Cooling plastic mold company



Once the hot polyester resin goes into the mold it ought to be cooled quickly. Cooling permits the molded component which will keep its preferred pattern when it’s demolded out of the mold. When cooling isn’t offered ,the hot polyester resin may normally heat up the mold steel to a level ,so component cooling to a solid  form may not be attained. Mold temperature is quite crucial, since it controls a great part of the general cooling cycle. You will find methods that mold cooling occurs.

The sketching demonstrated below symbolizes the cross-section of a mold base together with the molded component and its runner structure. The hot polyester resin may heat up the adjacent mold steels. one part of this heat may be carried out directly into the machine platens and some other heat may radiate directly into the air all around the mold base.
This sketching symbolizes the cross-section of a mold base together with the molded component and its runner structure. Water ways are machined into the mold cavity and core plates. This lets moving water to get rid of heat within the molded component by convection. water ways temperature, movement, and pressure might be controlled.
This sketching symbolizes the cross-section of a mold base together with the molded component and its runner structure. water ways are machined within the cavity and core plates. This lets a moving water/ethylene glycol mixture to get rid of heat within the molded component by convection. This mix is employed for excessive cooling demands and needs a chilling appliance.


Heat moves from a increased temperature body to a reduced temperature body. The temperature variation and the level of heat decides the movement. The larger the variance among the 2 bodies in temperature the higher the movement speed among them. Such a heat exchange transferring occurs from hot plastic resin contact to steel and after that to water water ways. The cooling effectiveness of a mold depends on the species of coolant employed, coolant pressure, movement speed and coolant conditions. The mold materials employed also have diverse heat conductivity.

A lot of mold manufacturers decide cooling demands by old knowledge. Some mold manufacturers decide cooling demands by employing a zone cooling strategy. A certain coolant hole dimension may zone cool a given diameter along the coolant hole. Mold cooling demands might be determined and you will find software applications programs to make ease of the time and job required using calculations. The next content may provide you with a better idea of what is required for calculations:

  • Equation A is made for figuring out the heat content of plastic material materials going into the mold.
  • Equation B is employed to determine convection, or the capability of a medium which will transport heat from one location to another.
  • Equation C is made for the computation of transferring or switching heat from 2 bodies in contact.
  • Equation D is most likely the Reynolds number formula. It is chosen to possess a turbulent coolant movement via the cooling water ways to allow them to gain improved heat exchange. The Reynolds number is really a way of measuring turbulent flow.


Designing the correct cooling structure for a given mold involves a lot of parameters. The mold developer ought to take into account:

  • Variety of plastic resin and its soften conditions.
  • Variety of coolant which will use.
  • Position of water ways.
  • Dimension, quantity, and amount of water ways.
  • Position of water ways within the mold
  • Efficiency of heat exchanger to be chosen.
  • Client cooling requirements and demands.




Polyester resin flows improved when heated up, but is cooled off as it moves past the water ways all around the cavity and core. Consequently, a perfect molding conditions ought to be held by manipulating the coolant conditions, pressure and movement speed. In case practical, the arriving coolant should cross the hottest molding areas initially, and after that cross the cooler mold areas.The illustration reveals a cooling layout for a thin, not deep, sole cavity mold. Equivalent coolant water ways are machined within the mold steel, and a tapered water line thread is utilized on each end, for convenient remove water line fittings. Heat is eliminated as the coolant moves across the channel.

This illustration symbolizes a cooling layout for a not deep, sole cavity mold. water ways are machined as demonstrated below. Each hole entrance is machined and tapped for a tapered water line thread and a tapered water line plug should be considered which will stop the movement and direct or deliver the coolant in directions required which will move close to the component cavity in order that most walls of the cavity will be cooled off.


This illustration symbolizes a cooling layout on a deep thin wall box. The core steel which will make the wall thickness isn’t demonstrated for readability. The red color below symbolizes the component cavity region. A vertical hole is machined and plugged as demonstrated in order to permit the water to help movement from position 1 to position 2.
The illustration below symbolizes a cross-section for a core cooling layout. Holes are typically machined and plugged as demonstrated. The patterns could be radial or move along with the core length based on the layout.

These illustrations display coolant moving into, splitting close to the circle cavity insert, and after that out. This layout might be linked to different inserts. 2 O-ring slots are made which will prevent leaking. A center slots is turned in order to offer 360 degrees of cooling close to the circle insert and cavity working surface.


