What is Vacuum forming?

What does Vacuum Forming Mean?

Vacuum forming can be described as a simplified version of thermoforming. This is where a plastic sheet is heated to a forming temperature, stretched into a concave or a convex, single-surface mould and then forced against the mould by a vacuum. Basically this is a procedure used in shaping any kind of plastic. This technique is used by designers, engineers, hobbyists and in many different industrial settings.

Thermoforming is among the oldest technique used in plastic shaping. Today, most of the plastics we see in our day to day life are produced using this method. Some common plastics shaped using this method includes polyethylene, acrylic, polystyrene and polycarbonate. Thermoforming is also used to fabricate car dashboards.

Process Vacuum forming is an amazing method of creating a seamless plastic. First you place plastic sheet inside the thermoforming machine. The plastic is then draped over the mould to cover all edges and the angles. The lid then is closed and tightly locked. After this, the vacuum machine is activated; this causes the interior part to heat to a certain pre-set temperature. Once the heat is on, plastic sheeting softens until it becomes very flexible. A vacuum is formed by the machine and this pulls this plastic down around a mould. The force from the vacuum will actually pull through the holes drilled' into the mould; this creates a bond with shaped like the mould.

When the whole process is complete, the machine is then turned off and left to cool down. During this time, the plastic also goes through its own cooling process and gets hard. After hardening, the plastic is now ready for the final finishing touches, like decorations and applying stickers. Many other everyday items are also constructed using this method because this technique is the easiest way of forming many plastic items.

Types of Moulds used: Depending on the type of job, thermoforming machines come in several different shapes and sizes.

Some of these machines are very big, filling up large walls to produce composite moulds for very large items such as automobiles. Some of the machines are very tiny and actually consist of a 2-sided mould; this enables a machinist to melt plastics around the mould. Below are the three main types of moulds used in vacuum forming.

1. Cast aluminium moulds These are cast at a foundry and have temperature control lines running through them. This helps in 2 ways; heating the plastic being formed and speeding up the fabrication process. Aluminium moulds can either be male or female in nature and can be used in pressure forming applications.

However, cost is a significant factor with this type of tooling.

2. Machined aluminium moulds These are similar to cast aluminium but are cut of a solid block of aluminium. This is done using a CAD program and a CBC machine. Applications include trays and packaging.

3. Composite moulds This is a lower alternative to cast or machined aluminum moulds. They are made from filled resins that start as liquid and then harden with time. Composite moulds can last a very long time and actually produce very high quality parts.