Surface finishing is a variety of industrial processes that can alter the surface of a manufactured item, product, or component in order to achieve or improve a property or characteristic. Surface finish has a large impact on how a part looks, feels, and functions, and it is critical to designing a successful product. While learning software and product design, we also need to understand those different surface treatment processes, so that we can understand product design better. Below are the most common-used surface finishing processes for consumer products.
#1 Plasma Electrolytic Oxidation
Plasma Electrolytic Oxidation (PEO) is a high voltage electrochemical method that generates a plasma discharge at the metal-electrolyte interface, transforming the substrate surface into a hard and dense ceramic oxide layer without causing damage to the substrate due to thermal expansion. When the applied voltage exceeds the “breakdown value,” plasma discharges occur (usually several hundred volts). Plasma Electrolytic Oxidation is a fast-increasing industry of surface engineering today, especially for the treatment of magnesium, titanium, and aluminum alloys.
#2 Brushed polish
Brushed polish or dull polish is often also referred to as dull or satin finish. It is produced by polishing the metal with a 120–180 grit belt or wheel then softening with an 80–120 grit greaseless compound or a medium non-woven abrasive belt or pad.
Commonly brushed metals include stainless steel, aluminum, and nickel. Brushed finishes are popular in both small appliances and whiteware, and feature in architecture and automotive design. The Gateway Arch and DMC DeLorean are both clad in brushed stainless steel. The intensity of the brushed finish is specified as surface roughness and is typically 0.5–1.5 micrometers Ra.
#3 Vitreous enamel
Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C (1,380 and 1,560 °F). The powder melts, flows, and then hardens to a smooth, durable vitreous coating. Enamels can be used on a variety of surfaces, including glass, ceramics, and, most typically, metals. Enamels can be used to color metals such as copper, silver, and gold. Powdered glass can be applied to a surface wet or dry. When heat is given to the enamel, it melts, flows, and fuses to the surface, forming a smooth coating. Generally, firing temperatures range between 1400 and 1,650 degrees Fahrenheit when utilizing a torch or a kiln. Because the method by which enamels are fired has an effect on the texture and color of the enamel design, enamelists must consider a variety of elements before burning their piece.
#4 Bead blasting
Bead blasting is a finishing method for a wide variety of products. Shot blasting is a subset of bead blasting. This procedure ejects small glass beads at high pressure to clean or polish a surface. Bead blasting is used to get a surface that is smooth, bright, and clean. Manufacturers use bead blasting to achieve a good surface finish on materials such as metals, plastic, glass, and rubber.
Sandblasting, also known as abrasive blasting, is a surface finishing process that uses a powered machine — typically an air compressor as well as a sandblasting machine — to spray abrasive particles under high pressure against a surface. Sandblasting is so named because it blasts the surface with sand particles. When sand particles hit the surface, they create a smoother, more even texture.
#6 Powder coating
Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or with ultraviolet light. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, drum hardware, automobiles, and bicycle frames.
Etching is a technique in which material is removed using strong acid or physical impact to cut into the unprotected parts of a metal surface to create a design. Usually referred to as etching, also known as photochemical etching, it refers to the removal of the protective film in the area to be etched after exposure to plate making and development, and contact with the chemical solution during etching to achieve the effect of dissolution and corrosion, forming concave-convex or hollow molding effect.
#8 In-mould decoration
The in-mold decoration(IMD) is used to mold high-precision plastic parts with exceptional color and appearance. The process involves placing an appliqué – a pre-made form made from a printed sheet of plastic, which then is formed and cut to size – into an injection mold and molding behind and around the appliqué. The surface layer is a hardened transparent film, the middle layer is printed with patterns, and the back is an injection molding layer, which can make the product resistant to friction, prevent the surface from being scratched, and prevent the surface from being scratched or oxidation.
#9 Out-mold decoration
The out-mold decoration is used to compensate for the single-color nature of ordinary injection parts. Place workpieces in a high-pressure vacuum forming machine to create a design that covers their whole surface. The procedure can mitigate the negative impacts of the plastic injection process’s high temperature and high forming pressure, as well as increase the process’s yield.
#10 Laser engraving
Laser engraving is a process that vaporizes materials into fumes to engrave permanent, deep marks. The laser beam acts as a chisel, incising marks by removing layers from the surface of the material. The laser generates high temperatures during the engraving process, which basically causes the material to evaporate. This is a fast process, as each pulse vaporizes the material. This creates a cavity in the surface that is perceptible to the naked eye and to the touch. To make deeper marks with the laser engraver, we can repeat the process several times.
#11 Wire-EDM machining
Electrical discharge machining (EDM) is a manufacturing process that implements electrical sparks to form a metal shape. Because of these sparks, EDM is also sometimes referred to as spark machining. In this process, the desired shape is cut from the metal when current discharges, or sparks, occur between two electrodes; where the sparking occurs, cuts are made into the metal, creating the desired shape and detaching it from the metal sheet. Wire EDM machines create an electrical discharge between the metal wire and the workpiece—using heat from the electrical sparks to continue the cut. The deionized water (which conducts electricity) prevents the sparking process from shorting out, ensuring consistent and dependable removal of workpiece material.