Cooling parts will be employed in order to handle coolant movement . All the different cooling parts is discussed on the next pages.
Pressure plugs tend to be made in order to stop or handle coolant movement within water ways. The tapered thread design comes with a seal utilizing a planned variation of taper among the water plug and the tapped opening. A hex socket head is employed for tightening. The headless model plug utilizes an extensible O-ring manipulated by rotating a hex wrench inside the plug .
Cascade water junctions are typically employed to allow them to cool inserted cores to arrive at regions of molds. Coolant goes into the base connection and moves up the center water line, splatters over similar to a water fountain, cooling 360 degrees when it goes down and leave from the appropriate connector.


plastic mold company

Mold Heating and Cooling



The course may discuss the fundamentals of mold heating and cooling about cold runner system. You may discover choice, utility, components and prevalent troubles connected with heating and cooling. The next topics are introduced in a practical way.



The handling of mold temperature by ways to heat and cool the mold cavity is essential to the shot process. For polyester resin to be appropriately produced to a component, the mold needs to get cooled or heated.


This illustration symbolizes a cooling routine for a thin, not deep, individual cavity mold. Equivalent coolant water ways are machined within the mold , and tapered water pipe thread is utilized on both sides for convenient remove conduit fittings. Heat is eliminated because coolant moves via the channel.



This sketching symbolizes the cross-section of a mold base together with a component and its particular runner structure. Water ways have been machined within the cavity and core steels which will make it possible for hot water to be distributed from an additional temperature handle device. The control device is generally located alongside the machine and piped to the mold.
The illustration below symbolizes setting up a mold exterior temperature regulation structure on top of a molding machine. The goal of the micro-processor regulator and its own mold detectors is to handle the mold exterior temperature by means of controlling the movement of water within the additional temperature regulate product. The cooling and heating cycle (time) is manipulated robotically.


plastic mold company



As plastic material is injected to a cavity, it ought to expel the air which can be previously there. Except the air is eliminated rapidly many things might appear. Air may get caught and after that compacted raising its temperature sufficient to allow them to result in burn markings or possibly a gap. Absence of correct venting can result in a rise within shot pressure, short shots, splay scars, negative weld marks, and a excessive level of internal stresses.


Most plastic molds has vent slot at some way. Air within molds can be released along the P/L, ejection pins, slides, and mold inserts. Generally it isn’t really sufficient due to the amount of air that ought to expelled rapidly. Which means mold designer ought to assume caught air areas and plan extra venting areas.

This image symbolizes polyester resin completing a cavity with no air vents. The air invited from heating the polyester resin are caught and can’t be expelled. This squeezes and increases the temperature of the air, resulting in the plastic material which will burn up or char, and perhaps resulting in an unsufficient fill shot.


There are several kinds of air vents and vent areas. A lot of  air vents on parting line works extremely well as needed. Ventilation could be produced on via ejector pins. Ventilation could possibly be intended on inserts, cores, leader pins installed on mold base.


The parting line vent demonstrated below symbolizes the most popular type of ventilation employed. A lot of more might be employed where needed. The vent is generally manufactured by milling a not deep, thin land, then a deeper slot. Component dimension, pattern, and kind of plastic material decide the venting land dimension. The vent relief slots assists to allow them to maintain the land open.



These sketches symbolize ventilation close to and below an ejector pin. Flats are machined in order to maintain the pin concentrated and permit ventilation. Air are able to vent via the flats, directly into the relief region, and after that released from mold base. Degree of the flats ought to fit the plastic resin viscosity to ensure that merely the air may release.


Parting line air vents manufactured very broad are susceptible to coining. Coining is alloy compression, triggered from shutting the mold under excessive clamping force, therefore sealing a vent. When slots are very narrow they might plug quickly, or various depths between numerous air vents may result in fill troubles. Never vent where component performance, looks, or flash could be a trouble.


The sketching below symbolizes a negative position for a vent because the caught air can be found at the opposite cavity end . The final location to fill, opposite the entrance is most likely the best area for a vent.

Vent Placement Solutions




plastic mold company





A gate stands out as the link between the runner  and the formed component. It ought to allow sufficient melt plastic movement which can occupy the mold cavity, additionally extra resin to compensate component shrinking and solidfying.
The gate is an extremely important section of the runner system. The gate model, position, and dimension carries a remarkable impact on the shaping course. It influences body qualities, presence, and dimensions of the component.


Side gate(edge gate)

The side gate demonstrated here is most likely the most popular form of gate. The arrow illustrates the plastic material movement out of the runner, via the gate, and directly into the cavity. One half on the rounded runner and  the whole gate is cut in the cavity part demonstrated below.


