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Glossary of industry terms
Air injection – See inert gas injection.
Air ejector – a device which ejects the moulding from the mould tool using compressed air.
Air mover (airflow amplifier) – A device that uses a low volume of high pressure air (fed through the machine arm) to create a high flow of oven temperature air aimed in a specific direction. They are used to heat deep-cored and other hard to reach features in mould tools so that the tool is at a more uniform temperature and therefore the moulding will tend to be of more uniform wall section.
Alignment key – Key mounted to the centre guide pin to align the top and bottom spiders and therefore the individual moulds on the frames.
Alignment pin & bush (dowel pin & bush) – Precision machined male & female parts fitted to the flange of the mould tool to align the sections of the tool one to another.
Anchor Insert – A commonly used insert for moulding-in which is made from either hexagonal or square stock with circular grooves machined to give very good torque and pull out resistance.
Annealing – The heating then gradual cooling of normally metallic components to relax internal stresses. Commonly mould tools and spiders are annealed to maintain consistent dimensions after the heating and cooling process used in rotational moulding and therefore avoid the need to carry out further engineering work after an initial period in production.
Anti static (anti stat) – 1. An additive that works as a processing aid by minimising the build up of static during mixing and moulding.
2. An additive that reduces the build up of static in the moulded product.
Arm – The part of the moulding machine extending out from the central turret of the machine to the point where the tools are fitted.
ARM – The Association of Rotational moulders. A USA based International organisation which represents and supports the industry.
Auto-reverse – A common feature on moulding machines where the machine rotates in one direction for a set period of time, and then reverses direction for a set period of time, and repeats this throughout the moulding cycle to produce a more uniform wall section moulding.
Big Head fastener – A commonly used insert for moulding-in which is made from a welded assembly of a male or female thread to a backing plate of either expanded metal or a custom pressing. Gives very good torque and pull out resistance, and offers a robust thread.
Biaxial rotation – The rotation taking place in the moulding process where the tool is rotated through 360° in two axes which are orientated at 90° to one another.
Blow hole – A void through the wall of a moulding caused by pores or holes in welds, poor insert fit, porosity in aluminium casting, poor mould flange condition, or a blocked or incorrectly sized vent.
Blueing in (matching in, fitting) – A method of matching mould parting lines to obtain a close fit. Engineers’ blue is smeared on one part and the other mating part offered to it and then viewed to see the areas of contact.
Bolt, receiver, and stop – This system is designed to quickly clamp and unclamp spiders . The system incorporates stops that prevent over-tightening and potential damage to moulds.
Boss – 1. A protrusion from the surface of a mould used to produce an indentation in a moulding.
2. A protrusion from the surface of a moulding produced by an indentation in the mould surface.
Bulk density – The term used to describe the density of the powdered polymer not the homogeneous polymer density. The figure is much lower at roughly 15%.
Bridging (webbing) – 1. Improper flow of powdered resin in the mould due to resin touching across one wall to another. This condition can be caused by narrow mould passages, poor mould and/or part design, improper rotation, poor powder flow properties, and incorrect resin type.
2. An engineered feature to create a ‘bridge’ of moulded material from one mould wall to another, most commonly to increase the stiffness of the moulding.
CAD – The acronym for Computer Aided Design.
CAM – The acronym for Computer Aided Manufacture.
Carousel – A rotational moulding machine design where the oven is normally located to the left, the cooling station to the right, and the service station at the front, with indexing taking place around a vertical axis shaft. The machine therefore resembles a fairground carousel, hence the name.
Cast – 1. To form a section of a mould tool by pouring a liquid metal (normally aluminium) into a cavity.
2. To form a section of a model or pattern by pouring a liquid resin into a cavity.
Casting – The finished product of the casting operation.
Casting contraction (casting shrinkage) – the allowance applied to the model or patterns used to make a cast mould tool to compensate for the shrinkage of the castings during cooling.
Cavity – The space inside a mould tool which forms the moulded product.
Centre guide assembly – The guide pin lines up the spider halves while the key prevents any rotation that could cause damage to parting lines.
Centre guide pin – Alignment device mounted to mounting hub to aid in opening and closure of mould spider frame.
