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DT 1.4
DT Spring Y12
| Question | Answer |
|---|---|
| Die cutting and creasing P+B | Die cutters to make nets/developments. Use plywood substrate board which the cutting dies and creasing rules are inserted into. Stock material then cut. Creasing rules lower and blunt: combo with creasing channel under stock. Ejection rubber round cutters |
| Bending P+B | Stamped net on folding table. May be a part of a die cutting machine. Bent automatically or difficult stuff by hand. |
| Laser cutting P+B | Perfect for prototypes and small-scale: cut, engrave, perforate, carve. Speed, accuracy, detail, flexible - just a 2d drawing downloaded - quick. |
| Vacuum forming overview | Easy MDF moulds - school workshop. Often batch - moulds time consuming. Thermoplastic sheets e.g. HIPS up to 6mm. Small draft angle needed. Slow. Aluminium moulds for larger scale: consistent and good finish. Diagram: toggle clamps hold shut |
| Vacuum forming process steps | Mould placed onto the bed - the 'platen', which is lowered fully Sheet clamped over mould and heater placed When soft platen raised and heat off Vac pump on Once cooled platen lowered and vac off Mould removed and excess trimmed |
| Thermoforming | Extra detail on polymer surface or for thick sheet. e.g. baths. Slow but v fine detail like lettering or embossing. Similar to vac except extra mould pressed in when vac applied. The two moulds trap the polymer between - extra detail. |
| Calendering overview | A smoothing and rolling process - towards end of paper manufacturing. Also for polymer for further processing. Purely an industrial production - specialist. Generally for continuous production. |
| Calendering process steps | Pellets heated and extruded into heated rollers and squashed to thin. Then finished on cooling rollers and chopped to stock size or rolled Diagram: feedstock and sheetstock |
| Line bending | Used to make bends in sheet thermoplastic. Electric heated element One-off or batch - slow and labour intensive. Good for school prototypes. |
| Laminaton (lay-up) | Fibre-based composites. Mould prep Coat release agent e.g. wax/PVA/parcel tape Top layer gel coat. If CFRP cured in autoclave Fibreglass matting cut, laid over. Resin brushed on and roller to push out air bubbles + smooth Repeat Let set |
| Injection moulding overview | Industrial for complex thermoplastic shapes. e.g. electronics casing. Good for when you have complex parts e.g. clip fastenings, screw posts, battery housing, circuit board holders: can only be formed by melting and forcing into mould. Mass - expensive |
| Injection moulding process steps excluding completion | Thermoplastic granules in hopper Screw thread rotated by motor so granules through chamber and heaters Melts When enough charge melted a hydraulic ram forces screw thread forward, injecting |
| Injection moulding process completion steps | Mould water cooled, opens; ejector pins to push moulding out, trimmed. Formers or jigs may be used to maintain dimensional accuracy while cools and hardens |
| Blow moulding | Continuous, hollow Polymer in hopper Archimedean screw pulls polymer to heaters, melts Extruded as tube = parison Mould closes around parison and air injected forcing polymer to sides Polymer allowed to cool for a few seconds, then release |
| Why do many products use an injection-moulded preform for blow moulding? | For greater level of tolerance e.g. for threads |
| Rotational moulding overview | Heavy duty, seamless hollow objects with large wall thickness e.g. traffic cones, kayaks, water tanks. Blow moulding would stretch too thin. Often HDPE and PP. Moulds changed quickly on same machine but setup costs high - large batch/mass. |
| Rotational moulding process steps | Powder/granules loaded into mould - clamped + sealed Mould into oven heated to 260 - 370C depending on polymer. Mould rotate slow (< 20/min) around 2 axes so it coats in Once correct thickness, cooled via fan/water Solid shrinks - removable |
| Extrusion overview | Solid, hollow, angle, or sections. Can coat electrical wires in e.g. PVC insulation. Similar to injection but forced through die. Continuous production of stock material so only by specialist manufacturers. Diagram: moving mould + back flow stop valve |
