Manufacturing Processes and Production Systems

Introduction and Context

Manufacturing converts materials, energy, information, and human or automated effort into useful products. For mechatronics engineers, manufacturing is not merely a downstream activity performed after design. Product architecture, material selection, sensing, actuation, control, software, assembly, maintenance, and end-of-life recovery are all influenced by manufacturing decisions.

A motor housing may be cast, machined, or additively manufactured. A robotic gripper may use formed sheet metal, injection-molded polymer components, and precision-ground pins. The appropriate process depends on geometry, material, dimensional accuracy, surface finish, production volume, cost, safety, environmental impact, and the capabilities of the available production system.

This chapter compares the principal manufacturing process families and explains how they are integrated into production systems. Particular attention is given to design for manufacturability and assembly (DFMA), process capability, quality control, automation, cost, sustainability, and the use of digital technologies.

Learning Objectives

By the end of this chapter, the reader should be able to:

1. Explain the principles and applications of casting, forming, machining, joining, molding, heat treatment, surface engineering, and additive manufacturing.
2. Select manufacturing processes using material, geometry, tolerance, volume, cost, and sustainability criteria.
3. Apply DFMA principles to reduce manufacturing and assembly difficulty.
4. Interpret basic process-capability and quality-control measures.
5. Compare conventional, automated, flexible, and digital production systems.
6. Analyze a manufacturing case involving quality, cost, automation, and environmental constraints.

1. Manufacturing Process Families

Manufacturing processes can be classified according to how they change a workpiece.

A process route normally combines several families. For example, a steel drive shaft may be forged, normalized, rough-machined, heat-treated, finish-ground, coated at selected locations, and finally inspected and assembled.

1.1 Process-selection criteria

A technically suitable process must also be economically and operationally suitable. Important criteria include:

• Material compatibility: melting temperature, viscosity, ductility, hardenability, thermal sensitivity, and chemical reactivity.
• Geometry: size, wall thickness, internal cavities, draft angles, undercuts, aspect ratios, and accessibility for tools.
• Tolerance and surface finish: whether the process can achieve the required dimensional and functional performance.
• Production quantity: one-off, prototype, low volume, batch, or mass production.
• Rate and capacity: cycle time, machine availability, labor content, and bottleneck capacity.
• Cost: tooling, equipment, labor, material, energy, inspection, maintenance, and scrap.
• Sustainability: material utilization, energy consumption, emissions, coolant use, waste, repairability, and recyclability.
• Risk: process maturity, safety, supplier capability, and sensitivity to variation.

A common mistake is to select a process based only on unit price. A low unit cost may conceal expensive tooling, long lead times, high scrap, or poor repairability.

2. Casting and Molding

2.1 Casting principles

Casting begins by melting a material and pouring or injecting it into a mold. During solidification, the liquid contracts and develops a microstructure influenced by cooling rate, alloy composition, mold material, and thermal gradients. Risers or feeders supply liquid metal during shrinkage, while gates and runners control filling.

Sand casting uses expendable sand molds. It is versatile and economical for large parts and low-to-medium quantities, but dimensional accuracy and surface finish are generally inferior to those of permanent-mold processes. Die casting forces molten nonferrous alloy into a reusable metallic die at high pressure. It provides high productivity and good repeatability, especially for aluminum, zinc, and magnesium components. Investment casting uses a ceramic shell around a disposable wax pattern and is suitable for complex shapes and fine detail. Centrifugal casting uses rotation to distribute molten material and is useful for cylindrical products such as pipes and bushings.

Typical casting defects include porosity, cold shuts, misruns, hot tears, inclusions, and dimensional distortion. Defect prevention depends on gating design, melt cleanliness, mold temperature, solidification control, and appropriate inspection.

2.2 Molding of polymers and composites

In injection molding, polymer pellets are heated, plasticized, and injected into a closed mold. After cooling, the mold opens and ejects the part. The process supports high production rates and integrated features such as bosses, ribs, clips, and living hinges. Tooling cost is high, so it is usually justified by medium or high volume.

