Manufacturing Process Applications: Part I 124

anvil

The bottom component on a drop hammer machine. The anvil holds the workpiece that is being forged.

backward extrusion

A process that forces material to flow backward around a punch as the punch presses through it. Backward extrusion is also called indirect extrusion.

bending

Creating angles in sheet metal, typically by using a punch and die. Bending compresses the interior side of the bend while stretching the exterior.

billet

A semi-finished piece of round or rectangular bulk metal stock. A billet is smaller than a bloom.

blank

A sheet metal shape resulting from a blanking operation. Blanks are then used in other processes, such as bending, punching, and drawing.

blanking

A shearing operation that removes an interior section of sheet metal. The removed section is the desired piece, which moves on to other forming operations, such as punching or drawing.

blending

Mixing binders, lubricants, and other materials with powdered metal. Blending is the second step in manufacturing powder metal parts.

bloom

A semi-finished piece of round or rectangular bulk metal stock. A bloom is larger than a billet.

bulk metal

A mass of unprocessed or semi-processed metal. Bulk metal shapes are the starting forms for many continuous metal shaping processes.

bulk metal drawing

Pulling bulk metal stock through a die opening that is smaller than the diameter of the stock. Bulk metal drawing elongates the microstructure of the metal.

bulk metal rolling

Compressing and elongating bulk metal stock using a series of rollers. Rolling can shape bulk metal into forms like plates, rods, and bars.

casting

A process that forms parts by pouring or injecting molten metal into a mold cavity. The resulting shape is called a casting.

chill

A metal insert added to a mold to regulate solidification of the molten metal. Chills can prevent defects in the casting.

chip

An unwanted piece of cut away metal. Chips are the by-product of machining.

clearance

The angled gap between the punch and die block in sheet metal shearing. Incorrectly calculated clearance can damage the sheared edge or the cutting tool.

closed die forging

Also called impression die forging, a forging process that compresses metal between two dies containing a negative shape of the part. Closed dies create flash that must be removed after forging.

cold working

Any metal shaping process that takes place when the metal is below its recrystallization temperature.

compacting

Pressing powder metal into a green compact using two opposing forces. Compacting is the third step in manufacturing powder metal parts.

continuous process

An uninterrupted metal shaping process. A continuous process usually creates long pieces with uniform cross sections.

cope

The top half of the mold in a casting operation. Most molds have two halves that are used together to shape the casting.

core

Shapes in the mold cavity that create the internal surfaces of the casting. When metal enters the cavity, it flows around the core and solidifies against it.

crystalline structure

The predictable arrangement of atoms in a metal. Each metal has a specific crystalline structure that determines its unique properties.

die casting

A casting process that involves forcing material into a mold. In metal die casting, the die acts as the mold.

dimensional tolerance

An unwanted but acceptable deviation from a specified dimension.

direct extrusion

A continuous process that forces material to flow forward through a container and past one or more die openings. Direct extrusion is also called forward extrusion.

drag

The bottom half of the mold in a casting operation. Most molds have two halves that are used together to shape the casting.

drop hammer

A vertically oriented forging machine with a top weighted ram and a bottom anvil. The force generated from the falling ram forges metal in a die on the lower anvil.

evaporative casting

A casting process that creates intricate parts from an expendable polystyrene pattern and expendable sand mold. Evaporative casting is also called lost foam casting.

extrusion

A shaping process that forces material to flow through a die or around a punch.

flash

An excess of metal that flows outside of the main impression during impression die forging. Flash helps fill the die cavity but must be removed after forging.

flashless forging

An impression die forging method that does not create flash. Flashless forging is also called precision forging.

flat die forging

A forging process that compresses metal between two flat dies. A skilled operator controls the shape of the metal workpiece by moving the metal. Flat die forging is also called open die forging or hand die forging.

forging

A metal shaping process that uses force to compress and align the metal's internal structure.

forward extrusion

A continuous process that forces material to flow forward through a container and past one or more die openings. Forward extrusion is also called direct extrusion.

gate

The entryway to the mold's cavity. The molten metal moves through the runner and past the gate where it enters the cavity.

green compact

The weak metal part created after compacting in powder metallurgy. Sintering strengthens the green compact by fusing the blended materials.

green sand molding

A casting process that uses an expendable wet sand mold and reusable pattern.

hand forging

A forging process that compresses metal between two flat dies. A skilled operator controls the shape of the metal workpiece by moving the metal. Hand forging is also called open die forging or flat die forging.

heading

A forging method that compresses a workpiece, decreasing its length and creating a mass at one end. Heading is often used to shape bolts, and is also called upset forging or hot heading.

hot heading

A forging method that compresses a workpiece, decreasing its length and creating a mass at one end. Hot heading is used to shape bolts, and is also called heading or upset forging.

hot working

Any metal shaping process that takes place when the metal is heated above its recrystallization temperature.

impression die forging

Also called closed die forging, a forging process that compresses metal between two dies containing the negative shape of the part. Impression dies create flash that must be removed after forging.

