Dip molding (dip moulding) is a process used to manufacture plastic parts, products and components. As one might expect, manufacturers perform the dip molding process by dipping a mold into liquid plastic and allowing it to set before removing it from the plastic.
Dip molding is an important plastic product formation process. The purpose of dip molding is both decorative and protective. For example, covering the handles of many everyday objects improves the comfort and grip, and can add an element of design to an object.
Dip molded parts and dipped products are popular for use in a wide variety of industries, including the consumer, medical, electronic and retail industries. In particular, dip mold products are important in the: biking, medical device, sanitation, appliance, and sports and recreation industries.
Dip molding produces dipped mold parts such as: plastic caps, plastic plugs and other sorts of plastic closures, handles and grips (like pump grips) for appliances, handle bars, plugs, sports and recreational equipment, gloves, and countless small plastic products.
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Image Provided By U.S. Plastic Coatings Corporation
The modern dip molding process got its start in the United States and the United Kingdom in the 1930s. While people used dip mold-like processes before the 20th century (ex. hot wax candle creation), it didn't take off as an industrial process until around World War II. World War II jumpstarted the dip mold industry because of its wide use of plastic and polymers. Around this time, manufacturers discovered that they could quickly and easily dip mold plastic shapes, which they could then use as containers, tool handles, and the like. Later, they discovered that, to get thicker walls, they could just dip mold the product again and again.
For the first fifty years or so of its existence, most dip molding was done using either natural latex or PVC. However, when the FDA announced in 1993 that between 2% and 10% of the US population had a latex allergy, the industry, particularly the medical glove industry, had to begin diversifying. At that time, they added a finishing process that involved removing process powders. They also tried to remove some of the offending proteins from latex itself. Even more, the dip molding industry began working with other polymer products, like nitrile rubber, neoprene, polyurethane, and SBR (styrene butadiene rubber).
Today, the dip molding industry is booming. The plastic dip mold industry is particularly big. In the coming years, you can expect to see this trend continue, as automation becomes more prevalent, equipment becomes more efficient, tooling costs drop, and more and more polymer blends become available.
Dip molding relies primarily on plastisol. However, the process can also be performed with materials like latex, neoprene, urethane, and epoxy.
The first step in the dip molding manufacture process is to warm the polymer or vinyl until it reaches a liquid state. Two variables to be considered that can affect both the quality and appearance of the product are the temperature of the mold part and the temperature of the material. That's why, once at the right temperature, the polymer must be kept in this state, and if necessary, heated to optimum viscosity.
Next, manufacturers must determine a consistent speed for dipping, or immersing, and withdrawing the mold from the liquid. They use these determinations during the third step.
During step three, manufacturers heat mandrels, or molds, in order to ensure that the molten polymer will stick to their surfaces. Then, they slowly lower the molds into the liquid plastic, making sure to allow for uniform surface coverage and even wall thickness. Because the plastic has been heated, this is called a hot dip process. The longer a mold is allowed to be immersed in the liquid for, the thicker the wall of the product will be, and so it is important to consider this manufacturing aspect before undergoing plastic dip molding.
Once the desired "dwell time" has been reached, manufacturers slowly remove the mold from the liquid and let it harden. Like when they first immersed it, they must remove the mold slowly and consistently in order to ensure a smooth finish on the surface, and to prevent wall thickness irregularities.
After this, some polymers, like plastisol, are further heat treated in an oven to fully set the mold.
Finally, the polymer is then stripped from the mandrel. If necessary, manufacturers move it on to secondary finishing. However, because dip molded products are relatively precise, most do not require extra finishing.
When designing plastic molding projects, manufacturers think about the necessary textures, hardness levels, dimensions, etc. of the parts they plan to create. Fortunately, they have a lot of design freedom; plastic can be manufactured in many different colors, and by using different techniques, manufacturers can aesthetically adjust the respective textures, hardnesses and surface appearances of the coatings.
There are a variety of different machines, systems, and tools used in dip molding processes.
To create the best product, manufacturers turn to many variations on and similar processes to the dip mold process. Learn more about them by reading the descriptions below.
