In-depth Discussion on Common Defects in Vacuum Formed Products and Their Solutions
Introduction of vacuum formed products
Vacuum forming is a widely used process capable of producing a variety of plastic products. However, no matter how mature the process is, vacuum-formed products may still encounter some common defects during production. These defects not only affect the appearance of the product but may also impact its functionality. In this article, we will explore these defects and their solutions in detail, while also introducing the advantages of thermoforming and the relevant knowledge about mold making.
1. Pull Lines (La Qiu)
Issue Description: Pull lines refer to undesired line protrusions that appear during the plastic molding process but are not part of the mold. This defect usually requires mold modification, such as reducing the mold height and increasing surface smoothness. Additionally, adding a pressure mold (known as an upper mold) can further improve the issue. If the pull lines are too large, the product is considered defective and cannot be used for high-end packaging. However, in some cases, such as component rotating trays, as long as the pull lines are neatly arranged and do not affect functionality, the product should be considered qualified.
Solution:
Add an upper mold to ensure surface flatness and avoid the formation of pull lines.
Redesign the mold to reduce height and enhance surface smoothness.
2. Scratches
Issue Description: Scratches refer to marks that appear on the surface of transparent plastic blisters. If these scratches are too long or large, they can negatively impact the product’s appearance, making it unsuitable for high-end packaging.
Solution:
Use protective films or other safeguards during handling to prevent scratches.
Regularly inspect molds and equipment to ensure smooth, undamaged surfaces.
3. Crystal Points
Issue Description: Crystal points are transparent flaws that occur when fine dust in the air settles on heated plastic material during the production of plastic sheets. This issue is especially problematic in the production of transparent plastic sheets. If the crystal points are too large or numerous, the product is considered defective.
Solution:
Consider using higher-grade raw materials to reduce the occurrence of crystal points.
Maintain a clean production environment to minimize airborne dust.
4. Bubbles
Issue Description: Bubbles form in the plastic sheet during production when heated plastic material contains air. This is particularly problematic in the production of transparent plastic sheets. If the bubbles are too large or numerous, the product is considered defective.
Solution:
Use vacuum pump systems to eliminate air residues during the molding process.
Implement stricter process controls to ensure air is minimized during the heating process.
5. Water Ripples
Issue Description: Water ripples can appear on the surface of plastic sheets due to differences in materials and processing techniques. This issue is particularly noticeable in the production of transparent plastic sheets. If the ripples are too pronounced, the product is considered inferior. Generally, the thicker the sheet, the more noticeable the water ripples. Qualified PET materials have fewer ripples, while most PVC materials exhibit this issue.
Solution:
Control sheet thickness to ensure a smooth surface on the final product.
Select appropriate materials and processing techniques to minimize the formation of water ripples.
6. Other Common Issues
Different plastic products may encounter different problems. For example, in carded blisters, the main issue is poor folding, which can cause the back to lift. In folding boxes, the primary issues include improper alignment and failure to buckle. These problems must be addressed based on the specific circumstances.
Advantages of Thermoforming
Thermoforming is a plastic forming process that offers several key advantages:
Flexible Mold Options: Temporary tooling provides an inexpensive short-term test for design issues and market acceptance before moving to mass production, allowing for adjustments based on small-batch testing.
Efficiency and Cost-Effectiveness: Thermoforming is suitable for producing plastic parts of various sizes, shapes, and quantities. Compared to injection molding, upfront costs are usually lower, and the tooling and production lead times are shorter.
Materials Used for Mold Making
In the production process, the choice of mold materials is crucial. Production molds are typically made from aluminum. Aluminum molds are temperature controlled, allowing for tighter tolerances, better detail, and shorter cycle times, which translates to lower production costs. For deeper molds, casting is usually employed, while shallower molds can be machined directly from a block of aluminum.
What Do We Need from You to Make a Part?
At Ditai, we can start from your design drawing (e.g., a UG drawing). If you have a concept or sample, we can create a design, including CAD models, renderings, and detailed drawings. If you already have a CAD (igs or stp) model or design, we can start from that and create molds and other tooling to produce the final product. Our services range from design and prototyping to production, and we can provide as much or as little support as you need.
By understanding these common defects in vacuum-formed products and their solutions, combined with the advantages of thermoforming and key factors in mold making, Ditai can better control product quality during production, ensuring that every product meets customer expectations. If you have more questions about quality control in vacuum-formed products or need assistance, feel free to contact us.
Get In Touch With Us！
Phone：+86 13825780422
Email：ditaiplastic01@gmail.com
Address：Ruida Industrial Park, 6 Daxing Street, Quantang community, Liaobu, Dongguan,Guangdong
