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DT 1.5
DT Spring Y12
| Question | Answer |
|---|---|
| Lamination P+B | Encapsulation (desk top laminator) in polymer pouch or film, heat sealed. PET and EVA mix. Border on edges. Surface coating: liquid (roller/spray) or film (hot or cold, PP with adhesive. Roller and pressure) |
| Embossing | Raised. Male and female die of stainless steel/brass. Cold or hot. Substrate placed and held under pressure. Can have ink/foil or can be left as a blind emboss |
| Foil blocking | Heat + pressure to metal foil. Heated die. Needs accuracy and consistency - if temp or pressure time wrong will bubble and peel or not stick |
| Varnishing | Clear ink on pre-coated (so wont soak up ink and swell/bleed) P+B for protection and colour enhancing. Applied as flood coat. UV: smooth finish but ink must be dry first. Specific machinery to cure instantly for best finish. Rollers then light. Spot |
| Spot varnishing | Applied in specific areas or spots rather than all. Plate(s) press surface and applies varnish there. Either varnish or UV varnish used. |
| Why printing important | Attracts customers and gives info (e.g. safety info and nutrition) |
| Screen printing | Simple. Small runs. Workshop: minimal setup. Substrate on machine base secured by upper section. Image to be printed made on stencil mesh in frame. Diff screen for each colour: time/cost. Ink placed and squeegee to force through. Dries. |
| Name for sheets in all processes | Substrate |
| Squeegee | Flexible polymer blade in rigid handle |
| CMYK | Cyan magenta yellow key |
| Registration sysetm | Set of precision marks on final print substrate outside print area for QC so all colours aligned. |
| Flexographic printing overview | Cheapest: fast-dry waterbased inks, simple. Rolls of substrate not sheets: continuous runs easy. |
| Flexographic printing process steps | Flexible printing plates on cylinders on a web press. WB or UV ink from first roller to anilox roller: consistent thickness and takes to plate cylinder. Impression cylinder - pressure to plate cylind to transfer image. Web printed: fed into overhead dryer |
| Pros of flexographic | High print speed Good for long runs Prints on variety of substrate materials including non-porous Cheap equipment and consumables Low maintenance |
| Cons of flexographic | Cost of printing plates high but last for millions of runs Lots of substrate needed to set up - excess may be wasted Time consuming to change for alterations |
| Offset lithographic printing types of machines | Versatile: one colour or 5 (CMYK + metallic) and ten-feature (CMYK, metallic, varnishing, spot varnishing, and duplex - both sides printed) on a ten-roller machine |
| Offset lithographic printing overview | Med + long print runs e.g. books Oil + water mixless so plate parts oleophilic or hydrophilic Fountain (dampening) solution of mainly water in thin layer to printing plate cylinder to hydrophilic non-image areas. Then ink to oleophilic |
| Offset lithographic printing steps | Substrate sheet-fed or web roll-fed into machine Print plates produced by computer to plate (CTP) process via laser etching images. Attached to machine and dampening rollered Ink to plate to blanket roller to substrate |
| Pros of offset lithographic printing | Consistently high image qual Suited to higher vol print runs of 1000+ Quick+easy production of print plates Long life print plates - only in contact with print blanket which is softer and less abrasive than substrate |
| Cons of offset lithographic printing | Expensive setup and running cost for small quantities. Only suitable for porous substrates |
| Digital printing | Speed efficiency. Full colour high detail with different designs on each page and both sides. Low and high vol print runs. Ideal for mass customisation like specific names on drinks cans due to fast drying inks like flexography. e.g. promotional flyers |
| Why polymers self finsihing | No extra processes. Surface texture from mould and also self colouring as added during manufacture. |
| Adding colour during moulding | Tiny particles = pigments. During manufacture of product or more often stock form. Smart pigments like thermochromic or phosphorescent similar. Other processes too e.g. GRP can use pigmented polyester resin gel coat |
| Acrylic paint | Fast dry. Water soluble but water res when dry. Better aesthetics, protection from UV and weathering, and mass customise eg cars - impractical to change granules for diff customers |
| Overmouldings | TPE often. Grip, texture, highlight components. e.g. PP toothbrush with TPE handle Either made with 2 injection moulds (removed placed into other one) or twin shot injection moulding |
| Twin shot injection moulding | Mould design for 1 cycle. 2 separate component cavities that can be rotated 180 degrees to line up with twin injection points. Part inject. Mould opens and rotates. Mould closes and injects. Continuous - as overmoulding happening new body being made |
| Metals: cellulose and acrylic paints | Colour. Texture. Corrosion barrier. Cheap metals often. Cleaned and degreased, primer coat (often red oxide primer) then undercoat (similar colour to top coats). Brush or spray. More specialist texture/effect paints, primerless, hammered/smooth |
| Electroplating | Metal to coat often cheaper metal. e.g. teapots for better looks and corrosion res from liquid inside. Kitchen taps chromium - water res and shiny/hardwearing. Product+donor in container with electrolyte. DC: product attracts donor |
| Polymer dip coating metals | e.g. wire coat hangers Metal heated to ~230C then dipped into tank of polymer powder with air blowing through (fluidisation bath) so more even coat. Polymer melts and is air cooled for evenly set coating |