| Extrusion process steps | Polymer granules into hopper Archimedean screw moves them past heaters, melts Once sufficient melted, hydraulic ram push screw, forcing through steel die - shape causes shape Extrusion supported by rollers as cooled water/air Cut to length |
| Compression moulding overview | Mould thermosets. e.g. urea formaldehyde light fittings/switches/plugs or MF plates, mugs, bowls |
| Compression moulding process steps | 'Slug' of pre-weighed thermoset inserted into pre-heated moulds Moulds closed and hydraulic pressure so shape taken. Moulds stay closed while cross-linking occurs and it 'cures' Once cured, opens and removed Deflashed |
| Injection moulding diagram additions | Moving mould with guide bars |
| Mandrel | For hollow extruded sections |
| Press forming overview (forming process) | e.g. car body panels. Often combined with punching to remove parts or trim. Combo with robots to put sheet in and move 3d shape to next process Medium steel and Aluminium - malleable ductile. Mass/large batch - cost+complex dies |
| Dies for press forming | Hardened steel, often machined using spark erosion and hand-burnished for high quality surface. Specialist,skilled - costly, so only valid when recouped by many sales |
| Press forming process steps | Sheet clamped over die that determines final shape. Hydraulic press push die in. Cutting blades to punch holes and trim excess. Die lowered and pressed component removed May be into other press machines if complex |
| Press forming diagram | Blank, blank holder. Female die and male die. Holding force on blank holder and drawing force on male die. |
| Spinning overview (forming process) | Alt to press form. Radial symmetry objects. Spin sheet of metal at high speed as pushed over former or 'mandrel'. Leaves parallel lines on surface of metal. Mass - CNC. Formers simple so can be batch when press forming too expensive. |
| Spinning process steps | Mandrel in chuck. Blank held between mandrel and tail stock. Roller tool into blank, rotated with mandrel - stretches metal Roller moved along as pressure maintained Roller moved to end of mandrel while still touching blank Removed Trimmed |
| Spinning process diagram | Head stock and spindle rotating connected to mandrel. Sheet metal, clamp, tail stock. Roller tool rotating. Can show individual 2d stages too |
| Cupping and deep drawing overview (forming process) | For tube-like shapes. 'Deep drawing' when depth exceeds diameter. Multi-operation process. Similar to a punch but with rounded punch - stretch not shear. High setup of presses and dies so only for mass. |
| Cupping and deep drawing process steps | Pressing blank clamped over deep drawing die using pressure pad or a clamping ring known as a retainer Hydraulic press moves punch in contact with blank. Then pushes blank into die cavity for cup shape Cup then pressed down through die for tube |
| Cupping and deep drawing diagram | 3 stages. Deep drawing punch, retained, press blank, deep drawing die all still Cup Tube |
| Drop forging overview (forming process) | Shape hot metal. When product is tough (impact res) and hard. e.g. pliers. Maintains internal grain structure so strong. Mass production - dies dedicated to one item, but dies can be changed quickly on same hydraulic ram. |
| Drop forming process steps | Die of cast tool steel secured to anvil Ram equipped w die Metal billet heated above recrystallisation temp so no work harden as cools: brittle Via tongs billet placed into anvil die and ram brought down Ram lifted, product out for cool+finish |
| Recrystallisation temp | Temp below melting point at which point it is possible to change the size and shape of the grains of the metal |
| Wrought iron forging overview (forming process) | Wrought iron suitable for forging, rolling, bending, not casting. V low carbon less than 0.08% - malleable and can be hammered into shape. Hydraulic/mechanical rams or hand tools. One-off or small batch - no dies/formers |
| Wrought iron forging process steps | Heated in gas or coke-fired forge. Shaped by holding with tongs and hammering over anvil or using other tools e.g. twisting bars. |
| Bending overview: press brakes | Bend sheet/plate in industry via a 'press brake'. Modern press brakes use 'back gauge' device to position metal so brake bends metal in correct place. Also can be computer controlled to bend repeatedly for complex. |
