Vacuum forming 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 for 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. From there, you can cast plaster, concrete, etc. into the plastic form.
Wood patterns are a common material to vacuum form but probably the most obvious. Wood is relatively inexpensive and allows the customer to make changes to the design easily. Using recycled objects or forms are the most sustainable way to make a vacuum form because they are 'found objects' at no additional cost. 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 you make the vacuum form from are deep enough and you leave gaps 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.