Glossary

Pressure Forming

A thermoforming process wherein pressure is used to push the sheet to be formed against the mold surface. Since compressed air of several barometric pressures is used, the molding pressure is higher than that of vacuum molding, providing excellent mold transferability and capability in molding tall and deep products.

Compression Molding

A process of molding a material in a confined shape by applying pressure and heat.

Annealing

A process in which internal distortion created by heat or mechanical stress is removed by maintaining the material at an appropriate temperature.

Angular Pin

A pin fitted at a predetermined angle to the direction of mold movement to move the side core as the mold opens and closes.

Undercut

A protrusion or indentation in a part that prevents it from being ejected from the mold without deforming the molded product or using a special mold structure.

Insert Molding

A molding process that involves adding inserts, particularly metal, into an injection-molded part. Placing the insert within the mold cavity occurs before injection.

Injection Blow Molding

An integrated molding process that molds a hollow preform (called a parison), which is then inflated with air inside the mold to form the final hollow shape of the desired product.

Blown Film Molding

A manufacturing process in which a tube is extruded from a die in an extruder, air is blown into the tube, and the tube is inflated to produce a tubular film.

Weld Line (Weld Mark)

A mark on a molded piece caused by incomplete fusion of two streams of molten polymer.

Ejector

An actuation device that ejects molded products from the mold.

Ejector Stroke

The maximum distance the ejector moves forward to eject the plastic part.

Ejector Force

Force to eject molded products from a mold.

Elastomer

A substance that exhibits thermoplastic-like behavior when heated to melt and rubber-like elasticity when cooled and solidified.

L/T

The value obtained by dividing the length (L) of the molding material flowed during injection molding process by the thickness (t) of the mold cavity.

Stretch Blow Molding

A blow molding method in which crystalline resin is mechanically stretched at a temperature below its melting point to generate molecular orientation along the stretch direction and improve mechanical strength.

Extruder

A plastic processing machine that plasticizes and mixes molding material while moving it in a barrel with a rotating screw, and extrudes it in a fixed quantity. Generally, there are two types of extruders: single-axis extruders with a single screw and twin-screw extruders with two screws.

Extrusion Molding

A method for continuously forming bar- or plate-shaped products with the same cross section, such as pipes, films, and sheets, mainly using thermoplastic resins. The molding material is melted in a heated cylinder and continuously extruded from a die equipped in the cylinder under extrusion pressure (transfer) by screw rotation.

Temperature Control Zone

Barrel and nozzle’s temperature control zones.

Rotational Molding

A method of making hollow molded products by using powdery or paste-like materials with good fluidity, placing them in a mold that can be divided, and rotating the mold while heating it.

Rotary Ram Type In-Line Screw Injection Mechanism

An injection mechanism in which the screw plasticizes the molding material and also acts as a plunger to fill the molten resin into the mold, while the injection ram rotates the screw and moves it forward and backward. This mechanism was invented by NISSEI’s founder Katashi Aoki and is still being widely used in the world including many competitors.

Guide Pins

Pins used to ensure precise alignment and positioning of parts or tools.

Plasticization

A process of softening the molding material and make it easier to flow.

Plasticizing Capacity

Mass of molding material that can be plasticized in given unit time.

Mold Clamping Unit

A device to open and close the mold and apply clamping force.

Mold Clamping Systems

There are three types of mold clamping systems: direct pressure, toggle, and compound types. 1. Direct pressure type: A method of generating clamping force by the hydraulic cylinder and motor. 2. Toggle type: A method of generating force by the hydraulic cylinder and motor, and amplifying the force to generate clamping force by the toggle mechanism. 3. A system in which the mold clamping force generation and the mold opening/closing operation are operated by separate actuators (hydraulic cylinder, electric motor, etc.) and equipped with a device to switch between the two operations.

Mold Clamping Force

An opposing pressure needed to keep the mold closed during the filling process.

Mold Opening Force

Force to open the mold for product take out.

Mold Opening Stroke

A moving distance of the movable platen needed to take out the molded products.

Movable Platen

The movable side of the die plate in an injection molding machine to which the movable side of the mold halve is attached.

Mold

A tool made from metal that shapes molten plastic into a specific product.

Die Plate Dimensions

Stationary or movable platen’s mold mounting face dimensions.

Barrel (Heating Cylinder)

A cylindrical housing in which molding material is fed and heated. It incorporates a rotating screw or plunger and can be heated externally with heater bands or similar device.

Cell

A unit of foam structure that forms the plastic foam.

Bubbles

Bubbles that form in the molded products.

Cavity

A space created by the female and male mold halves. It can also refer specifically to the engraved surface of a female mold.