Enlargement “A” illustrates a really tiny mark remaining once the gate has been eliminated. If appearance and layout performance allow, this gate might be ripped away manually. Otherwise, the component gate exterior can be enhanced manually nipping, or putting the component and runner structure in a fit fixture.


Sprue Gate

Component Arrangement
The arrows on the image stand for the plastic material movement coming from a nozzle via the sprue gate and thereafter radially to occupy the plate cavity. This form of gate is employed at a big, sole cavity mold. Gating in the center grants an effortless flow, lowest pressure decline, and removes stuck air and weld marks. Shortcomings are degating .
Resin Filler
Nearly every kind of plastic material works extremely well with this particular kind of gate because the entrance of the sprue gate to the mold cavity is big. There should not be any trouble with viscosity or fulfilled resins.


Figure below demonstrated here represents a sizable mark remaining from cutting  the sprue gate. Consequently, it is essential to gate in a non-cosmetic place or exterior which don’t modify the component performance. Additional aesthetic issues are potential flow lines exuding away from sprue, or sink spots reverse the sprue.


Component Arrangement
The arrows from the sketching here symbolize the plastic movement coming from a feed runner into the periphery of the lengthy, hollow pipe. Subsequently it moves radially over the ring gate and evenly along the whole pipe. The material moves effortlessly on lengthy, hollow, rounded components. Ring gates avoid weld lines, stuck air, or tension concentration surrounding the gate.
Plastic resin Filler
Nearly every resin/filler works extremely well with this particular kind of gate due to the big radial movement section of the gate. Despite the fact that gate thickness might be a essential element, there shouldn’t be any trouble with viscosity or stuffed resins in the most common materials.


The subsequent sketching shows the hollow plastic pipe having the circle gate/runner system eliminated. Because a mark or spot resides it is desired to gate into a non-cosmetic area. In the event the pipe inside diameter is big sufficient ,a disk gate (opposite of a circle gate) can be employed. This will retain the gate mark away from the outside component surface.


point gate

The arrows on the sketching demonstrated below symbolize the plastic material movement within the sprue, runner system, point gate, and directly into the mug pattern cavities. A Three plate mold structure instantly degates the component and sprue. The Three plate mold sets apart the runner structure, and also part within the cavity part, and demold everything within the mold base. This layout needs a trapezoidal runner model by way of sucker pins to break the entrances.


The tiny cross-sectional entrance of the point gate turns into a trouble for resin fulfilled plastic. This kind gate might be a trouble with lower viscosity, lengthy fiber. The tiny gate constraint might increase the soften temperature and have an effect on heat sensitive plastic material. Neglecting these aspects could lead to excessive mold preservation.





Benefits of the gating strategy drawn below are automated degating. Gating within the bottom up helps venting, and gating set into ribs, bosses, without display regions enhances cosmetics. The component is stripped from the gate in the event the ejector pins push the component and runner out . The tunnel gate/runner ought to curve enough to allow them to come out of its constrained area.
Plastic resin Filler
The tiny cross-sectional entrance of the sub gate turns into a trouble relating to resin fulfilled plastic material. This kind gate might be a trouble because of lower viscosity, lengthy fiber, or bead fulfilled plastic material. The tiny gate constraint might increase the soften temperature and have an effect on heat sensitive plastic material. Neglecting these aspects could lead to excessive mold preservation.


Sub or tunnel entrances leave a really tiny gate mark on the component (diameter close to .020  to .060 ) which makes them extremely appealing. Moreover, the sub gate makes an opportunity to allow them to stay on a non-cosmetic areas. By layout, the mark is elimited clean, automatically.D3-13

The arrows on the sketching symbolize the plastic material movement from the sprue, runner, edge entrance, tab, and set into the component cavity. This strategy forbids jetting within the cavity or any other exterior flaws. A stronger component will be acquired from the improved movement pattern within the cavity and stress/strain is kept within the tab.
Plastic resin Filler
The tab gate possesses the same constraints as the side gate. Because an edge gate is situated before the tab, there might be difficulties for lower viscosity, lengthy fiber, or some bead fulfilled plastic material.


Enlargement “A” illustrates a large mark remaining within the tab that has been eliminated. The mark might be eliminated by snipping or by putting the component inside a trim fixture. Because it is a fairly huge mark a good idea is to allow them to stay the tab on top of a non-cosmetic/non-functional region. Based on component design/function perhaps it’s feasible to allow the tab.


