In the design experience of many people, sometimes they design perfect parts, but they do not know the correct process of manufacturing them.
For designers, the more they know about the way things are made, the better they will be at designing new parts. This is why thermoforming can be a huge asset in the toolbox when planning production designs. Thermoforming is sometimes masked by the more common injection molding, which is a unique process and can even provide the opportunity to create detailed geometry.
Before we go deep into the basic principles of thermoforming, let's start with the basic principles and see how thermoforming works.
Thermoforming basics
Hot forming starts with heating and mold. A piece of thermoplastic is heated and stretched on a mold to make a part. Generally, the heat generated by the machine is not enough to completely melt the sheet, but its temperature should be such that the plastic can be easily formed. The mold can be a female mold or a male mold, which is made of a variety of materials, and then the thermoplastic is made into a shape. Once the sheet has cooled on the mold, it can be trimmed to leave the required parts.
There are two main types of thermoforming: vacuum thermoforming and pressure thermoforming. Vacuum forming removes the air between the part and the mold to make the material as close to the surface as possible. Pressure molding adds air pressure to the upper surface of the part to push it toward the mold.
When selecting materials for thermoforming, various thermoplastics can play a good role. Some of the more common materials include HIPS, PET and ABS, but other materials such as PC, HDPE, PP or PVC can also be used. Sheets of different thicknesses can be formed.
When to use thermoforming
Immediately, it is easy to compare thermoforming with injection molding because they have some correlation. Injection molding uses molten plastic or rubber and injects it into the cavity, while thermoforming uses flat materials and stretches them into parts.
Compared with other processes, size is the biggest advantage of thermoforming, because it can produce larger parts. For example, if you have a very large and uniform thickness part, thermoforming is a potential option. For large molds using injection molding, greater force is required to close them. However, this is not a problem for thermoforming.
It is also good at making thin gauge parts. Thermoforming is widely used in the packaging industry. It can easily manufacture disposable cups, containers, lids and trays with high cost efficiency. Thin materials also allow more room for gyration and undercut.
Precautions for hot forming
Although thermoforming sounds great, there are several things to note when preparing for forming. First, it is important to pay attention to the corners and the changes that may occur during the molding process. Try to maintain the radius at the corners and edges so that these areas do not become thinner during molding.
Also consider the depth of the cavity. It cannot exceed a certain limit because the material must be stretched to create each feature. If the stretch is too large, the material will be too thin to form a shape. A certain pullout modulus is also required to ensure that the part can be demoulded from the mold.
If one side of the part needs a higher dimensional accuracy than the other, it is important to specify this as early as possible, because the use of male and female dies can help achieve this.