Compression molding places a measured charge into a heated mold and applies pressure. It is common for thermosets and fiber-reinforced composites. Blow molding forms hollow polymer articles by inflating a hot tube or preform against a mold. Rotational molding rotates a heated mold containing polymer powder, producing large hollow parts with relatively low tooling cost.

Polymer parts require attention to shrinkage, warpage, weld lines, sink marks, residual stress, and fiber orientation. Uniform wall thickness, appropriate draft, rounded transitions, and carefully placed ribs reduce defects. A rib should generally be thinner than the adjoining nominal wall so that it does not create a heavy section and sink mark; the exact proportion depends on polymer, geometry, and tooling practice.

3. Forming Processes

Forming changes shape by plastic deformation. Because material is redistributed rather than removed, forming can provide high material utilization and favorable grain flow.

• Rolling reduces thickness or produces sections by passing material between rotating rolls.
• Forging compresses material between dies. It may be open-die or closed-die and is widely used for shafts, connecting rods, gears, and high-load components.
• Extrusion forces a billet through a die to produce a constant cross-section. Direct extrusion pushes the billet in the same direction as ram motion; indirect extrusion reduces relative motion between billet and container.
• Sheet-metal stamping performs blanking, bending, drawing, or piercing with a punch and die.
• Tube bending and hydroforming create tubular structures with efficient use of material.

Forming is governed by flow stress, strain hardening, friction, temperature, and tool geometry. Cold forming can improve strength through work hardening but may reduce ductility and increase forming loads. Hot forming lowers flow stress and permits larger deformation, but oxidation, scale, thermal gradients, and dimensional variation become important.

Springback is elastic recovery after unloading. It is significant in sheet-metal bending and may be compensated through over-bending, tooling modification, or process control. Cracking can result when local tensile strain exceeds material formability. Formability is often assessed using tensile data, forming-limit diagrams, and production trials.

4. Machining and Material Removal

Machining uses a cutting tool or abrasive to remove unwanted material. Principal operations include turning, milling, drilling, boring, reaming, broaching, grinding, electrical discharge machining (EDM), and abrasive waterjet cutting.

For turning, the material-removal rate is approximately:

where Q is material-removal rate in mm³/min when compatible units are used, D is workpiece diameter in mm, N is rotational speed in rev/min, and f is feed per revolution in mm/rev. The expression assumes a cylindrical cut and neglects the small difference between initial and final diameters. For a radial depth of cut a_p, a more complete approximation is:

Here Q is in mm³/min if D, f, and a_p are in mm and N is in rev/min. Actual values vary with engagement, tool path, interrupted cutting, and machine dynamics.

Cutting speed for a rotating workpiece is:

where v is peripheral speed, commonly in mm/min if D is in mm and N is in rev/min. Dividing by 1000 gives m/min. Cutting speed, feed, and depth of cut must be selected with regard to tool material, workpiece material, rigidity, coolant, chip control, and required finish.

Worked example. A turning operation uses a diameter of 50 mm, speed of 800 rev/min, feed of 0.20 mm/rev, and radial depth of cut of 1.5 mm. The approximate material-removal rate is:

Q ≈ π(50)(800)(0.20)(1.5) = 37,699 mm³/min, or approximately 37.7 cm³/min. The corresponding cutting speed is v = π(50)(800) = 125,664 mm/min, or 125.7 m/min. These are planning estimates; tool limits and machine power must still be checked.

Machining offers flexibility and accuracy but generates chips, consumes cutting tools, and can require significant energy. Grinding achieves fine dimensions and surface finish but may cause thermal damage if heat is not controlled. EDM removes electrically conductive material through controlled sparks and is valuable for hard materials and intricate cavities, although it is relatively slow and requires dielectric management.

5. Joining Processes

Joining may be permanent or detachable. The selection affects strength, sealing, repair, inspection, and disassembly.

Fusion and solid-state welding

In fusion welding, joint surfaces melt and solidify. Processes include shielded metal arc welding, gas metal arc welding, gas tungsten arc welding, submerged arc welding, laser welding, and resistance spot welding. Heat input influences the weld pool, heat-affected zone, residual stress, distortion, and metallurgical transformations.