Centring nut – A large receiver and stop assembly mounted in centre of spider to allow closure of larger spiders and eliminate operators reaching in over spiders .
Clamp – Various types of device used to hold the various parts of a mould tool together during moulding and then allow opening of the mould tool for de-moulding and filling.
Clamping pressure – The pressure required during the moulding operation to keep the mould closed.
Clamshell machine – A rotational moulding machine design where heating and cooling occur in the same place. The doors of the machine are curved and open vertically hence the name.
Closure (Lid) – The sections of a mould tool removed from the section of the tool fixed to the moulding machine to allow the moulding to be removed.
CNC model – A model produced from a 3D CAD file with moulding shrinkage allowance and casting contraction built in. From the model resin patterns are produced which are then used to cast the sections of the mould tool.
CNC mould – A mould produced by directly machining CNC from 3D CAD files aluminium mould plate.
CNC tool path – The programme written to control the CNC machining centre when it cuts the mould tool cavity.
Cooling time (cooling cycle) – the amount of time the mould tool is in the cooling chamber cooling the polymer.
Compound – Polymer that has been mixed (normally to colour it) by extrusion compounding.
Core pin – A pin used to form a depression on the outside of a rotationally moulded part which is an undercut to the way the mould is pulled apart. Core pins are removed before the basic mould is pulled apart. There are two categories of core pins; fixed and removable, the removable pin is usually used per the definition “which is an undercut to the way the mould is pulled apart“. It can also be used when its direction is with the direction of mould opening as is the case with fixed pins. Core pins are most often a machined feature.
Cored through hole (through hole) – the area of a moulding resulting from internal protrusions in a mould which, when the mould is assembled, come together to touch creating a tube through the moulding.
Counter balance – Machined weights and mounting system to counteract the weight of the tool(s) and allow the moulding machine to rotate smoothly.
Date code wheel – Machined insert to track moulding day, month, year and shift.
De-moulding – The act of removing parts from a mould.
Drool – Unwanted flow of moulding material on the internal surface of the moulding under the effect of gravity. This is normally caused by rotation being stopped before the material has cooled sufficiently.
Double walled moulding – A part design which contains two walls in close proximity, forming a single-walled structural component. This design may contain kiss-offs or be filled with foam for added stiffness.
Draft (draft angle, draught angle) – A taper designed into the mould. This is normally used to facilitate removal of a moulding from the mould, or to allow a tool to be cast successfully. Draft is normally designed in degrees.
Double-stacked tool (piggy-backed tool) – Arrangement of tools on the machine where one set of tools sits above the other to increase the tool carrying capacity of the machine. The top set of tools is normally removed from the machine to allow the lower set to be de-moulded.
Draw – The direction in which the moulding is removed from the tool, common usage “the feature is in the line of draw”.
Drill points (drill pips) – A small protrusion in the mould which leaves an indentation in the moulding used to locate the point of a drill when drilling holes in secondary operations.
Drop arm (offset arm) – A machine arm where the mould mounting plates are ‘dropped’ and are therefore ‘offset’ to the centre of the actual spherical operating area of the machine. Normally used to allow larger (but fewer) tools to be fitted to a given size of moulding machine.
Drop box (dump box) – An insulated hopper mounted to the inside or outside of the mould for holding plastic resin or powder that can be released at any time during the moulding cycle to produce a multi-layered moulding wall section.
Dry Flow – Term used to describe the measure of dry powder flow which is important in rotomoulding as it gives a good indication of the way material will flow in actual moulding. The standard method for measuring dry flow is to put a predetermined volume of powder into a standard funnel and measure the time taken for the powder to flow through it.
Dry Mix (Dry blend) – Polymer that has been mixed (normally to colour it) in a mixing machine. The polymer and the pigment are in powder form but the pigment has a much smaller particle size than the polymer.
Electroforming (electrodeposited) – A process to produce moulds in which a relatively thin layer of metal (normally Nickel) is electrically deposited onto a model to create the mould tool. The metal is usually backed up with another metal (copper) for added strength.
Engraving – The process used to create mirror image letters, numbers, etc. by cutting into the mould wall to create a mirror image of the result required on the moulding.
