1.19 The Use of Finishes Flashcards
Paper and Board Finishing
Lamination via encapsulation
A desktop laminator and the sheet of paper is encapsulated by a polymer pouch or film roll
Paper and Board Finishing
Lamination via a surface coating
Liquid lamination (for signage) or film lamination (meu cards)
Paper and Board Finishing
Embossing
Creates a raised design on the surface of the paper or card to give a visual and tactile effect (greetings cards, chocolate box lettering)
Paper and Board Finishing
Debossing
Produces an imprinted depression that sits below the surface of the paper or card
Paper and Board Finishing
UV varnishing
Provides a very smooth finish, usually high gloss or matt and chemcial resistant. Applied to a sheet via a set of rollers, then passed under UV light to cure
Paper and Board Finishing
Spot varnishing
Applied in specific areas or spots rather than to the whole surface area
Paper and Board Finishing
Foil blocking
Heat and pressure applied to a metallic paper (foil) to create areas of depth and texture to add aesthetic impact
Paper and Board Printing
Screen Printing
- Can be carried out in a workshop with minimal set-up costs due to the use of basic screens and printing inks
- A different is required for each colour
- Quite a slow process with a reasonably high cost per product
- Used for small print runs of items such as posters, display boards and textile T-shirts
Paper and Board Printing
Flexographic printing
- Four colours (cyan, magenta, yellow, key (black)) are printed on top of one another in various quanties on to the substrate surface to create the print colour required.
- It is used for newspapers, comics, catalogues, folding packaging cartons, labels, carrier bags and continous pattern products such as wallpaper and gift wrap.
Paper and Board Printing
Advantages of flexographic printing
- High print speed
- Ideally suited for the long run
- Prints on a wide variety of substrate materials
- Low cost of equipment and consumables
- Low maintenance
Paper and Board Printing
Disadvantages of flexographic printing
- The cost of the printing plates is relatively high, but they last for millions of print runs
- Takes a large amount of substrate to set up the job; excess material may be wasted
- Time consuming to change for any alterations to the print content
Paper and Board Printing
Offset lithographic printing
- Extremely versatile printing process of producing one colour, five colours and a ten colours
- Used for printing medium and long print runs of products such as books, business forms and documentation, magazines, posters and packaging.
Paper and Board Printing
Advantages of offset lithographic printing
- Consistently high image quality
- Suited to higher-volume print runs of 1000 or more
- Quick and easy production of printing plates
- Long life of printing plates because they only come into contact with the printing blanket, which is softer and less abrasive than substrate
Paper and Board Printing
Disadvantage of offset lithographic
- Expensive set-up and running costs for small quantities
Paper and Board Printing
Digital printing
- Produces full-colour, highly detailed print runs with the option of different designs on each page, both front and reverse sides
- Widely utilised resources for printing products, due to their speed and efficiency
- Can be used for low and high volume print runs
- Used for mass customisation, such as the printing of specific names on drinks cans.
Polymer Finishing
Overmoulding
Overmoudling is moulding a second polymer over specific parts of a products
- TPE (thermoplastic elastomer) is often used
- Overmouldings provide areas of grip or texture
- Overmoulding can highlight different colours for different component Polymer Finishing parts on the product
Polymer Finishing
Two injection moulding moulds
- One mould for the product and one mould for the grip areas
- Product is injection moulded, then placed into a second mould where the overmoulding polymer is injection-moulded on to the body
Polymer Finishing
Twin-shot injection moulding
- The injection moulding machine has a mould designed to produce the product in one cycle
- The mould has two separate component cavities and can be rotated through 180° so that they line up with the twin injection points
- First, the main product part is created in the first mould cavity
- The mould opens slightly and rotates 180° to the secondary position
- The mould closes and the second injection applies the overmould
Polymer Finishing
Acrylic spray paints
- Fast-drying
- Water-soluble paint
- Water resistant when dry
- Improves aesthetics and provides additional protection against the effects of UV light and weathering
- Often used for mass customisation, particularly in the automotive industry, such as colour coding bumpers and wing mirrors on cars.
Polymer Finishing
Adding pigments
- Provide colour to the polymer
- Smart pigments such as thermochromic or phosphorescent pigments can be added
- Can also be added to gel coats when laying up GRP
Metal finishing
Cellulose and acrylic paints
- Provide colour and a textured finish
- Provide a barrier against corrosion
- Specialist paints provide texture or special graphic effects such as pearlescence
- Primarily used on low-cost metals such as steel.
Metal finishing
State the method of application of cellulose and acrylic paints
- Paints are primarily used on low-cost metals such as steel. The surface of the metal is cleaned and degreased, which ensures that the primer coat has a sound surface to ‘key’ (or grip) to
- Red oxide primer is often used, followed by an undercoat in a similar colour to the final top coats
- Paints can be applied by brush or spray
Metal finishing
Electroplating
- A protective layer, a more hardwearing finish, and enhanced aesthetics
- The product and donor material are placed in a container with an electrolyte solution. As the direct current is applied, the product attracts the donor metal and the product is electroplated.