| Bending process steps | In press brake: stock metal clamped between matching punch and die. Hydraulic/pneumatic/mechanical brake holds metal sheet/plate and lowers punch to bend sheet. |
| Bending overview (forming process) | Can also be used to make seams between 2 sheets of metal and hemming sheet to be safe to handle by edges. Unlike press forming not normally any punching/trimming. One-off is possible for bending, but when press brakes used normally large-scale batch |
| Rolling overview | Hot metal above recrystal (hot rolling) or below recrystal (cold rolling). Used to make stock forms (I beams, bars) and eg railway tracks. Many schools have a set of bench rollers for making tubes from sheet metal or hoops from thin bars |
| Hot rolling | Uniform properties - not stressed/deformed so less faults. But carbon deposits on surface - removed via acid pickling. More generous tolerance of dimensions due to carbon deposits on surface. |
| Cold rolling | Usually room temp. Tighter tolerance from no carbon deposits. Surface finish therefore much better. Often for home appliances, filing cabinets, steel drums, saucepans, etc. |
| Sand casting overview (redistribution process) | For high melt point metals. Often in specialist factories - 'foundries'. Slow and labour intensive with single-use moulds - one-off and batch. e.g. vices, drain covers. Not high quality surface finish |
| Sand casting process first 2 steps | Pattern of wood made, placed in bottom of drag. Filled with sand around pattern: packed, levelled. Drag turned and cope clamped over top. Top half of pattern added to mate with bottom. Wooden stakes into cope (form the sprue/runner/riser). |
| 'Drag', 'cope' | Steel box |
| Sand casting process steps 3 - 4 | Sand into cope around runner/riser/pattern. Small depression on surface around sprue to make pouring basin. Cope and drag separate. Stakes and patterns carefully removed. Connecting channels cut to join sprue/riser to pattern cavity. Cope+drag together |
| Sand casting process steps 5 - 6 | Small metal spikes inserted and moved to make vent holes so gases from casting escape. Molten metal in pouring basin. Flows down runner into cavity. Once full, flows up riser showing its full. Once cool, sand removed, runner, channels, riser hacksawed |
| Sand casting diagram | All 6 steps 2D. Strickling off packed box Sprue pins Sand + basins Sprue removed and channels cut Vents cut Metal in |
| Die casting (redistribution process) | For moulding low melt point. Reusable steel moulds - cost+complex so mass. V high qual surface finish so eg collectable figures Gravity and pressure die casting (hot chamber and cold chamber pressure) |
| Gravity die casting | Make parts with a thicker/heavier section than pressure but thinner sections than sand. Runner, riser, locating pin. |
| Pressure die casting brief overview | Produce cast items quickly in high volumes. |
| Hot chamber pressure die casting | Molten metal stored in chamber in machine. Pneumatic/hydraulic plunger forces 'shot' of molten metal through the 'goose neck' into the die. High pressure - all mould filled - fine detail. V fast as molten metal not transported |
| What metal cant you do Hot chamber pressure die casting for | Aluminium because it picks up iron from the steel chamber, so cold must be used |
| Hot chamber pressure die casting diagram | Die with ejector pins and cavity connected to a nozzle to a goose neck to a chamber and plunger. |
| Cold chamber pressure die casting | Molten metal kept separately in melting crucible, Then ladled into the shot chamber and hydraulic ram forces it into mould cavity. When hardened, mould opens and ejector oins push it out. |
| Cold chamber pressure die casting diagram | Fixed die half connected to moveable die half with ejector pins. Ladle placing metal into shot chamber with ram. |
| Investment casting overview (redistribution process) | aka 'lost wax casting'. Casting intricate shapes impossible otherwise e.g. jewellery, collectable figures or medical Wide range of metals. Allows for high qual products with excellent finish. Repeatable as wax patterns cast from master mould |
