Glossary and terms

Glossary & Terms

Having been in the business of working at the shop floor level of molding, casting and forming operations around the world for over 50 years, we have heard a lot. Based on that experience we have put together this handy glossary of terms that you may find useful.

b

  • bag-in-well tire curing press
    A tire curing press in which the curing bladder is clamped into the mold assembly at the bottom part of the bladder only. At the start of the shaping process the bladder is inflated and emerges from the “well” into the green tire from the bottom to locate inside the uncured tire. At the end of the curing process the bladder is usually forced back into the “well” either by vacuum or with the aid of a downward stroking ram.
  • bag-o-matic (B.O.M) tire curing press
    A tire curing press in which the curing bladder is clamped at both the top and bottom on a center post, which travels up and down to help effect the tire shaping process and finished tire removal.
  • biscuit
    Excess of ladled metal remaining in the shot sleeve of a cold chamber die casting machine. It is part of the cast shot and is removed from the die with the casting.
  • bladder life
    The number of tires a curing bladder cures before needing to be replaced.

c

  • cavity
    The recess or impressions in a die in which the casting is formed.
  • cold chamber machine
    A type of high-pressure die casting machine, where the flow path through which the molten metal enters the cavity is open to ambient air. Also see hot chamber machine.
  • cold shut defect
    A surface defect of a metal casting in the form of a discontinuity where two streams failed to unite.
  • creep
    The phenomenon of continuing plastic strain over long periods of time at loads below the yield point. Creep only happens at high temperatures, which vary depending on the alloy type and composition.
  • cure cycle
    The process of converting an uncured (green) tire to a cured finished article using a heating process in a mold installed into a tire curing press.
  • cure cycle time
    The time taken to complete the cure of a tire in a curing press from the time of initial tire shaping to the time the press opens.
  • cycle time
    The time taken to complete one set of operations in a die casting machine from metal injection till it is ready for the next injection of metal.

d

  • die casting
    Is a process in which molten metal is injected into a precisely dimensioned and reusable steel mold very quickly under high pressure, which is maintained until solidification is complete.
  • die lubricant
    Chemical formulation applied to the die to facilitate casting release and prevent soldering.
  • dilution ratio
    The ratio of water to concentrated die lubricant is referred to as the dilution ratio.
  • ductility
    Is the ability of a material to deform under application of a tensile force or to withstand plastic deformation without rupture. A measure of ductility is % elongation, which compares the increase in gage length after application of the tensile force to the initial gage length.
  • durable inside tire paint
    An inside paint that is applied to the inside of one green-tire and then transfers to the curing bladder during the cure cycle to provide a reservoir of slip and release for several more untreated green tires before replenishment becomes necessary. Also see inside tire paint.

e

  • emulsion
    Is a mixture of two immiscible liquids in which small droplets of one liquid are suspended in the other liquid.

f

  • filled inside tire paint
    An inside paint that contains specific fillers to help provide enhanced air-bleed to evacuate air-trapped between the inside of the tire and the curing bladder. Also see inside tire paint.
  • fish eyes
    Are defects in coatings characterized by small circular craters that look like a fish's eye.

g

  • gas porosity
    Is the presence of trapped gas bubbles in a solidified casting.
  • gate
    Passage for molten metal which connects the runner with die cavity.
  • green tire
    A term used for an uncured tire.

h

  • hardness salts
    A common reference for bicarbonates, carbonates, sulfates and chlorides of calcium and magnesium
  • high-pressure die casting
    A process for producing engineered parts by injecting molten metal at high pressure into reusable steel molds (moulds).
  • hot spot
    Refers to a localized area of high temperature on a die surrounded by relatively cooler areas.
  • hot tearing
    Is the initiation of cracks during the solidification of an alloy.
  • hot-chamber machine
    Type of high pressure die casting machine where the flow path through which the molten metal enters the die is immersed in molten metal in the holding furnace.

i

  • impact strength
    The ability of a material to withstand shock loading.
  • inside tire paint
    A coating applied to the inside of green tires, prior to cure. These provide the needed slip for the curing bladder to locate centrally within the tire, as well as aid with the evacuation of air trapped between the bladder and the inside of the tire. They also provide release from the curing bladder at the end of the curing cycle. Also see; filled inside tire paint, unfilled inside tire paint and durable inside tire paint.
  • intensification
    Is the process of applying pressure through the piston in a die cast machine, after the cavity is filled and while solidification is taking place.
  • investment casting
    Is a process where the shape to be cast is initially molded in wax, which is then replaced with molten metal. Also called lost-wax casting. Also see lost foam casting.

l

  • leidenfrost effect
    Is a phenomenon in which a liquid, in near contact with a surface significantly hotter than the liquid's boiling point, produces an insulating vapor layer which keeps that liquid from touching the metal surface. The Leidenfrost temperature is the temperature at which the liquid starts to touch the surface.
  • liquidus temperature
    Is the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium. Above the liquidus temperature the material is homogeneous.
  • lost foam casting
    Is similar to investment casting except that polystyrene foam is used instead of wax.
  • low-pressure die casting
    A process for producing engineered parts by injecting molten metal at low pressure (typically using air between 15 - 100 kPa) into reusable steel molds (moulds).
  • lubricity
    Is a measure of the reduction in friction by a lubricant.

m

  • machinability
    Refers to the ease with which a metal can be machined to an acceptable surface finish. Materials with good machinability require little power to cut, can be cut quickly, easily obtain a good finish, and do not wear the tooling much.
  • metal flow
    refers to the ease with which molten alloy can fill a die cavity.
  • metal-casting
    Is a process of pouring liquid metal into a mold for the purpose of making a desired shape.

