Vacuum Forming

Vacuum forming machines made simple

You can now make your own vacuum forming machines, using house hold items such as a vacuum cleaner, kitchen oven, if you want to know more about making your own vacuum forming machine, contact APH WEB

Vacuum Forming Moulds or Plastic Fabrication?

Specialisation in making vacuum form moulds or tools has been the keystone of the growth of APH over many years. Often clients with requirements for plastic components have approached us with a preconceived idea that plastic fabrication is the solution to their problem.

Of course APH can offer fabrication in a range of plastics, but frequently Acrylic is the material of choice, due to its availability in many colours and thicknesses and its robustness when assembled. This can usually mean bonded joints, mechanical joints either bolting or even slotting one part into another. Point of sale items, are often made in this way, but at APH we have employed plastic fabrication to produce scale models, model display stands/cases etc.
But back to the original question that customers would ask, how much will it cost to fabricate a few prototype or production parts. The advice given would depend upon the shape of part or parts and the material flexibility, in fact vacuum forming would offer more choice in materials than those suitable for fabrication. But more often than not, the shape would lend itself to vacuum forming, maybe with slight changes to the corner radii, angle of sides or thickness or type of material. With few comprises their parts could have a very low cost vacuum forming mould hand made or machined in wood or MDF. From such a mould their quantity requirements would be met to a production quality finish without seams as in fabrication and the advantage of production intent surface textures, like haircell or pinseal. From the vacuum forming moulds, the part will need trimming of excess material, which again offers more complexity in shape than plastic fabrication could achieve. Sometimes a combination of the two processes will be utilised. The customers shape may be best made, by bonding a plastic fabrication with a part from vacuum forming. This could be described in simple terms, say a rectangular tube 200×200x400lg (fabricated) with a domed closure bonded to one end or both(vac. formed). With ABS using very specific adhesives like MEK achieves a seamless parent material like join between fabrications and or vacuum form part.

Vacuum forming machines,tooling & processes

Vacuum forming machines consists of a single or double heating element, frame for holding the plastic, moving platen or table to hold the tool or pattern used to make the shape of the part you wish to produce and a vacuum tank.

The heaters are usually at the back of the vacuum forming machine and the clamping frame and platen at the front. The platen sits within the frame and can be moved up and down, whereas the clamping frame is in a fixed position for holding the plastic over the tool during the moulding process. Some vacuum forming machines are manually operated and others are semi automatic or fully automatic.

The object of each type of machine is the same in that they all heat plastic materials until soft enough to mould over a tool, pattern or mould, under vacuum. When the plastic is under vacuum, the suction achieved is around 28 HG about 1% less than what might be considered as ultimate vacuum.

The tool can be made using various materials providing that they are strong enough not to collapse when under vacuum. These materials include:- wood & MDF for prototype or low volume, through to resin tooling board or cast resins for mid volume parts, up to aluminium  either machined or cast for high volume The latter would depend on depth of feature and thickness of material and hence heat required to soften material prior to forming. All tooling would be vented to vacuum side by small 0,5-1,0mm dia. holes around the tool and at key draw areas and features to pull the plastic to form over the tool.

The surface of the tool will reach around 60 to 80 degree’s when used in production. Various plastics require different temperatures to become soft enough to mould. * Materials such as High Impact Polystyrene and ABS plastics will soften at between 150/190 deg C and Polycarbonates at around 185/205 deg C*. The design of the tool is very important, you need to build into your design a draft or taper down the sides of 2 degree’s or more and add radii to all corners, the bigger the better for ease of forming.

There is a rough formula for moulding recesses or pockets that might be needed in the tool. The width and length of the recess should be twice that of the depth of the recess to allow the material to be drawn down into the pocket without the material becoming so thin that it splits when under vacuum.  Once the tool has been designed and made with the all foregoing in mind, you are now ready for moulding.
The tool is fastened to a board, which is in turn fastened to the platen. The platen is lowered and a plastic sheet is placed onto the frame and clamped in position. The heater or heaters are brought over the plastic and left in position until the plastic becomes soft and pliable, timing is critical, so checking and recording for repeatable quality forming is essential. The heaters are then withdrawn and the tool brought up into the plastic, the vacuum switched on to suck the plastic around the mould to remove all of the air between the tool and the plastic, thus creating a replication of the surface of the tool. Whilst the vacuum is on, the sheet is cooled using fans and or compressed air until it becomes solid and retains its shape.

Once this has been done, the tool and platen can be dropped down and the plastic removed from the clamping frame ready for trimming to obtain finished part. You can mould as many parts as needed, providing that the tool has been designed and made using the right materials for the quantities required. * Information about mechanical properties of vacuum forming plastic materials and uses can be found on various plastic manufacturers web sites.

Welcome to the Vacuum Forming Blog

Here you will be updated about vacuum forming, and vacuum forming procedures, such as plastic fabrication and projects and moulds formed using vacuum forming machines and processes of vac forming, vacuum forming plastics and fibreglass and other materials and the process of designing prototypes and methods to mass produce products.

We hope you enjoy this blog and feel free to comment.