In solid-state welding, joining occurs without bulk melting. Friction welding, friction-stir welding, diffusion bonding, and ultrasonic welding are examples. These processes can reduce solidification defects and are useful for selected dissimilar or difficult-to-fuse materials.

Brazing, soldering, adhesives, and mechanical fastening

Brazing uses a filler metal that melts above 450 °C but below the melting temperature of the base materials. Soldering uses a lower-temperature filler. Both rely on capillary flow and clean, properly gapped surfaces.

Adhesive bonding distributes load over an area and can join dissimilar materials while providing sealing and vibration damping. Its limitations include surface preparation, cure time, temperature sensitivity, aging, and difficulty of nondestructive inspection.

Bolts, screws, rivets, clips, and snap-fits support serviceability or allow assembly without heat. Threaded joints require appropriate preload, which can be estimated from torque but is strongly affected by friction. A production design should control the actual clamping force rather than assuming that torque alone gives a precise preload.

6. Heat Treatment and Surface Engineering

Heat treatment changes a material's microstructure through controlled heating, holding, and cooling. In steels, transformations between ferrite, pearlite, bainite, and martensite strongly influence hardness and toughness.

• Annealing generally softens material, relieves stress, and improves ductility.
• Normalizing refines or homogenizes the structure of many steels.
• Quenching rapidly cools austenitized steel to form hard structures, often martensite.
• Tempering reheats quenched steel below the transformation temperature to reduce brittleness and adjust hardness and toughness.
• Aging strengthens some alloys through controlled precipitation.

Heat-treatment specifications must identify material grade, austenitizing or solution-treatment temperature, time, cooling medium, hardness range, and inspection method. Distortion and residual stress may require fixturing, machining allowances, or process modification.

Surface engineering modifies the surface without necessarily changing the bulk material. Examples include carburizing, nitriding, induction hardening, thermal spraying, physical vapor deposition, chemical vapor deposition, electroplating, anodizing, and shot peening. Selection depends on the dominant failure mode: abrasive wear, adhesive wear, corrosion, fatigue, galling, friction, or electrical contact degradation.

A hard coating is not automatically a good solution. Adhesion, substrate support, coating thickness, thermal expansion mismatch, porosity, and edge effects must be evaluated. Environmental and regulatory requirements may restrict hazardous plating chemistries or encourage alternatives.

7. Additive Manufacturing

Additive manufacturing (AM) builds components by depositing or selectively consolidating material from digital data. Important categories include polymer extrusion, vat photopolymerization, powder-bed fusion, directed-energy deposition, binder jetting, and material jetting.

AM is valuable for prototypes, customized products, lightweight lattices, internal channels, low-volume production, and replacement parts. It can reduce assembly count by integrating several functions into one component. However, AM may involve anisotropic properties, residual stress, rough surfaces, support structures, powder handling risks, limited build envelopes, slow throughput, and substantial post-processing.

Design for additive manufacturing differs from conventional design. Orientation influences strength, support requirements, surface quality, and build time. Designers should consider minimum feature size, trapped powder, thermal distortion, scan strategy, access for finishing, and inspection of internal features. Qualification is especially important for safety-critical parts because defects may be difficult to detect.

AM should not be treated as universally sustainable. It can reduce scrap and enable lightweighting, but energy per unit volume may be high, and powder production, inert gas, failed builds, and post-processing contribute to environmental impact. A life-cycle comparison is more reliable than a simple comparison of material waste.

8. Production Systems and Automation

A production system combines facilities, equipment, people, information, material handling, quality control, maintenance, and management policies.

• Project production creates a unique product at a fixed location, such as a bridge or large machine.
• Job-shop production uses general-purpose equipment for varied, low-volume work.
• Batch production makes groups of similar products, balancing flexibility and efficiency.
• Cellular manufacturing groups machines according to product families and supports reduced travel and lead time.
• Flow or line production uses a sequence of dedicated operations for high-volume standardized products.
• Continuous production operates nearly continuously for materials such as chemicals, cement, and steel.

