Friday, November 12, 2010

Manufacturing of Siding

Technical excellence, processing expertise, and an
unwavering commitment to quality characterize the equipment,
processes, and personnel at our three vinyl siding
manufacturing plants. Since our company’s beginning,
CertainTeed has been developing innovative products and
processes to improve the look and durability of building
products. Today, tried and true manufacturing methods are
tested and retested to ensure that you consistently receive the
highest quality siding and accessories.
The manufacturing process begins as resin is unloaded from
railroad cars through an air-conveying system into silos holding
up to 250,000 pounds. From these main storage silos, resin is
conveyed to the blender where TiO2 and other micro-ingredients
are added to create the processing compound. This precise
measuring of ingredients and uniform blending under proper
heat conditions are critical for production of uniform, high
quality products.
CertainTeed Vinyl Siding Master Craftsman Education & Development Program
5. Manufacturing
In this chapter, you’ll learn about the processes used to
manufacture vinyl siding and Cedar Impressions
polypropylene panels:
• Extrusion
• Co-extrusion
• Embossing
• Post-forming
• Cutting
• Injection Molding
Incoming resin
inspected to
exacting quality
State of the art extruders
maintain precision
Specially designed rollers,
fixtures, sizers and dies,
form distinctive profiles
Exclusively built finishing
equipment cuts and prepares
panels for trouble free installation
Panels packed in sturdy cartons
protect the siding, making proper
handling easy from the factory to
the jobsite
Rail car
Extruder/Die Embossing
Inspection Packaging
Resin Silo Blender Compound Compound Silos
Computer controlled blending
assures consistent compounding
Massive silos store uniformly
colored components
After blending, the compound is conveyed to the siding
extrusion line where it is carefully metered so a consistent
amount enters the extruder.
Basically, extrusion is a process in which a thermoplastic resin
(one that softens when heated and hardens when cooled) is
pushed through a heated barrel and die by two large, precisely
tooled screws. As they turn, the screws knead and thoroughly
mix the PVC compound. Both the screws and the barrel of the
extruder are heated, which melts the resin and makes it easier
to mix and push. The heat (300° to 400° F) also accelerates
the physical reaction (fusion) between PVC and the microingredients
in the compound.
All vinyl siding is extruded, but CertainTeed was the first to
extrude all its siding and accessories1 with twin-screw extruders.
Twin-screw extrusion is preferable to single-screw extrusion
because it heats and distributes material more evenly, resulting
in a product with better physical properties. As the PVC compound
is forced ahead of the rotating screws, the very tight
tolerances in the double barrel promote complete fusion of the
ingredients. Color concentrate is added at the extruder, a technique
that produces rich, durable color in every siding panel.
Co-extrusion is the joining of two flows of molten PVC
compound from two extruders in a single die to produce a
single sheet made of two layers of material: substrate and
capstock. This is how we incorporate ASA/AES plastic on our
dark color sidings.
Co-extrusion technology allows us to concentrate the most
important, expensive micro-ingredients in the capstock, which
acts as a shield of protection for the panel.
As it exits the extruder, the vinyl sheet is still very hot, nearly
molten. Between the extruder die and cooling tank, the sheet
passes between a textured roller and a rubber roller for
embossing. Depending upon the rollers, CertainTeed siding and
vinyl accessories are embossed in either rough cedar,
woodgrain, smooth brushed, or smooth textures.
CertainTeed adopted the post-form extrusion process two
decades ago after its research demonstrated that post-form
extrusion produces more batch-to-batch consistency in thickness
and profile. In addition, post-form locking devices have
tighter tolerances and more intricate interlocking devices,
which result in higher wind load ratings. The specially designed
pre-sizers and vacuum sizers immediately prior to the cooling
bath create the distinctive profiles and wide range of available
sizes of vinyl siding. In a vacuum sizing calibrator, the siding is
given its crisp finished profile.
Water Tank
The siding profile enters a water tank immediately after vacuum
sizing. Once the hot profile is in the cooling tank, the panel
temperature quickly drops and the final shape thermally sets.
Nail Punch and Cut Off
After passing though a cooling tank, the ribbon of siding is
punched at precise intervals for nail holes. Finally, it is cut to
length, inspected2, and packaged.
CertainTeed Vinyl Siding Master Craftsman Education & Development Program
Injection Molding
We use the injection molding process to manufacture our Cedar
Impressions family of siding and accessories. The process itself
is fairly straightforward. Basically, the resin is poured into a
hopper where it mixes with pigment and other additives. The
compounded resin drops into the throat of the equipment,
where the pellets form a solid bed. This bed of resin is pushed
through the barrel of the equipment by a metal screw, and the
mechanical shear between the screw and the barrel heats up
the compound.
The hot compound flows into the cavity of the mold. Processing
additives and computer controls ensure that the compound
flows smoothly into every nook and cranny. Under the proper
heat and pressure, the polypropylene panel sets. After the mold
opens and ejector pins push the panel out, robotic arms lift it
and place it into a conveyor, where it slowly cools.
Operators inspect each panel as it comes off the conveyor,
apply the patented PanelThermometer,™ and package the
finished siding.
CertainTeed Vinyl Siding Master Craftsman Education & Development Program
• Vinyl siding is manufactured by a process called extrusion.
Basically, PVC resin is pushed through a heated barrel and
die by two precisely tooled screws. Vinyl sheets are pushed
out of the die.
• CertainTeed uses the co-extrusion process—two flows of
molten PVC compound into a single die—to incorporate the
plastic that protects dark colors from fading.
• After they are extruded, smooth vinyl sheets are embossed
with either a rough cedar, wood-grain, smooth, or brushed
• In the post-forming operation, the vinyl sheets are formed
into the distinctive profiles and sizes of CertainTeed siding.
• Cedar Impressions siding is injection molded.

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