o

  • outside paint
    A coating applied to the outside of some green-tires, prior to cure, to help evacuate air trapped between the green-tire and the mold to improve rubber flow and enhance finished tire appearance.
  • overflow
    A recess in a die connected to a die cavity by a gate to assist in proper venting and filling.
  • overspray
    Refers to application/accumulation of die lubricant and other contaminants outside the die cavity.

p

  • part release
    Refers to the ease with a casting or molded (moulded) part can be ejected from a mold (mould) or die cavity.
  • permanent mold (mould) casting
    Refers to all processes which employ a reusable mold (mould) to make parts or castings.
  • plunger tip
    Replaceable front end of the ram or piston which forces molten metal into a die. Made of cast iron, steel or copper-beryllium alloy.
  • pore-free die casting
    Is a special method in which die casting is accomplished by filling die cavities with oxygen gas, which easily combines chemically with molten metal to prevent gas bubbles in the product.
  • porosity
    Voids or pores resulting from trapped gas, or shrinkage during solidification.

r

  • rheocasting
    Is a method of semisolid metal casting where molten liquid is converted to a thixotropic slurry formed through thermal management of cooling and solidification and then injected into a die cavity. Also see semi-solid casting and thixocasting.
  • runner
    Die passage connecting the plunger hole of a die to the gate where molten metal enters the cavity.

s

  • sand casting
    Is a process by which molten metal is poured in sand molds to produce parts in an economical manner.
  • semi-solid casting
    Process in which the charge to the die casting machine is partially solidified. Also see rheocasting, thixocasting and thixomolding.
  • shaping
    The process in which the curing bladder is inflated inside a green tire.
  • shear strength
    The strength of a material or component against sliding failure along a plane that is parallel to the direction of the force.
  • shot
    That segment of the casting cycle in which molten metal is forced into the die. Also used to refer to the total volume of metal injected.
  • shot sleeve
    Cylindrical chamber which is partially filled with molten metal prior to injection in a cold chamber die cast machine.
  • shrinkage porosity
    Void space inside the casting due to dimensional reduction that accompanies the freezing (solidification) of metal passing from the molten to the solid state.
  • silicone
    Family of polymers made up of a silicon and oxygen backbone with organic side groups that attach to the silicon atoms. Also termed polysiloxanes.
  • slush casting
    See semi-solid casting.
  • softened water
    Water with low levels of calcium and magnesium ions.
  • soldering
    Adherence of molten metal to portions of the die.
  • solidus temperature
    Is the minimum temperature at which melting of a substance begins. Below the solidus temperature the material is homogeneous.
  • spreading
    The ability of a material to cover a surface after making contact. Also see wetting.
  • squeeze casting
    A method by which molten alloy is cast without turbulence and gas entrapment at extremely high pressure.

t

  • thixocasting
    Is a process that requires specially processed billet material that is reheated to the semi-molten state just before injection. Also see thixomolding, semi-solid casting and rheocasting.
  • thixomolding
    Is a semi-solid casting process that uses metal chips which are fed into the back end of a heated barrel through a volumetric feeder. A screw feeder located inside the barrel feeds the metal chips forward as they are heated into the semi-solid temperature range. The screw rotation provides the necessary shearing force to generate the globular structure needed for semi-solid casting and inject the slurry into a steel die.
  • tire curing bladder treatment
    A protective coating applied to the outside of a new tire curing bladder, prior to its use. The specific aim is to protect the bladder against abrasive and chemical attack during service to enhance bladder life.
  • tire curing envelope treatment
    A coating applied to the working surface of a curing envelope, used in the retreading of tires. It ensures good slip so the envelope can readily conform to the contours of the pre-cured tread pattern, as well as provide protective film to prevent the adhesion of excess tread adhesive to the surface of the curing envelope. Both these things help to prolong the service life of the curing envelope.
  • tire curing press
    A machine into which tire molds are installed to cure vulcanize (vulcanise) the tires. There are usually two molds installed into each press.
  • tire mold (mould)
    A metal mold (mould) specifically designed with the tire tread pattern and sidewall name plates in which finished tires are formed.
  • tire mold (mould) treatment
    A coating applied to a hot tire mold (mould) to help improve rubber flow and protect against the build-up of mold (mould) fouling, which in turn improves finished tire appearance.
  • tire retreading
    A process in which a new tread is applied to the carcass of a used tire to enable that tire carcass to be reused. This process is typically carried out on truck and bus tires as well as earth-mover and some aircraft tires.

u

  • ultimate tensile strength
    Is the maximum stress that a material can withstand while being stretched or pulled before fracture.
  • unfilled inside tire paint
    An inside paint that does not contain any filer, used where optimum tire appearance is desirable and where the pattern embossed on the curing bladder is deemed sufficient to provide adequate air-bleed. Also see inside tire paint.

v

  • vent
    Narrow passage at the top of the die which permits air to escape from the die cavity as it is filled with molten metal.
  • vulcanization (vulcanisation)
    Also referred to as curing, it is a process in which uncured mixed rubber compounds, of the type used in tire manufacturing, are converted from an essentially plastic state to an essentially elastic state through the formation of crosslinks formed by reaction with sulfur in the presence of heat and pressure.

w

  • wear
    Is the material loss caused by friction.
  • wetting
    Is the ability of a liquid to establish and maintain contact with a solid surface.

y

  • yield strength
    Is the stress at which a material begins to deform plastically.
  • young's modulus
    Is a measure of the stiffness of an isotropic elastic material. It can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.

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