| Investment casting process steps | Exact pattern wax cast. If many items, might be joined in a 'tree' with replica of runner to pour metal in. Pattern dip coated in refractory clay. Kiln fired - wax burnt away Molten metal in Cool Mould broke Runners/channels machined off |
| Master mould for investment casting | Steel/aluminium master mould if batch produced |
| Low temp pewter casting overview (redistribution process) | Low melt point alloy for school projects and commercial crafts. Good for small items and decorative items. Easy to make variety of material moulds - one-off v suitable. Moulds can be machined from aluminium/steel for higher scales of production |
| Low temp pewter casting process step 1 - making the mould | Mould made from mdf/plywood/high density modelling foam. For MDF/ply may be laser cut or with a fret saw. Includes sprue/runner to pour in pewter |
| Low temp pewter casting process later steps | Mould clamp between 2 pieces of MDF: top of mould level with side pieces. Pewter melted in ladle and poured into sprue Once cooled, removed. Sprue/riser removed with junior hacksaw Casting filed and cleaned with wet/dry abrasive paper Polished |
| MIG welding overview (addition process) | Metal inert gas. Welding thin gauge metal (usually med C steel) or aluminium. Localised heat so wont burn through or distort thin gauge. One-off or mass where spot weld too weak. Uses inert gas (CO2, argon) to form flux shield over area so no oxidation |
| MIG welding process steps | Electric arc melt joint area. Wire electrode same metal as joined: melts in arc, fills gap between pieces Operator swirls welding gun over joint to form continuous bead of weld Electrode wire on reel advances through welding gun as trigger pressed |
| TIG welding (addition process) | Tungsten inert gas. For stainless and non-ferrous. Electric arc too but electrode doesn't melt in process: separate filler rod used. Grater control by operator: more accurate, stronger welds, but skilled and slow. e.g. stainless steel car exhausts |
| MIG welding diagram | Wire-fed consumable electrode coming from welding gun. Arc and shielding gas over molten weld pool |
| TIG welding diagram | Weld direction marked on. Tungsten electrode in welding gun with an arc and shielding gas under it. Filler rod held in. Solidified weld metal behind. |
| Oxy-acetylene welding overview (addition process) | For low-carbon steel where no arc welding. Mostly obsolete except quick repairs or remote locations without energy. High pressure gasses oxygen and acetylene mix: 3500C flame. Mixed in blowtorch. Valves: mix changed for intensity change: cut,weld,braze |
| Oxy-acetylene welding process | Metal prepped by grinding an angle on the edges of the 2 pieces to make a V shape so weld runs through entire thickness of metal. Joint area heated to form melt pool as steel filler rod introduced. Melt pool extended to form continuous bead on joint |
| Melt pool for Oxy-acetylene welding how to control | Molten metal flows to hottest part of metal by capillary action so by moving torch along joint line a continuous seam is formed. |
| Oxy-acetylene welding diagram | 2 cylinders with regulators lading via hoses to welding torch with filler rod on base metal. |
| Brazing overview (addition/fabrication process) | aka hard soldering Oxy-acetylene or a gas+compressed air brazing hearth. Lower temp than weld so thinner gauge. Weaker than weld but good for general fabrication Filler rod melts at 850C School projects and for joining dissimilar metals |
| Brazing process steps | Material to be joined cleaned and degreased Two pieces clamped together A flux is applied (helps prevent joint oxidising) Joint heated with torch to temp of ~850C Brazing rod applied to joint area |
| Brazing how to control metal movement | Same as oxy-acetylene. The brazing 'spelter' flows along joint by capillary action to hottest part so can be made to follow joint line by manipulating torch. |
| Soldering overview (addition/fabrication process) | Similar to brazing but for lightweight and thin gauge. Precious metals e.g. jewellery and copper plumbing. Metal must be V clean - no gaps in area joined. Filler material (alloy of tin+copper) lower melt than join metal: soft solders |
| When soldering silver | Solders contain high percentage of silver |
