Design & Technology – Production techniques -Part 2

Source:http://www.bbc.co.uk/schools/gcsebitesize/design/resistantmaterials/processtechniquesrev1.shtml

Batch production tools

When making several identical products or parts, jigs, formers, templates, patterns and moulds are used to ensure the parts are all the same.

  • A jig is used to make sure that parts are made exactly the same, without the need for marking out. For example, when drilling through a block of wood with two holes in, it will make sure that the holes are drilled in the same place in each component.
  • A former is used to make sure that parts are shaped or bent to exactly the same shape.
  • A template is something that you can draw around to mark a shape onto material, so that it can be cut or shaped.
  • A pattern is used to make a mould when casting in metal or plastic resin. It is a replica of the finished object and may be made in wood or another soft material. Patterns are also used when shaping plastics in a vacuum-forming machine.
  • A mould is a hollow shape used when casting metal or plastic resin. Moulds for casting metal can be made in a special type of sand, in metal or in plaster. Moulds for casting resin can be made of plaster or rubber.

Shaping by wasting

Shaping by wasting means cutting away material to leave the desired shape. It gets its name because the material which is removed is usually thrown away. Shaping by wasting can be done on any type of material.

Shaping by wasting which can be done by hand

Process Wood Metal Plastics
Cutting straight lines Tenon saw (dovetail saw for fine work) Hacksaw (junior hacksaw for small work) Hacksaw (junior hacksaw for small work)
Cutting curved lines Coping saw (fret saw for fine work) Abra saw (piercing saw for fine work). Tin snips can be used on thin sheet metal Abra saw (piercing saw for fine work). A coping saw can also be used
Trimming cut edges to a straight line Jack plane or smoothing plane Flat or hand file Flat or hand file
Trimming cut edges to a curved line Spokeshave or rasp Round or half round file Round or half round file
Cutting grooves and slots Tenon saw to cut sides, then wood chisel or coping saw Drill holes at ends, then use abra saw Drill holes at ends, then use abra saw or piercing saw

Machine wasting

Cutting timber on a circular saw bench

Almost any wasting technique can be mechanised.

Common machines used for shaping by wasting

Process Wood Metal Plastics
Cutting curved lines Jig saw, either fixed or portable, with suitable blade. Band saw (teachers only) Bench mounted Jig saw (with suitable blade). Band saw (teachers only) Jig saw, either fixed or portable, with suitable blade. Band saw (teachers only)
Making holes Drilling machine and suitable drill bits Drilling machine and twist drills Drilling machine and twist drills
Creating round shapes of different diameters Wood turning lathe Metal turning lathe Metal turning lathe
Cutting grooves and slots Hand router or Computer Numerical Control (CNC) milling machine Vertical milling machine or CNC milling machine Vertical milling machine or CNC milling machine

CAM and wasting

Shaping machines may also be controlled by computers – an example of CAM. Computer control allows the work to be completed more accurately. The task can be repeated more frequently and quickly without any deviation from the standard.

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