19-The Use of Finishes Flashcards
What are the 4 Purposes of finishes?
- Prevent material from absorbing moisture
- Protect material from decay or corrosion
- Protect against insect attack
- Enhance the appearance
- Name 6 Paper and Board Finishing Processes
- Lamination via Encapsulation
Lamination via Surface Coating - Embossing
- Debossing
- UV Varnishing
- Spot Varnishing
Paper and Board Finishing Processes:
1 - Lamination via encapsulation
2 - Lamination via surface coating
1 - Paper is encapsulated in a polymer pouch which is the heated to form around the paper
2 - Liquid lamination, often used for signs
Paper and Board Finishing Processes:
1 - Embossing
2 - Debossing
1 - Gives a raised effect on the surface of the board to give a visual and textured effect
2 - Produces an imprinted depression that sits below the surface level of the board
Paper and Board Finishing Processes:
1 - UV Varnishing
2 - Spot Varnishing
1 - Applied to a sheet using rollers, then passed under UV light to cure. Abrasion and Chemical resistant
2 - Applied to specific regions of the board as opposed to the whole thing. Used to enhance colours
Name 4 Paper and Board Printing Processes
- Screen Printing
- Flexographic printing
- Lithographic Printing
- Digital Printing
Paper and Board Printing Processes: Screen Printing
- Multiple screens will be designed with open areas that let the pigment through
- A different screen is required for each different colour
- A squeegee will be used to spread the ink around the screen
- Slow process so usually used in smaller scale production
Paper and Board Printing Processes: Flexographic Printing
- Uses a 4 colour process: Cyan, Magenta, Yellow, and Key (Black): (CMYK)
- Uses water based inks and colours are printed on top of one and others in various quantities to produce a given colour
- Used in newspapers, catalogues, comics
Paper and Board Printing Processes: Lithographic Printing
- Most versatile printing process
- Can use CMYK colours + a metallic colour, Spot varnishing, and printing on both sides
- Used mainly for longer print runs like books and documents
Paper and Board Printing Processes: Digital Printing
- Directly printing a digital image
- Can be done on high and low print runs just as effectively
- Very fast drying ink
- Used in leaflets, business cards
Paper and Board Printing Processes: Advantages of Flexographic Printing
- Low maintenance and equipment costs
- High Print speed
Paper and Board Printing Processes: Disadvantage of Flexographic Printing
- Can be very time consuming to make any alterations to the print content
Paper and Board Printing Processes: Advantages of Lithographic Printing
- Consistent high quality imaging
- Very fast and efficient printing process
Paper and Board Printing Processes: Disadvantage of Lithographic Printing
- High set up and running costs if printed in small quantities
Name 3 polymer finishing processes
- Overmoulding
- Acrylic Spray Paints
- Pigments
Polymer finishes - What type of material is used for Overmouldings?
- Elastomers
Polymer finishes - What two benefits do Overmouldings have?
- Can provide areas of grip or texture
- Can add additional colours
Polymer finishes - What are the two methods of Overmoulding?
- Two injection moulding moulds
- Twin shot injection moulding
Polymer finishes - Overmoulding - Two injection moulding moulds
- One mould for the product and one for the grip areas
- Product is injection moulded, then placed into the second mould where the overmoulding polymer is injection moulded onto the body
Polymer finishes - Overmoulding - Twin shot injection moulding
- Polymer and Overmoulding applied in one process
- Mould will have two cavities for injection
- Main product part is moulded using the initial mould, the mould will then rotate 180 degrees to the secondary position where the second injection is applied
Polymer finishes - Outline the use of Acrylic spray paints
- Fast drying paint that becomes water resistant when dry
- Improves aesthetics and can provide protection from UV light
- Used often on polymer car parts like bumpers or wing mirrors
Polymer finishes - Outline the use of pigments
- Added to the liquid polymer during the manufacturing process
- Smart pigments can be used (e.g. thermochromic pigment)
Name 10 Metal Finishes
- Acrylic Paints
- Electroplating
- Polymer dip coating
- Galvanising
- Powder coating
- Metal varnishing
- Sealants
- Preservatives
- Anodising
- Cathodic protection (Sacridicial anodes)
Metal Finishes - Outline the method and purpose of: Acrylic Paints
- Often used on lower cost metals like steel
- Metal is first cleansed and degreased before the primer is applied
- Red oxide primer is common
- Can be applied using a brush or a spray
- Provides enhanced aesthetics and can create a barrier against corrosion
Metal Finishes - Outline the method and purpose of: Electroplating
- Metal placed into an electrolyte solution with a donor metal
- As the current is applied the main metal will attract the donor metal and will form a coating around the original metal
- Gives a protective layer and enhanced aesthetics
Metal Finishes - Outline the method and purpose of: Polymer dip coating
- Metal is heated to 230 degrees celcius
- Then the metal is dipped into a container containing fine polymer granules
- The temperature of the metal causes a layer of polymer to melt around the metal
- Used often to soften metal edges, on coat hangers so the end of the wire isn’t sharp
Metal Finishes - Outline the method and purpose of: Galvanising
- Steel is dipped into molten zinc
- This is done as zinc is less corrosive than steel so will provide protection
- Used frequently in car bodies to stop the effects of weathering
Metal Finishes - Outline the method and purpose of: Powder coating
-The metal is negatively charged, and the polymer is positively charged.
