About Dip Molding and Dip Molders Including: Dip Coaters, Dip Coating, Dip Molders, Plastic Caps, Plastic Closures, Plastic Coating, Plastic Plugs, Plastisol Coating, Polymer Coatings, PVC Coating, UV Coating & Vinyl Coating.
Dip molding is the process of molding plastic parts, products and consumables by dipping a mold into liquid plastic then treating the product with heat. Most dip molding manufacturers also provide dip coating services, which use a similar process to partially or fully coat parts and products in various types of polymers. Both processes are common in consumer industries, medical equipment and electronic connectors. Dip molders produce plastic closures like plastic caps and plastic plugs for packaging and furniture industries, as well as latex gloves, handle grips, bellows and condoms for consumer industries. Plastic coating is typically a polymer coating or vinyl coating, the most common being PVC coating and plastisol coating. In outdoor applications, UV coating is used to guard against harmful ultraviolet rays. Polyethylene coatings and urethane coatings are also applied by dip coaters. Dip moldings may be made from all of these materials as well.
During the dip molding process, the polymer or vinyl material is kept in a liquid state while heated and primed aluminum or steel "mandrels", or molds, are dipped into the plastic from an overhanging rack. Wall thicknesses can be determined by how long the mandrels are left in the plastic as well as at what temperature the liquid plastic and mandrels are kept. Double walls may be applied with multiple dippings. Plastisol, which is a vinyl compound and the most common polymer used in dip molding and dip coating, is liquid at room temperature, solidifying permanently when heated. The polymer on the mandrel is heat-treated even if it is not plastisol, as most polymers' properties are improved with some heat processing; when the polymer has fully solidified, it is stripped from the mandrel and moves on to secondary processing. In this way, a long list of protective parts and products are made, including gas pump handles, floats, boots, cleaning gloves, end caps and hole plugs.
Dip coating is performed the same way dip molded parts are manufactured, except that instead of dipping mandrels into liquid polymers or plastisol, the parts which require coating are hung from an overhead rack and dipped. Some products and parts may be fully immersed, such as plastic coated fences, wire forms or racks, while others are half-coated to serve as grips, tool handles, electrical connectors or cushion covers. Many types of garden tools, fitness equipment and outdoor equipment have protective plastic handle grips or foot grips to make for easier, safer handling and longer equipment life. Electronic connectors such as jumper cable connectors have insulating plastic-dipped grips to protect from electric shock while handling. Although plastisol is by far the most commonly used polymer for plastic dip molding and dip coating, other polymers such as vinyl, PVC, latex, neoprene, urethane, silicon and rubber are used to manufacture dip coatings and dip molded parts as well.
Plastic dip molding and dip coating fill a unique niche in manufacturing which no other plastic or rubber processes are fully capable of replicating. Dip moldings and coatings are highly cost-effective, as there are no dies to fabricate, and most plastic coated and molded parts require little - if any - secondary processing. Labor costs are low, and the dip molding and coating processes can manufacture high volumes in a short time. In addition to providing a colorful, attractive finish to various products, plastic coatings and plastic caps provide corrosion resistance, scratch and wear protection and a smooth, tactile, resilient grip for safe, easy handling. A variety of finishes are available for dip molded parts and coatings, from smooth satin finishes to rough matte finishes. Specialized types of urethane or nitrile molding can coat or mold products in the form of foam, providing extra cushioning.
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Dip Molding and Dip Molder
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Dip Molding Types
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dispensing plastisol into a mold, placing it in an oven and then heating
it so the plastisol fuses into the finished part. This process is capable
of producing multi-colored parts.
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is used mostly for thin coatings of plastisol. In this process, the
object is dipped in plastisol without preheating, and then placed in
a heated chamber.
- is the process of submersing an object in a tank full of coating material.
- is a thermal process by which metal molds are dipped and coated.
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is the process in which an object is heated, dipped in plastisol and
then placed in a heated chamber where fusion takes place.
- are plastic covers formed through the process of dip molding.
- is a process in which metals are coated with plastic.
- are plastic caps formed through the process of dip molding.
- Polymer coatings act as a protective covering in corrosive environments by enhancing the abrasion resistance of the component's surface.
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is a method that involves placing a limited amount of plastisol in a
mold and then rotating it as heating takes place so the liquid is equally
distributed. This is used to create hollow products.
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is the method of completely immersing an object in liquid plastisol
and then letting it gel so that the object is totally covered.
- Vinyl coatings are wear resistant vinyl compounds that undergo dip coating processes to form rigid smooth or textured protective coatings over substrate surfaces, typically metals.
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Dip Molding Terms
- A test that determines the ease
of removing air bubbles from plastisol.
- Used mostly with
rotary dip molding machines. The advantage of this system is that it
raises the amount of operator positions for reloading and unloading without
taking the racks offline, and also permits extra positions for cooling
and priming metal parts for coating preparation or for automatically
lubricating mandrels.
- An irregularity on the surface of fused plastisol, caused
by the contamination of water, air or solvents.
- A high temperature
air mover that raises turbulence and heat transfer to the mandrel or
tool in the preheat oven, also used in
the cure oven to accelerate curing and lower heat stratification.
- A measure of the viscosity of plastisol.
- A device in the dip tank that completely stops
the flow of plastisol over the weir during the dip cycle. Its use requires
synchronization with the dip tank agitation and recirculation pump cycle.
- Removal of trapped air from plastisol by using a vacuum
during mixing or later in the process.
- The uppermost edge of the dipped plastic coating.
- A material that upon being stretched to twice its length
at room temperature will immediately snap back into place.
- A measure of how far fused plastisol can be stretched
without breaking.
- Added materials used to reduce costs or modify the finished
product.
- When plastisol becomes immobile after its liquid has
been absorbed by the resin.
- When plastisol travels out of fused or partially-fused
vinyl film.
- Forms the internal
shape of a dip molded part, made of steel, aluminum or other alloys. Multiple
mandrels are usually mounted to a bar that is placed into a master rack
or mounted directly on the arm of a machine.
- A frame of aluminum or steel with pins or indentations
symmetrically positioned for retaining adapter bars. Typically, the designs
of master racks are for specific dip molding machines and can be used
with many similar bars of tooling.
- A plastisol into
which solvent has been added.
- Used for multiple dips or several colors
or grades in a constant process. The two-axis design removes preheated
racks of parts or tools from the machine by using the vertical axis,
and then moves the parts laterally to any of up to four dip tanks.
- Overhead dip stations use this J-shaped gripper to grab
the rack of tools to be dip coated. Typically these are used in pairs.
- Solids with low melting points or liquids with high
boiling points that are used to give flexibility to PVC resins.
- A liquid substance made of a blend of polyvinyl chloride
(PVC) resins and liquid plasticizers. It is a thermoplastic that can
be used to produce coatings or moldings through a heat process.
- Uses programmed positions, speeds and dwell
times to alter the dip speeds of a tool or mandrel. This is for controlling
the drip and the thickness, and may be used with traditional moving tank
designs or with overhead dip systems.
- Small particles of PVC that are mixed with
plasticizer to form plastisol.
- A measure of the viscosity of plastisol.
- Dark specks in fused plastisol of burnt resin caused by
overheating.
- An electric heater in most cure ovens that is typically
mica insulated. Airflow over these heaters moves the heat from the strip
heater to the plastic coating to be cured.
- An agent that is used in plastisol to reduce its viscosity
and enhance air release.
- An electric heater with a high surface temperature,
typically in the preheat section of the machine. Air flow as well as
infrared radiation over the elements moves the heat to the mandrel or
tool to be coated.
- The tendency of plastisol to become more viscous
while in storage.
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