The dip coating process is a similar service that is also offered by many dip molders that partially or fully coats products with a protective material. Dip coaters apply coatings to products in the same method as dip molding, by dipping them in liquid plastic or liquid plastisol. Plastic coatings are typically a polymer coating or a vinyl coating. The most common, however, are PVC coatings and plastisol coatings The biggest advantage of dip coating is its protective and insulative properties. For example, electrical wires and components such as jumper cables or extension cords are dip coated to provide electrical insulation. Also, both plastic coating and plastisol coating improve a product's noise reducing and vibration dampening properties, add excellent thermal insulation and eliminate the need for deburring (because coating reduces sharp edges on metal parts). Coating around wires and fences improves the corrosion resistance of the products and extends their lifespan, especially when used outdoors.
Powder coating is a coating process that, instead of liquid plastic, uses a free-flowing, dry powder. Manufacturers apply the powder electrostatically, and then cure it under heat. One of the advantages of powder coating is that it does not require a solvent to keep the binder and filler parts in liquid suspension. Also, using powder coating, manufacturers can produce parts with much thicker walls without having to worry about sagging or running. Furthermore, powder coating allows for specialty effects that cannot be accomplished with conventional coating. Finally, powder coatings take less time to cure, and they release little or no Volatile Organic Compounds (VOCs) while doing so.
Injection molding is a manufacturing process that, like dip molding, uses a mold and liquid material to form a part. Injection molding, though, uses a ram or screw-type plunger to force molten plastic material into a mold cavity, where it contours to the form of the mold, cools, and solidifies. Once solidified, it is a shape that has conformed to the contour of the mold. One of the most common types of injection molding is plastic injection molding. Injection molding is cost-effective, efficient, creates little waste, and produces a high yield of durable products.
Blow molding is yet another a mold process that primarily works with plastic. Manufacturers use blow molding to make hollow plastic parts. The three main types of blow molding are: extrusion blow molding, injection blow molding, and injection stretch blow molding. During these processes, manufacturers start by melting down plastic. Then, they form it into a parison, or in the case of injection and injection stretch blow molding (ISB), a preform. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass. After that, they clamp the parison into a mold and blow air into it. The resulting air pressure pushes the plastic out until it matches the mold. Once the plastic cools and hardens, manufacturers can open the mold and eject the newly formed part. This dip molding service is popular for its low tool and dies costs, its fast production rates, and its ability to create complex parts.
UV coating is a process in which manufacturers apply UV curable coatings to products. These coatings render the products resistant to wear, scratch, fogging, chemicals, microbes, and, of course, damaging ultraviolet rays. UV coating is best used on outdoor products. They are mostly applied via spray, dip, roll, or flow processes. Because UV coating processes do not require heat, they are popular with formed plastic parts.
There are many advantages to dip molding, as well as dip coating. First, dip molding is suitable for fast prototyping because it has short lead times and, unlike other manufacturing methods, it has minimal setup costs. The latter fact is because both the equipment and process are basic. In addition, since the process is almost entirely automated, dip mold labor costs are also low. Plus, as the process is straightforward, it has relatively high turnaround times.
Furthermore, dip molded parts are highly flexible and malleable; therefore, manufacturers can easily strip even the most complex parts from the molds. Even better, dip molded products require little or no secondary processing. This ensures that there is minimal material wastage during the process.
In addition to providing a colorful and attractive finish to various products, plastic moldings and coatings provide corrosion resistance, scratch resistance, wear protection, and a smooth, tactile grip for safe and easy handling. Finally, dip molding and dip coating are both incredibly versatile. They offer a wide range of wall thicknesses, wall textures, and part sizes.
If you're interested in investing in dip molding services, it's important that you work with an experienced dip mold manufacturer that you can trust. While many suppliers offer dip molding and similar services, not all of them are equal, and not all of them are right for you. Find the right manufacturer for you by discussing your application at length with multiple dip mold companies. Make sure they understand your requirements and specifications, are willing and able to work within your budget and deadline, and, most importantly, that they're dedicated to delivering you a high-quality solution. Get started by checking out the many excellent dip mold manufacturers that we have listed above.
Dip Molding Terms
- A test that determines the ease
of removing air bubbles from plastisol.