- The powder is then sprayed through a spray gun causing a strong attraction
- The metal will then be baked in an oven to melt the polymer in an even coating
- Protection from corrosion and gives aesthetic appeal
- Used on fences and railings
Metal Finishes - Outline the method and purpose of: Metal Varnishing
- The metal is polished to a shine and any grease is removed
- A varnish will then be applied via brush or spray
- Provides corrosion protection for the metal whilst the colour of the base metal can still be seen
Metal Finishes - Outline the method and purpose of: Sealants
- Sealant is applied using a cloth to produce a film around the metal
- This is then cured
- Creates a very strong polymer based coating
- This is often use to combat the effect of weathering in the automotive industry
Metal Finishes - Outline the method and purpose of: Preservatives
- Applied by cloth, spray, or submersion
- Often used on moulds and dies to prevent decay
- Not necessarily long term
- Will often be frequently reapplied
Metal Finishes - Outline the method and purpose of: Anodising
- Uses electrolysis to build up the oxide layer on the surface of the metal
- This oxide layer is then often secured with a clear varnish to provide further protection
- Commonly used in aluminium to enhance the natural oxide layer
- Can also provide colour
Metal Finishes - Outline the method and purpose of: Cathodic Protection - Sacrificial anodes
- Anodes of a more reactive metal are placed around the surface of a metal
- This will cause them to react to molecules in the environment and corrode first, therefore prolonging the life of the Product
- Often used on large boats
- They can be continuously reapplied
State and explain the 3 ways in which natural wood degrades?
- Wet Rot: Moisture within the wood causes the fibres to break down and causes a fungal spread the wood becomes soft, wet, and crumbly
- Dry Rot: Fast spreading fungus causes the wood to turn to a dry powdery state.
- Insect attack: Many insects will lay their eggs in wood. The larvae will then eat into the wood forming tunnels
What needs to be done to the wood before applying a wood finish?
- Ensure the surfaces are smooth by planing or sanding
- Make sure all dust is removed from the surface
Name 9 wood finishes
- Acrylic Varnish
- Water based paints
- Stains
- Colour Wash
- Wax
- Yacht Varnish
- Danish Oil
- Teak Oil
- Pressure Treating
Wood Finishes - Outline the Method and Purpose of: Acrylic Varnish
- Several thin coats applied with a brush.
- Glass paper often used to rub down between coats
- Produces a clear protective finish
Wood Finishes - Outline the Method and Purpose of: Water Based Paints
- Predominantly used for aesthetic purposes however does provide slight protection from moisture
- Knotting solution should first be applied to knots to stop them from releasing resin that may disrupt the finish of the paint
- Primer and undercoat should be used
Wood Finishes - Outline the Method and Purpose of: Stains
- Applied with a brush, roller, or spray
- Only Aesthetic benefits
- Often used to make cheaper wood look more expensive
Wood Finishes - Outline the Method and Purpose of: Colour Wash
- Colour applied using a wet sponge
- Provides colour while grain still being visable
- Often described as providing a ‘vintage’ aesthetic
Wood Finishes - Outline the Method and Purpose of: Wax
- Applied with a brush, and then buffed with a lint free cloth once dry
- Clear glossy finish that provides surface hardness and toughness
Wood Finishes - Outline the Method and Purpose of: Yacht Varnish
- Applied with a brush or spray
- Suitable for wood that is outside all year round
- Increases hardness, toughness , and weather protection
Wood Finishes - Outline the Method and Purpose of: Danish Oil
- Applied with a lint free cloth in the direction of the grain
- Leave to dry for 5 mins then wipe away any excess oil
- This process is repeated multiple times with light sanding occurring between each coat
- Used often on indoor furniture to maintain the natural appearance of the timber
Wood Finishes - Outline the Method and Purpose of: Teak Oil
- Apply with lint free cloth in the direction of the grain
- Leave to soak in for 5 mins then wipe away any excess
- Used for naturally oily woods
- Used for outdoor woods for increased weather and insect protection
- Enhances the aesthetics of the natural grain
Wood Finishes - Outline the Method and Purpose of: Pressure treating
- Wood is held in a pressure chamber with copper sulphate and other preserving salts
- The pressure forces the preservative deep into the wood fibres
- The wood is then Steam dried
- Long term wood protection often used in deckings or bridge construction
- Protects wood for up to 50 years from rot, insect and fungal attack, and weathering