Gate

An orifice through which the molten resin enters the cavity.

Core

A movable component within the mold that shapes the internal features of a plastic part or a component that molds under cut part.

Core Pin

A pin-shaped core in which a relatively narrow hole is formed during the molding process.

Stationary Platen

The non-moving side of the die plate in an injection molding machine to which the stationary side of the mold halve is attached.

Side Core

A core with an axial center in a direction other than the direction in which the mold opens and closes. A movable core component that creates undercuts.

Injection

A process in which plasticized molding material is poured into a pre-closed mold at a set speed and pressure.

Injection Molding Machine

A plastic processing machine that performs a series of operations including feeding, heating/plasticizing, injecting, cooling/solidifying the molding materials as well as opening/closing the mold and taking out the molded products.

Injection Unit

A device that plasticizes the molding material and injects it into the mold.

Injection Methods

Refers to the types of injection systems. Injection methods include inline screw type, pre-plunger type, etc.

Injection Stroke

A moving distance of the screw or plunger when the molding material is injected.

Injection Compression Molding

An injection molding method in which a slightly open mold is filled with molding material, and then closed.

Injection Pressure

The force applied by the screw or plunger to push molten plastic resin into the mold cavity.

Injection Speed

Forward speed of the screw or plunger.

Injection Rate

Theoretical injection volume per unit time. The cross-sectional area of the screw or plunger multiplied by the injection velocity.

Injection Weight

A mass of the molding material per shot.

Short Shot

In injection molding, failure to fill the mold completely.

Vacuum Forming

One of the most popular sheet thermoforming techniques. A process whereby a heated plastic sheet is drawn against a mold surface by evacuating the air through pores or slits in the mold. Almost all molded products with a thickness of 0.15 to 1 mm are formed using this method. This method is used for the molding of large products, such as inner casing of refrigerators and signboards as well as small items such as cups, trays, and lids.

Screw

A shaft with spiral grooves that rotates in the heated cylinder of an injection molding machine to transfer, melt, and knead the molding material. It generally consists of three zones: the feeding zone, the compression zone, and the metering zone.

Screw Head

A component attached to the tip of a screw that primarily prevents backflow of molding materials.

Screw Diameter

Nominal external dimensions of the screw.

Screw L/D ratio

The ratio of screw effective length (L) to screw diameter (D).

Screw Compression Ratio

The ratio of volume available in the first flight at the feeding zone to the last flight at the metering zone of the screw.

Screw Speed

Screw's rotation per minute.

Screw Torque

Torque to rotate the screw.

Sprue

A path used to transfer molten molding material from the nozzle to the runner or gate in injection molding.

Warpage

A concave or convex deformation of molded products, which are mainly flat, due to strain after molding. Deformation parallel to the edges is called warpage, and deformation in the diagonal direction is called torsion.

Tie Bars

Bars that support the die plate in injection molding machines and guide the opening and closing of the mold. A part of components that receive mold clamping force.

Distance Between Tie Bars

Internal clearances between the tie bars of an injection molding machine. Shown in horizontal and vertical dimensions respectively.

Die Plate

A thick steel plate to which a mold is attached in an injection molding machine.

Daylight

The distance between the movable and stationary platens of an injection molding machine when the movable platen is fully opened.

Electric Type Injection Molding Machine

An injection molding machine in which the rotational energy of the servo motor is directly transferred to each actuator by means of ball screws, gears, link mechanisms, etc., to drive the actuator. In general, electric injection molding machines offer superior precision and response compared to other types.

Projected Area

The area of the shadow produced when a parallel beam of light is projected onto a molded product in the mold clamping direction. It serves as the basis for calculating the clamping force required during molding. Clamping force F = injection pressure P x projected area A

Dry Cycle Time

The minimum operating time required for one cycle when the injection molding machine is run dry in basic operation without supplying molding material.

Naphtha

An oil consisting of hydrocarbons with low boiling points obtained by distillation of petroleum, coal tar, and oil shale. Petroleum naphtha produces lower olefins, such as volatile oils, aromatic compounds, ethylene, and propylene. Many compounds derived from these products can be used as raw materials for plastics.

Two-Color Injection Molding Machine

A molding machine equipped with a pair of injection units, which is capable of simultaneously or continuously injecting two colors or two types of molding materials.

Twist

A concave or convex deformation of molded products, which are mainly flat, due to strain after molding. Deformation parallel to the edges is called warpage, and deformation in the diagonal direction is called torsion.

Thermoplastic Resin

A synthetic resin that softens and flows when heated and hardens again when it is cooled.