Fabrication lines (bolted parting lines, bolted split lines) – A type of parting line where the separate parts or sections of a mould are fitted together and permanently bolted to form a tight seal. A small witness of this fabrication can be seen on the moulding. This is normally required where it is either impossible to manufacture a cast or CNC tool in one piece, or where it is more cost effective to manufacture the tool in several pieces.
Fabricated mould – A mould tool made by machining, forming, welding or fastening metal together. In general, fabricated rotational moulds are made from cold or hot rolled steel or stainless steel. Also used to describe the less common mould tools made from plates or sheets of aluminium.
Family mould – A mould which makes more than one part but the parts are different.
Ferris wheel machine (vertical machine) – A rotational moulding machine design where the oven is at the top, the cooling station at the back, and the service station at the front, with indexing taking place around a horizontal axis. The machine therefore resemble a fairground Ferris wheel, hence the name.
Filling – The placing of moulding material into the mould tool.
Filling port (Loading port) – A port in the tool to allow material to be poured in after the tool is closed where due to the geometry of the moulding it is difficult to load the tool with material when the tool is conventionally open.
Finish – The quality or texture of the surface of a mould which forms the part. The finishes commonly used in rotational moulding are machined, ground, blasted using sand, shot, etched, engraved, or plated. Various surface finishes required by customer, i.e. cast, 120 grit, 180 grit, etc. through mirror finish.
Fins – See heat deflectors.
First off – 1. Initial mouldings produced from a new tool.
2. First moulding produced from a new production run. 3. First finished product produced from a new production run.
Fish Hooks – Witness left on the internal surface of a moulding by the last material still flowing prior to gelling, this only effects moulding made from PVC plastisol.
Flaming – 1. Process used to make the moulding more attractive by increasing the surface gloss level and make split line trimming less noticeable.
2. Process used to oxidise the surface of a moulding prior to applying labels, paint etc.
Flange – The metal added to a split line area of a mould to strengthen the area and to permit the use of bolts and clamps to hold the mould together during moulding.
Flange release – grades of release coating used only on tool flanges to prevent moulding material adhering. These typically give much higher levels of release than ones used on surfaces of the tool that form the moulding.
Flash line – The line on a moulding which occurs at the split (parting) or fabrication lines of the mould.
Flash – Excess material attached to a moulding along the split (parting line) or fabrication lines.
Flat split line – A type of split line that has no detail on its vertical surface except for steel dowels and bushes along its length for alignment.
Flexible pattern – A type of pattern that, due to its flexibility, allows casting with undercuts or reverse draft to be produced.
Fluorination – A process carried out after moulding to coat the moulding with a layer of fluorine to improve barrier properties. Normally only used on petrol (gasoline) tanks to meet weight loss from permeation standards.
Frame – The framework around the mould tool used to make it more robust and rigid. It also provides a location for the clamps to hold the tool together and for mounting the fixed sections of the tool to the machine and lifting points on the removable parts of the tool.
Gemini mould (double cavity mould, twin cavity mould) – A mould which makes two identical mouldings. Commonly used when a moulded part with a large cut-out area can be combined with a second part so that the cut-out area is not formed.
Glass beading – The process of applying a finish to the mould tool to produce a semi-gloss finish on a moulding. Glass beads are impacted by compressed air against the surface of the tool whilst it is contained in a cabinet.
Guide pin &bush – A male &female attachment to the mould frame or spider used to achieve the initial alignment of the parts of the mould tool prior to the alignment pins & bushes engaging to achieve the final alignment.
Hairs and tails – A term used to describe a type of fault affecting moulding material. It is the result of poor micro-grinding where the powder is not cut cleanly into particles and instead has shape abnormalities of fine hair like protrusions or larger tapered protrusions looking like tails. The result is poor dry low times and poor flow in the mould tool.
Heat fins – A detail that is normally cast onto the exterior of the mould and increases the surface area that is subjected to the oven air during moulding and therefore increases the rate at which these areas heat up. They are used to increase the mouldability of hard to heat areas.
Heat pipe (heat pin) – A sealed tube containing a heat transfer medium (usually water) which is capable of transferring heat rapidly. Used in moulds to transfer heat to and from areas are difficult to heat and cool.
