In order to better comprehend the capabilities of World Plastic, we will present in this section a guide to the technology of profile extrusion. This overview will include equipment, capabilities, material selection and material coloring.
I. BASICS OF PROFILE EXTRUSION
If you ever had a “PLAYDOH” set as a child then you already have performed the basic functions of profile extrusion. Using “PLAYDOH” you have your basic raw material. You put it into a chamber and force it out of an opening (die) of your choice, which forms it into a shape. Plastic Profile Extrusion works by the same principles.
Plastic profile extrusion starts with a raw material, in this case thermoplastic resigns are used in pellet form. The material is placed in a hopper chamber mounted on top of the extruder. The material is gravity fed into the rear end of the extruder.
The extruder itself is made up of a number of key components
The barrel is a hollow metal tube which acts as the oven. Heater bands are placed on the outside of the barrel to heat up the thermoplastic pellets. The barrel also acts as a chamber to hold the screw.
PictureThe screw is similar in many ways to hardware screws. The function of the screw is to take the material fed from the hopper and move the material forward as the screw turns. The turning action of the screw combined with the heat in the barrel will melt the thermoplastic pellets. The screw forcing the material forward and up against the barrel will also create frictional heat and a mixing action which will help the material melt in a uniform manner.
The motor creates the power to turn the screw. The heaters create the thermal conditions to melt the material. The heaters are divided into different zones, so you can control the heat at various points along the barrels.
Once the material is uniformly melted and in the proper viscosity, it will reach the front end of the extruder, commonly known as the head. This is where the die is mounted. An infinite number of shapes can be made – see the catalog section for the shapes World Plastic currently has available.
In front of the extruder is the area known as “downstream”. This area will have one or more of the following components.
Post forming, sizing
The profile, once extruded, has to be cooled. This is done by either air, water immersion or water mist. The profile also has to be formed into its final close tolerance dimensions. This is achieved by post forming die sets which are downstream and will help size the profile.
The take off equipment consists of a puller which will consistently move the profile at a constant rate. The cutoff is after the puller and can automatically cut the length you desire for the profile.
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Secondary operations such as laminating, taping, slitting, spooling and coiling can also be completed in line.
This is a process when two or more materials or colors are combined using multiple extruders. These extruders are in line and multiple streams of melted material are combined in a manifold. Co-extrusion can produce profiles of multiple colors using similar materials, a hinge effect or a gasket area.
World Plastic Extruders, Inc. co extrudes various grades of impact polystyrene with a flexible component to produce parts that are less expensive than co-extruded PVC parts. Polystyrene resin is less expensive and allows higher production rates than PVC. These two factors, combined with a lower specific gravity, equate to overall savings. Now, even co-extruding large cross sections can be cost effective. The use of polystyrene also offers more design options since there are very few color restrictions. more importantly, polystyrene allows for easier solvent bonding or welding.
World Plastic Extruders unique co-extrusion technology combines rigid and flexible materials in a variety of shapes, including a hinge or gasket effect and multiple colors. World can produce custom profiles using a variety of materials including all impact grades of polystyrence, rigid and flexible PVC , cellulosics, polyethylene, acrylic, ABS, polypropylene, and K Resin.
III. MATERIAL SELECTION GUIDE
This section is geared toward the P.O.P. designer and buyer.
High Impact Styrene (HIS) is a cost effective material with good impact resistance that can be easily colored, even in a small quantity. It extrudes with a uniform mate finish. HIS is used for indoor applications and UV inhibitor can be added, if necessary. It is translucent in its natural state and translucent to opaque when colored.
Rigid Vinyl (R/PVC) is a moderately priced material that provides good clarity. R/PVC is suitable for outdoor as well as indoor applications. It is tough and versatile, and available in clear to opaque colors with a moderately lustrous finish. Color matching may be expensive for small orders.
Butyrate (CAB) provides very good quality clear. The material has good flexural strength and a high gloss finish. Butyrate is usually used for it’s clear form. Color matching may be a problem in some projects.
ABS is tougher and shinier than High Impact Styrene. It is worth the higher price, if its properties are really needed. Unlike HIS, coloring may present problems for small orders.
Polyethylene (PE) is an economically priced flexible material, unlike most of the plastics used in POP work. PE (in most extruded forms) can be coiled or spooled and cut in the field. In extrusions it may be translucent to opaque in somewhat muted colors. High density formulations are available when more rigidity is required.
Flexible Vinyl (F/PVC) is tough and flexible, with a rubber or leather like feel. It is often the material of choice for bumper edges, gaskets and seals. Ideal for components that have to bend easily.
Acrylic also called Plexiglass1 affords an excellent clear. It is a very rigid and stable material, extremely resistant to the effects of weathering and ultra-violet light making it a good choice for outdoor applications.
SAN is a high gloss, very rigid material available in a good clear. It is one to keep in mind for solving problems of bonding a clear extrusion to molded styrene.
Polypropylene is similar to high density polyethylene. It is the material from which the “living hinge” extrusions are made.
K-Resin2 is a lightweight translucent material with good flexural strength. A good choice for semi rigid components.
IV. COLORING METHOD
Dry Color is a powdered colorant that is mixed with pelletized plastic extrusion compound. High impact styrene (the most commonly used material for plastic extrusions in displays) is usually colored with dry color. The advantage of using this material is that colorant can be produced quickly and inexpensively even in small quantities.
Color Concentrate is produced by impregnating plastic pellets with an intense dye. A small quantity of concentrate is mixed with pellets of the same formula dispersing the color evenly in the resultant extrudant.
Concentrate is not economical for many short runs. Color labs usually require a large minimum order.
PicturePrecoloring by compounders (i.e., material manufacturers) produces excellent results. However, it is usually expensive and time consuming and rarely suitable for smaller production runs.
In point of purchase applications custom extruded plastic usage is almost limitless. This usage falls into three basic categories as follows:
Additions to existing display units, such as price tag moldings, shelf talkers, shelf dividers and organizers, bumpers, corner protectors, decorative trims, mounted or free standing sign holders and hanging sign holders.
In-store installations for which the outstanding items are slatwall and headers. Lighting covers and shields and often less obvious or hidden components, such as raceways, insulators, gaskets, connectors and separators are in this category.
Free standing and mounted displays which utilize all of the extrusions in the first two categories. In addition gravity feed tubes, tracks and runners, “T” moldings, clips and hooks, unique internal assembly components, bottom edge protectors, shelves, step-shelves and shelf-plus parts are also commonly used.
Custom plastic extruders attuned to the needs of the point of purchase field compare very favorably with such manufacturers in other trades. The process is continuous (i.e., noncyclical), fast, machinery intensive and reliable. Repeat orders and orders using existing house tooling are usually processed in three weeks. Additional time is needed for secondary cutting, mitering, drilling, punching, notching and post forming.
Lead time for new profiles depends on many factors. In custom plastic molding extrusions, the profile size, complexity and material specified are the primary factors.
Many people familiar with extrusion think of the basic process as one used primarily for long shapes with rather small profiles. However, the process also lends itself to the production of certain small plastic parts that can be automatically cut in line. Some small plastic parts are extruded, cut and popped into cartons faster that the human eye can follow them.
High impact styrenes, rigid vinyls and ABS formulations are the material most frequently used for display applications.
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The ever increasing usage of custom plastic extrusions for displays is now being accelerated by technologically advanced processors. We are producing extrusions up to 24 inches wide (and selectively even wider) on a true custom basis.
1 Registered Trademark of the AtoHaas. Americas Inc.
2 Registered Trademark of the Phillips 66 Co.