| What method of heating for soldering | As lower melt point metals used, gas/air or just gas torch used |
| Electrical solder | 60& tin 40% lead and contains flux. Lead solders gradually being phased out due to toxicity. Components pushed through pre-drilled circuit board holes. joint made by heating the leg of the component with the circular pad where the leg is pushed through |
| Soldering process steps | Metal cleaned and degreased Joint area wired up or clamped Metal heated up to melt point of the solder Solder added to metal. Will flow along joint using capillary action Metal cleaned to remove flux residue |
| Riveting overview (addition/fabrication process) | Permanent join method for sheet metal/plate Rivets are metal fasteners with 'head' at one end and shaft/tail at the other end |
| Riveting process steps | In traditional cold riveting, two pieces overlapped and drilled. Rivet shaft inserted into hole. A 'set' tool placed over the head (also known as a snap). End of shaft hammered to squeeze two pieces together. e.g. handle of trowel to blade |
| Riveting diagram | Hammer on top. Set tool on bottom. 2 overlapping sheets with rivet in them |
| Pop riveting (addition/fabrication process) | More modern form of riveting - thin sheet metal. Rivet and a pin. Rivet head pushed through drilled hole. Riveting pliers grip and pull the pin, squashing head and pulls the two pieces of metal together. Pin breaks off and disposed. |
| Where is pop riveting useful | Where the underside of the joint is inaccessible e.g. sheet metal ducting for ventilation. Form of pop riveting also used in aircraft production to join sheet aluminium to structural parts |
| Screws, bolts, etc are what type of fasteners | Temporary fasteners |
| Self-tapping screws | Thin sheet metal. Pilot hole drilled. Coarse thread of hardened steel. Cuts its own thread to hold in place. Also used on polymers as adding a screw thread to injection moulding is hugely expensive for the mould. |
| Machine screws | Usually with metric thread. Bolt for joining thicker pieces of metal together - typically machine parts like inspection covers or maintenance parts. Thread along entire length of shaft. |
| Machine screws material preparation required | Where 2 pieces to be joined, top piece has larger clearance hole than thread. Bolt screwed into threaded hole on second piece. Often tightened with spanner or allen key. No nut |
| Nut and bolt functionality | Similar to machine screws but not threaded hole: all the way through both pieces, nut tightened on end. Spacers called 'washers' under head of bolt and under nut to not dig into surface. Spring washers keep tension on joint: not undone if moved/vibrated |
| Nut and bolt materials | Range for both. Nyloc nuts have a nylon collar insert at end of the nut so it elastically deforms over bolt thread - helps prevent coming undone through vibration so good for movement prone machines. |
| Milling (wasting process) | Wasting process. Work clamped to table. Can cut slots, shape edges, or drill/thread holes. Manual or CNC. |
| Metal turning (wasting process) | On centre lathe. When long piece, can be supported by a tail stock. Variety of bars and tubes. Manual or CNC. Cutting tools held in a tool post which can be moved. Tools from either HSS or tungsten carbide. Often liquid coolant flooded over tools |
| e.g. operations when metal turning | e.g. bar held in rotating chuck and machined to thin diameter, square (face off) the end, thread, drill |
| Why liquid coolant flooding | To prevent tool from blunting and maintain a good finish on the component being machined |
| Flame cutting (wasting process) | Oxy-acetylene gas and special flame-cutting torch 3500C. Cutting low C and alloy steel plate Similar to welds - melt pool forms, then jet of oxygen to intensify flame and pierce metal. Cheap to setup. Any location - no electric. CNC for repetitive |
| Cons of flame cutting | Hard to maintain parallel line with high tolerance. May be deformation, structural changes, and tempering on cut edge. |
| Plasma cutting overview (wasting process) | Super-heated conductive ionised gas. Transfers energy to conductive material e.g. steel plate. Faster and cleaner than flame. 28000C quickly burns material and blows it away. One-off e.g. steel plate for sign. |