#12 Laser ablation
Laser ablation is a subtractive technique consisting of the fabrication of micropatterns through the removal (ablation) of small fractions of a substrate material under the action of a focused pulsed laser beam. laser ablation is to remove material from a solid surface in a controlled fashion. Laser machining and particularly laser drilling are examples; pulsed lasers can drill extremely small, deep holes through very hard materials. Very short laser pulses remove material so quickly that the surrounding material absorbs very little heat, so laser drilling can be done on delicate or heat-sensitive materials, including tooth enamel (laser dentistry). Several workers have employed laser ablation and gas condensation to produce nanoparticles of metal, metal oxides and metal carbides.
Also, laser energy can be selectively absorbed by coatings, particularly on metal, so CO2 or Nd:YAG pulsed lasers can be used to clean surfaces, remove paint or coating, or prepare surfaces for painting without damaging the underlying surface. High-power lasers clean a large spot with a single pulse. Lower power lasers use many small pulses which may be scanned across an area.
#13 Pad printing
Pad Printing is the process of transferring a 2-D image onto a 3-D part. The offset printing process requires the use of an etched plate (also known as cliche) and pad to transfer the image. Pad printing machines range in style depending upon the number of colors and size of the image. Pad printing operations are used in a wide variety of industries, most prominently: industrial, promotional, and garments.
#14 Silkscreen printing
Screen printing, also called serigraphy or silkscreen, is a method of printing using a stencil supported on a fine woven screen mesh stretched and bonded to a frame. The material to be printed is placed beneath the frame and the fluid ink is forced down through the porous material by means of a “squeegee”, reproducing the image not blocked out by the stencil. Unlike other forms of printing, screen printing employs high ink film weights of pigmented inks, which sit on the surface of the paper, resulting in intense and vibrant colors.
#15 Direct Thermographic printing
Thermographic printing is a fantastic printing technique that is commonly used on greeting cards, wedding invitations, and other printed materials that require embossing with a natural look.
#16 Thermal-transfer printing
Thermal-transfer printing is a printing method in which an image or text is applied to a label (or other types of material) by melting a thermal transfer ribbon as it passes under a thermal transfer printhead. The ink melts from the ribbon and transfers to the label/material.
#17 Planographic printing
Planographic printing means printing from a flat surface, as opposed to a raised surface (as with relief printing) or incised surface (as with intaglio printing). Lithography and offset lithography are planographic processes that rely on the property that water will not mix with oil. The image is created by applying a tusche (greasy substance) to a plate or stone. Certain parts of the semi-absorbent surface being printed on can be made receptive to the ink while others (the blank parts) reject it. Typically, the image will be drawn directly onto a flat slab of stone or metal plate using specialized pencils. Ink is then applied to the image; the blank areas of the image will repel the ink whereas the drawing will hold it. A piece of paper (or an alternative material) will then be laid upon the image and the slab will pass through the litho press to print the image onto the paper. Lithography is ideal for medium to long printing runs and is utilized to print magazines, books, posters, packaging, maps and much more.
Rotogravure (or gravure for short) is a type of intaglio printing process, which involves engraving the image onto an image carrier. In gravure printing, the image is engraved onto a cylinder because, like offset printing and flexography, it uses a rotary printing press. Once a staple of newspaper photo features, the rotogravure process is still used for commercial printing of magazines, postcards, and corrugated (cardboard), and other product packaging.
#19 Hot stamping
Hot stamping or foil stamping is a printing method of relief printing in which pre-dried ink or foils are transferred to a surface at high temperatures. The method has diversified since its rise to prominence in the 19th century to include a variety of processes. After the 1970s, hot stamping became one of the most important methods of decoration on the surface of plastic products.
#20 Water transfer printing
Water transfer printing, also known as immersion printing, water transfer imaging, hydro dipping, water marbling, cubic printing, Hydrographics, or HydroGraphics, is a method of applying printed designs to three-dimensional surfaces. The resulting combinations may be considered decorative art or applied art. The hydrographic process can be used on metal, plastic, glass, hardwoods, and various other materials.
Calendering of textiles is a finishing process used to smooth, coat, or thin a material. With textiles, the fabric is passed between calender rollers at high temperatures and pressures. Calendering is used on fabrics such as moire to produce its watered effect and also on cambric and some types of sateens. In preparation for calendering, the fabric is folded lengthwise with the front side, or face, inside, and stitched together along the edges. The fabric can be folded together at full width, however, this is not done as often as it is more difficult. The fabric is then run through rollers at high temperatures and pressure that polish the surface and make the fabric smoother and more lustrous. Fabrics that go through the calendering process feel thin, glossy, and papery