A

ABS: Acrylonitrile Butadiene Styrene — known widely as ABS — is among the most popular and versatile of the resins in the styrene family (which includes polystyrene). Its availability, strength, and limited shrinkage all help make it widely used as the default choice for most plastic products.
Additive: Material such as colorant or volumizer (blowing agent) added in small amounts to basic resins to change characteristics of the finished material.
Anisotropy: Property of material to be aligned along a certain grain and thus react to stresses differently dependent on the directionality of force.
ANSI: American National Standards Institute. – One of the governing bodies for units of measurement.
A-Plate: See “Hot Half”.

B

Balanced Runner: A common goal of injection molding to have similarly sized cavities located equal distances from the sprue in order to accommodate even filling.
Barrel: The part of an injection molding machine which contains the screw and wherein the resin is made molten.
Bead Blast: A bead blast refers to one of the many finishes you can put on a tool in order to change the appearance of the plastic parts. A bead blast can be light, moderate, or heavy.

Blister-: -Packaging – An inexpensive container consisting of a plastic bubble glued or otherwise affixed to a cardboard backing used for shipping and displaying mass-produced products.; -Defect – A blister is an imperfection near the surface of a finished part caused by a pocket of air or gas trapped in the material.
Blowing Agent: A Volumizer or “blowing agent” is an additive for plasitc resins which help avoid common molding issues like
Blow-Molding: Blow-Molding is a plastic molding process that combines extrusion and vacuum-forming to create hollow vessels similar to a gallon milk-jug. It creates thin walls and should not be used for pressure-filled or structural elements. A better choice for those applications might be rotational molding.
Blushing: The tendency for plastic to turn lighter or white in places that are bent, deformed, or stressed beyond the elasticity of the material.

Boss: A functional extrusion or tab on a plastic part normally used to locate or fasten two adjoining parts or to add strength (see also ribs)
B-Plate: See “Ejector Half”.

C

CAD: Computer Aided Drafting variously Computer Aided Design.; CAD Designers use computer programs like Solidworks or ProEngineering to create an exact, to-scale computer model of a part or assembly of parts. The CAD model is then used for testing, presentation, and moldmaking.
CAM: Computer Aided Machining; CAM operators use CNC machines to create mold cavities using cutter paths driven directly by the CAD models.

Cavity: The part of the mold that contains a void or negative of the part to be molded. Hot fluid plastic is squeezed into the cavity through runners and a comleted part is then cooled and ejected.
CNC Milling Machine: A CNC (Computer Numeric Controls) milling machine uses CAD/CAM cutter paths to cut away metal blocks into the various parts of an injection mold and then add the cavities and ejector pin holes.
Colorant: An additive to resin that colors the resulting plastic parts. Colorant can affect the base color as well as the hue and several other properties such as fluorescence with out altering the strength or elasticity of the material to a significant degree.
Cooling: Various methods such as water lines, refrigerated lines, heat sinks and copper inserts are used to keep the mold at optimal running temperatures which results in better parts and faster cycle times.
Core: Often refered to as part of a core/cavity split, the core is the eject half side of the cavity that often forms the inside of the part and so looks more like a protrusion in the tool
Core-Pin: Similar to the core, core-pins are used to create the insides of through or blind holes and are often separate pins that can be removed for replacement or resizing.
Corners (sharp, small, inside, & outside): Small and sharp corners may present difficulties and weaknesses in both the tool and the part and are best avoided if possible.; Inside and outside corners on a part are reversed in the mold and may require fillets or other means to make the tooling.
Cosmetic Side or Finish: The cosmetic side is the side that the ejector pins are not on and it leaves a surface without marks which can then be treated with various process to create particular finishes.
Cutters: You will hear tool-makers talk about cutters and cutter sizes. The cutters are the part of the CNC milling machine that actually spin on the spindle and cut the metal. The radius of the cutter is important because it is approximately the smallest radius that can be machined before having to use an alternate process such as EDM

D

Draft: In injection molding the cooled parts must be ejected from the mold halves and in order to achieve this a slight slope, or draft, is added to the walls of the part that are perpendicular to the direction of the mold pull. A normal two or three degree draft is preferred but occasionally a draft as small as a half of a degree is permissible while in other instances (such as metal to metal contact) five to seven degrees is required.
Drier: Material (resin) is put through a drier before being added to the molding machines in order to remove moisture and reduce the occurrence of defects like blistering and splay

