Choosing the Right Material for your Thermoforming Tool

We go through the pros and cons of the 4 most common types of vacuum tools inside.

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Pros

• Material cost is very inexpensive
• Good for short run items
• Good for flat items (eg. trays)



Cons

• Material is weak
• Can de-laminate easily
• Difficult to repair the mold
• Even if the mold is sealed, it will still absorb a large amount of mold release.
• Edges are very difficult to seal.
• When heated, the glue lines become more pronounced, possibly showing through to the part
• The mold will "wear out" quickly

Pros

• Very cost effective. You get a very strong mold for an affordable price
• Mold is very easily repairable
• Molds are often changeable. They can be modified or even added to.
• Mold can be sealed, allowing a release to work very well
• Can hold somewhat of a sharp edge
• The wood grain can be aligned to maximize strength in critical areas.



Cons

• Sharp edges on the mold can wear with time and can be difficult to repair
• If different species of wood are used, they will move differently when heated, possibly to the point where repair is needed.
• Different types of wood will react differently to the heat.
• The wood will expand and contract differently depending on species and orientation.
• If the wood is too 'green' when used, the mold will move when heated.



Things to Remember

• It isn't a good idea to mix types of hardwood used on a mold. Different types of wood will react differently to the heat. The wood will almost always expand and contract differently.

Pros

• Extremely durable mold. This is good for high production runs.
• Mold will hold heat well (which is necessary for some thermoplastics)
• Mold can be polished.
• If the mold is polished, it will minimize mark-off on the thermoplastic being formed.



Cons

• Can be expensive to create the molds
• Not easy to repair/change



Things To Remember

• For most applications, aluminum is the hardest material needed to form plastic. There are some thermoplastics where steel molds are necessary, but aluminum will suffice for the most part.

Pros

• Can be considerably more durable than hardwood
• Because the molds are usually made from a mold, it's easy and cost effective to make multiples.
• Good for small items
• Can hold a lot of detail (decorative items)
• Some composites will hold heat better than hardwood, while others wont
• Mold releases work very well with composites



Cons

• Material can be unpredictable. Because the material is usually mixed in batches, it can vary slightly from mold to mold.
• Extremely difficult to repair/change
• Can be expensive

We're not calling this the definitive pros and cons list, but hopefully it will give a better understanding of why and when certain materials are used.

There are 4 main factors when choosing the material for your vacuum mold: Cost, Durability, Ease of Repair/Change, and holding heat. There are other factors such as the shape of mold. But that is usually determined on a case by case basis. We'll list the types of molds based on these 4 factors from best to worst.



Cost (Cheapest to most expensive)

MDF -> Hardwood -> Composite -> Aluminum

Recommendation: Hardwood



Durability (Most to least)

Aluminum -> Composite -> Hardwood -> MDF

Recommendation: Aluminum



Ease of Repair/Change (Easiest to most difficult)

Hardwood -> Aluminum -> MDF -> Composite

Recommendation: Hardwood



Holding Heat (best to worst)

Aluminum -> Hardwood -> Composite ->MDF

Recommendation: Aluminum



As you can see, hardwood and aluminum came out on top. For a cost effective, overall great thermoforming tool, we recommend using hardwood (but use it properly). For high production runs, durability, and holding heat, we recommend aluminum.

Do you have a vacuum mold you're not happy with? Let us take a look at it to see how it can be improved. We can even turn it into a foundry pattern to get metal molds made. Fill out our contact form here.

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