ACIS
A widely used computer file format for CAD data exchange, primarily associated with AutoCAD programs. The acronym ACIS originally stood for “Andy, Charles, and Ian’s System.”
Additive Manufacturing (3D Printing)
Also known as 3D printing, additive manufacturing is a process where a CAD model or scanned object is built layer by layer into a physical three-dimensional part. Common additive manufacturing methods include stereolithography (SL), selective laser sintering (SLS), fused deposition modeling (FDM), and direct metal laser sintering (DMLS).
A-Side
Also referred to as the “cavity,” the A-side of a mold typically forms the exterior surface of a cosmetic part. Unlike the B-side, the A-side usually does not contain moving components.
Axial Hole
A hole that runs parallel to the axis of revolution in a turned part. While it aligns with the axis, it does not necessarily have to be concentric with it.
Barrel
The section of an injection molding machine where resin pellets are heated, compressed, and injected into the mold’s runner system.
Bead Blasting
A surface finishing process that uses pressurized air to propel abrasives, creating a textured surface on the part.
Bevel
Also referred to as a “chamfer,” it is a sloped or angled edge that replaces a sharp corner.
Blush
A cosmetic defect that appears as a mottled discoloration near the injection gate, caused by the way resin flows into the mold.
Boss
A protruding cylindrical feature designed to accommodate fasteners or provide support for components passing through it.
Bridge Tool
A temporary mold used for producing parts until the final high-volume production mold is ready.
B-Side
Also called the “core,” it is the mold half that houses ejectors, side-action mechanisms, and other complex components. It typically forms the inner features of a cosmetic part.
Build Platform
The base in an additive manufacturing machine where parts are constructed. The maximum part size is constrained by the dimensions of this platform, which often accommodates multiple parts with different geometries in a single build.
Bumpoff
A molded feature that includes an undercut, requiring the part to flex or stretch slightly during ejection from the mold.
CAD
An abbreviation for Computer-Aided Design, a technology used to create digital models for engineering and manufacturing.
Cam
A mold component that moves into position when the mold closes, typically using a cam-actuated slide mechanism. Side actions are often employed to accommodate undercuts or vertical surfaces without draft angles. When the mold opens, the side action retracts, allowing the part to be ejected. Also referred to as a “side-action.”
Cavity
The hollow space formed between the A-side and B-side of a mold, which is filled with molten resin to create an injection-molded part. The A-side is sometimes called the cavity as well.
Chamfer
Also known as a “bevel,” it is a slanted or angled edge that replaces a sharp corner.
Clamp Force
The pressure needed to keep the mold tightly closed during injection, preventing resin from escaping. This force is measured in tons, such as in a “700-ton press.”
Contoured Pins
Ejector pins that have shaped ends to conform to the sloped surfaces of a molded part, ensuring smooth ejection.
Core
A mold component that extends into the cavity to form internal features of a part. Cores are typically found on the B-side of the mold, which is why the B-side is sometimes called the core.
Core Pin
A fixed mold element used to create holes or voids in a part. It is often manufactured separately and inserted into the mold’s A-side or B-side as needed. Steel core pins are sometimes used in aluminum molds to provide extra strength for forming tall, thin features.
Core-Cavity
A term describing the mold structure created by joining the A-side and B-side halves.
Cycle Time
The total duration required to complete one molding process, including mold closing, resin injection, cooling, mold opening, and part ejection.
Direct Metal Laser Sintering (DMLS)
A metal 3D printing process that uses a fiber laser to selectively fuse fine metal powder layer by layer, forming a solid metal part. After each layer is fused, a fresh layer of powder is spread over the surface, and the process repeats until the final part is built.
Direction of Pull
The path along which mold components move as they separate from the molded part, either when the mold opens or when the part is ejected.
Draft
A slight angle applied to vertical surfaces of a molded part to prevent sticking or damage during ejection by reducing friction between the part and the mold.
Drying of Plastics
Since many plastics absorb moisture, they must be dried before injection molding to maintain their appearance and mechanical properties.
Durometer
A scale-based measurement of a material’s hardness, with lower values indicating softer materials and higher values representing harder materials.
Edge Gate
An entry point along the mold’s parting line where molten resin is introduced into the cavity, typically positioned at the outer edge of the part.