E

EDM: Electrical Discharge Machining (EDM) is a process using tooled diodes to electrically remove material from the cavities of the mold and is commonly used to create very small detail and sharp inside corners on the tool.; EDM adds significant cost to the creation of a mold and is generally avoided using techniques like fillets and raised detail.
Elasticity: A property of material that determines how far they can bend without being permanently deformed.
Ejector Half: The eject half of the mold is the half that is designed to hold the part when the mold opens and then eject the part. The eject half is composed of the b-plate, the rails, the eject and return plates, the base plate and the support pillars.
Eject Pins: Eject pins push the completed part out of the mold cavity. They leave small marks and are generally placed on the non-cosmetic side of the part.
Ejection Plate: The ejection plate pushes all of the eject pins at one time and can be controlled for multi-stage ejection or timed ejection.

F

Family Molds: Molds which contain more than one part of an assembly that are either meant to be left on the runner or assembled prior to packaging.; Family molds may present some difficulties running if the parts are of greatly differing volumes or surface area and are generally avoided in high-volume molding.
Fatigue: Fatigue refers to the breakdown of material integrity when subjected to repeated bending or deformation. Plastics like ABS show relatively high fatigue and break or rip if bent repeatedly. Other plastics like polypropylene show little fatigue and can stand repeat deformation in applications like clips or .

FDM: Fused Deposition Modeling is a type of rapid prototyping that is generally cheap than other processes like SLA and creates a model in many of the same materials (ABS etc) but usually has a lower resolution than other processes.
Flash: Flash is a defect on plastic parts that results in a thin membrane of material extending along the parting line. It is caused by overpacking, lack of support, unbalanced molds, overly hot material, and a host of other causes.

G

Gate: The point in the mold where the plasticized resin flows into the cavity. The gate bridges the cavity and the runner and partially controls the speed at which the cavity is filled.
Grinder: A grinder is used to trim eject pins to the correct length and is responsible for the striations sometimes observed inside eject pin marks.

H

Hot Half: The half of the mold that contains the cosmetic side of the cavity and no injection. This is also the half through which the sprue runs and injects the hot plastic.

I

Injection Molding Cycle Time: The complete cycle of injection molding including mold closing, shot injection, cooling, mold opening, and ejection.; Cycle time is a direct driver of part cost and many techniques like cooling and venting are used to speed it up.
Injection Molding: Injection molding takes molten resin and squeezes it through a mold into a cavity which then produces a finished plastic part.
Insert: An insert is used in mold repair to replace part of a mold without remaking the entire thing; to create feature like sharp inside corners without using more expensive processes like EDM; and to save material and machine time by working on two parts of the same component simultaneously or starting with material more closely matching the finished tool.
Insert Molding: Insert molding cuts the cost of a traditional mold by making the core/cavity into a set of inserts that fit into standard prefabricated bases thereby negating the need to make the entire mold.

L

Lettering / Logos / Text: For inexpensive tooling all lettering must stand up on the part and contain radii of no less than .023″. If logos or lettering is required to be sunken or more crisp then the more expensive process of EDM must be used.
Living Hinge: A joint designed with a very thin segment of plastic that is meant to be repeatedly bent and forms a functional hinge between two parts.

M


Molding: Molding is the process of inexpensively creating a high volume of copies of objects ranging from a tiny gear or needle to car panels and garbage cans using cavities or molds. Some usual processes include injection molding, blow molding, rotational molding, extrusion, blow film, vacuum forming, injection-blow molding, and others.
Mold Operator: The mold operator is responsible for keeping the mold running by clearing finished parts and runners, adding material, trimming parts, and performing in-mold tasks like lubrication and decorating.; Mold operators are a direct driver of cost and if a mold can be run with minimal supervision it cuts part costs dramatically.
MUD (Base): A Master Unit Die (MUD) tool is a set of pre-made bases that industry-wide standard inserts fit into and can be used like traditional injection molds. Using a MUD cuts cost and speeds fabrication.
Multi-cavity: By adding multiple cavities on one mold, tooling costs will be increased, but, since two or more parts are made instead of one each shot, part cost will be cut dramatically. Multi-cavity molds are essential for effective high-volume molding with some mega-volume tools being created with upwards of 200 cavities.