Indexing – The movement from one station on the rotomoulding machine to another. On a fixed arm (or turret) design of machine all of the arms move together, the tools in the service station moving to the oven, the tools in the oven moving to the cooling station, the tools in the cooling station moving to the service station. On an independent arm machine the process is similar but each arm moves when the control system determines, this may not be at the same time as the other arms. Machines of this type are configured with more stations than arms to allow this independent movement.
Impregnation – The process of filling voids in a material which has a tendency to be porous, such as cast aluminium, to prevent evidence of the porosity showing on the moulding.
Induction time – The portion of the heating cycle from the beginning of the oven cycle to when powder starts to fuse to the inside mould surface.
Inert gas injection (gas injection) – The use of an inert gas pumped through the arm of the moulding machine and into the mould tool to remove air and therefore prevent certain moulding materials reacting with oxygen during the moulding cycle. This allows otherwise unmouldable materials to be moulded successfully and can also improve the mechanical properties of others.
Insert – 1. A metal (or other material) component moulded into a moulding for example a metal threaded nut.
2. A part of a mould which is removed prior to part de-moulding normally forming an undercut in the moulding that would prevent it from being pulled out.
Insert holder – An attachment on the inside or outside of a mould tool which secures an insert in place during the moulding cycle.
Ionised cleaning – The use of ionised air to reduce static and therefore static ‘cling’ during cleaning.
Jack nut – A commonly used insert for secondary finishing operations giving good torque and pull out resistance.
J bolt – A type of bolt used to receive a clamp fitted to mating part of the tool.
Jig – Term used for an item fitted to a moulding to allow manual machining of post-moulding trim details such as routed apertures, drilled holes, etc.
Kiss point (kiss-off) – 1. Internal circular protrusions in a mould which, when the mould is assembled, come together at a dimension less than twice the thickness of the moulding.
2. The feature created in the moulding by the use of 1.
Kiss strip (kiss-off strip) – 1. Internal strip protrusions in a mould which, when the mould is assembled, come together at a dimension less than twice the thickness of the moulding.
2. The feature created in the moulding by the use of 1.
Knife edge – A detail in a mould tool that allows for easier removal of a scrap area by producing a thinner wall section around its periphery.
Label area (decal panel) – A special surface designed into a part on which to apply a label. This commonly requires a textured mould to have a smooth surface in that area.
Laser marking – A method used to apply primarily sequential identification numbers to mouldings.
Leonardo machine – A design of machine which is automatic (no machine operator is required as such) and which uses oil running through channels on the mould tool to heat and then cool the tool and therefore melt and solidify the polymer.
Lever area (lever point, pry point) – An area of the frame or tool to help the opening of the mould tool by allow leverage to be applied.
Lift – the production of a moulding or mouldings from one arm of a moulding machine.
Lift rings (lift hooks) – Attachments on a mould or mould frame for attaching a hoist and help with mould opening.
Logo area – An area of the mould tool into which mirror image letters, numbers, or graphics are cast or engraved to provide product branding, identification, instruction, etc.
Logo block – A removable logo area of the mould tool to allow the logo to be interchanged normally for alternative product branding.
Material reservoir – An excess cavity in a mould to permit enough material to be placed in the mould in the bulk form to complete the moulding to the desired wall thickness. The term may also be used to describe a feature used to make loading a narrow mould tool easier.
Maximum swing – The diameter of the largest imaginary sphere, with its centre located at the intersection of the minor and major axes that could be placed in both the oven and cooling chamber, individually.
Maximum weight per arm – The maximum total weight which can be safely supported and set in motion on a single machine arm. This weight includes mould spider or mould frames, moulds, counterweights, and material.
MFI – Melt flow index. A measure of how easily a material flows when molten.
Micro-grinding (pulverising) – The process of reducing polymer in pellet form down to a powder.
Micropellet (Gala pellet) – A form of pelletised polymer suitable for using directly in rotational moulding without the need to reduce it to powder.
Mismatch – Parts of a mould which do not align accurately are said to be mismatched. Normally refers to split lines.
Mixer (Blender, high speed blender, high speed mixer) – A machine used to mix additives with powder polymer (usually pigment).
Model – 1. Physical representation of the moulding normally made from resin or wood (or both) used for manufacturing cast tooling and made at a calculated size to allow for moulding shrinkage and casting contraction.
