The 6 Stages Of The Vacuum Forming Process

Plastic is something that is used in all types of manufacturing and it is therefore important to make sure that it can be moulded into a wide variety of shapes and sizes according to its use. This is done through a process of vacuum forming where thermoplastics can be moulded into all sorts of different shapes suitable for use in the automotive, packaging and medical industries, to name just a few.

The vacuum forming process is a complex one, so here, Ansini look at the six stages that are involved in creating these versatile moulded plastics.

1. Design and preparation

The whole process relies on a mould that will be used to shape the thermoplastic material and so it is important to design this carefully. It can be created through machining, casting or 3D printing, and it will need to consider the shape and dimensions of the final product including any additional features that it might have. It is then important to get the thermoplastic sheet ready. This is a thin flexible material such as polycarbonate or ABS and needs to be cut to the appropriate size and shape.

2. Heating the thermoplastic sheet

The thermoplastic sheet will start life as something solid and so you need to make it pliable and flexible in order for it to take on the shape of the mould. This means that it needs to be clamped in place before heat is applied to it using an oven or heat gun. The temperature that is reached will vary depending on the material that is being used, and it is important to remember that getting this temperature wrong can lead to defects in the plastic.

3. Place the sheet on the mould

As the thermoplastic sheet reaches the desired temperature, it needs to be moved away from the source of heat and positioned over the mould itself. This needs to be done extremely carefully in order to avoid wrinkles or folds forming as part of the movement, as these can also create defects.

4. Creating the vacuum

This is the point where the vacuum pressure needs to be applied. A vacuum pump is used in order to remove the air that forms in the space between the sheet and the mould. This means that the thermoplastic material will conform tightly to the outlines of the mould in order to create the desired shape. The vacuum needs to be placed beneath the mould in order to draw the material down and form the desired shape. The vacuum needs to be strong enough to ensure that the plastic is able to conform precisely.

5. Cooling and solidifying

Once the thermoplastic sheet has taken on the desired shape then it needs to be left to cool. As its temperature drops, it will harden and solidify into the final shape. Often cool air is blown over the sheet or it is immersed into a cooling bath in order to make sure that the process is done slowly enough to avoid warping or distortion, but quickly enough to ensure that the manufacturing process can keep moving. Once the product has been called sufficiently, it can then be released from the mould.

6. Trimming and checking

As part of the process, there may be some areas of excess material which need to be trimmed away and additional finishing touches such as painting, polishing, drilling, or adding any other texture can be applied. Once complete, the vacuum formed part needs to be inspected for quality, uniform thickness throughout, and accuracy.

This vacuum forming process has proved to be one of the most successful ways to shape plastics into the wide variety of uses that we have for them across the world.