P

Platens: Platens are the plates on the molding machine upon which the molds are mounted. Platens have a certain footprint depending on the capacity/tonnage of the machine and cannot be superseded for safe operation of the molding machine.
Product Development Cycle: Generally refers to either a marketing/analysis or manufacturing/engineering.; An example manufacturing-centric product development cycle might resemble the following: Idea generation and screening; Concept testing and refinement; Design; Prototyping; Tooling; Production; Market
Product Life Cycle: Generally a marketing term used to refer to the explosive growth, plateau, and decline of a product or brand, a product life cycle can also refer to the iterative process of improving a product over time through major redesigns or replacement of obsolete versions.
Prototypes: Prototypes are pre-manufacturing models of a part or assembly meant to test, form, fit, and/or function.
Polybags: Polybags are among the most inexpensive packaging available for low to medium volume production.
Polycarbonate: Polycarbonates are a group of thermoplastics made up of polymers linked by carbon group. They are a widely utilized plastic particularly for use in clear applications such as CD jewel cases, lenses, and light covers. Some forms are used for single use food containers and water bottles, but the material is not considered food-safe for reused or washed containers.
Polyethylene: Also known as PE with variants LDPE, HDPE, and MDPE, polyethylene is one of the most common thermoplastics and is used in film-bags, poly-bags, tubing, bearings, toys and buckets among other things.
Polypropylene: Polypropylene is a thermoplastic that, while not as clear or cheap as polycarbonate, is safe for reusable containers and laboratory tools. It has particular resistance to fatigue which makes it ideal for living hinge applications.
Polystyrene: A very cheap and versatile thermoplastic, polystyrene’s rigidity and limited elasticity has caused it to be supplanted with ABS in most applications, but is still popularly used for architectural modelling, poster-board, foam cups, and expanded polystyrene (EPS) used as packaging foam.

R

Rails: Rails support the B-Plate and are clamped to the base plate. The rails provide room for the ejection system to move.
Rapid Prototyping: Using one of many machine processes to create a single prototype directly from data (usually .stl format). The processes include 3D Printing, Fused Deposition Modeling (FDM), Multi Jet Modeling (MJM – variously Thermojet Modeling) StereoLithography (SLA), and Selective Laser Sintering (SLS).
Resin: Resin is another name for plastic and generally refers to the pelletized raw form of the pre-injected plastic.
Return Plate: The return plate is attached to the top of the ejection plate and returns the ejector pins to their neutral location using springs or hydraulics.
Ribs: Ribs are features that usually run along the bottom of a part and serve to add strength while preserving consistent wall thickness.
Rotational Molding: Rotational molding is a manufacturing process generally reserved for large thick-walled containers like trash cans.
Runners: Runners bring the plasticized resin from the sprue to the part. Runners require room on the tool, use extra material in every shot, and affect how the part if packed, so efficient placement is essential for optimal part price and performance.

S

Sand Blast: A sand blast finish has a finely dimpled surface and creates a nice, even, fingerprint-free texture in parts. An aggressive sand blast may also be used on non-cosmetic areas to help the part stick to the eject half.; See our page comparing various finishes for part surfaces.
Screw: The screw is located in the barrel of the injection molding machine and advances the resin from the hopper to the sprue through a heat element that changes the resin from pellets to flowing plastic.
Shrink: Mold cavities are built scaled larger than the resultant parts to account for the tendency of material to shrink when it is cooled and its molecules become less active. Shrink factors for materials are known and published by the maker of the various resins.; Shrink contributes to many molding defects and issues but can be avoided if the parts are built properly. Due to shrink factor compensation, molds are designed for particular resins and might not perform as well for materials with greatly differing shrink factors.; See our page on avoiding common molding defects.
SLA: Stereo-Lithography is a rapid prototyping process that, while more expensive than other forms, produces parts with better detail.
Slide: When a mold contains a feature that requires a side-pulling action (usually a hole in a vertical wall), and there is enough volume expected to make a hand-loaded insert cost-prohibitive, then a slide is used to automatically place the feature in the tool upon the closing of the mold.
Sink Marks: Sink marks are causes when the surface of the part cools faster than the inside of the part and shrinkage from the inside deforms the surface of the part.; See our page on avoiding common molding defects.