EDM (Electric Discharge Machining)
A manufacturing process used in moldmaking that employs electrical discharges to shape metal. This method enables the creation of fine details such as tall, thin ribs, engraved text on raised features, and sharp external edges that may be difficult to achieve with traditional milling.
Ejection
The final step in the injection molding process, where the cooled part is removed from the mold using ejector pins or other mechanisms.
Ejector Pins
Cylindrical pins located in the B-side of the mold that push the molded part out after it has solidified and cooled.
Elongation at Break
A measure of how much a material can stretch or deform before breaking. This property, particularly in liquid silicone rubber (LSR), allows certain complex parts to be flexed and removed from molds without damage. For instance, LR 3003/50 has an elongation at break of 480%.
End Mill
A rotary cutting tool used in CNC machining to shape and refine mold components.
ESD (Electrostatic Discharge)
An electrical phenomenon that can cause damage in sensitive applications. Some specialized plastics have conductive or dissipative properties to prevent static buildup and reduce the risk of ESD-related failures.
Family Mold
A type of mold that contains multiple cavities, allowing different parts made from the same material to be produced in a single molding cycle. Each cavity typically forms a unique part number. See also “multi-cavity mold.”
Fillet
A rounded transition where a rib connects to a wall, designed to enhance material flow during molding and reduce stress concentrations in the final part.
Finish
A surface treatment applied to certain areas of a part, ranging from high-gloss polishing to textured patterns. These finishes can enhance aesthetics, improve grip, or mask minor imperfections.
Flame Retardant
A plastic formulation designed to resist combustion and slow the spread of fire.
Flash
An unwanted, thin layer of excess material that seeps into gaps along the mold’s parting line, forming a thin extension of plastic or liquid silicone rubber that must be trimmed off.
Flow Marks
Visible streaks or patterns on the surface of a molded part that indicate how the resin flowed through the mold before solidifying.
Food Grade
Materials, such as resins or mold release agents, that are certified safe for contact with food in consumer applications.
Fused Deposition Modeling (FDM)
A 3D printing process in which a filament of thermoplastic material is heated and extruded through a nozzle, layer by layer, to build a three-dimensional object.
Gate
A general term for the entry point in a mold where molten resin flows into the cavity.
GF (Glass-Filled)
A designation for resins that contain embedded glass fibers. These reinforced materials offer increased strength and stiffness compared to their unfilled counterparts but tend to be more brittle.
Gusset
A triangular support feature used to strengthen connections, such as where a wall meets a base or where a boss attaches to a surface.
Hot Tip Gate
A type of gate that directly injects molten resin into the part’s surface on the A-side of the mold. Unlike traditional gates, it eliminates the need for a runner or sprue system.
IGES
Initial Graphics Exchange Specification, a widely used file format for exchanging CAD data. Protolabs can use IGES files, either solid or surface, to produce molded parts.
Injection
The process of forcing molten plastic or resin into a mold cavity to shape the part.
Insert
A component that is either permanently installed into the mold after machining or temporarily placed between mold cycles to assist in forming specific features.
Jetting
Flow marks that appear when molten resin enters the mold at an excessive speed, usually near the gate, causing irregular patterns on the surface of the part.
Knit Lines
Also called “weld lines” or “stitch lines,” and “meld lines” when multiple gates are used. These are visible imperfections where two or more streams of molten material meet and fuse, often resulting in weak bonding or a noticeable line on the part’s surface.
Layer Thickness
The thickness of each individual layer in additive manufacturing, which can be as thin as a few microns. Parts are typically made up of thousands of these layers stacked together.
LIM (Liquid Injection Molding)
A molding process used for shaping liquid silicone rubber (LSR) into parts.
Live Tooling
A machining process in which a rotating tool is used on a lathe to cut material. This allows the creation of features such as flats, grooves, slots, and holes (both axial and radial) directly in the lathe.
Living Hinge
A very thin section of plastic that connects two parts, allowing them to flex open and closed without separating. These hinges require careful design and gate placement, and are commonly used in products like boxes with a lid.
LSR (Liquid Silicone Rubber)
A type of silicone material used in molding processes, often referred to as liquid silicone rubber.
Medical Grade
A type of resin that is specifically designed and tested for use in medical applications, ensuring it meets the necessary safety and performance standards.