indirect extrusion

A process that forces material to flow backward around a punch as the punch presses through it. Indirect extrusion is also called backward extrusion.

ingot

A solid mass of metal that is in a suitable shape for shipping, storing, or further processing.

investment casting

A casting process that creates intricate shapes using an expendable wax pattern and expendable ceramic mold. Investment casting is also called precision casting.

lancing

A shearing operation that cuts through an interior section of sheet metal without creating scrap. Lancing creates louvers, like the vents in gym lockers.

lost foam casting

A casting process that creates intricate parts from an expendable polystyrene pattern and expendable sand mold. Lost foam casting is also called evaporative casting.

melt atomization

Manufacturing powder metal by spraying liquid metal with water, air, or inert gas in an atomization chamber. The spray causes the metal to cool and solidify into particles.

mold

A hollow cavity used to shape material. In metal casting, the mold is filled with liquid metal, which takes the shape of the mold as it solidifies.

near-net shape

Having dimensions that are close to a final form after initial manufacturing steps. Parts that are near-net shape require little subsequent machining.

neutral axis

The boundary between the stressed and compressed surfaces in bent metal.

nibbling

A shearing operation that cuts overlapping holes in sheet metal. Nibbling is used to create curved, non-linear cuts.

notching

A shearing operation that removes an area around the edge of the sheet metal. Notched workpieces can then be bent into shapes, such as a box.

open die forging

A forging process that compresses metal between two flat dies. A skilled operator controls the shape of the metal workpiece by moving the metal. Open die forging is also called hand forging or flat die forging.

parting

A shearing operation that separates two pieces of sheet metal by cutting away the section in between. Parting dies have two cutting edges which create the opposite ends of the blanks.

parting line

The division between the cope and drag on a mold. This division is where the top and bottom half of the mold meet.

pattern

A replica of the part or casting that is used to create a negative impression in a mold. Creating a pattern and mold is the initial step in the casting process.

perforating

A shearing operation that creates many separate, individual holes in sheet metal. Perforated parts are useful for screens and grates.

permanent mold casting

A casting process that uses a reusable mold and no pattern. In metal casting, permanent molds are usually made of metal.

piercing

Also called punching, a shearing operation that creates a hole in sheet metal. The metal removed to create the hole is scrap.

plastic deformation

The permanent distortion of metal due to stress. Plastic deformation occurs after excessive elastic deformation.

PM

Powder metallurgy. A metal shaping process that creates near-net parts from powdered metal. Powder manufacturing, blending, compacting, and sintering are the main steps in PM.

powder metallurgy

PM. A metal shaping process that creates near-net parts from powdered metal. Powder manufacturing, blending, compacting, and sintering are the main steps in powder metallurgy.

precision casting

A casting process that creates intricate shapes using an expendable wax pattern and expendable ceramic mold. Precision casting is also called investment casting.

precision forging

An impression die forging method that does not create flash. Precision forging is also called flashless forging.

punching

Also called piercing, a shearing operation that creates a hole in sheet metal. The metal removed to create the hole is scrap.

riser

An elevated reservoir. In metal casting, metal risers feed extra metal to the cavity to prevent shrinkage voids.

roll forming

A metal shaping process that uses pressure from a series of contoured rollers to bend metal sheets or strips. Roll forming can create tubes and complex cross sections by gradually bending metal through a number of roll passes.

runner

The channel that connects the sprue to the cavity on a mold. As the molten metal is poured through the sprue, it moves through the runner and fills the mold.

scale

A flakey film that forms on the surface of a metal that has been heated to high temperatures.

shear force

The amount of pressure required to force the internal structure of sheet metal to slide against itself and separate.

shearing

Cutting sheet metal into smaller sections without forming chips. Punching, notching, blanking, slitting, lancing, nibbling, perforating, and parting are shearing operations.

sheet metal

Flat metal stock that is no greater than 0.25 in. (0.64 cm) thick. Sheet metal is often sheared, bent, or drawn.

sheet metal drawing

A sheet metal forming operation that creates cup-like shapes by forcing a flat blank between a punch and die.

shell molding

A casting process that uses an expendable sand mold and a reusable metal pattern. Shell mold castings have a better surface finish than green sand castings.

sintering

Heating powder metal parts to bond the blended materials and melt off binders and lubricants. Sintering hardens the green compact and is the last main step in manufacturing powder metal parts.

slab

A semi-finished piece of flat, rectangular bulk metal stock. A slab is thicker than a sheet.

slitting

A shearing operation that cuts sheet metal into straight strips without forming scrap. Slitting creates thinner strips from a larger sheet.

springback

The tendency of bent metal to return to its original size or dimension after being compressed.

sprue

The channel where molten metal enters the mold. At the beginning of the casting process, molten metal is poured into the mold cavity through the sprue.

tundish

The reservoir or funnel. In metal atomization, the tundish funnels molten metal into the atomization chamber.

upset forging

A forging method that compresses a workpiece, decreasing its length and creating a mass at one end. Upset forging is used to shape bolts, and is also called heading or hot heading.