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Compression molding is one of the simplest and easiest fabrication techniques used in various manufacturing sectors.

The entire process is quite simple and straightforward as it pertains to the insertion of the material onto the mold, closing, and finally, heat and pressure are applied. Afterward curing is done, the mod is opened removing the finished part or product. Quite simple right!

To add the icing on the cake, the whole process is completely autonomous and repeatable thus it doesn’t require a huge number of personnel saving you time and money in the long run. At first, the whole process may seem a bit complicated but, trust me it’s not.

Before choosing this manufacturing technique, you need to know all the facts about compression molding, luckily for you, we’ve made this easier as we will be discussing everything you need to know about compression molding.

Compression molded components

Compression molded components

What is compression molding?

Compression molding is a simple manufacturing technique that uses two techniques to create parts/products: compression and conventional injection molding.

There are mainly two stages used in compression molding: the melted polymer is inserted into the mold till its fully or partially filled and opening of the mold partially in the second phase.

The next is the compression process, in this phase the mold is exposed to both heat and pressure, after the mold material has finally set-in, it’s in turn ejected from the cavity. What makes the whole process quite effective and unique is the fact that it uses both pressure and heat which will ultimately influence the features and characteristics of the final product.

The heat will assist both the mold and material to expand, the pressure exerted makes the whole process more efficient and effective.

Key aspects that you should consider during compression molding

When you’ve finally decided to go with compression molding, here are some of the factors that you need to pay special attention to.

  • The mode/type of the heating method
  • Mold design used
  • The amount of pressure exerted
  • The amount of heat
  • The quantity of thermoplastics and thermoset plastics

Note that there are two main types of materials used in compression molding: thermoplastic and thermoset. Thermoset plastics are pliable plastics like the hydraulic seal that does not change its shape or structure when heated.

Thermoplastic is material that hardens when heated before turning into liquid form. These types of materials can be cooled and heated repeatedly without changing the stability and integrity of the material.

The temperature used on the mold cavity differs depending on the material, the time is taken to complete the whole process also differs depending on the thickness and material of the part used. The most important part that you should pay special attention to is filling the crevices of the mold which ensures the final product is perfect without any defects.

Tools used compression molding

One of the most vital factors when selecting tools is checking on the quality of fiber used. You will need a long-fiber BMC with huge fiber content and pressure of up to 2000 psi that will fill all the features and crevices.

The tolerance of the cavity and center halves must be well-controlled ensuring all the air is trapped. Due to the requirements, it will drive up the total tooling costs but in the long run, it will be worth it.