Automation may be fixed, programmable, or flexible. Industrial robots support welding, handling, dispensing, inspection, and machine tending. CNC systems provide programmable machining. PLCs coordinate sensors, actuators, safety interlocks, and sequence logic. Manufacturing execution systems (MES) connect production orders, traceability, quality data, and performance information.

A useful productivity measure is overall equipment effectiveness (OEE):

where each factor is expressed as a fraction between 0 and 1. Availability is typically operating time divided by planned production time; performance compares actual production rate with the ideal rate; quality is good units divided by total units. Definitions must be applied consistently, because maintenance exclusions and ideal-cycle assumptions can otherwise make comparisons misleading.

Worked example. Suppose a machine has availability 0.90, performance 0.85, and quality 0.98. Then:

Thus OEE is approximately 75.0%. Improvement should be directed toward the largest losses rather than treating OEE as a target independent of safety, quality, and delivery requirements.

9. Design for Manufacturability and Assembly

DFMA integrates manufacturing and assembly considerations during design rather than after a design is frozen.

Design for manufacturability

A manufacturable design:

• selects a process compatible with material and required performance;
• uses standard materials, sizes, radii, fasteners, and tooling where practical;
• avoids unnecessary tight tolerances;
• provides suitable draft for molding and casting;
• uses uniform wall thickness where possible;
• avoids deep, narrow, or inaccessible machining features;
• provides tool access and datum references;
• separates critical functional surfaces from noncritical cosmetic surfaces;
• specifies surface treatments only where needed; and
• includes realistic inspection and process-control methods.

Tolerance should be functional, not decorative. Tight tolerances increase machining time, tool wear, inspection effort, and rejection risk. The design team should use tolerance analysis to determine which dimensions actually control function.

Design for assembly

Assembly cost is reduced when a product has fewer parts, fewer orientations, fewer fastener types, and easier access. Parts should locate themselves, resist incorrect orientation, and be easy to grasp and insert. Symmetry can reduce orientation errors; intentional asymmetry can provide poka-yoke, or mistake-proofing, when a component must be inserted only one way.

A conceptual assembly-efficiency indicator can be used during comparison:

where E_a is an index, t_min is an estimated theoretical minimum assembly time, N is the actual number of parts, and t_a is average assembly time per part. This is a comparative design aid, not a universal law; values depend on the organization’s timing method and product type.

Designers must balance integration against serviceability. Combining parts may reduce assembly but make repair or replacement difficult. For mechatronic products, connectors, wiring, sensors, batteries, and electronic modules require access, strain relief, electromagnetic compatibility, thermal management, and error-proof connection.

10. Quality, Process Capability, and Inspection

Quality is designed into the process. Inspection alone cannot compensate for an unstable or poorly understood process.

A process is stable when its variation is predictable over time. It is capable when its predictable variation fits within the specification limits and the process is centered adequately. For a normally distributed characteristic with process mean μ and standard deviation σ, capability indices are commonly defined as:

Here USL and LSL are upper and lower specification limits. C_p measures potential capability assuming centering; C_pk also reflects displacement of the mean. These indices assume a meaningful estimate of within-process variation and are inappropriate when the process is unstable or the distribution is strongly non-normal without suitable analysis.

Worked example. A shaft diameter specification is 20.00 ± 0.05 mm, so USL = 20.05 mm and LSL = 19.95 mm. If the process mean is 20.02 mm and standard deviation is 0.01 mm:

C_p = (20.05 − 19.95)/(6×0.01) = 1.67

C_pk = min[(20.05−20.02)/(3×0.01), (20.02−19.95)/(3×0.01)] = min(1.00, 2.33) = 1.00

The process has reasonable spread relative to the tolerance but is shifted toward the upper limit. Centering the process could improve capability without necessarily changing the machine.

Quality tools include control charts, measurement-system analysis, first-article inspection, sampling plans, capability studies, failure-mode and effects analysis (FMEA), design of experiments, and root-cause analysis. Measurement-system variation must be separated from process variation. A gage that is inaccurate or poorly repeatable can lead to incorrect decisions about process capability.