The arrows on the sketching below symbolize the plastic material movement within the sprue, runner, fan entrance, and set into the component cavity. For huge or thick component sections the fan entrance gives a smooth changeover coming from a runner until the cavity. The fan entrance may also be used to spread the movement model on thin materials in order to assist reduce the chance of movement lines.
Plastic resin Filler
Just about any resin/filler works extremely well with this kind entrance due to the huge cross-sectional region entrance to the component. Additionally there is a smooth changeover of movement from the runner toward the cavity. There shouldn’t be any trouble to viscosity, or most fulfilled plastic material.


Enlargement “A” illustrates a huge mark remaining within the fan entrance that has been eliminated. The entrance is best eliminated by employing a trim fixture, particularly on top of a thick section component. Because it is a fairly huge mark, a good idea is to allow them to place the entrance on a non-cosmetic/non-functional region, if feasible.


The arrows on the sketching symbolize the plastic material movement within the sprue, runner, flash entrance, and set into the component cavity. A really thin, lengthy flash entrance is designed for thin dials, and huge flat sections, by way of an consistent straight edge. This kind entrance helps to allow them to distribute the plastic material  into the cavity with a wide model.
Plastic resin Filler
The entrance demonstrated {during|on} this cross-section is very lengthy and thin, allowing a wide choice of plastic material . Nonetheless, the thin, flash type entrance to the cavity may result in difficulties for lower viscosity and a lot filler type plastic material.


Enlargement “A” illustrates a really thin, lengthy mark remaining from the flash entrance. This entrance possesses the advantage of leaving a really tiny aesthetic trace on the component, in addition to being conveniently eliminated manually. A cut fixture may just be employed when preferred.


Gate design troubles:









gate plastic mold company runner vent

Overview of Runners, Gates and Vents


Runner and Gate Design

The article will discuss the fundamental kinds and operations of runners, gates(entrances) and air vents during injection molding. Additionally, you will obtain choice, utility, and customary difficulties connected with runners, entrances, and air vents.


Injection Molding Cycle

This sketching describes a reciprocating screw of press. Polyester resin within the hopper goes into the extruder screw and turns into liquid for the shear of the spinning screw . The screw moves pushing the plasticized materials in a closed mold. The screw comes back and the course of action is recurrent.


This sketching displays plastic injection mold base especially for its cross sectional  view . The nozzle of the press stayes in the sprue bushing. Plastic moves in a routine from the sprue to the component. Water channels cool down the plastic resin, the mold opens up, and the component and runner system are demolded.


That photo demonstrates a whole runner structure of a plastic tea spoon, cutting knife, and fork mold. Demonstrated are the sprue, runners, entrances, and also molded components.



The sprue can be described as path for the plastic material to move from the nozzle of the press to the runner in the mold. It can be rounded, tapered, and it has an undercut on the big end. This undercut retains and divides the sprue off of the nozzle as soon as the mold has opened up and the sprue and runner system demolded.D1-04




The runner is considered the path with regard to the plastic material to move through the sprue to the entrances of the mold cavities. This image illustrates the plastic moving via the sprue and runner.



The gate can be described as confined path used for the plastic material to move through the runner into the mold cavity. This image illustrates the plastic moving through the runner into the gate.


The cavity location is in the model of the plastic component to be manufactured. The image the following illustrates the entire movement of the plastic material from the sprue bushing  to the mold cavity to generate the component.



Since the mold cavity is full of plastic material, air might be captured and has to be vented. This displacement is achieved through slots around the parting line or by way of ejection pins. In the event the air isn’t venting the compressed air will produce plenty heat which can burn the plastic material. The cartoon below illustrates ventilation of air from the cavity at a place across from the entrance




plastic mold company

Glossary of Terms (3)


