Finishing and Coatings

  • Created by: lala2127
  • Created on: 09-06-19 13:08

Types of Finishing

SELF FINISHED:

a material that has an acceptible finish after processing

SELF COLOURED:

a material that has an acceptible colour after processing

APPLIED FINISH:

a substance applied to the material after processing

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Paper and Board Finishing

Provides protection for the material and allows material enhancement which is important to attract customers.

Examples:

  • Laminating
  • Embossing
  • Debossing
  • Foil Blocking
  • Varnishing
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Laminating

Two main methods:

lamination via encapsulation and lamination via a surface coating.

LAMINATION VIA ENCAPSULATION:

Desk top laminator - sheet of paper encapsulated by polymer pouch or film roll.

Paper fed through laminator and heat sealed leaving a polymer sheet cover on both sides.

Laminating Polymer = PET & EVA (ethylene-vinyl acetate)

LAMINATION VIA A SURFACE COATING:

  • Liquid lamination: applied with roller or spray - e.g. hot and cold process for business cards. Protect against moisture and UV light.
  • Film lamination: usually made of PP with adhiesive. Laminate fed from roller and pressure is applied as paper feeds through.
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Embossing

a raised design on the surface of the paper or card.

Examples:

  • greeting cards, invitations, packaging

PROCESS:

Uses 2 dies - male and female - made from stainless steel/brass - cold or heated.

1. Substrate places between 2 dies (moulds) and held under pressure.

2. Embossed area is formed.

3. Can have ink/foil applied to raised area or natural (blind emboss).

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Debossing

imprinted depression which sits below the surface of the paper or card.

Examples:

  • greeting cards, invitations, packaging

PROCESS:

1. paper or card goes between 2 dies.

2. depression is made - indent the card

(same process as embossing)

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Foil Blocking

application of heat and pressure to a metalic paper (foil) to create areas of depth and texture.

Purpose: add aesthetic impact.

Different types of foil:

  • metallic, gloss, matt, clear, holographic

Examples:

  • business cards, company logos

PROCESS:

1. Design stamped onto material through the foil (special machine - heated die)

2. Heat allows foil to stick to paper or board

requires accuracy and consistancy

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Varnishing

Varnish: clear, non pigmented ink used on pre coated paper and boards to enhance the colour and provide protection.

2 types of varnishing:

  • UV Varnishing and Spot Varnishing

UV VARNISHING:

Smooth finish - ink must be dry before applied - spesific machine - high quality finish (high, gloss, matt) - abrasian & chemical resistant - sheet passed through UV light to cure.

SPOT VARNISHING:

Applied to spesific areas - plate or set of plates press onto surface - varnish is applied to that spot - can use varnish / UV varnish.

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Polymer Finishing

Polymers = self finishing materials - need no additional finishing process

Ready to use.

Pigments can be added during manufacture to enhance colour, and surface textures are produced from the mould.

Different processes include:

  • Adding colour in the moulding process
  • Acrylic spray paint
  • Overmouldings
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Adding Colour in the Moulding Process

Pigments: tiny particles, added to the polymer to create a particular colour.

   - added during manufacture process.

   - manufacture would buy pre-pigmented granuels.

SMART PIGMENTS:

  • e.g. thermochromic or phosphorent pigments (glow in the dark)

added in same way - produce ready-finished products.

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Metal Finishing

Most metals = oxide layer - provide barrier against environmentle effects

Example - COPPER:

  • Bright red colour (originally)
  • Overtime - oxide layer forms to protect from corrosion and environmentle attack

Finishes are applied because... enhance apperance and provide barrier against corrosion

Different metal finishing processes:

  • Cellulose and Acrylic Paints
  • Electroplating
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Cellulose and Acrylic Paints

Paint - provides colour & textured finish to metals & barrier against corrosion.

usually used on low cost metals (e.g. steel)

1. Surface of metal must be clean and degreased before application - can 'grip' onto metal

Application:

  • brush or spray

REQUIRE PRIMER LAYER BEFORE PAINT

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Electroplating

using a metal to coat a base metal.

Provides... protective layer, aesthetics, barrier from corrosion.

Commonly used metals:

  • silver, gold, zinc, copper, tin

Process:

1. product and coat metal placed in container with electrolyte solution.

2. direct current is applied.

3. product attracts coat metal and product is electroplated.

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Dip Coating

Polymer dip coating.

Examples of products:

  • wire coat hanger, dish drainers, dishwasher racks, outdoor play frames

Process:

1. metal heated to approx. 230 degrees celsius.

2. hot product is dipped into tank of fine polymer powder.

3. air blows through it (fluidisation bath).

4. fluidisation = even coating.

5. retained heat - polmer melts over metal & is air cooled.

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Metal Dip Coating

metals coated with other metals.

Before... must be clean and degreased.

TIN PLATING: e.g. food cans

  • Sheets of steel through molten tin tank (320 dc).
  • Non corrosive coating.

ZINC PLATING: e.g. animal pen

  • aka. galvanising
  • Dipping steel into molten zinc (460 dc).
  • Industrial and agricultural applications.
  • Protective layer.
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Wood Finishing

Purpose of wood finishing:

  • prevent moisture absorbtion
  • protect against decay / insect attack
  • enhance apperance

Natural wood can degrade by...

1. Alternating wet and dry

2. Insects

Preperation:

  • make it smooth - planning or sanding (direction of grain)
  • cloth - wipe away excess dust
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Acrylic Varnish

Types of surface finish: gloss, satin or matt

Available in: clear or colour

How to apply:

  • brush, roller or spray
  • several thin coats - rub down between coats

Properties:

  • hard, tough, heatproof, waterproof
  • clear finish - grain can be seen
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Water - Based Paints

Available in... gloss, satin, matt and metallic

How to apply:

  • brush, roller or spray

Before Application:

1. treat wood knots

2. prime surface & add undercoat

Properties:

  • protection, colour, indoor / outdoor, softwoods, aesthetic, resistant to moisture
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Pressure Treating

Process:

1. wood is placed in a pressure vessel - solution (copper sulfate + salts)

2. vaccum and pressure controlled to force preservative into fibres of wood

2. wood is steam dried

Properties:

  • protect wood up to 50 years
  • protect from rot, insect and fungal attack

Examples of products... decking, harbour, bridge

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