| Plasma cutting explanation of process | Plasma arc from torch where gas forced through tiny nozzle. Electric arc from transformer forms jet of plasma. |
| Typical setup of plasma cutter system | Power supply which converts AC mains to DC between 200 VDC to 400 VDC depending on material thickness. Arc starting console - spark inside torch to start arc Plasma torch - contains electrode and nozzle which are consumable. Manual or CNC |
| Plasma cutter diagram | Work on the bottom with a cut. Plasma line coming down from tube containing cutting gas and a torch electrode with electrical charge. Shielding gas sent down in further out channels in tube around cut. |
| Flame cutter diagram | 3 tubes above heated work. Oxygen tube in centre with fuel gas and oxygen in other 2 tubes with heating flame coming out of them. Slag jet coming out of middle jube through material. |
| Slag jet | When the flame pierces the metal it forces out a jet of melted metal and carbon = slag |
| Laser cutting (wasting process) overview | Uses CAD file Fast process with easy software, so one-off or batch. Fine cut, high qual surface finish Less warp and distortion with small heat zone More accurate and lower energy than plasma but thinner materials |
| Interesting point about how laser cutters are developing | Some modern industrial ones are approaching the power of plasma but currently way more expensive |
| Laser cutting process explanation | High-power laser through optics. Melts material and high-pressure gas blows melted material through sheet. Beam emitted from laser tube, reflected through series of mirrors into 'laser head' which has lens to focus into fine beam |
| Laser cutting tolerance | Usually very fine tolerance - amount of material removed can be less than 1mm. |
| Punching/stamping (wasting process) overview | CNC stamp out sections of sheet using hardened punches following CNC program. x and y movement under punch. Modern machines programmed using graphic UI so no specialist programming needed. Info taken from 2D cad for correct tooling and nesting |
| Punching/stamping process explanation | Shearing action between upper punch and lower die. Punch push through sheet: punching slug drops in hole in die into chute for work or recycling. Or punched parts tabbed into the sheet with micro joints so can be removed as whole sheet |
| Tools on punching/stamping machines | Single tool head or multi-tool turret to punch out shapes from stock material. Suitable for small and medium production runs, normally of sheets between 0.5 and 6mm thick |
| Traditional wood joining | Wood joints |
| Butt joints | Relies on adhesive. Very lightweight. Easy: cut square then glue applied and clamped |
| Dowel joint | Hardwood pegs - some have grooves to let glue flow when hammered into place. Position measured and marked, drilled, glued, then hammered in dowels. Clamped until dry. Simple, strong, easy, often joined with KDF for flat-pack |
| Mitre joint | Often use mitre jig for straight corners. |
| Comb joint | Boxes. Increased gluing SA so very strong. Cut easily with bandsaw or laser or skilfully with tenon saw and wood chisel. |
| Dovetail joint | Drawers because they have directional strength. Impossible to pull apart once glued. Cut by hand with dovetail saw or more commonly with router and jig for less skill. |
| Mortise and tenon joint | Heavy duty for furniture. Square/rectangle hole is the mortise, made by mortise machine or router, or simple by drilling and cutting with chisel. Second piece cut with tenon saw or band saw. PVA glue then clamped. |
| Housing joint | Framework construction, cabinets, shelving. Groove cut across one piece and end of second piece inserted. Could be glued for permanent or unglued to be taken apart or adjusted. Structurally strong Made with a tenon saw and chisel or by a router |
| Half lap joint | Simple frames or boxes. Cutting a 'step' in end of each piece. Easy and stronger than butt. Easy to mark out and cut with tenon/band saw |
| KDF | Flat-pack. Non-assembled products so way cheaper. Reduces make time and easier to store and transport. Simple tools, often included. Buy, take home instantly. Easier to go through doors and upstairs. Standardised, interchangeable, so wide range products |
| KDF how are they made | Made by specialist component manufacturers and supplied to furniture manufacturers. |