11. Manufacturing Economics and Sustainability

A simplified annual cost model can support early process selection:

where C_total is total relevant cost, C_f is fixed or tooling cost, N is production quantity, C_v is variable cost per unit, C_q is quality-related cost, C_e is energy and environmental cost, and C_l is logistics or other relevant cost. The model is only as good as its cost definitions and should not double-count labor or overhead.

For two alternatives, a break-even quantity occurs when their total costs are equal. If fixed costs are F₁ and F₂, and variable costs per unit are v₁ and v₂, then, provided v₁ ≠ v₂,

This result ignores capacity, quality differences, taxes, financing, and changing costs, so it is a screening calculation rather than a complete investment analysis.

Sustainable manufacturing seeks to reduce material loss, energy use, hazardous substances, water consumption, emissions, and waste while maintaining product function and worker safety. Strategies include near-net-shape production, efficient nesting, closed-loop coolant management, renewable energy, remanufacturing, repairable assemblies, modular design, and process monitoring. Life-cycle assessment should consider raw-material extraction, manufacturing, transportation, use, maintenance, and end-of-life treatment.

Ethical responsibilities include safe working conditions, responsible sourcing of minerals and materials, honest reporting of quality data, protection of operators from machine hazards, and avoidance of unsafe pressure to meet production targets. Automation must be introduced with risk assessment, safeguarding, training, and clear accountability.

12. Applied Case: Illustrative Robotic Actuator Housing

Background

A manufacturer produces 8,000 aluminum housings per year for a robotic actuator. The housing contains mounting bosses, cable passages, bearing seats, and an internal cavity. The existing design is machined from a solid billet. It meets dimensional requirements but has long cycle time, high chip volume, and variable assembly alignment.

Problem

The company wants to reduce unit cost and mass while maintaining a bearing-seat tolerance of ±0.025 mm, leak resistance, stiffness, and reliable assembly. The annual volume is too high for repeated one-off machining but too low to justify a highly specialized transfer line.

Analysis

Three routes are considered:

1. Five-axis machining from billet: low tooling cost, high material waste, flexible, and capable of tight tolerances.
2. High-pressure die casting followed by machining of bearing seats and datum surfaces: higher tooling cost, lower material waste, high repeatability, and possible porosity.
3. Metal powder-bed fusion: excellent geometric freedom, but relatively high cost, build-time limitations, powder handling, and extensive qualification.

The design team performs tolerance analysis, casting simulation, finite-element analysis, and assembly trials. The housing is redesigned with more uniform walls, draft, radiused transitions, accessible datums, and machining allowances on critical seats. Noncritical surfaces are assigned wider tolerances. Bearing seats remain machined after casting because the as-cast process cannot reliably meet the functional tolerance.

Approach and solution

The selected route is die casting followed by heat treatment where appropriate, CNC machining of datums and bearing seats, leak testing, surface treatment, and robotic assembly. A locating feature is made intentionally asymmetric to prevent incorrect orientation. The assembly uses a standard fastener and a connector with mechanical keying.

A control plan monitors melt condition, die temperature, casting fill indicators, critical dimensions, leak rate, and tool wear. Automated vision checks confirm connector presence and housing orientation. A capability study is performed only after the process is demonstrated to be stable. Preventive maintenance is linked to shot count and measured tool condition rather than calendar time alone.

Outcome

The redesigned product reduces machining time and chip generation while retaining precision at functional surfaces. Assembly errors decline because of keyed connectors and poka-yoke features. The die-casting route increases initial tooling expenditure, so its economic advantage depends on achieving the forecast volume and controlling scrap. The company also establishes a recycling route for clean aluminum scrap and evaluates energy use per acceptable housing rather than energy per machine hour.

Learning points

The case illustrates that process selection is a system decision. No single process provides all desired properties. Near-net-shape casting reduces bulk material removal, machining supplies precision, surface treatment supports durability, automation improves repeatability, and quality planning verifies that the complete route—not merely one operation—meets requirements.