2. Physical representation of the moulding normally made from resin or wood (or both) used for evaluation of the shape, styling etc. and made at size or sometimes scaled (1/2 full-size).
3. Electronic data defining the geometry of the moulding – 3D cad model.
Mould – A tool in which material is placed and then acted upon by pressure or heat to form a part which conforms to the shape of the mould. In the case of rotational moulding, material is placed in the mould, heated, and rotated, so the material collects on the inside surface of the mould. Once the total material has collected and “cured” on the mould, the mould is cooled until the material has “set-up”. The mould is then opened and the part removed. Rotational moulds are usually produced by casting using aluminium, machining out of solid material, or fabricating out of sheet stock. The term normally includes all of the components flanges, clamps, mounting plates, etc. that are required to run the mould on a machine. That which forms the cavity, along with cast-in parts such as flanges and posts. Tool is the “package” mould, clamping, mounting plate, frame etc. Verb: The act of forming parts by using a mould.
Moulded-in Graphic (in mould graphic) – A graphic which is applied to the tool and moulds into the moulding to provide an attractive and durable result.
Moulded-on Graphic – A graphic which is applied to the moulding to provide an attractive and reasonably durable result.
Mould enhancer – A chemical system applied to the mould tool to improve the surface finish of the moulding.
Mould pressurisation (pressurisation, air injection) – The use of low pressure air pumped through the arm of the moulding machine and into the mould tool to control the distortion and shrinkage of a moulding. A variation of this process using higher pressures can improve the surface finish of mouldings.
Mould tool (mould, tool) – Term used to describe the mould that the polymer powder is placed in to produce the moulding.
Mould wall thickness – The thickness of the mould tool. This must be relatively uniform or in some cases deliberately adjusted to ensure that the resultant moulding is of uniform wall thickness or in some cases deliberately varies, as required for the application.
Multi layer – Term used to describe a moulding that has more than one layer within the wall section. These layers may be the same basic polymer but with different properties i.e. an outer layer of high density polyethylene of one colour, and an inner layer of medium density polyethylene of another colour. They can also be different basic polymers i.e. an outer layer of medium density polyethylene, and an inner layer of nylon. Sometimes a further layer (tie layer) is required to join them.
Multi layer one shot – Term used to describe moulding materials that form more than one layer within the wall section of the moulding although they are introduced into the mould tool in a single shot.
Nest (fixture) – Term used for an item which holds the moulding during CNC or manual machining of post moulding trim details.
Neutral axis – Term used to describe the intersection zone of the two axes on the rotational moulding machine where the linear velocity is effectively zero. Placing a mould tool incorrectly with some sections of the tool entering this area can lead to significant reduction in the wall section of the moulding.
Offset arm – A machine arm whose mould mounting plate is offset to one side of the actual spherical mould area.
Oven – The part of the moulding machine where the tools are heated to form the moulding.
Oven time (oven cycle) – the amount of time the mould tool is in the oven melting the polymer.
Particle size distribution – Term used to describe the distribution of the various particle sizes within a moulding powder. Performance of a powder is not solely determined by the sieve size, it is also determined by the size of smaller particles and the proportion of the overall that they represent.
Permanent mould release – A release which is sprayed onto the mould tool and then baked and provides multiple releases for months or even years of production. Typically the release agent is PTFE (Teflon) based, and provides a gloss or lustre finish to the tool and therefore the moulding.
Pinholes (pinholing) – Small voids visible on the surface of a moulding.
Photo-etching – A method for applying a range of textures to the internal surface of the mould tool which transfer to the moulding to provide an attractive surface finish.
Plaster casting (ceramic casting) – An alternative to sand casting for the production of cast aluminium mould tools. Instead of using sand to form the cavity into which molten aluminium is poured, a form of plaster is used. This creates a higher definition tool ‘as cast’, and through the use of flexible patterns allows the production of undercuts.
Plastisol – The liquid form of PVC (Poly Vinyl Chloride) used in rotational moulding.
PlusNut – A commonly used insert for secondary finishing operations which gives good torque resistance and pull out resistance and offers a robust thread.
