Specialist Techniques & Processes

Production Aids

Before any material is cut or shaped, designers and manufacturers set up datum points and use production aids to ensure accuracy and repeatability. Working to a datum means all measurements are taken from a single fixed reference point or edge — this prevents the accumulation of small errors that would occur if each measurement were taken from the last cut. Templates allow a shape to be reproduced identically on multiple workpieces: a plywood template for a curved guitar body, or a card net template for a packaging blank. Jigs hold the workpiece and guide the tool — a drilling jig ensures holes are made in exactly the same position on every component in a batch, which is essential for interchangeable parts.

Calculating Material Quantities

Before manufacturing begins, a designer must calculate how much material is needed to avoid waste and control costs. For sheet materials, this involves calculating the material yield — how many components can be cut from a standard sheet with minimal offcuts. Nesting shapes closely together on a sheet, or arranging pattern pieces on fabric to follow the grain efficiently, maximises yield. In commercial production, computer-aided manufacturing (CAM) software automates this nesting process. For timber, the volume needed is calculated from finished dimensions plus allowances for sawing, planing and shrinkage during seasoning.

Wastage Processes

Wastage processes start with a block or sheet and remove material until the finished shape is achieved. In commercial paper and board production, die cutting uses a shaped steel blade pressed into the board to cut out net shapes for boxes and packaging in a single action — many thousands of identical cartons are die-cut every hour in automated lines. Perforation creates rows of small holes to allow controlled tearing, used on tear-off strips in packaging and stationery. For metals and timber, sawing (circular saw, bandsaw) removes material along straight or curved lines; drilling removes cylindrical cores; milling uses rotating cutters to remove material from flat or profiled surfaces; turning on a lathe removes material from a spinning workpiece to produce cylindrical or tapered forms. Cutting and shearing — guillotine cutting for sheet metal, rotary cutting for fabric — remove material along a straight line rapidly and with little waste.

Addition Processes

Addition processes join materials or build up shapes. Welding melts and fuses metal parts together — MIG welding is the standard commercial process for steel structures, gates and metal furniture frames. Brazing joins metals using a filler alloy at a lower temperature than welding, preserving the base metal's properties — used for copper pipework and cycle frames. Soldering uses a low-temperature tin-based alloy to make electrical connections on PCBs; the solder flows into the joint and hardens on cooling. Lamination bonds layers of material together to create a composite with improved properties — laminated safety glass, plywood, and foam-backed textiles are all examples. 3D printing is an addition process — fused deposition modelling (FDM) deposits thermoplastic filament layer by layer to build complex forms impossible to achieve by conventional machining. Batik uses wax applied to fabric to resist dye, adding pattern. Sewing joins fabric panels using interlocking thread stitches — the fundamental process in garment assembly. Bonding uses adhesives (e.g. epoxy resin, contact adhesive, acrylic cement) to join materials without heat. Printing adds ink to surfaces — screen printing, digital printing and pad printing each suit different substrates and batch sizes.

Deforming & Reforming Processes

Deforming and reforming processes change shape without losing material. For polymers, vacuum forming heats a thermoplastic sheet until it softens, clamps it over a mould, then evacuates the air beneath so atmospheric pressure forces the sheet to conform to the mould's shape — used commercially for blister packs, trays and chocolate box inserts. Blow moulding forces compressed air into a hot polymer parison (tube) inside a split mould, inflating it to the mould's shape — the standard process for HDPE containers such as milk and shampoo bottles. PET drinks bottles instead use injection stretch blow moulding, where an injection-moulded preform is reheated, stretched with a rod and blown to shape. Injection moulding forces molten polymer under high pressure into a precision steel mould cavity — it produces complex, high-detail parts in seconds and is used for everything from bottle caps to car dashboard components. Extrusion pushes molten polymer through a shaped die to produce continuous profiles — guttering, window frames and plastic pipes are all extruded. For metals, pressing (e.g. deep drawing) forces sheet metal into a die to produce hollow forms such as cans and sinks; casting pours molten metal into a mould and allows it to solidify. For papers and boards, creasing uses a blunt rule to compress the board along a line so it folds cleanly without cracking — essential for packaging nets. Drape forming softens a thermoplastic sheet, usually acrylic, and drapes it over a former so it takes that shape as it cools — used for curved display stands and machine guards. For textiles, pleating and gathering fold fabric to add shape and volume to a garment. Bending and folding apply to both sheet metal and thermoplastic sheet — a press brake bends metal along a straight line; a strip heater softens acrylic along a narrow zone so it can be bent by hand.

Manufacturing to a Tolerance

In commercial production, no two components will ever be absolutely identical — slight variations are unavoidable. Tolerance defines the acceptable range of variation: a component with a nominal diameter of 20 mm and a tolerance of ±0.5 mm is acceptable anywhere between 19.5 mm and 20.5 mm. Tolerances must be tight enough to ensure parts fit together and function correctly, but not so tight that they become expensive to achieve. Measuring instruments such as micrometers and vernier callipers are used to check whether components fall within tolerance. Components outside the tolerance range are rejected at the quality control stage — a process called inspection.