Dip molding is a manufacturing process used to create hollow plastic parts by dipping a mold, usually made of metal, into a liquid polymer. The process typically involves the following steps:

1. Mold release: A non-stick coating is applied to the tool to allow easy removal of the part from the mold.

2. Pre-heating the mold: A metal mold is heated to a specific temperature.

3. Dipping: The heated mold is dipped into a polymer, such as PVC (polyvinyl chloride), latex, or silicone. The heat causes the liquid to gel or fuse around the mold.  The thickness of the coating is influenced by factors like the mold temperature and the duration of immersion.

4. Curing: The mold, now coated with the polymer, is heated in an oven to cure or solidify the plastic.

5. Cooling and part removal: Once cured, the mold is cooled, and the part is removed, often by simply pulling it off the mold.

What is dip coating?

Dip coating is a manufacturing process in which an object is submerged into a liquid polymer, then withdrawn and allowed to cure, forming a protective or decorative layer on its surface. It is a simple and effective technique used to apply coatings evenly to a wide variety of objects.

Steps Involved in Dip Coating:

1. Preparation: The object to be coated is cleaned and prepared to ensure good adhesion of the coating material. Sometimes a primer is applied to make the coating permanent.

2. Pre-heating: The part to be coated is heated to a specific temperature.

3. Dipping: The object is immersed in a bath or tank containing the liquid polymer.

4. Curing: The coated object is placed in a second oven to cure or harden the coating.

5. Cooling: Once cured, the part is cooled and removed from the production line.

Dip molding excels in certain applications due to its simplicity, cost-effectiveness, and ability to create uniform coatings or molded parts. The process is ideal for producing flexible, soft, and durable products with consistent surface finishes. Here are some of the best applications for dip molding:

1. Medical Devices:

• Application: Nasal cannulas and tubing connectors are commonly made through dip molding.

• Why It's Ideal: The process allows for the creation of thin, flexible, and durable products that are biocompatible and comfortable for prolonged use. The process allows for producing flexible, airtight components with precise control over thickness and shape.

 2. Grips and Handles:

• Application: Dip molding is frequently used to create soft, non-slip grips and handles for tools, medical devices, sports equipment, and industrial machinery.

• Why It's Ideal: The process provides a smooth, flexible, and comfortable finish, and multiple layers can be applied to achieve varying thicknesses.

3. Protective Caps and Covers:

• Application: Protective caps for electrical components, pipe ends, and machine parts are commonly produced using dip molding.

• Why It's Ideal: The process offers precise control over size and shape, and the finished product provides a protective, insulating barrier that is resistant to moisture, chemicals, and abrasion.

4. Electrical Insulation:

• Application: Dip molding is widely used for insulating electrical components like wires, connectors, and terminals.

• Why It's Ideal: Plastisol (PVC) provides excellent insulation and protection against moisture, chemicals, and wear, making it perfect for electrical applications.

5. Balloon and Bladder Manufacturing:

• Application: Products such as medical balloons, flexible tubing, and air bladders for sports equipment can be made using dip molding.

• Why It's Ideal: Dip molding creates thin-walled, flexible, and durable structures.

6. Custom Components for Aerospace and Automotive:

• Application: Aerospace and automotive industries use dip molding to create protective coatings and flexible components like wire harness covers, tubing, and seals.

• Why It's Ideal: The coatings provide resistance to extreme temperatures, chemicals, and abrasion, which is crucial for high-performance applications.

7. Coated Racks and Hooks:

• Application: Industrial hooks, racks, and fixtures are dip-coated to add a durable protective layer.

• Why It's Ideal: The plastisol coating provides protection against corrosion, chemicals, and wear, making it suitable for industrial environments.

Dip molding offers several advantages over injection molding, particularly in specific applications. Here are the key benefits of dip molding:

1. Lower Tooling Costs: Dip molding requires simpler and less expensive molds, often made from metal rods or shapes, compared to the complex, multi-part molds needed for injection molding. This makes it a more affordable option for prototypes or low-volume production runs​.

