The Most Common Design Considerations For Vacuum Forming

There are several important design considerations to keep in mind when creating a product that will be vacuum forming:

Wall thickness: The walls of the vacuum formed product should be thick enough to be strong and durable, but not so thick that they take a long time to cool and become brittle.

Draft angle: It is important to include a draft angle (taper) on the sides of the product to make it easier to remove the part from the mold.

Undercuts: Vacuum forming molds cannot have undercuts, as the part needs to be able to be removed from the mold.

Parting lines: The mold should have a clear parting line to allow for easy separation of the two halves.

Material choice: The material used for vacuum forming should be chosen based on the properties required for the final product, such as strength, flexibility, and resistance to heat and chemicals.

Mold design: The design of the mold is important to ensure that the final product has a high quality finish and accurate dimensions.

Radius of curvature: The radius of curvature can be an important design consideration, as it determines the amount of stretch and deformation that a sheet of plastic will undergo as it is drawn over the mold. The radius of curvature of the mold should be chosen based on the desired final shape of the product, as well as the properties of the plastic material being used. A larger radius of curvature will result in less stretch and deformation, while a smaller radius will result in more stretch and deformation. It is important to choose a radius that is appropriate for the material being used, as excessive stretch or deformation can result in defects or failure of the final product.

Wall thickness

Wall thickness is an important factor to consider in vacuum forming because it affects the strength and durability of the final product. Thicker walls are generally stronger and more resistant to deformation, but they may also take longer to heat and form, and may require a larger and more expensive mold. On the other hand, thinner walls may be more prone to deformation and may not be as strong, but they are easier to heat and form, and can be molded using a smaller and less expensive mold. It is important to choose an appropriate wall thickness for the final product, taking into consideration the desired strength, dimensional stability, and cost.

How to overcome the thick wall in vacuum forming?

There are several ways to overcome the challenge of creating a vacuum formed product with thick walls:

  • Use a stronger material: Using a stronger material with a higher tensile strength and lower elongation can help reduce the amount of deformation and sagging that occurs during the vacuum forming process. Materials such as high impact polystyrene or acrylonitrile butadiene styrene (ABS) may be more suitable for thick walled products.
  • Increase the material thickness: Increasing the thickness of the material being used can also help reduce deformation and sagging. However, it is important to keep in mind that thicker material may take longer to heat and form, and may also require a larger and more expensive mold.
  • Use a two-stage process: A two-stage vacuum forming process can be used to create thick walled products. In the first stage, the sheet of plastic is heated and a partial vacuum is applied to draw it over the mold. The plastic is then cooled and removed from the mold. In the second stage, the cooled plastic part is re-heated and a full vacuum is applied to complete the forming process. This can help reduce the amount of deformation and sagging that occurs, as the plastic is only partially heated and stretched in the first stage.
  • Use internal ribbing or stiffening: Adding internal ribbing or stiffening to the design of the product can help increase its overall strength and stiffness. This can be accomplished using inserts or by designing the product with structural features such as ribs or webs.
  • Use a mold with a larger radius of curvature: A mold with a larger radius of curvature will result in less stretch and deformation of the plastic material, which can help reduce sagging and ensure a better quality final product.
  • Use a mold with a texture or finish: A mold with a texture or finish can help create a thicker, more durable final product. A rough or porous surface can help increase the overall strength of the product, as it creates more surface area for the plastic to bond to.
  • Use a post-forming process: After vacuum forming, a post-forming process such as stretching or thermoforming can be used to further shape and strengthen the product. This can be particularly useful for thick walled products, as it allows for additional shaping and reinforcing of the plastic material.

Draft angle

A draft angle, also known as a taper, is a slope or angle that is incorporated into the sides of a product to make it easier to remove from the mold. In vacuum forming, the draft angle is important because it allows the plastic part to be easily removed from the mold without deforming or breaking. Without a draft angle, the plastic may stick to the mold and be difficult or impossible to remove, or it may deform or break as it is pulled away from the mold.

The size of the draft angle will depend on the material being used, the shape and complexity of the product, and the size of the mold. A larger draft angle may be necessary for materials that are more prone to deformation or for products with complex shapes, while a smaller angle may be sufficient for simpler shapes or for materials that are more rigid. It is important to include an appropriate draft angle in the design of the product to ensure that it can be easily removed from the mold without damaging the final product.