Meld Lines
These occur when multiple gates are used, creating imperfections where separate flows of resin meet and merge, often resulting in weak bonding and visible lines on the part.
Metal Safe
A design modification that only requires removing material from the mold to achieve the desired part geometry. This is particularly useful when the design of a part changes after the mold has been made, as it allows for mold adjustments rather than complete remachining. Also referred to as “steel safe.”
Mold Release Spray
A liquid spray applied to the mold to help parts release more easily from the B-side, especially when they are difficult to eject due to sticking.
Multi-Cavity Mold
A mold that contains more than one cavity, allowing for the production of multiple parts in a single molding cycle. Typically, all cavities will produce the same part number. See also “family mold.”
Net Shape
The final form of a part, which does not require any further machining or shaping before it can be used.
Nozzle
The tapered connector at the end of the injection molding press barrel where the molten resin exits and enters the sprue.
On-Axis Hole
A hole that is aligned with and concentric to the axis of rotation of a turned part. It is typically located at the center of the part’s end.
Overflow
Excess material that is created at the end of the filling process, usually connected to the part by a thin section. The overflow is included to enhance part quality and is removed during a secondary operation.
Packing
The process of applying additional pressure during injection molding to force more material into the mold. This helps address issues like sink marks or incomplete filling, but can also increase the risk of flash and may cause the part to stick in the mold.
Parasolid
A widely used file format for exchanging CAD data.
Part A/Part B
LSR (Liquid Silicone Rubber) is a two-part compound, with the components (Part A and Part B) kept separate until they are combined during the molding process.
Parting Line
The line on a part where the two halves of the mold meet and separate.
Pickouts
Mold inserts that remain attached to the ejected part and need to be manually removed and placed back into the mold for the next cycle.
PolyJet
A 3D printing process in which tiny droplets of liquid photopolymer are sprayed from multiple jets onto a build platform and cured layer by layer to form elastomeric parts.
Porosity
The presence of unwanted voids or air pockets in a part, which can vary in size and shape and typically result in reduced strength compared to a fully dense part.
Post Gate
A specialized gate where resin is injected through a hole that an ejector pin passes through, leaving a post vestige that generally requires trimming after ejection.
Press
An injection molding machine used to inject molten material into molds to form parts.
Radial Hole
A hole created by live tooling that is perpendicular to the axis of rotation of a turned part. It is also known as a side hole, and its center line does not necessarily have to intersect the part’s axis of revolution.
Radiused
An edge or corner that has been rounded off, typically as a result of the milling process. When a radius is intentionally applied to an edge, it is referred to as a fillet.
Ram
A hydraulic system component that pushes the screw forward in the injection molding machine’s barrel, forcing the molten resin into the mold.
Recess
A depression or indentation formed on the surface of the plastic part, usually caused by the impact of ejector pins during part ejection.
Reinforced Resin
A type of resin with added fillers, such as glass or carbon fibers, to increase strength. These resins are typically harder and stronger but more prone to warping and are more brittle compared to unreinforced resins.
Resin
A general term for the chemical compounds used to create plastic parts when injected into molds, commonly referred to as “plastic.”
Resolution
The level of detail that can be achieved in parts produced through additive manufacturing, such as 3D printing. Techniques like stereolithography and direct metal laser sintering can achieve very high resolutions, allowing for the creation of fine, intricate features.
Rib
A thin, wall-like feature commonly found on plastic parts to add structural support to walls or bosses. It is typically aligned parallel to the direction of the mold opening.
Runner
A passage or channel within the mold that directs the molten resin from the sprue to the mold cavities. Runners are generally parallel to and contained within the parting surfaces of the mold.
Screw
A component inside the injection molding machine’s barrel that compresses resin pellets to generate the heat and pressure necessary to melt them before they are injected into the mold.
Selective Laser Sintering (SLS)
A 3D printing method where a CO2 laser fuses thermoplastic powder into a solid by scanning over a heated bed of powder. After each layer is fused, a roller spreads a fresh layer of powder, and the process repeats.
Shear
The force exerted between layers of resin as they slide past each other or against the mold surface. This friction generates heat within the resin.
Short Shot
An incomplete part resulting from insufficient resin filling the mold cavity, leading to missing or under-formed features.