SPRUE PULLER PIN Pin located directly under the opening of the sprue. Used to pull the molded sprue out of the bushing after a shot has been made.
STONING The process of refining all surfaces of the cavity or core with manufactured stones.
SUPPORT PLATE Mounted behind the core retainer plate to keep this plate from bending under the high pressure used in injection molding. (Also called BACK-UP PLATE)
SHOCK RESISTANCE The ability to resist the sudden application of an external force that results in the rapid build-up of stress.
SHORT SHOT Partial filling of a mold cavity or cavities.
SINK Small depressions on the molded surface caused by different cooling and shrinkage rates, typically between thick and thin sections.
SLIDE A portion of the mold that is designed to travel at an angle to the normal ejection movement of the mold base. Typically used to produce holes, recesses, or undercuts, by the use of a core attached to the slide mechanism. The slide pulls away before the molded part is ejected.
SPLAY Material flow marks, visible on the molded part. Caused by either contaminated or degraded material, or by material that is too cold and fills too slowly. 
SPRUE The round, tapered portion of the runner system that connects the machine injection nozzle with the runner system of the mold.
STRESS A force exerted upon a body that tends to put a strain on its shape. AII plastic parts have some degree of internal stress molded in. Too much internal stress is undesirable.
SUCKER PIN Typically a pin with a ball-shaped end. Plastic is molded around it, and it serves as an undercut and holds the plastic. The ejection system then forces the molded undercut off of the sucker pin.
TENSILE STRENGTH The resistance of a material to a force tending to stretch or extend the material.
THERMOPLASTIC RESIN A group of plastic materials that are capable of being molded when heated and hardened when cooled. A physical change takes place during the molding process, but a chemical change does not.
THERMOSETTING RESIN A group of plastic materials that are set by the application of heat and pressure. A chemical reaction takes place during molding, and the material cannot be restored to its original state after molding.
THREE PLATE MOLD A mold base with three separate parting lines, designed to automatically separate the runner system from the molded part.
TOOLS Special fixtures, molds, dies, or other devices that enable a manufacturer to produce parts.
TOOL STEELS Steels used to make cutting tools and dies. Many of these steels have considerable quantities of alloying elements such as chromium, carbon, tungsten, molybdenum, and other elements. They form hard carbides that provide good wearing qualities but at the same time decrease machinebility. Tool steels in the trade are classified for the most part by their applications, such as hot die, cold work die, high speed, shock resisting, mold, and special purpose steels. 



TOP FRONT CLAMPING PLATE Holds the stationary part of the mold to the stationary platen of the injection machine.
TOUGHNESS The ability of a metal to absorb energy and deform plastically before fracturing.
TURBULENT An agitated flow of a liquid that is desired in a cooling circuit, because it removes more heat than one that is not agitated. The Reynolds Number is a measure of turbulent flow.
UNBALENCED RUNNER SYSTEM A runner system typically used for a family of parts. The Unbalanced Runner System has unequal diameters or length runners, and/or different size gates, and is used to achieve equal fill on molded cavities. This system is not a preferred method.
UNDERCUT A raised or recessed area of the mold cavity or core that impedes, or makes impossible, ejection of the molded part.
UNIT DIE SET A master mold base used in molds for injection moldings into which individual molds are inserted. These molds are filled by a centrally located sprue.
VENT A shallow groove or recess typically machined into the parting line of a mold. The vent allows trapped air or gases to escape the cavity as it is being filled with molding resin.
VISCOSITY The internal friction of a fluid to resist the tendency to flow.
WEAR RESISTANCE The capacity to withstand surface damage from contact with other metals, non-metallic particles or flowing liquids. Wear generally involves the progressive loss of surface material due to motion of that surface and a contacting surface or substance. 
WELD LINES A visible line appearing on a mold surface where two or more streams of material meet, then fuse together. 


plastic mold company

Glossary of Terms (2)


FREEZE TIME The time it takes to set the molded plastic resin for a variety of functions. For example, freeze time describes the time it takes to set the molded resin, in order for ejection to occur.
GATE An opening at the end of the runner through which the material enters the cavity.
HARDENABILITY The ability of a material to become harder by the addition of alloying elements and heat treatment processes. It should not be confused with hardness.
HARDNESS The resistance of a metal to surface indentation (denting) or abrasion (scratching). Indentation hardness can be measured with the Rockwell or Brinell methods.
HEAT SINK A heat absorber or collector. It is used as a mold component or insert into the component to collect heat in an area that is hard to reach by typical cooling design. Materials typically used are copper, beryllium copper, tungsten alloys, and gas or liquid thermal pins.
HOT RUNNER MOLD A molding method in which the runner system is kept hot and insulated from the cavity portion of the mold. The mold parting line is typically at the gate. This runner system is not ejected to become waste or regrind material, as it is in the cold runner system.
INJECTION The process of forcing a plastic material or a molten alloy into a mold.
INJECTION MOLDING The process in which the plastic material is heated to a molten state in a heating cylinder, and then forced into a cooled mold to produce the desired shape.
INSERT Integral inserts – parts which are machined separately from the basic core and cavity, and are then installed in the proper position in the core and cavity, and which become part of the molded part after the molding material has hardened.
INSERTS, MOLDED-IN Loaded inserts – not part of the mold, but separate metal pieces placed in the mold which become part of the molded part after the molding material has hardened.
KNOCKOUT PINS Term given to ejector pins.
LEADER PINS Hardened and ground steel pins pressed into one of the plates. They align the two halves of the mold base. (Also called GUIDE PINS)
LOCATING RING Fits into a counterbore in the top clamping plate and is used to locate the mold on the platen of the press so the nozzle and sprue bushing are aligned.
MACHINABILITY The relative ease of which a metal can be machined or worked on with tools.
MICROPROCESSOR A computer chip integrated circuit, capable of controlling the (Integrated Circuit) input and output functions, for which it was designed – such as automatically controlling the cooling cycle of a mold. 