Spindle: A spindle is the part of a CNC Milling machine that holds the cutters and spins at speeds of up to 12000RPMs. Due to the presence of the spindle, some cuts – particularly very deep and narrow cuts – require special set-ups and attention.
Splay: Splay is a defect similar to blisters that is caused by escaping gas or water and which affects the surface of the finished parts. Generally this is caused by an improperly vented tool, use of material that has not been dried sufficiently, poor gating, or operating in overly humid conditions.
Split-: split line – The split line is a faint line along the finished part that shows where the mold halves came together during the molding. The flatter the parting line is, the cheaper it is to create tooling.; mold split – The mold split generally refers to the need to split the surfaces of the parts into two halves. This disallows features like undercuts or hollow areas and creates the need for planning and special attention for uneven split lines, shut-offs, side-pull features, and inserts.
Springs: Springs are sometimes used to return the ejection to a neutral position.; See our page on the anatomy of a mold.
Sprue-: A sprue refers to both the chamber and the resultant waste the transfers the molten plastic from the barrel to the runner system inside the mold.; -puller – Often just a small stump of plastic opposite the sprue, the sprue puller removes the sprue (waste) and the runner from the mold and is ejected along with the part.; -hot-tip – A hot-tip sprue (known variously as a hot-tip runner or hot sprue tip) adds a heating element to the sprue, keeping the plastic in molten form until it reaches either the gate or the runner system and eliminates the wasted material in the sprue (which can make up the bulk of the waste in small parts) as well as allowing a hotter, faster-flowing packing of the mold.
Stripper Plate: For parts that cannot have ejector pins used (for either mechanical or cosmetic reasons) are often ejected by a plate tied to the ejection system which strips the part off of the core.
Sub-gate: A sub-gate is a type of gate that flows into the cavity from the runner through a small tunnel in the b-plate. Sub-gates automatically trim and separate the runners from the parts and remove the need for post-injection trimming.
Support Pillars: When a mold is injected at such high pressures, the force of the injection causes the plates to flex, and even if they flex by less than a few hundredths of an inch, the part will flash. Support pillars reduce the flex and are a key technique for controlling flash.

T


Tooling: Tooling is another name for both the process of creating the molds and other tools necessary for producing parts and the actual molds.; Beware of companies that charge a “non-recurring tooling charge” or “one-time engineering fee” without explicitly stating that ownership of the tool is retained by the customer, you might have to remake the tool(mold) if you decide you want someone else to produce the plastic parts.
Tooling Marks: In non-cosmetic or unpolished finishes tooling marks, tiny circular scratches that show the path of the cutter, are visible. The marks are transferred to the parts the mold produces and can be considered undesirable if it is a cosmetic surface.

U

Undercut: Undercuts are areas in a part that are inaccessible from the mold split. Generally these areas must be designed out or use an insert or slide.

V

Vinyl: A durable and flexible material, vinyl is widely used for everything from fencing to containers to upholstery. It is tough and resistant to tearing, but can be soft and have trouble holding its shape.
Volumizer: A Volumizer or “blowing agent” is an additive for plastic resins which help avoid common molding issues like sink marks.

W

Wall Thickness: Very thick or inconsistent wall sections are undesirable in mold making because they are often the cause of defects like sink marks in the finished part. An even and appropriately sized wall provides the most effective mold shot. The wall must no be so thick as to cause warpage or add cooling time to the cycle, but it must be thick enough to allow plastic to flow easily though the entire cavity.
Weld Mark: A weld mark (aka knit line) is sometimes seen as a faint line where flowing plastic joins together after being separated by a core pin or multiple gates. The weld is structurally weaker than the surrounding area and should be taken into consideration when designing runners and gates.

#

3D CAD Modeling: Computer Aided Drafting variously Computer Aided Design.CAD Designers use computer programs like Solidworks or ProEngineering to create an exact, to-scale computer model of a part or assembly of parts. The CAD model is then used for testing, presentation, and moldmaking.
3D Printing: 3D Printing is a process used in Rapid Prototyping that, along with FDM, is among the cheapest RP processes, however is has limited material selection and poor resolution relative to other processes.