Shrink
The reduction in size of a part as it cools and solidifies during the molding process. This shrinkage is anticipated and factored into the mold design based on material properties.
Shutoff
A feature that creates an internal through-hole by bringing the A-side and B-side of the mold together, blocking the resin from entering the hole during injection.
Side-action
A mold feature that moves into position during mold closure via a cam-actuated slide. It is used to handle undercuts or allow an undrafted wall. When the mold opens, the side action moves away from the part, facilitating ejection. Also referred to as a “cam.”
Sink
Surface imperfections like dimples caused by uneven cooling rates in different areas of the part, often due to thick sections of material.
Splay
Visible streaks or discoloration on the surface of a part, often resulting from moisture in the resin.
Sprue
The entry point for molten resin into the mold. Positioned perpendicular to the parting faces, the sprue directs resin to the runners.
Steel Pins
Cylindrical pins used to create small-diameter, high-aspect-ratio holes in parts. These pins are strong and smooth enough to withstand ejection stresses while ensuring clean part release.
Steel Safe
Also known as “metal safe,” this refers to part design modifications that only require metal removal from the mold to achieve the desired shape, often applied when part designs change after the mold is made, allowing for mold modification instead of re-machining.
STEP
A file format for exchanging 3D product model data, commonly used for CAD interoperability.
Stereolithography (SL)
A 3D printing process where an ultraviolet laser solidifies a liquid thermoset resin layer by layer. Each laser pass forms a cross-section, and the process is repeated to build a full 3D part.
Sticking
A molding issue during ejection where a part gets stuck in the mold, making removal difficult, usually due to insufficient draft in the part design.
Stitch Lines
Also known as “weld lines” or “knit lines,” these are visible imperfections where two separate flows of material meet and fail to fully bond, resulting in a visible line. This often happens when multiple gates are used.
STL
A widely used file format for 3D printing and rapid prototyping, though not ideal for injection molding applications.
Straight-pull Mold
A simple mold design consisting of only two halves, typically used for parts without undercuts, side actions, or other features that require complex mold movement.
Tab Gate
A gate aligned with the parting line of the mold where resin enters the cavity. Also known as “edge gates,” they are typically placed on the outer edge of the part.
Tear Strip
A feature added to the mold, which is removed after the molding process to help achieve a clean edge on the part. It is often used alongside an overflow to improve part quality.
Texture
A surface treatment applied to some or all faces of a part. This can range from smooth, polished finishes to highly patterned textures that help conceal surface imperfections and enhance the part’s appearance or tactile feel.
Tunnel Gate
A gate that is routed through the body of one side of the mold, creating an entrance for resin without leaving a visible mark on the part’s exterior surface.
Turning
A machining process in which a lathe rotates rod stock while a cutting tool removes material to shape the part into a cylindrical form.
Undercut
A feature of a part where one section of the part overlaps or “shadows” another, creating a lock between the part and one or both halves of the mold. For example, a hole that is perpendicular to the mold’s opening direction and drilled into the side of a part. Undercuts can prevent the part from being ejected or cause difficulty in opening the mold.
Vent
A tiny opening (usually between 0.001 in. to 0.005 in.) in the mold cavity, often located at the shutoff surface or through an ejector pin tunnel, that allows air to escape as the resin is injected.
Vestige
A small imperfection left on the part after the molding process, typically where the plastic runner system (or a hot tip gate) was attached. Once the runner is trimmed or the hot tip dimple is removed, a vestige remains, marking the point of attachment.
Wall
The term used for the surfaces of a hollow part. It’s crucial for these walls to maintain consistent thickness to ensure part quality.
Warp
The deformation or bending of a part as it cools, caused by uneven cooling rates across different areas. This leads to internal stresses. Parts made from filled resins may experience additional warping due to the varying shrinkage rates of the resin and fillers, and fiber alignment can create anisotropic stresses.
Weld lines
Also called “stitch lines” or “knit lines,” and “meld lines” when multiple gates are used. These imperfections occur when separated flows of resin meet and merge, often leaving a visible line and sometimes resulting in weak bonds.
Wireframe
A type of CAD model that consists only of lines and curves in 2D or 3D. Wireframe models are not suitable for rapid injection molding due to their lack of detail for producing solid parts.
