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Terms Used In Dip Coating
Air Release – A test that determines the ease of
removing air bubbles from plastisol.
Automatic Rack Transfer System (ARTS) Station – 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.
Blister – An irregularity on the surface of fused plastisol, caused by
the contamination of water, air or solvents.
Blower – 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.
Brookfield Viscosity – A measure of the viscosity of plastisol.
Closeable Dam – 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.
Deaeration – Removal of trapped air from plastisol by using a vacuum
during mixing or later in the process.
Dip Line – The uppermost edge of the dipped plastic coating.
Elastomer – A material that upon being stretched to twice its length at
room temperature will immediately snap back into place.
Elongation – A measure of how far fused plastisol can be stretched
without breaking.
Fillers – Added materials used to reduce costs or modify the finished
product.
Gelatin – When plastisol becomes immobile after its liquid has been
absorbed by the resin.
Leaching – When plastisol travels out of fused or partially-fused vinyl
film.
Mandrel – 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.
Master Rack – 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.
Organosol – A plastisol into which solvent has been added.
Overhead Dip Station – 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.
Pawl – Overhead dip stations use this J-shaped gripper to grab the rack
of tools to be dip coated. Typically these are used in pairs.
Plasticizers – Solids with low melting points or liquids with high
boiling points that are used to give flexibility to PVC resins.
Plastisol – 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.
Profile Dripping – 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.
PVC Dispersion Resin – Small particles of PVC that are mixed with
plasticizer to form plastisol.
Severs Viscosity – A measure of the viscosity of plastisol.
Specks – Dark specks in fused plastisol of burnt resin caused by
overheating.
Strip Heater – 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.
Surfactant – An agent that is used in plastisol to reduce its viscosity
and enhance air release.
Tubular Heater – 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.
Viscosity Aging – The tendency of plastisol to become more viscous
while in storage.
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