MIRROR FINISH A diamond finish that shines and reflects light.
MOLD The entire mechanism (cavities, cores, plungers, holder blocks, etc.) needed to mold parts from plastic materials or from non-ferrous alloys.
MULTIPLE CAVITY MOLD A mold which has a number of cavities and produces more than one part in each cycle.
ORANGE PEEL A condition caused by too much pressure, speed, or both when diamonding. When orange peel occurs the surface becomes bumpy and irregular.
O-RING A tire-shaped, round cross-section of a synthetic rubber gasket or seal. A coolant seal can be formed by a compression fit of the O-ring and itÆs mating parts.
PARALLELS Mounted on the bottom clamping plate under the support plate to form a space (ejector housing) which allows the ejection stroke when the piece parts are ejected. (Also called RAILS)
PARTING LINES Marks on a molding where halves of the mold meets in closing.
PIECE PART The article or part to be molded.
PILLARS Bars placed between the support plate and the bottom clamping plate. Bolted or doweled to the bottom clamping plate, they are used as additional support for the core retainer plate.
PLATENS The mounting plates of a press to which the mold assembly is bolted. 
PROFILER Profiler is a brand name commonly used to refer to any reciprocating hand piece.
PROTOTYPE MOLD A temporary or experimental mold construction made in order to obtain information on part design, tool design, and market reactions.
RADIATE Emitting rays of heat, such as a mold-base radiating heat from the molding process.
REAMED HOLE A round, hard, multi-cutting edge scraping tool. It is used after a hole is drilled in order to improve the hole geometry. It will produce a rounder, straighter, and smoother hole than drilling.
REDUCE DEFORMATION Elements added to control the amount of change in a metal due to stress, thermal change, change in moisture or other changes.
RELEASE The ability of a mold to eject a part. 
RETURN PINS Located in the ejector retainer plate. These pins force the ejector plate and ejector retainer plate and, therefore the ejector pins, to the bottom position as the mold closes. (Also called EJECTOR RETURN PINS, SAFETY PINS, or PUSH BACKS)
REYNOLDS NUMBER A number used as a measure of turbulent flow for a liquid.
RUNNERS Channels through which plastics flow from the sprue to the gates of mold cavities.
RUST RESISTANCE The ability of a ferrous metal to resist oxidation in the presence of water (rust).
SCAR An undesirable cosmetic mark left on the mold surface due to a variety of reasons, such as degating the part from the runner system.
SENSORS A variety of devices designed to detect, measure, or record physical phenomena such as temperature.
SHRINKAGE ALLOWANCE The additional dimensions that must be added to a mold to compensate for shrinkage of the plastic molding material on cooling.
SPACER BUTTONS Pressed into the bottom clamping plate, they are lands for the ejector plate. (Also called STOP PINS)
SPRUE BUSHING Butted up against the nozzle of the injection machine. Has a conical-shaped hole through which the material is forced into the mold runner. 