Pock mark – A blemish on the surface of a cross linked polyethylene moulding caused by out gassing from the cross-linking agent.
Porosity – 1. Term used to describe voids in a mould. This is undesirable because it can adversely effect the surface finish of the moulding by reproducing the void as a small bump on the moulding and it may also lead to blow holes in the moulding if the porosity in the tool contains trapped air. Porosity may be present in the base material of cast aluminium moulds and in welded joints.
2. Term used to describe some types of voids in mouldings.
Powder – The form in which most polymers are used in rotational moulding.
Preheat (preheating) – The manual or automatic heating of a static tool prior to rotation in the oven.
Prototype mould – A preliminary mould, usually made as inexpensively or as quickly as possible, to prove out the design concept for a moulding. Methods of manufacture are:
a. GRP fabrication using high temperature epoxy reinforced with carbon fibre.
b. Flame spraying of molten metal onto a master until a shell of predetermined thickness is achieved.
c. Direct CNC machining of aluminium stock. Only in the case of CNC machining can the tool give a normal production life.
Ratio – The interrelationship of the speeds of the primary and secondary rotation on the moulding machine.
Receiver – Threaded sleeve mounted in receiver tube to allow closure by tightening a receiver bolt through the top spider.
Reverse draft – Draft on a moulding which runs against the draw and relies on shrinkage for the feature to de-mould successfully.
Ripple – Term used to describe the surface finish on the inside of a moulding when it is only just fully fused or when made from certain materials and correctly fused.
Rock and roll – The rotation taking place in the moulding process where the tool is rotated through approximately 45° either side of horizontal in one axis (Rock) and 360° in the other (Roll).
Release (release coat, mould release, release agent) – A chemical system applied to the mould tool to facilitate easy removal of the moulding from the tool, may be semi-permanent or permanent.
Ring (plate) – A circular steel fabrication which is attached to end of the mould machine arm to provide a location for fixing tools.
Rotational mold, rotational molding – US spellings of rotational mould, rotational moulding.
Rotational moulding (rotomoulding, rotamoulding, rotational casting) – A process used to mould hollow parts. The material is placed in the cavity of a mould that rotates on two axes. The mould is subjected to heating and then cooling while rotating. The material melts and adheres to the cavity walls to form the shape desired, and is then cooled to solidify it.
Rotational mould – A mould tool specifically designed for the rotational moulding process.
Rotation – The motion of the machine and the tool which forms the moulding.
Rotation speed – The speed at which the primary and secondary axes of the moulding machine rotate.
Routing – The term used to describe the secondary operation of machining which is used to create apertures and edge profiles on mouldings.
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.
Tongue and groove split line – A type of split line that has male and female features cast or machined into it which locate with one another for alignment. They are sometimes supplemented with steel dowel pins and bushes.
Trim allowance (trim stock) – Material added to a moulding to complete the moulded one-piece wall, but which will be trimmed away after moulding. Frequently added between the cavities of a Gemini tool.
Thread plug – A part of a mould which forms a thread and must be removed from the mould before the part can be removed or turned out of the part after removal.
Toggle clamp – An over-centre type clamp used to hold mould parts together.
Tool (mould, mould tool) – Term used to describe the rotational mould tool used to produce the moulding.
Tooling feature – A hole or protrusion not functional to the basic piece part, but used later to locate the moulding for secondary work.
Undercut – A feature of a moulding which protrudes into or out of it and interferes with the removal of the part from the mould.
Universal plate (universal ring, universal spider) – A plate fabricated with a steel grid which allows “T” bolts to be used to fix the mould tool in many positions. Normally used for optimising the position of the tool relative to rotation axes during development prior to the production of the final tool framing.
Vent tube (air tube, breather tube) – A tube in the mould tool which extends into the inside of the moulding to allow the equalisation of pressure. Air moves out of the tool during the oven cycle and in during cooling helping to prevent mouldings with excessive flash, blow holes, faces distorted inwards.
Wear bush (insert bush, core pin bush) – A bushing made from steel or other hard material fitted to the mould tool where an insert or core pin is fitted to prevent wear of the mould wall.
Web (gusset) – A brace which is usually triangular for reinforcing a flange or mounting post cast or machined in the mould tool.