Thermosetting Resin

A synthetic resin that initially has low molecular weight, but under the influence of heat, catalysts, or ultraviolet light, undergoes chemical reactions that cause bridging bonds to develop, increasing its molecular weight to become a polymer with a three-dimensional network structure, which hardens and becomes permanently infusible and insoluble.

Heat Distortion Temperature

Load Deflection Temperature. The temperature at which a plastic exhibits a given deformation when the temperature is increased at a constant rate under a constant load.

Nozzle

A hollow cored metal nose screwed into the end of the heating cylinder to form a passageway that leads the plasticized molding material to the mold.

Nozzle Dimensions

Dimensions of the nozzle tip. Generally indicated in terms of spherical radius (r) and inside diameter (d).

Nozzle Touch Force

The force that pushes the nozzle against the sprue bushing surface of the mold.

Nozzle Projection

Dimensions of the nozzle protruding from the mold mounting surface of the stationary platen.

Purging

Cleaning one color or type of material from the cylinder of an injection molding machine by forcing it out with the new color or material to be used in subsequent production.

Parting Line

The dividing surfaces of the female and male molds of a die. It also refers to the dividing surfaces of the base mold and side cores.

Back Pressure

The tip pressure of a screw or plunger when plasticizing molding material.

Hybrid Type Injection Molding Machine

An injection molding machine that combines both a hydraulic system (hydraulic pump) and an electric system (AC servomotor) as the drive source. (1) A combination of hydraulic clamping unit and electric injection unit. (2) A combination of electric clamping unit and hydraulic injection unit. NISSEI also refers the servo-hydraulic injection molding machines as hybrid type.

Flash

An excess portion of a molded product that has solidified due to molten molding material protruding through the parting line.

Parison

Molding material in a molten state in hollow cylinder or tubular shape. In extrusion blow, this is directly inserted between the molds.

Heating Capacity

The total heater power of heating cylinder and nozzle section.

Sink Mark

A shallow depression or dimple on the surface of an injection molded part. Each resin has its own mold shrinkage rate. A sink mark occurs when the resin filled in the mold cools and solidifies with the front side facing the mold first, and the inside solidifies later.

Plunger

A rod-shaped piston that injects molding material into the mold.

Preform

A preformed product that has been formed in advance into a bottomed cylindrical shape. In an injection blow molding machine, the preform is blow molded in the next process; in a two-stage blow molding machine, the preform is reheated and blow molded.

Blow Molding

Method of fabrication in which a warm plastic parison or preform is placed between the two halves of a mold cavity and forced to assume the shape of that mold cavity by use of air pressure.

Flow Mark

A pattern of molded material flow traces in the mold cavity that remain on the surface of the molded product, resulting in defective appearance.

Pelletizer

A machine used to make pellets. A device that extrudes molten polymer from an extruder die through numerous holes into a string-like shape and cuts it into pellets.

Pellets

Granular molding materials in cylindrical, prismatic, or spherical shapes.

Vent

A groove or hole for venting air or gas from a cavity or heating cylinder.

Holding Pressure

The tip pressure of the screw or plunger to compensate for shrinkage of the molded product after the mold is filled with injection molding material.

Void

A cavity or bubble that forms in the molded products.

Hot Runner Mold

A mold for injection molding with a runner section that is always kept in a molten state, eliminating the need to dispose of the runner after each shot.

Hopper

A conical feeding reservoir for supplying molding material to a molding machine.

Hopper Drier

A hopper with a material dyer.

Hopper Loader

A device that sends molding materials to a hopper by means of pipes or hoses.

Burned Mark

Yellowing (browning) due to thermal decomposition of resin in injection molding. It can be caused by overheating of the resin, excessive injection pressure, poor venting, etc.

Hydraulic Type Injection Molding Machine

An injection molding machine that converts the rotational energy of the motor into kinetic energy of the hydraulic fluid and then drives it indirectly. The hydraulic pump is driven by the motor, and the pressure, flow rate, and direction of the generated hydraulic oil flow are controlled by various valves to provide reciprocating and rotating motion to each actuator using hydraulic cylinders and hydraulic motors.

Pre-Drying

Heat drying hygroscopic molding material at relatively low temperatures prior to molding to remove moisture from the material.

Runner

In an injection or transfer mold, the channel, usually circular, that connects the spruce with the gate to the cavity.

Runnerless Mold

A type of mold for injection molding of thermoplastic resin in which the resin in the sprue and runner portions remains molten. Hot runner molds are examples of this type of mold.

Calculated Injection Volume

The tip cross-sectional area of a screw or plunger multiplied by the stroke.

Locating Ring

A part of an injection molding die used to align the nozzle of an injection molding machine with the die.

Locating Ring Diameter

The diameter of the hole corresponding to the mold locating ring on the stationary or movable plate of an injection molding machine.