The construction of vacuum forming mold is the most important part of the vacuum forming process that should be done in the construction It takes a lot of sensitivity because vacuum forming package is formed with it. .
The mold is made according to the product and the customer’s needs, and aluminum is used in their construction, which is made by CNC machine.
Aluminum and wood can be used to make molds, wooden molds are used for prototyping and aluminum molds are used for large and high production.
Vacuum forming mold material
Mold design and construction is the most important stage of the vacuum forming process.
In this section, the 3D design of the mold is first designed and then it is made as a physical object with a CNC machine to be used for shaping thermoplastics.
It is not possible to shape thermoplastics without a vacuum forming mold, so the mold is the most important part of vacuum forming.
Of course, there is an exception in vacuum skin, and in this type of vacuum packaging, a mold is not used.
The vacuum forming mold must be designed in a standard way in order to have a quality product in the final output, otherwise, the mold may lose its stability and shape in the work process and we will end up with a poor quality and inappropriate product.
There are several important points such as the shape, material of the mold, size and volume of the product in the design and manufacture of the mold that should be considered.
We will further examine this issue.
Material and type of mold
The meaning of material is the material used in mold making, which is usually aluminum, wood, MDF, clay, resin, etc. used in mold making.
Mainly in Iran, aluminum molds are used for mass production and wooden molds are used for prototypes.
Aluminum mold is very suitable for large and high production because it has high resistance and easily dissipates heat in the vacuum forming process.
Due to their high strength, stability and extremely light weight, these molds are ideal and desirable for extensive vacuum forming productions.
Aluminum molds are made in two ways, which are:
- CNC machine: In this method, first the 3D design is designed with a computer, and then it is made and machined by a CNC machine.
- Casting: In this method, the mold is made by casting process. Today, this method is used less or not at all to produce vacuum mold.
Designing and making a wooden mold is cheap and easy, and it can be made using many tools and techniques.
Usually, a wooden mold is used to make a prototype of the product.
Using a wooden mold, you can produce prototypes of the product and fix its defects.
Due to its low strength and stability, wood cannot be used for many productions, because it expands and contracts with the cycle of cold and heat, and this action causes it to lose its shape and crack.
Simple carpentry tools and CNC machines are used in making wooden molds.
Important points in designing and making molds
In addition to the material of the mold, the requirements and important points in the design should also be taken into account in order to achieve a quality and ideal product.
In this section, we briefly review some basic and essential items.
Angles and slopes
The angles and slopes of the mold should be designed so that during the molding process, the thermoplastic material is well absorbed and distributed over the entire surface of the mold, and the release of the mold is done easily and without problems.
Vacuum forming is highly dependent on air flow to draw the heated plastic into the mold through embedded holes.
It is very simple; The more suitable the air flow and air discharge conditions are, the more successful the vacuum forming process will be.
With this in mind, any mold made should have air vents to allow air to escape between the plastic sheet and the mold.
These holes should be created on the mold to create a channel for air evacuation by the vacuum pump.
Any place on the mold that has significant depressions and grooves will need 1-2 drain holes.
These holes are responsible for attracting the plastic sheet to the mold and will not be visible on the final product.
The positive and negative aspects of the format
Basically, there are two types of vacuum forming molds: male (positive) and female (negative).
See the following figures:
Undercut is a depression or protrusion that prevents the part from being removed from the mold.
There are two types of undercoat, internal and external, and it is rarely seen in vacuum forming molds.
Things that the template designer should pay attention to:
- Undercuts should be avoided as much as possible to make the production process easy and low-cost.
- If possible, remove the undercut with design techniques in the form of a female or male mold or cover it with other materials so that there is no defect in the shape of the piece.
- If this is not possible, advanced templates should be used, and this work will involve a lot of costs.