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IAT 336 (11)
Ken Zupan (11)

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Interactive Arts & Tech
IAT 336
Ken Zupan

Finishing Materials Finishing Plastics: Adding Artwork Printing Silk-screening is inexpensive and yields a high-quality print with good physical properties The silk-screening process exerts only sight pressure on the part during decoration Since registration for intricate designs is difficult, the process is usually limited to two colors Flexography is a form of printing process which utilizes a flexible relief plate -it is essentially a modern version of letterpress which can be used for printing on almost any type of substrate including plastic, metallic films, cellophane, and paper -it is widely used for printing on the non-porous substrates required for various types of food packaging -it is also well suited for printing large areas of solid color Pad Transfer Printing has been used for many years to decorate watch faces and chinaware Pad transferring uses a silicone rubber pad as a printing surface The pads are created from photo-engraved plates made of hard steels Pad printing can reproduce fine lettering and 200 line half-tone and is recommended for precision printing The shapes and textures are almost limitless It can also print multi-colors wet-on-wet without intermediate drying Hot Stamping is a dry printing method in which a heated die and foal are used to apply graphics to a surface. This is one method of security printing During the process, pigmented wood-grained or metallic designs are sandwiched between special coatings on a release tape and then transferred to the part using a heat stamping die In designing parts to be hot stamped, special care must be taken to obtain part walls thick enough to take stamping pressure As well, large areas to be imprinted should be as flat as possible Hot transfer is the process of transferring images to a large variety of products without messy inks by-products or screen is possible with Heat Transfer Technology -the process is fast, it lasts, and is profitable In the early days, Heat transfer printing was principally used in the printing of novelty items such as polyester tops and t-shirts Heat transfer printing is clean and environmentally safe There are no suspect liquid by-products. The only by-product is paper Artwork is transferred to fabric from film that is place between product and heat press however heat transfer needs a flat surface to work well Hydro Printing Hydro Printing or Hydro Dripping also known as immersion printing, water transfer printing, water transfer imaging or cubic printing is a method of apply printed designs to three- dimensional objects such as curves The hydrographic process can be used on metal, plastic, glass, hardwoods, and various other materials In the process, the substrate piece to be printed is pre-treated and a base coat material is applied A polyvinyl alcohol film is gravure printed with the graphic image to be transferred and is then floated on the surface of a vat of water An activator chemical is sprayed on the film to dissolve it into a liquid and activate a bonding agent The piece is then lowered into the vat through the floating ink layer which wraps around and adheres to it After removing the piece from the water, a top coat is applied to protect the design. With multiple drippings, hydrographic printing can achieve full 360 degree coverage of the part surface including small crevices Decals are pigmented decorations printed on pre-cut transparent plastic with adhesive backing When the release sheet is removed, the decal is easily applied to the plastic surface Decals are available in endless colors, styles, transparencies, etc. Care must be taken in their selection that the plastic film is compatible with the end user -the adhesive can chemically attach the plastic -parts which generate heat such as an outboard motor/cowling cover can damage the decal Patterns (Textures) There are companies which specialize in altering plastic and metal tooling to provide patterns and textures that are molded in the final part The rule of thumb is that 1 to 1.5 degrees of draft for every 0.001 inch depth of texture must be added to the original draft. This assists the parts being ejected from the mold There are more than 10,000 patterns available. Some may be altered photographically to provide a unique variation -unique or custom patterns may cost more Design Criteria needed for a high quality finish Draft angles to eliminate the use of mold releasing agents which can affect finishing adhesion and resolution Ribs and boss design-avoid visible sink marks on finished parts Wall thickness must take into account to withstand hot stamping pressures. Thin walls will deform Fabricated plastic parts can often be finished by buffing Flocking and Suede Flocking are two unique methods for putting a soft touch or finish on resin parts -in these processes, fibers are fist adhered to the part surface followed by electrical charge to make the fibers stand erect -the final composite resembles a soft, fuzzy rug in appearance -it is popular for auto interiors and jewelry packaging or cases Finishes Metallization is available via electroplating, sputtering vacuum metallization and flame spraying Electroplating-specifically formulated resins are not meant for parts requiring high performance -in the process, a molded part is first etched with strong acids -second, an electro-less process is used in conjunction with activators to deposit a nickel or copper finish on the part Sputtering provides a bright, durable metallic finish with abrasion resistance -it is cheaper than electroplating Sputtering usually requires the use of a base coat and topcoat that sandwich a metallized layer -the metal layer is either chrome or stainless steal -it is bombarded with ionized molecules that cause the atoms to break away from the target metal and then deposited on the plastic metal Surface Treatment/Finishing Metals Mechanical Metal Finishing Deburring-burrs are razor-like thin triangular ridges created when a sheet is sheared or a cast or forged part is cleaned by trimming shear Machining produces a burr along the tool path. Burrs may interfere with assembly and may cause jamming/misalignment -electrical components can also be short-circuited Finishing Processes Grinding Fluids reduce wear and lower power consumption. They also prevent temperature elevation in the work piece and improve finish Polishing-using a fine abrasive and a soft smearing material to produce a lustrous finish -polishing disks or belts are made of fabric, leather, or felt embedded with an abrasive -fine powders of aluminium oxide or diamond are used to provide the cutting medium Short or Sandblasting involves high velocity air jet propels abrasive particles on to the work piece giving it a mat finish -primer and paint can then be added to the part Chemical Metal Finishing Electroplating involves the coating of an electrically conductive object with a layer of metal using electrical current Metallic ions travelling through the electrolyte solution deposit on the work piece surface Usually, the process is used to deposit an adherent surface layer of a metal having some desired property such as abrasion and
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