How to overcome the challenge of large or complex draft angle

There are several ways to overcome the challenge of creating a vacuum formed product with a large or complex draft angle:

  • Use a more rigid material: Using a material with a higher modulus of elasticity or a higher flexural strength can help reduce the amount of deformation that occurs during the vacuum forming process. Materials such as high impact polystyrene or acrylonitrile butadiene styrene (ABS) may be more suitable for products with large or complex draft angles.
  • Use a two-stage process: A two-stage vacuum forming process can be used to create products with large or complex draft angles. In the first stage, the sheet of plastic is heated and a partial vacuum is applied to draw it over the mold. The plastic is then cooled and removed from the mold. In the second stage, the cooled plastic part is re-heated and a full vacuum is applied to complete the forming process. This can help reduce the amount of deformation that occurs, as the plastic is only partially heated and stretched in the first stage.
  • Use a mold with a larger radius of curvature: A mold with a larger radius of curvature will result in less stretch and deformation of the plastic material, which can help reduce the difficulty of removing the product from the mold.
  • Use a mold with a texture or finish: A mold with a texture or finish can help create a thicker, more durable final product. A rough or porous surface can help increase the overall strength of the product, as it creates more surface area for the plastic to bond to. This can make it easier to remove the product from the mold, as it will have a stronger bond to the surface of the mold.
  • Use a post-forming process: After vacuum forming, a post-forming process such as stretching or thermoforming can be used to further shape and strengthen the product. This can be particularly useful for products with large or complex draft angles, as it allows for additional shaping and reinforcing of the plastic material.
  • Modify the design: If the draft angle is causing difficulties in removing the product from the mold, it may be necessary to modify the design of the product to make it easier to remove. This could involve adding features such as a handle or a release mechanism, or reducing the overall complexity of the shape.

Undercut

An undercut is a feature of a product that extends beyond the plane of the mold and cannot be removed from the mold in a straight motion. In vacuum forming, undercuts can be a challenge because the plastic part needs to be able to be removed from the mold in order to complete the forming process. If the part cannot be removed from the mold, it will be stuck in place and the vacuum forming process cannot be completed.

How to overcome the challenge of undercuts

There are several ways to overcome the challenge of undercuts in vacuum forming:

  • Use a material with a higher elongation: Using a material with a higher elongation can allow the plastic to stretch and conform to the shape of the mold, even if it has undercuts. Materials such as polyethylene or polypropylene may be more suitable for products with undercuts.
  • Use a two-stage process: A two-stage vacuum forming process can be used to create products with undercuts. In the first stage, the sheet of plastic is heated and a partial vacuum is applied to draw it over the mold. The plastic is then cooled and removed from the mold. In the second stage, the cooled plastic part is re-heated and a full vacuum is applied to complete the forming process. This can allow the plastic to stretch and conform to the shape of the mold more easily, as it is only partially heated and stretched in the first stage.
  • Use a flexible mold: A flexible mold can be used to create products with undercuts. The mold is made of a flexible material such as silicone, which allows the plastic part to be removed from the mold even if it has undercuts.
  • Use a collapsible core: A collapsible core can be used to create products with undercuts. The core is placed inside the mold and is designed to collapse or fold down as the plastic is drawn over it. This allows the plastic part to be removed from the mold even if it has undercuts.
  • Modify the design: If the undercuts are causing difficulties in removing the product from the mold, it may be necessary to modify the design of the product to eliminate or reduce the number of undercuts. This could involve changing the shape of the product or adding features such as a release mechanism to allow the part to be removed from the mold.

Now please allow me to do a brief introduction about our vacuum forming factory:

About Ditaiplastic

Ditaiplastic has been working in the field of vacuum forming since 1997 and today has more than 60 large production machines, more than 40 product patents, 80 employees, and a factory covering 12,000 square meters! It is one of the largest suppliers of vacuum forming in China! Kindly visit us at https://www.ditaiplastic.com contact us at amy@dgdtxs.com.cn or WhatsApp: +86 13825780422

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