Manufacturing Processes: Metal Forming, Machining, Tooling, Economics, and Grinding

Comprehensive vocabulary flashcards covering metal forming, bulk deformation, sheet metalworking, machining mechanics, machine tools, cutting-tool technology, machining economics, and grinding processes.

Metal Forming

A large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces through stresses applied by a tool (usually a die) that exceed the metal's yield strength.

Cold Working (Cold Forming)

Metal forming performed at room temperature or slightly above, which provides closer tolerances, better surface finish, increased strength and hardness via strain hardening, and improved directional grain properties.

Warm Working

Metal forming operations carried out at temperatures above room temperature but below the recrystallization temperature, typically with a lower threshold around $0.3\,T_m$ (where $T_m$ is the metal's absolute melting temperature).

Hot Working (Hot Forming)

Plastic deformation performed at temperatures above the recrystallization temperature (typically somewhat above $0.5\,T_m$), enabling substantial shape changes with lower forces, increased ductility, and absence of strain hardening.

Bulk Deformation Processes

Metal forming operations characterized by significant shape changes in workpieces having low surface-area-to-volume ratios, starting from elementary forms such as cylindrical billets, rectangular bars, and slabs.

No-Slip Point (Neutral Point)

The point along the contact arc between the work and rolls in flat rolling where the linear velocity of the work equals the peripheral roll speed ($v_r$), and where roll pressure reaches its peak value.

Ring Rolling

A deformation process in which a thick-walled ring of smaller diameter is rolled between an idler roll and a driven roll to simultaneously reduce its wall thickness and increase its diameter.

Roll Piercing (Mannesmann Process)

A specialized hot working rolling operation used to make seamless thick-walled tubes by subjecting a solid cylindrical billet to circumferential compressive stresses from opposing skewed rolls, generating tensile stresses at the center that open an internal crack over a mandrel.

Coining

A special application of closed-die forging in which high die pressures impress fine surface details into both faces of the workpiece with minimal metal flow.

Swaging

A forging process used to reduce the diameter or create a taper on the end of a rod or tube, accomplished by rotating dies that hammer the workpiece radially inward as it is fed.

Radial Forging

A forging process similar to swaging in which the hammering dies maintain a fixed angular orientation while the cylindrical workpiece rotates as it feeds into the dies.

Extrusion Ratio

The ratio of the original cross-sectional area of the billet to the final cross-sectional area of the extruded part, defined mathematically as $r_x = \frac{A_o}{A_f}$.

Draft (Drawing)

The absolute difference between the starting diameter and the final diameter of the processed work in bar and wire drawing, given by $d = D_o - D_f$.

Plate

Metal stock with a thickness exceeding $6\,\text{mm}$ ($1/4\,\text{in}$), distinguishing it from thinner sheet metal stock.

Angular Clearance (Sheet Metal Cutting)

The relief angle machined into the lower portion of a cutting die opening—typically $0.25^\circ$ to $1.5^\circ$ on each side—allowing punched blanks or slugs to drop freely through the die.

Shear Angle

A bevel ground into the cutting face of a punch or die that distributes the shearing cut over time, significantly reducing maximum instantaneous cutting force while keeping total energy constant.

Springback

The elastic recovery that occurs when bending force is removed from sheet metal, causing an increase in included bend angle and bend radius.

Bottoming

A technique to overcome springback in bending by squeezing the sheet metal part at the end of the press stroke to induce plastic deformation across the bend zone.

Ironing

A sheet-metal process in which the cylindrical wall of a drawn cup is forced through a die clearance smaller than the original sheet thickness, making wall thickness uniform and lengthening the cup.

Gap Frame Press (C-Frame Press)

A press characterized by a C-shaped frame that provides open front and side clearance for tool changeover, coil feeding, and ejection of finished parts.

Open-Back Inclinable (OBI) Press

A gap-frame press mounted on a tiltable base that allows gravity discharge of finished stampings through the rear opening.

Roll Forming (Contour Roll Forming)

A continuous bending process where strip or sheet stock passes through sequential pairs of contoured rolls to progressively produce long parts of uniform cross section.

Conventional Spinning

A sheet-metal forming process where a circular sheet metal disk is held against a rotating mandrel and incrementally formed to shape by a roller or manual burnishing tool.

