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Vacuum Forming: Vacuum forming is a simplified variant of thermoforming. In this process, a plastic sheet (available in various forms such as HIPS, ABS, HDPE, etc.) is heated to a specific forming temperature. The heated sheet is then stretched over a single-surface mold and pressed against the mold using a vacuum. This technique is commonly employed to shape plastic into permanent objects.
For deeper parts, the formable sheet can be mechanically or pneumatically stretched before it comes into contact with the mold surface and the vacuum is applied.
Materials: Vacuum forming typically utilizes thermoplastics. Among these, high impact polystyrene sheeting (HIPS) is the most common and user-friendly thermoplastic.
Molding Process: The heated plastic conforms to the contours of a wooden, structural foam, or machined aluminum mold, allowing it to take on almost any desired shape.
Applications: Vacuum forming is suitable for transparent materials like acrylic, which find extensive use in aerospace applications. For instance, passenger cabin window canopies in military fixed-wing aircraft and compartments for rotary-wing aircraft benefit from vacuum-formed components.
Advantages: Vacuum-formed parts can serve as alternatives to complex fabricated sheet metal, fiberglass, or plastic injection-molded components.
Types of Molds: Vacuum forming offers versatility in creating various patterns. An innovative approach involves replicating a small item multiple times and then vacuum forming the new pattern. This process effectively consolidates individual pieces into a cohesive mold that can be easily reproduced.

Types of molds


There are numerous patterns one can make with vacuum forming. The most inventive way to use vacuum forming is to take any small item, replicate it many times and then vacuum form the new pattern to create a more cohesive form. The vacuum forming helps tie the individual pieces together and make one mold out of many pieces that can easily be replicated.


Wood

 

patterns are a common material to vacuum form as it is relatively inexpensive and allows the customer to make changes to the design easily. The number of samples that one is able to get from any pattern depends on the size of the part and the thickness of the material. Once the specifications of the part have been met, the pattern is then used to create a ceramic composite mold, or cast aluminum mold for regular production. Potentially, there are ways to create holes in plaster with a vacuum form if the replicated forms made from the vacuum form are deep enough and gaps are left between them for the plastic to form into. Then, once the plastic is used to cast a plaster mold, the deep plastic areas will leave holes if the mold is not completely filled.


Cast aluminium

 

molds are cast at a foundry and typically have temperature control lines running through them. This helps to set the heat of the plastic being formed as well as speed up the fabrication process. Aluminium molds can be male or female in nature, and can also be used in pressure forming applications. The main drawback with this type of mold is the cost.

Machined aluminium

 

molds are like cast aluminium, but are cut out of a solid block of aluminium using a CNC machine and a CAD program. Typically, machined aluminium is used for shallow draw parts out of thin gauge material. Applications may include packaging and trays. Cost is a significant factor with this type of tooling.

Composite molds

 

are a lower cost alternative to cast or machined aluminium molds. Composite molds are typically made from filled resins that start as a liquid and harden with time. Depending on the application, composite molds can last a very long time and produce high quality parts.

Finishing methods


A sheet of vacuum-formed plastic. The pieces needed (in this case parts for a model aeroplane) will need to be cut out of the sheet. Once a vacuum forming has been created out of a sheet of plastic, a finishing operation will be needed in most cases to turn it into a usable product. Common vacuum forming finishing methods include:


Guillotining:

 

The product is cut out of the sheet by pressing a blade through the product into a die underneath. This is a clean way of removing vacuum formed parts from the material sheet. It doesn't require a special cutting tool to be made for an individual product and is therefore suitable for low volumes of parts where straight lines are no problem. Cutting only straight lines and being a fairly slow approach compared to other finishing methods, guillotining can be expensive for projects with larger, more complex quantities.

 


Drilling:

 

If simple round holes are the required finish, manually drilling them is a good solution for small quantities. Drilling guides can be used to ensure holes can be drilled quickly in the right place. As this is a labour-intensive method, it is only suitable for small production
quantities.

Roller cutting:

 

Process whereby the vacuum formed product is placed on a custom made cutter and pushed through a roller cutter machine. An efficient way of cutting vacuum formed items from the original sheet of vacuum forming material. The cutter can also cut any necessary holes, such as cable or access holes, at the same time. Roller cutting is suitable for fairly large
items, where precision alignment is not required. As the vacuum forming’s and the cutter are rolled sideways through the roller cutter machine, some misalignment can occur. Roller cutting can't be used for making holes or features in the sides of vacuum forming’s, as the cutter tool always cuts vertically from the bottom.

 


Press cutting:

 

This is a very precise method of cutting which uses a press and a custom precision made cutting tool. This method is very suitable for items where the roller cutter process wouldn't achieve the precision required. It is often used for punching very small finished items out of a plastic sheet, rather than punching features into a product. Press cutting can't be used to make features in the sides of vacuum forming’s.

 


Cutting with a CNC machine:

 

Machining is a very precise method of creating holes & features. The real advantage is that it can be used to create features in the sides of vacuum forming, e.g. guide rails for a tray that needs to slide onto shelving. It can also cut sidewalls of a different depth than the pockets—something which cannot be done with roller or press cutting.

 



Vacuum forming has a vast territory of applications in different industries. Here are the vacuum-formed arts that can be used in equipment or machineries:

- Internal & External parts of Refrigerator and Freezer
- Bathroom Tubs and Jacuzzi
- Automobile floor & cargo liners
- Dental unit in dentistry
- Plastics made for sport equipment
- Plastic parts in Busses, Train & specialized vehicles such as Ambulances (does not include plastic parts in engine)
- Wall and Ceilings covering for Houses and Commercial buildings

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