- Metals for electroplating include sliver, gold, zinc, copper and tin
Metal finishing
State the method of application of electroplating
- The product and donor material are placed in a container with an electrolyte solution
- As the direct current is applied, the product attracts the donor metal and the product is electroplated
- Metals used are sliver, gold, zinc, copper and tin
Metal finishing
Polymer dip coating
1) Used on products such as wire coat hangers, kitchen dish drainers, coat hooks, dishwasher racks, and outdoor play equipment frames
Metal finishing
State the method of application of polymer dip coating
- The metal product is heated to approximately 230°C
- The hot product is then dipped into a tank of fine polymer powder, which has air blowing through it (fluidisation bath) to provide an even coating on the product.
- The retained head from the product melts the polymer powder over the product, which is then air cooled allowing the coating to set evenly
Metal finishing
Metaldip coating
1) Provides a barrier against corrosion
2) Tin plating: often used to provide a non-corrosive coating to food cans
3) Zinc plating: used for many industrial and agricultural applications such as beams, gates, and animal pens. Also, like the first protective layer in car bodies made from low carbon steel.
Metal finishing
State the method of application of metaldip coating
- Metals are coated by dipping the product into a tank of molten plating metal (the donor metal)
-The metals must be clean and degreased - Tin plating:
• pass sheets of steel through a tank of molten tin at approximately 320°C - Zinc plating (galvanising):
• dipping steel into molten zinc at approximately 460°C
Metal finishing
Powder coating
- Protection from corrosion and aesthetic appeal, more hardwearing than paint
- Used on washing machine bodies, dishwasher bodies and refrigerator bodies, metal gates, fencing, and railings.
Metal finishing
State the method of application of powder coating
- The product to be coated is statically charged (negative)
- Thermoset polymer resin (positively charged) is then sprayed through an airgun
- The use of charge results in a strong attraction between the powder and the product
- The product is then baked in a oven; the heat melts the powder over the product to give an even coating
Metal finishing
Metal varnishing
- Protects the metal and allows the colour of the base metal to show through.
- Used on aluminium, brass, and copper
Metal finishing
State the method of application of metal varnishing
- The metal is polished to a shine and any surface grease removed
- The varnish is then applied by either a spray or with a fine brush
Metal finishing
Sealants
- Tough polymer-based sealant coatings to protect polished surfaces from decay and tarnishing.
- Often used in the automotive industry against the effects of weathering, road salts, and insect attack
Metal finishing
State the method of application of sealants
- The sealant is applied with a cloth or machine pad to produce a film that is then allowed to cure for up 15 minutes
- It is then buffed with a cloth to a shone
Metal finishing
Preservatives
1) Can provide temporary in-processes or final post-processing, medium to long term protection for metal surfaces
2) Often used on moulds and dies for preventing fingerprints showing on surfaces, minor atmospheric corrosion, or condensation build-up
Metal finishing
State the method of application of preservatives
- Applied by wiping on with a cloth, spray, or immersion of the product
- Silicon sealants can also be classed as preservatives and can be used on machine beds to provide a smooth, snag-free surface to allow materials to be pushed across the bed more easily and safety
Metal finishing
Anodising
- Commonly used for aluminium products to enhance the natural oxide layer, resulting in increased hardness and toughness
- Can also provide colour
- Used in the outer casings of torches, external hard drives covers, and casings for mobile phones or digital music players
Metal finishing
State the method of application of anodising
- The electric current passes through the sulphuric acid electrolyte solution from the part to be treated to a negative cathode
- As the current flows from the part to be treated (positive anode) to the negative cathode, the aluminium oxide layer builds upon the treated part, producing the anodised finish
- Anodised products can then be finished with a clear lacquer or varnish to seal the finish and provide further protection against surface scratches
Metal finishing
Cathodic protection
A method used to control the rate of corrosion of metals
Wood finishing
Polyurethane varnish/acrylic varnish
- Provides a hard, tough, heatproof, waterproof finish
- Clear finish allows the grain of the wood to be seen through the finish
Wood finishing
Water-based paints
- Paint provides both protection and colour. It can be applied for both indoor and outdoor use and is predominantly used for softwoods
- Paint makes surfaces more aesthetically pleasing, tougher, harder and resistant to moisture
Wood finishing
Stains
- Help colour and enhance the grain
- Stains can be used to colour an inexpensive wood to make it look more expensive or to add colour
- Stains do not have any specific protective properties
Wood finishing
Colour wash
- Used to help colour the wood to make it more aesthetically pleasing or to add a vintage style while allowing the grain to show
Wood finishing
Wax
- Can be buffed to provide a high gloss finish
- Increases the surface hardness and toughness
- Clear finish allows the grain of the wood to be seen through the finish
Wood finishing
Yacht varnish
- Suitable for woods that are outside all year round such as doors, window frames or boat parts
- Increases toughness, hardness, and weather resistance
Wood finishing
Teak oil
- Primarily used for outdoor wood products to improve weather resistance and resistance to fungal and insect attack
- Aesthetically pleasing as grain is enhanced
Wood finishing
Pressure-treating
- Helps protect the wood for up to 50 years from rot, insect and fungal attack, and weathering
- Suitable for products such as decking, overhead cable poles, harbour or bridge construction
Wood finishing
Danish oil
- Maintains the natural appearance of the timber, soaks into the wood, and enhances the grain
- Not a hardwearing finish but regular application and subsequent coats build up a matt, water-resistant finish
Wood finishing
Yacht varnish
- Suitable for woods that are outside all year round such as doors, window frames or boat parts
- Increases toughness, hardness, and weather resistance