| Modesty blocks | Small, rigid polymer blocks. Cupboards Moulded holes to take screws to join to panels Simple to use but not very strong joint and unattractive, so becoming outdated |
| Barrel nut and bolt | Common KDF. Cross dowel fitted into one piece then bolt through the other and tightened into cross dowel often with allen key. Bed frames. |
| Cam-lock connector | Metal dowel screwed into one side with screwdriver. The cam is a disk that fits in pre-drilled hole in the other wood piece. When disk rotated via screwdriver, collar on the dowel locks it in and pulls both pieces together tight. Bookcase shelves |
| Wood screws | Coarser pitch (less threads per inch) than for metal. Often the shank does not have a thread so easier to screw two pieces together where thread only needed on the bottom. Can be countersunk so flush with surface but countersunk hole needed |
| How to use wood screws | Top part drilled with clearance hole the screw simply pushes through. Bottom piece has pilot hole so coal pitch bites into timber. |
| 3 types of wood screw | Slot head, Phillips, Pozidriv |
| Slot head screws | Simplest, cheapest. Not suitable for power screwdriver. Often supplied with products to be fitted to walls. |
| Phillips screw | Improved contact with screwdriver so more torque can be used. Accepts tip of screwdriver with angle of 57 degrees. If too much torque the screwdriver slips so that the thread of the screw isn't stripped. |
| Pozidriv screw | Further refined. Improve contact with screwdriver allowing greater torque. Good for power screwdrivers. Preferred kind for woodworking jobs with multiple joints. Has further diagonal slots on the screw to make better contact with driver bit. |
| Coach bolts | Used to join wood pieces together. Thread runs 2/3 along. under the domed head is a square piece that digs into the wood so it can't be rotated out with a spanner (because rounded). Useful for fitting bolts or locks to wooden doors if domed part outside. |
| Wood turning types (wasting process) | Turning between centres, turning on faceplate, or turning in chuck. Can change speed of rotation. Rough pass first. Tool rest. Sandpaper. QC with micrometer or callipers |
| Turning between centres | Used to machine spindle to reduced diameter. Normally by hand using tools held on tool rest |
| Turning on faceplate | Domes or bowls. Screwing thick piece of timber to faceplate where it can be machined to turn outside circumference and remove inside. |
| Turning in chuck | Only when necessary. Grips item while machining. e.g. end of spindle needs to be drilled. Can also be used to machine sides and inside of bowls/vases. Rim gripped by jaws of chuck allowing access to sides and inside |
| Routing timber (wasting process) by hand | Slots and holes or decorative mouldings on edges. Most common type is portable electric plunge router: variety of bits, adjustable depth, guide accessories for continuous grooves along or across timber Deep channels have to be in stages |
| Routing timber CNC | Machine range of natural timbers and manufactured boards as well as high density modelling foam. CAD drawings downloaded and converted into control program. 2D drawings to machine sheets. 3D for e.g. moulds for vacuum forming. Fully enclosed and extracted |
| Milling timber (wasting process) | Too slow for accurate cutting timber, but good for small, basic jobs like prototypes and roughing out small holes and channels. Lower range of movement (work area) as routers so small items. Manual or CNC |
| Lamination (forming process) | Veneers or thin boards glued and bent over former for thicker board in shape. Laminates clamped or more commonly a vacuum bag while drying. |
| Vacuum bagging | Former and veneers placed under polythene sheet. Edges of sheet taped down to table. Valve fitted to polymer sheet and vacuum pump sucks out air, with resulting pressure pulling laminates together hard. No gaps in laminating ensured. |
| Steam bending | Heat + steam make strips of timber pliable for shaping. Bent over former then clamped until dry. Quicker than laminating - no glue dry time. Less wasteful because laminated parts often need trimming to final size. |