Material Removal Rate ($R_{MR}$)

The volume of metal removed per unit time during a machining cut, expressed for single-point turning as $R_{MR} = v f d$, where $v$ is cutting speed, $f$ is feed, and $d$ is depth of cut.

Discontinuous Chip

A segmented chip formed when machining brittle metals or ductile metals under low cutting speeds, large feeds, and high tool-chip friction, resulting in an irregular surface finish.

Built-Up Edge (BUE)

A lump of ductile work material that cyclically adheres to the tool rake face near the cutting edge under low-to-medium speeds, causing tool wear and surface roughness when dislodged.

Serrated Chip (Shear-Localized Chip)

A semi-continuous chip with a saw-tooth profile produced by alternating cycles of high and low shear strain, typical when machining difficult-to-cut metals like titanium alloys at high speeds.

Merchant Equation

An analytical relationship defining the shear plane angle ($\phi$) as a function of tool rake angle ($\alpha$) and friction angle ($\beta$), establishing that maximizing $\phi$ reduces shear plane area, cutting force, and cutting energy.

Rotational Part

A part geometry characterized by a cylindrical or disk-like shape, generated by turning or boring against a rotating work part.

Nonrotational (Prismatic) Part

A block-like or plate-like part geometry formed by combining linear motions of the workpiece with rotating or linear motions of the cutting tool (e.g., milling, shaping, planing).

Boring

An internal turning operation in which a single-point cutting tool is fed linearly parallel to the axis of rotation along the inside surface of an existing hole.

Chip Load

The size of the uncut chip formed by each cutting tooth on a milling cutter, represented as feed per tooth ($f$) and related to table feed rate by $f_r = N n_t f$.

Machining Center

A computer numerical control (CNC) machine tool equipped with an automatic tool changer and pallet shuttle, capable of performing multiple milling, drilling, and tapping operations in a single setup.

Broaching

A machining operation using a multi-toothed linear tool with progressively taller roughing, semifinishing, and finishing teeth to cut precise internal or external geometries in a single pass.

Form Milling (Gear Cutting)

A gear machining process where teeth are cut individually using a milling cutter shaped to the exact geometry of the gear tooth space, requiring indexing between passes.

Taylor Tool Life Equation

The empirical relationship $v T^n = C$, where $v$ is cutting speed, $T$ is tool life, $n$ is an exponent reflecting the tool material, and $C$ is the cutting speed yielding a $1\text{-minute}$ tool life.

High-Speed Steel (HSS)

A highly alloyed tool steel formulated to preserve high hot hardness, categorized by AISI into tungsten types (T-grades, such as 18-4-1) and molybdenum types (M-grades).

Honed Edge (Insert Edge Preparation)

A cutting insert edge treatment that applies a tiny radius or rounding (typically about $0.025\,\text{mm}$ or $0.001\,\text{in}$) to strengthen the edge against brittle chipping.

Helix Angle (Twist Drill)

The angle formed by the spiral flute of a twist drill relative to the drill axis, typically around $30^\circ$, which provides a channel for removing chips from the hole.

Tooth Set (Saw Blade)

The lateral offset of alternating saw teeth that cuts a kerf wider than the thickness of the blade body, preventing binding against the cut walls.

Theoretical Arithmetic Average Surface Roughness ($R_i$)

The ideal surface finish calculated from feed ($f$) and tool nose radius ($NR$) for single-point tools via the formula $R_i = \frac{f^2}{32\,NR}$.

Maximum Production Rate Cutting Speed ($v_{\max}$)

The cutting speed that minimizes cycle time per piece in turning, given by $v_{\max} = C\left(\frac{n}{1-n}\cdot\frac{1}{T_t}\right)^n$, where $T_t$ is tool change time.

High-Efficiency Range

The operating window of cutting speeds lying between the speed for minimum cost per unit ($v_{\min}$) and the speed for maximum production rate ($v_{\max}$).

Friability

The ability of an abrasive grain under grinding forces to micro-fracture when dull, cleaving away worn surfaces to continuously expose sharp cutting edges.

Borazon

The trade name for cubic boron nitride (CBN) abrasives, known for high hardness ($4700\,\text{HK}$) and utilized for grinding hardened tool steels and aerospace alloys.

Size Effect (Grinding)

The phenomenon where extremely small chip thickness in grinding produces a specific cutting energy ($U$) roughly 10 times higher than that observed in conventional machining operations.