Glossary of industry terms S
Sand casting - The method normally used for the production of cast aluminium mould tools.
Sand blasting - A method of cleaning or roughening the cavity surface. In fact regulations prevent the use of sand in other than wet blasting applications which is unsuited to use on mould tools and therefore custom abrasive media is used.
Semi-permanent mould release - A release which is sprayed onto the mould tool and baked, which then provides about 10 - 100 releases before needing a further light application to be carried out on the moulding machine during production. They are based on various chemistries, and provide a gloss, lustre, or matt finish to the tool and therefore the moulding.
Service time (de-mould time) - The amount of time the mould tool is in the service area of the machine being de-moulded, cleaned, and filled, in preparation for the next lift.
Shielding (heat shield) - 1. Insulation material added to or around the external surface of the tool to reduce material formation, often used in scrap or throw away areas of the moulding.
2. Insulation material added to the internal surface of the tool to produce an aperture in the moulding.
Shot - 1. The amount of material that is put into the mould tool to produce a moulding.
2. The media (cast steel shot) used for shot peening.
Shot peening - A method of applying a texture to the cavity surface. It is achieved by impacting the surface of the mould cavity with cast steel shot in a blast cabinet until 100% coverage is achieved. The mould tool can be masked to give accurately defined areas with different textures, smooth, polished etc.
Shrinkage - The reduction in size of a moulding by comparison with the size of the tool that produced it.
Shrinkage allowance - the allowance applied to the mould tool to compensate for shrinkage.
Shuttle machine - A rotational moulding machine design where the tool moves between heating and cooling stations normally linearly and back and forth, hence the name.
Sieve size - Term used to define the size of the powder used to mould rotational mouldings. The figure given is the size of sieve which all material will pass through and therefore specifies the maximum size.
Skarsden - A type of hand tool used for scraping away flash from the flash line.
Sliders (slides) - An assembly attached to side cores and the main body or frame of a tool to allow the side cores to be easily retracted and put back by sliding in a track.
Snapsert - A custom item used to hold female threaded inserts in the mould tool without the need to screw them in place or unscrew them for de-moulding.
Spider (spider frame) - A tool mounting system which allows a number of tools to be opened simultaneously, thereby improving productivity. They consist of a bottom spider onto which the bottom halves of the mould tools are fixed and a top spider for the top halves; both spiders are fabricated from steel section. A key arrangement is normally used to achieve the initial orientation of the top and bottom spiders and then precision dowels and bushes achieve the final alignment of the tools during closing. A central clamping device provides the clamping force often in conjunction with springs, to take out tolerances in the assembly and some movement of the spiders which can occur even though they are stress relieved prior to assembly with the mould tools.
Split line (parting line) - The line along which the mould splits for de-moulding.
Spring-loaded frame - A frame work where the clamping force is transferred from the clamps onto springs which in turn transfer the force to the parting line. The intent is to provide a more even pressure over the flange faces at the split line and to ensure the pressure is more consistent when relative tool movement occurs.
Stamp - A tool used to create an impression in the mould, normally for identification purposes.
Station - 1. Term used to describe areas of the moulding machine i.e. cooling station, service station.
2. Term used to describe other production areas i.e. trimming station, assembly station.
Straight arm - A machine arm where the mould mounting plates are located at the centre of the actual spherical operating area of the machine.
Stress relieving - A process that uses heat applied to either the mould or the frame to relieve stresses, thereby reducing the chances of subsequent movement during production leading to miss-matches, miss-fitting etc.
Surface enhancer - A solvent that is applied to areas of the mould to eliminate pin holes and porosity in finished parts.
Surface finish - The internal surface finish of a mould which produces the outside surface finish of a moulding.
Swing bolt - A type of clamp most commonly used on small mould tools or inaccessible areas of larger tools that need a clamping force applied.
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