2. Faster and More Cost-Effective Setup: The simpler mold design and setup process for dip molding allow for shorter lead times and lower upfront costs. Injection molding, on the other hand, involves more complex tooling that can be expensive and time-consuming to produce​.

3. Flexibility in Material Thickness: With dip molding, you can easily control the thickness of the finished part by adjusting the dip duration or the number of dips. This flexibility is more difficult to achieve in injection molding, where the part's thickness is typically constrained by the mold design​.

4. Ideal for Small-Volume Production: Dip molding is better suited for small-batch or custom parts because of its low-cost tooling and flexibility.

5. Smooth, Seamless Parts: Dip molding naturally produces parts without seams, making it ideal for applications where smooth surfaces are important, such as medical devices. In contrast, injection molding can leave visible parting lines where the mold comes together​.

6. Ability to Handle Complex Shapes: Dip molding is well-suited for producing hollow, flexible, or tubular shapes (e.g., grips, balloons, or catheter tubes) that would be more challenging and expensive to create using injection molding​.

At Production Sciences we primarily work with plastisol.  Plastisol, a liquid form of PVC, can be modified with various additives to change its properties for different applications. Here are common additives used to adjust the characteristics of plastisol:

1. Plasticizers:

   • Purpose: Increase flexibility, softness, and pliability.

   • Effect: Higher levels of plasticizer make the plastisol more flexible and softer, while lower levels make it stiffer.

2. Stabilizers:

   • Purpose: Enhance heat stability and prevent degradation during processing and in the final product.

   • Effect: Stabilizers protect against yellowing, brittleness, and breakdown due to heat or UV exposure.

3. Fillers:

   • Purpose: Reduce cost, increase volume, and modify mechanical properties like hardness, weight, and opacity.

   • Effect: Fillers can increase rigidity and impact resistance or provide specific textures and finishes.

4. Pigments and Dyes:

   • Purpose: Provide color to the plastisol.

   • Effect: Customizes the color and opacity of the final product.

5. Foaming Agents:

   • Purpose: Create a lightweight, expanded or foam-like structure.

   • Effect: Produces a spongy, foam-like material, commonly used in flooring, gaskets, and cushions.

6. Antimicrobial Agents:

   • Purpose: Inhibit the growth of bacteria, mold, and fungi on the plastisol surface.

   • Effect: Provides long-lasting microbial resistance, useful for medical and hygiene products.

7. Antistatic Agents:

   • Purpose: Reduce static electricity build-up on the surface of the plastisol.

   • Effect: Useful in applications where static charge build-up is undesirable, like electronics.

By incorporating these additives, plastisol can be fine-tuned for specific performance requirements, from increased flexibility to improved durability or aesthetic appearance.

Most dip coating is performed with liquid polymers.  However, by utilizing a fluidized bed, a powder can behave like a liquid.  Air is forced upwards through a very fine powder causing the individual particles to be suspended in the air flow.  With the powder fluidized, the same steps as outlined above (preheat, dip, cure, cool) can be used to apply a coating to a metal part.  The key advantages to this type of molding are:

1. Thermoplastics:   Not all materials can be dipped as a liquid.  Thermoplastics must be applied as a powder which are melted by the heat of the part to be coated. This allows us to coat parts with alternate materials to achieve different properties. These materials include Nylon, PVC, polyethylene, and polypropylene.

2. Thin, Uniform coating: The process can create coatings that are thinner than can typically be created with liquid. The fluidized bed provides a consistent and even coating, even on complex shapes with sharp bends or corners.  

3. Good coverage: It effectively coats all surfaces of the object, including hard-to-reach areas.

Common applications:

• Coating wire goods, such as baskets and racks.

• Providing protective coatings for electrical components.  

• Applying wear-resistant coatings to metal parts.