Glossary of Terms

Glossary of Terms


ABRASION RESISTANCE The ability to resist localized surface damage from contact with other material in use, such as gouging, grinding, scratching or erosion.
ANSI (American National Standards Institute) A privately funded, voluntary membership organization that identifies industrial and public needs for national consensus standards, and coordinates development of such standards. Many ANSI standards relate to the safe design and performance of equipment, such as safety shoes, eyeglasses, smoke detectors, fire pumps and household appliances; and safe practices or procedures, such as noise measurement, testing of fire extinguishers and flame arrestors, industrial lighting practices, and the use of abrasive wheels.
“A” PLATE Part of the stationary section of the mold into which the leader or guide pins are mounted. Also used to hold core, cavity blocks, and sprue bushing.
ASTM (American Society for Testing Materials) A voluntary membership organization with members from a broad spectrum of individuals, agencies, and industries concerned with materials. As the world’s largest source of voluntary consensus standards for materials, products, systems, and services, ASTM is a resource for sampling and testing methods, health and safety aspects of materials, safe performance guidelines, and effects of physical and biological agents and chemicals.
AUTOMATIC MOLD A mold designed and constructed in which the material is loaded into the mold and the finished parts are ejected from the mold without an operator.
BACK TAPER Sometimes called back draft or reverse draft.
BALANCED RUNNER SYSTEM A runner system that is designed to fill each mold cavity equally, continuously, and simultaneously.
BALL END MILL A hardened cutter, capable of machining a half-round slot, or shape into annealed metal using the milling machine.
BENCHING Term used to define the initial steps in polishing to prepare cavity and core blocks for the actual polishing process. 
BERYLLIUM COPPER Beryllium is added to copper to form a hard, strong alloy. It is excellent as a heat sink, or heat absorber, for a component portion of the mold that is hard to reach by typical cooling design. It can also be used to conduct heat.
BOTTOM CLAMPING PLATE Holds the moving portion of the mold to the movable platen of the injection machine.
“B” PLATE Top plate of the movable section of the mold. Forms the parting line of the mold with “A” plate. Used to hold the leader pin bushings as well as core and cavity blocks.
BUSHINGS Hardened and ground steel bushings which are pressed into one of the plates. They serve as bearing surfaces for the leader pins.
CAVITY The depression or female portion of the mold which gives the external surface to the part being produced.
CHILLING UNIT A mechanical refrigerator designed for outgoing water of a specific temperature. Ethylene glycol can be added to the water if a temperature below freezing is required.
COLD SLUG WELL A recess or groove, at the end of a long length that traps the leading cooled plastic. A Cold Slug Well is typically machined in a runner part of a balanced runner system, and can be used to prevent or minimize weld lines.
CONDUCTION Transferring heat from two or more bodies that are in contact with each other, such as heat conducted by mold-base steels.
CONVECTION The ability of a medium to carry heat from one place to another, such as coolant traveling through mold steel channels



COOLING CHANNELS Holes drilled into the various plates or into the various mold components, or channels machined into components, to allow the flow of a cooling medium (water) in order to keep the mold at the proper molding temperature.
COOLING TOWER Heated coolant from a mold is pumped to a cooling tower, inside or outside of the factory, where it falls by gravity past a grid. Some cooling takes place during the fall, but fans are typically used to add extra cooling. The cooled liquid is then collected and returned to pass through the mold again.
COOLING UNIT A mechanical refrigerator designed for outgoing water of a specific temperature. Ethylene glycol could be added to the water if temperatures below freezing were required.
COOLING UNIT A system of cooling channels and components designed to give effective cooling to a molded part or parts.
CORE The male portion of a mold that shapes the interior of a hollow molded part.
CORE PIN A pin for forming a hole or opening in a plastic molded piece.
CUSTOM MOLDS Molds owned by the customer and used by the molder.
CYCLE TIME The total time required to produce a molded part. Cycle time includes the time from the injection of the plastic resin into the mold, to the ejection of the molded part.
DEGATING Separation of the gate and runner system from the molded part. Degating can be done by hand, in a trim fixture, or automatically.
DEOXIDIZERS Elements added during the manufacture of steel to control the residual amount of oxygen that remains in the steel.
DIAMONDING Act of shining molding surfaces with diamond compound and brushes and buffs.
DIMENSIONAL STABILITY The ability of a plastic part to keep the precise shape in which it was molded.
EJECTOR PIN A pin (in a mold) that directly pushes the molded part out of the cavity. Sometimes called a knockout pin. A number of these pins may be used in one mold.
EJECTOR PLATE Bolted together with the ejector retainer plate to form a unit. Contains the plate for the pins in the ejector retainer plate.
EJECTOR RETAINER PLATE Counterbored for the heads of ejector, ejector return pins, and sprue puller pins.
ETHYLENE GLYCOL A colorless, viscous liquid used as antifreeze.
FATIGUE RESISTANCE The ability of a metal to resist fracture from repeated application of stresses. Fatigue failure usually occurs at loads which if applied statically would have little effect, but repeated cycles of the stress or strain lead to eventual failure.
FATIGUE STRENGTH The highest cyclic stress a material can withstand for a given number of cycles before failure occurs.
FLASH A thin piece of plastic material that typically forms along the parting line of a molded part. Flash is a result of a parting line surface or surfaces that is not matched or is shutting off the flow of plastic resin



Design of Runner and Gate

The runner system is the passage way for plastic material to move from the sprue to the entrance. The runner technique is extremely important with respect to filling cavities. In the event the runners are extremely small in size the mold cavities will not likely fill properly. If the runners are too big, then the cooling time will probably be increased and cycle time reduced. Suitable runner design can reduce the negative impacts of stress, sink and weld spots.