| How to set up steam bending | Box made from plywood. Wallpaper stripper steamer for the steam. Usually angled slightly and a drain fitted so condensed steam can run away |
| Main adhesives | Polyvinyl acetate (PVA), contact adhesives, UV hardening adhesives, solvent cement |
| PVA | Woods and wood-based materials. Water-based. Soaks into surface of wood and sets once the wood has absorbed the water content. Not usually waterproof but some water res ones developed. Wood joints - furniture |
| Contact adhesives | Large areas like sheets. Same or different materials together. Both surfaces coated in contact adhesive and left for 10 mins or until adhesive feels 'tacky'. Instant adhesion upon contact so no clamping needed. eg MF sheet to chipboard in kitchen worktop |
| UV hardening adhesives | Clear liquid which cures when UV light. Contains photo indicator. Many applications and most materials e.g. metal, glass, polymers. eg school projects like stationary holders. |
| Pros of UV hardening adhesives | Pros: Excess can be wiped off before curing, giving solid and clean joint. Fast curing and unlike epoxy no need for premixing. Good for where transparency or clarity important: good for glass joints. |
| Solvent cement | Different types e.g. Tensol 12, which is an acrylic cement. Most commonly a clear liquid called dichloromethane. Used to join polymers. Used in plumbing to bond non-pressure ABS or PVC pipes. Acrylic stuff in school workshops. |
| How does solvent cement work | Softens the surface of polymers to be joined allowing them to fuse |
| What is a fixture | Holds work in given position while manufacturing process takes place |
| What is a jig | Both holds the work and guides a tool |
| Main reasons for jigs and fixtures | So components can be made repeatedly and accurately. Jigs also can speed up manufacture. e.g. jigs for drilling same spot consistently means there is no need to measure and mark out each time |
| Mitre blocks | Type of jig used to cut 45 degree angles in wood pieces. Place in vice or clamped onto bench. Wood held in block and cut at 45 degrees with saw e.g. tenon saw |
| Sanding jigs | Used to hold and guide timber as it is sanded on disk/belt sanders. Means it is always accurate and consistent when e.g. sanding angles on the end of edges of timber. |
| Router jigs | Help shape wood accurate and consistent. eg angle router in fixed position as end of timber is run against the bit eg a circle-cutter jig to make circles in timber/boards. Router fixed to long piece of timber which is adjustable for diff diameters |
| Things you need for a laser cutter | Set speed + power (paper needs lowest power and highest stable speed) Adjust focal length Import 2D file from CAD Extraction fan |
| What are perforations? | Lines of small sections cut. Areas to rip |
| When to use cold vs hot adhesives | Cold glue for e.g. cardboard. Hot glue when waxed |
| How to QC check calendaring | Micrometer occasionally |
| Injection moulding conditions | Say the pellets are melted - also it's under high pressure |
| Steam bending more precise info | Temp gauge in box. Stack planks for even air flow. Still needs drawing to tension, clamping as it goes - holes in former for clamp ends (e.g. winch/drill tightened clamps). Hours of steaming for planks. Spray release agent on mould. Plane to shape after |
| Plane to shape after for steam bending | So use larger planks to start with |
| Things to add to blow moulding (and all similar) | Release agent. Additives. Gate and flash. Repeats for mass. |
| More detail on deep drawing | Cold forming process. Done in stages to limit material stress. |
| What to do with metal offcuts | Remelt - reduces waste so environment and cheap |
| Digital printing cons | Thin layer of ink so bad vibrancy on dark materials |
| Screen printing cons | Doesn't use CMYK so needs all individual colours |
| How overmouldings attached | Mechanical interlocks - holes/grooves |
| What are the techniques/systems used by companies to make mass manufacturing systems efficienct? | Bulk buying discount pressure Stainless steel moulds for high qual and long last Low excessive material - nesting software and standard size projects Automation Vertical in-house JiT Division of labour - modular production - specialised workers QA |
| Why QA good | No lost batches or bad damage for replacement |
Created by:
Pyrogearos2