Manufacturing Processes Attributes of Manufactured Products

Type of Industries Industry – produces or supply goods and services Types Primary – cultivate and exploit natural resources Examples – mining, agriculture, etc. Secondary – takes outputs of primary industries and convert them into consumer and capital goods. Tertiary – service sector Estaremos trabajando con las industrias secundarias. En el contexto del curso manufactura se refiere a la producción de piezas, herramientas y equipos.

Types of Industries

Secondary Industries

Type of Products Consumer Goods – purchased directly by consumers. Examples: cars, personal computers, TVs, etc. Capital Goods – purchased by other industries to produce goods and supply services. Examples: aircrafts, railroad equipment, construction equipment, etc. Otros incluye materiales, componentes y suministros utilizados por compañías para hacer productos. Ej. Láminas, barras y otros suministros de metal; resinas, libricantes, etc.

Product Variety and Production Quantity Low 1 to 100 units/year Medium 101 to 10,000 units/year High 10,001 to millions of units/year Variety Soft - small difference between products Hard – products differ substantially

Quantity vs Variety La relación entre cantidad y variedad es inversamente proporcional.

Manufacturing Capability Planta de manufactura Interdependencia entre materiales, procesos y sistemas. Capability Technical and physical limitations of a manufacturing industry. Manufacturing processes Product size and weight Production capacity

Materials Metals (usually used as alloys) Ceramics 1/2 Metals (usually used as alloys) Ferrous – steel, cast iron, etc. Non-ferrous – aluminum, copper, gold, etc. Ceramics Compound that includes metallic and non-metallic (O, N,etc.) elements. Clay - hydrous aluminum silicates Silica - basis of all glass products Alumina and Silicon Carbide – abrasive Crystalline and glasses

Materials 2/2 Polymers – compound formed of repeating structural units called mers. Carbon + one or more of H, N, O, Cl, etc. Plastic Types Thermoplastic Thermosetting Elastomers

In addition to the three basic categories, there are: Composites ‑ nonhomogeneous mixtures of the other three basic types rather than a unique category Figure 1.3 – Venn diagram of three basic Material types plus composites

Geometric Attributes

Shape Classification

Machine Tool Movement and Control

Limitations Axial symmetry Nonrotational symmetry Surface Two dimensional axes Nonrotational symmetry Min of two dim axes Surface Min 1 axes

Surface Limitations

Dimension ANSI (American National Standards Institute) Numerical value expressed in appropriate units of measure and indicated on a drawing and in other documents along with lines, symbols and notes to define the size or geometric characteristic, or both, of a part feature. Length, width, height, diameter, angles, etc. 12’’ 3’’ 4’’

Dimensioning Systems U.S. Customary System (USCS) Inch (in) International System (SI) Meter (m)

Tolerance ANSI The total amount by which a specific dimension is permitted to vary. Tolerance = Max Limit – Min Limit Types Bilateral Unilateral Limit dimension Variations occur in any manufacturing process, which are manifested as variations in part size. Tolerances are used to define the limits of the allowed variation.

Bilateral Tolerance Variation is permitted in both positive and negative directions from the nominal dimension It is possible for a bilateral tolerance to be unbalanced; for example, 2.500 +0.010, -0.005 Figure 5.1 ‑ Ways to specify tolerance limits for a nominal dimension of 2.500: (a) bilateral

Unilateral Tolerance Variation from the specified dimension is permitted in only one direction, either positive or negative, but not both Figure 5.1 ‑ Ways to specify tolerance limits for a nominal dimension of 2.500: (b) unilateral

Limit Dimensions Permissible variation in a part feature size, consisting of the maximum and minimum dimensions allowed Figure 5.1 ‑ Ways to specify tolerance limits for a nominal dimension of 2.500: (c) limit dimensions

Tolerance must be… close enough to allow functioning of the assembled parts. as wide as functionally possible.

Tolerance

Tolerances and Manufacturing Processes Some manufacturing processes are inherently more accurate than others Examples: Most machining processes are quite accurate, capable of tolerances = 0.05 mm ( 0.002 in.) or better Sand castings are generally inaccurate, and tolerances of 10 to 20 times those used for machined parts must be specified

Other Attributes See table 5.1 Angularity – a part feature is at specified angle relative to a reference surface. http://www.delvest.com/angularity.htm

Other Attributes See table 5.1 Circularity/Roundness – the degree to which all points on the intersection of the surface and a plane perpendicular to the axis of revolution are equidistant from the axis.

