds both inexpensive and easy to alter. If a component needs to be changed slightly, this change can be made to the mould simply and cheaply, making wooden moulds one of the best assets to vacuum thermoforming companies.
Once the mould and vacuum former have been invested in, the actual cost of vacuum thermoforming is very low per unit – making this a perfect method of producing many identical items at the lowest possible cost.
Thanks to the low unit costs and ability to alter a mould on the fly, vacuum thermoforming is ideal for prototyping components before full-scale manufacturing starts. Small changes can be made quickly and easily, and a new component recast with ease, helping ensure that the finished prototype is completed as quickly as possible.
Ease of Moulding
Vacuum thermoforming is a relatively straightforward moulding process, requiring very few steps and little specialist equipment. It doesn’t take much time and doesn’t require specialist preparation, making it faster and cheaper than other moulding techniques.
A Range of Finishing Methods
Once freed from the mould, the components will have to be finished – usually this is done by cutting them free from the plastic sheet which they were formed from, but it can also include cutting new grooves and shapes, tapping holes and otherwise cutting into the final piece to reshape it or add functionality.
The available finishing methods include guillotining and roller cutting, both of which can quickly cut a component out of its sheeting, but lack flexibility, and press cutting and CNC machining, which are extremely precise and flexible cutting methods which take a slightly longer time and require more specialist equipment.
The Disadvantages of Vacuum Thermoforming
Possible Problems with the Vacuum Thermoforming Process
It is possible for a range of problems to occur during vacuum thermoforming, including absorbed moisture expanding in the heat and thermoforming bubbles in the plastic, weakening it – however, this can be prevented by drying the plastic at a high heat before thermoforming. If the plastic is heated to high “webbing” can form on the corners of the mould, too – this can be resolved by carefully controlling the plastic temperature.