Vacuum forming is a process in which a sheet of plastic is heated to a pliable temperature and then stretched over a mold using a vacuum. The most common design features of a mold for vacuum forming include:
- Smooth surface: The surface of the mold should be smooth and free of defects, as rough or uneven surfaces can result in imperfections in the finished product.
- Draft: The mold should have a slight angle or “draft” on the sides to allow for the easy release of the formed part.
- Undercuts: Molds for vacuum forming should not have any undercuts or protrusions that would prevent the formed part from being removed from the mold.
- Ejector pins: Ejector pins are often used to help remove the formed part from the mold. These pins are typically located on the back side of the mold and are activated by a mechanism to push the part out.
- Vacuum ports: The mold should have vacuum ports to allow the vacuum to be applied and hold the plastic sheet in place while it is being formed.
- Heating elements: The mold may also include heating elements to help heat the plastic sheet to the proper forming temperature.
- Cooling channels: To help the formed part retain its shape, the mold may include cooling channels to allow for rapid cooling of the plastic.
The smooth surface on the mold in vacuum forming
The smoothness of the surface of the mold is a critical factor in vacuum forming, as it can significantly impact the quality and appearance of the finished product. A smooth mold surface will result in a smooth surface on the formed part, while a rough or uneven surface on the mold may result in imperfections in the finished product. There are a few reasons why a smooth surface is important in vacuum forming:
- Improved aesthetics: A smooth surface on the finished product will generally have a more attractive appearance than a rough or uneven surface. This is particularly important in applications where the formed part will be visible or handled, such as in consumer products or packaging.
- Better dimensional accuracy: A smooth mold surface can help to ensure that the formed part has the desired dimensions and shape. An uneven or rough surface on the mold may result in a formed part that is distorted or misshapen. This is particularly important in applications where the formed part must fit precisely with other components or meet specific dimensional tolerances.
- Easier release from the mold: A smooth mold surface can help to facilitate the release of the formed part from the mold. A rough or uneven surface may cause the plastic to stick to the mold, making it more difficult to remove the part. This can increase the risk of damage to the formed part and increase production time and costs.
There are a few different factors that can impact the smoothness of the surface of the mold:
- Machining process: The machining process used to create the mold can have a significant impact on the smoothness of the surface. A high-quality, precision machining process such as CNC milling or EDM (electrical discharge machining) is generally recommended to achieve a smooth surface.
- Surface finish: The surface finish of the mold can also affect the smoothness of the surface. A fine finish, such as a high-quality polish, can help to achieve a smoother surface.
- Maintenance and cleaning: Proper maintenance and cleaning of the mold can help to maintain the smoothness of the surface over time. The mold should be regularly cleaned to remove any debris or contaminants that may accumulate on the surface.
- Plastic sheet quality: The quality of the plastic sheet used in the vacuum forming process can also impact the smoothness of the finished product. A smooth, uniform plastic sheet will result in a smoother surface on the formed part.
Overall, the smoothness of the surface of the mold is an important consideration in vacuum forming, as it can have a significant impact on the quality and appearance of the finished product. By using a smooth mold and high-quality plastic sheet, it is possible to achieve a smooth, attractive surface on the formed part.
The draft angles
In vacuum forming, the draft angle refers to the slight angle or slope on the sides of the mold. This angle is necessary to allow the formed part to be easily released from the mold.
The amount of draft required depends on the material being used, the size and shape of the part, and the complexity of the mold. In general, the larger and more complex the part, the more draft will be required. There are a few factors to consider when determining the appropriate draft angle for a vacuum forming mold:
- Material properties: The material being used will determine the amount of draft required. For example, softer materials may require less draft than harder materials.
- Part size: Larger parts will generally require more drafts than smaller parts, as they may be more difficult to remove from the mold.
- Part complexity: More complex parts with deep undercuts or intricate features may require more drafts to ensure that the part can be easily removed from the mold.
- Mold complexity: The complexity of the mold can also affect the amount of draft required. For example, a mold with a lot of undercuts or intricate features may require more drafts to ensure that the part can be easily removed.
It is generally recommended to use a draft angle of at least 1-2 degrees for vacuum forming molds. However, the exact draft angle will depend on the specific requirements of the application.
In addition to facilitating the release of the formed part from the mold, the draft angle can also help to prevent warping and distortion of the part during the forming process. When the plastic sheet is stretched over the mold, it will tend to shrink as it cools. If the draft angle is not sufficient, the part may become distorted or misshapen as it shrinks.
There are a few different methods that can be used to calculate the appropriate draft angle for a vacuum forming mold:
- The tangent method: This method involves calculating the draft angle based on the tangent of the radius of the mold.
- The parallel method: This method involves calculating the draft angle based on the length of the part and the radius of the mold.
- The perpendicular method: This method involves calculating the draft angle based on the height of the part and the radius of the mold.
No matter which method is used, it is important to carefully consider the material properties, part size and complexity, and mold complexity when determining the appropriate draft angle for a vacuum forming mold. By using the appropriate draft angle, it is possible to ensure that the formed part can be easily removed from the mold and has the desired shape and dimensions.
The undercut
An undercut is a feature on a mold that extends beyond the surface of the mold, making it impossible to remove the formed part without damaging it or the mold. In vacuum forming, it is important to avoid undercuts on the mold to ensure that the formed part can be easily removed without damaging it or the mold. There are a few reasons why undercuts should be avoided in vacuum forming:
- Difficulty in removing the formed part: Undercuts make it difficult to remove the formed part from the mold without damaging it or the mold. This can increase production time and costs and may result in defective parts that need to be reworked or discarded.
- Risk of damage to the formed part: If the formed part becomes stuck in the mold due to an undercut, it may be damaged when attempting to remove it. This can compromise the integrity and function of the part.
- Risk of damage to the mold: If the formed part becomes stuck in the mold due to an undercut, it may also cause damage to the mold when attempting to remove it. This can result in costly repairs or downtime in the production process.
To avoid undercuts in vacuum forming, it is important to carefully design the mold and consider the process for removing the formed part. It may be necessary to use a mechanism such as ejector pins or a slide action to remove the part from the mold. Alternatively, it may be possible to modify the design of the part to eliminate the undercut.
In general, it is best to keep the design of the mold as simple as possible in vacuum forming to avoid undercuts and other features that may make it difficult to remove the formed part. By avoiding undercuts on the mold, it is possible to ensure that the formed part can be easily removed without damaging it or the mold, reducing production costs and improving efficiency.
In this article, we talk about some common design features on the mold for vacuum forming, including the smooth surface, the draft angles, and the undercut. In the next article, we will talk about the ejector pins, vacuum ports, heating elements, and cooling channels on the mold, now please allow me to introduce our company to you:
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
Ditaiplastic wish you a great day!