| Metal dip coating | Dip into molten plating metal (donor metal). Often cheap meals e.g. low carbon steel. Cleaned, degreased. Tin plating: Steel sheets at ~320C food cans Zinc plating: galvanising. ~460C. Industry and agriculture |
| Powder coating metals | Product negatively statically charged. Polyester resin +ve charge sprayed through airgun. Strong attraction. Then baked in oven: melts powder for even coating much more hardwearing than painting Many domestic goods e.g. fridge bodies |
| Metal varnishing | Clear finish to protect. Allow colour of base metal through. Often for expensive metals e.g. aluminium, bras, copper with good aesthetics. Metal polished to shine and degreased. Spray or fine brush. |
| Metal sealants | Rough polymer-based coating to protect from decay/tarnish. Silicon based often in car bodywork against weathering, road salts, insects. Cloth or machine pad to make film. Allowed to cure for 15 mins then buffed with cloth to shine. |
| Metal preservatives | Temporary in-process or final post-processing. Medium to long term protection. Often on moulds/dies to stop fingerprints, minor atmospheric corrosion, or condensation. Cloth, spray, immersion |
| Silicon sealants as metal preservatives | Can be classed as. Used on machine beds for smooth, snag-free surface to allow easy and safe material pushing. |
| Anodising overview | Finishing process. Often aluminium. Enhances natural oxide layer: hard/tough. Colour e.g. torch casings Can then be finished with clear lacquer or varnish to seal the finish and further protect against surface scratches |
| Anodising process explanation | Electric current through sulfuric acid electrolyte from product to negative cathode. Aluminium oxide layer builds up. |
| Cathodic protection why necessary | All metals have natural voltage so when joined there is a current. If water present, electochemical cell so one corrodes. |
| Cathodic protection explanation | Used to control rate of corrosion by using sacrificial metal more easily corroded so base metal protected (the product becomes the cathode rather than the anode). Protecting steel structures buried in soil/water Impressed current and sacrificial anodes |
| Impressed current | Product connected to power supply. Impressed DC fro inert electrode to product via any liquid e.g. to a pipe underground, making the pipe the anode. Cathode corrosion monitored and replaced when needed |
| Sacrificial anodes | Basic. Uses sacrificial metal to product product. More electrochemically active metal wrapped around or joined to product to provide corrosion res. On large structures monitored for corrosion and replaced once useless |
| Wood finishing purpose | Stop absorbing moisture Protect decay Protect insect attack Enhance appearance |
| Main ways wood can degrade: wet rot and dry rot | Alternate we+dry so moisture absorbed below surface. Wet rot - fibres broken down and fungus (likes damp, oxygenless) spread. Soft, wet, crumbly. Dry rot: diff fast-spreading fungus turns wood into dry, soft, powdery |
| e.g. insect attacks | Furniture beetle (woodworm) or deathwatch beetle (lay eggs in wood, hatch and eat into it creating tunnels out) |
| Surface prep for wood finishes | Made smooth by planing/sanding with progressively finer grades of glass paper in direction of grain to stop scratching. Cloth to wipe away remaining dust before finish applied. |
| Polyurethane varnish and acrylic varnish How applied | Thin coat with brush in grain direction Several thin coats sanding finely between each |
| Polyurethane varnish and acrylic varnish How it helps | Hard, tough, heatproof, waterproof Clear allows grain to be seen through |
| Water-based paints How applied | Brush, roller, spray Wood knots treated with knotting to prevent resin oozing out and spoiling finish Surface then primed and undercoat applied prior to paint finish |
| Water-based paints How it helps | Protection, colour. Aesthetically pleasing, tougher, harder, res to moisture. Often softwoods, indoors or outdoors |
| Stains How applied | Brush, roller, spray Grease-free before application Water or spirit based |
| Stains How it helps | Colour and enhance grain. Make cheap look expensive or just add colour while not covering grain No protective properties specifically |
| Colour wash How applied | Wet sponge |
| Colour wash How it helps | Colour with grain still showing Vintage style or just better looks |
| Wax How applied | Brush or stockinet cloth Once dry, buff with clean, lint-free cloth |
| Wax How it helps | Buffed for high gloss. Increases surface hardness and toughness. Clear so grain can be seen |
| Pressure treating How applied | Placed in pressure vessel with [copper sulphate and other preserving salts or preservatives] solution. Vacuum and pressure control to force deep into fibres of wood and then wood steam dried |
| Pressure treating How it helps | Protect wood for up to 50 years from rot, insect + fungal attack, and weathering Outdoor decking, cladding, bridges, etc |
| Yacht varnish How applied | Brush or spray |
| Yacht varnish How it helps | Suitable for woods outside all year e.g. doors Toughness, hardness, weather resist |
| Danish oil How applied | Clear and colour tints Lint-free cloth, rub in direction of grain. Leave to absorb for 5 mins then rub away excess with clean cloth Lightly sand or rub with wire wool to open grain between coats |
| Danish oil How it helps | Maintain natural appearance, enhancing grain Oil not very hardwearing but regular application and subsequent coats build up matt, water-res finish |
| Teak oil How applied | Available in clear. Lint-free cloth in direction of grain. Leave wood to absorb for 5 mins then rub away excess with clean cloth |
| Teak oil How it helps | Primarily for outdoor wood products to improve weather res and res to fungal and insect attack Aesthetically pleasing as grain enhanced |
| LDPE printing | Can be screen printed on - is a benefit of LDPE |
Created by:
Pyrogearos2