Other Attributes See table 5.1 Concentricity – the degree to which any two (or more) part features have a common axis. 5" OD x 2" ID x 2" long. 5' OD and 2' ID will be concentric within .020' TIR (5" OD - 2" = 3" separation).  http://www.delvest.com/concentricity.htm

Other Attributes See table 5.1 Cylindricity – the degree to which all points on a surface of revolution are equidistant from the axis of revolution.

Other Attributes See table 5.1 Flatness – The extent to which all points on a surface lie in a single plane. http://www.delvest.com/flatness.htm

Other Attributes See table 5.1 Parallelism – the degree to which all points on a part feature are equidistant from a reference plane, line or axis. http://www.delvest.com/parallelism.htm

Other Attributes See table 5.1 Perpendicularity/ Squareness – the degree to which all points on a part feature are 90° from the reference plane, line or axis. http://www.delvest.com/perpendicularity.htm

Other Attributes See table 5.1 Straightness – the degree to which a part feature is a straight line. http://www.delvest.com/straightness.htm

Surfaces What we touch when holding a manufactured part. Nominal surfaces – intended surface contour. Actual surfaces of a part are determined by the manufacturing processes used to make it Importance Aesthetic Affect safety Friction and wear Affect mechanical properties Affect assembly Smooth surfaces make better electrical contacts The nominal surfaces appear as absolutely straight lines, ideal circles, round holes, and other edges and surfaces that are geometrically perfect. The variety of manufacturing processes result in wide variations in surface characteristics.

Surface Components The topography and geometric features of the surface: When highly magnified, the surface is anything but straight and smooth. It has roughness, waviness, and flaws. Figure 5.2 ‑ A magnified cross‑section of a typical metallic part surface

Surface Attributes It also possesses a pattern and/or direction resulting from the mechanical process that produced it.

Four Elements of Surface Texture Roughness - small, finely‑spaced deviations from nominal surface determined by material characteristics and process that formed the surface Waviness - deviations of much larger spacing; they occur due to work deflection, vibration, heat treatment, and similar factors Roughness is superimposed on waviness

Lay: predominant direction or pattern of the surface texture

4. Flaws - irregularities that occur occasionally on the surface Includes cracks, scratches, inclusions, and similar defects in the surface Although some flaws relate to surface texture, they also affect surface integrity

Surface Attributes It also possesses a pattern and/or direction resulting from the mechanical process that produced it.

Surface Roughness and Surface Finish Surface roughness - a measurable characteristic based on roughness deviations Surface finish - a more subjective term denoting smoothness and general quality of a surface In popular usage, surface finish is often used as a synonym for surface roughness Both terms are within the scope of surface texture

Surface Roughness Average of vertical deviations from nominal surface over a specified surface length Figure 5.5 ‑ Deviations from nominal surface used in the two definitions of surface roughness

Surface Roughness Equation Arithmetic average (AA) is generally used, based on absolute values of deviations, and is referred to as average roughness where Ra = average roughness; y = vertical deviation from nominal surface (absolute value); and Lm = specified distance over which the surface deviations are measured

An Alternative Surface Roughness Equation Approximation of previous equation is perhaps easier to comprehend: where Ra has the same meaning as above; yi = vertical deviations (absolute value) identified by subscript i; and n = number of deviations included in Lm

Cutoff Length A problem with the Ra computation is that waviness may get included To deal with this problem, a parameter called the cutoff length is used as a filter to separate waviness from roughness deviations Cutoff length is a sampling distance along the surface. A sampling distance shorter than the waviness width eliminates waviness deviations and only includes roughness deviations

Figure 5.6 ‑ Surface texture symbols in engineering drawings: the symbol, and (b) symbol with identification labels Values of Ra are given in microinches; units for other measures are given in inches Designers do not always specify all of the parameters on engineering drawings

Material Properties Mechanical – strength, toughness, ductility, hardness, elasticity, fatigue, creep, ratios Physical – density, specific heat, thermal expansion, thermal conductivity, melting point, magnetic and electrical qualities Chemical – oxidation, corrosion, degradation, toxicity, flammability Manufacturing – manufacturability, effects on product properties, service life, cost