[ezcol_1half] The illustration reveals a well-balanced H layout runner system employed to mold four rectangular chips. The arrows display the plastic material move from the sprue via the runners, entrances, and directly into the cavities. What’s so great about the proper H layout will probably be discussed afterwards. D2-02

Two of the most common runner types available today are the full spherical and the trapezoidal. The entire spherical style is used in most cases.D2-03

The sketch shows a cross section view of a entire spherical runner produced directly into the P/L(parting line) of a mold base. Be aware that half of the runner is in the top plate and the other half of the runner is incorporated in the bottom plate. The runner is stripped out of the mold base with the molded part.D2-04

A skin of plastic material  gets frozen against the cooled mold surface and causes melted plastic to flow via the core of the runner. The spherical runner provides the least amount of scrubbing to its volume, least pressure drop, ideal movement, and is the simplest runner to remove from the mold. Nonetheless, more works and skill matching the runner into both mold halves is needed.D2-05




[/ezcol_1half][ezcol_1half_end]This illustration represents the method employed to engrave one half of the round runner into the mold steel .A very hard ball end mill cutter and its fixer are spun in the spindle of a milling equipment. The cutter marks left over the runner surface must be eliminated through polishing with rotary abrasives.D2-06


The spherical runner dimension is decided by the species of plastic material employed to mold the component. A lot of mold developers depend on client or plastic material resin provider in order to indicate dimension. The runner dimensions vary from 3/16 in order to 3/8 . Big size runners decrease strain, bending, and sink scars. Nonetheless, runners have to be possible small in order to decrease injection dimension and cycling time.D2-07


This sketching shows a cross-section of a trapezoidal runner engraved directly into the P/L of a mold base. Be aware that the entire runner is engraved in one plate. The runner is stripped out from the mold base along with the component.D2-08

A plastic material skin gets frozen contrary to the cooled down mold surface and results in melted plastic material to move via the core of the runner. Despite the fact that trapezoidal runner is simpler to engrave because it is machined into just one plate, this particular advantages could be outweighed through the more move constraint. Choice of this runner could be for the Three plate mold or plastic mold that might not permit a entire spherical runner structure.D2-09

plastic mold company

Mold Base Technology

Mold Base Technology




Cavity Plate, A Plate
This plate holds the cavity in the mold. Its thickness is normally decided by the “depth” of the part. The runner system and gating are sometimes machined (half) in the surface of the plate. This surface is also the parting line surface and “shut off” (sealing) must be obtained or flash will occur.



Core Retain Plate, B plate
This plate holds the cavity in the mold. Its thickness is normally decided by the “depth” of the part. The runner system and gating are sometimes machined (half) in the surface of the plate. This surface is also the parting line surface and “shut off” (sealing) must be obtained or flash will occur.


Top clamping Plate
This plate holds the cavity in the mold base. Its thickness is normally decided by the “depth” of the part. The runner system and gating are sometimes machined (half) in the surface of the plate. This surface is also the parting line surface and “shut off” (sealing) must be obtained or flash will occur.


Supporting Plate
The primary purpose of the supporting plate is to reinforce the mold during injection. It is actually a thicker plate that will not bows during the injection stage of the molding process. The ejector mechanism (pins) moves though the supporting plate.




Ejector bottom  Plate
The actual ejector plate stands out as the floating plate during the ejector process. Its thickness is determined with the level of pressure necessary to remove the component and the part/mold dimension. This plate furthermore fastens the ejector system (pins or plate) inside the ejector retainer plate.
Ejector top  Plate
The ejector bottom plate is adopted in a mold to fix the ejector system (ejection pins, return pins, and so on) on the ejector plate. The retainer plate is head recessed  for every pin. The pin bottoms change to be flush with the back  on the plate and also the ejector plate then fastens straight to the retainer plate. In the course of ejection, the retainer plate “draws” the ejector system (pins) to its original position.
Stripper  Plate
The stripper plate is usually an ejector system employed to aid in component stripping. This plate is mounted on the ejector return pins and actuated traditionally. The plate thickness is determined with the pressure necessary to take away the component. The cavity shape should be precisely machined in to the stripper plate to prevent extreme tool wear and enable the stripper plate to “stay” properly whenever it’s retracted.