13. Contemporary Developments and Best Practices

Industry 4.0 links machines, sensors, production planning, quality systems, and digital models. Useful applications include real-time tool-condition monitoring, predictive maintenance, digital work instructions, machine-vision inspection, traceability, and digital twins. Artificial intelligence can detect patterns in vibration, acoustic emission, images, and process histories, but models require representative data, validation, cybersecurity, and human oversight. A prediction system should not be trusted merely because it achieves high accuracy on historical training data.

Best practice is to:

1. Define functional requirements and critical-to-quality characteristics before selecting a process.
2. Select materials and processes concurrently, not sequentially.
3. Use process-specific design rules and realistic tolerances.
4. Prototype the highest-risk features early.
5. Validate measurement systems before capability studies.
6. Design inspection into the process and use feedback to prevent recurrence.
7. Automate repetitive, hazardous, or variation-sensitive work while preserving safe human access and decision authority.
8. Compare alternatives using total cost, capacity, quality, lead time, and life-cycle effects.
9. Document change control, traceability, maintenance, and operator training.
10. Treat sustainability and worker safety as design requirements rather than optional improvements.

Chapter Summary

Manufacturing processes transform materials through solidification, deformation, removal, joining, thermal treatment, surface modification, or layerwise addition. Casting and molding support complex shapes and high productivity; forming provides material efficiency and favorable mechanical properties; machining provides flexibility and precision; joining creates assemblies; heat treatment adjusts bulk properties; surface engineering controls wear and corrosion; and additive manufacturing enables complex, customized, and low-volume parts.

Production systems range from job shops to continuous lines and increasingly combine CNC equipment, robots, PLCs, inspection systems, MES platforms, and data analytics. DFMA reduces cost and risk by considering process capability, tolerances, tool access, part count, orientation, serviceability, and mistake-proofing during design. Quality depends on stable processes, suitable measurement systems, capability analysis, and feedback control. Economic selection must include tooling, variable cost, quality, capacity, energy, logistics, and life-cycle consequences. Sustainable and ethical manufacturing requires safe work, responsible materials, waste reduction, truthful data, and accountable automation.

Key Terms

Manufacturing process: A method of transforming material into a product or component.

Casting: Forming a part by solidifying material in a mold.

Forming: Shaping material through plastic deformation.

Machining: Removing material with a cutting or abrasive tool.

Joining: Connecting two or more components into an assembly.

Molding: Shaping a material in a cavity, commonly under pressure.

Heat treatment: Controlled heating and cooling used to alter material properties.

Surface engineering: Modification of a surface to improve functional performance.

Additive manufacturing: Layerwise production from digital geometry.

DFMA: Design for manufacturability and assembly.

Poka-yoke: Mistake-proofing that prevents or detects incorrect operation.

Process capability: The ability of a stable process to satisfy specification limits.

USL: Upper specification limit.

LSL: Lower specification limit.

OEE: Overall equipment effectiveness, combining availability, performance, and quality.

FMEA: Failure-mode and effects analysis for identifying and prioritizing risks.

MES: Manufacturing execution system used to coordinate and record production.

Near-net-shape: Production close to final geometry, minimizing subsequent removal.

Traceability: Ability to connect a product with its materials, processes, measurements, and history.

Life-cycle assessment: Evaluation of environmental impacts across a product’s life.

Review Questions

Short Answer Questions

1. What are the principal differences between casting, forming, and machining?
2. Why are bearing seats often machined after casting?
3. State two advantages and two limitations of additive manufacturing.
4. What do C_p and C_pk measure?
5. Name three DFMA principles that can reduce assembly errors.

Long Answer Questions

1. Compare sand casting, die casting, and investment casting for a mechatronic housing.
2. Explain how heat treatment and surface engineering can be combined to improve the performance of a steel shaft.
3. Discuss the effects of tolerance selection on cost, quality, and assembly.
4. Explain the operation of a flexible manufacturing system and identify suitable automation technologies.
5. Describe how sustainability should influence manufacturing-process selection across a product life cycle.

Analytical / Application Questions

1. A process has USL = 10.10 mm, LSL = 9.90 mm, mean = 10.04 mm, and standard deviation = 0.02 mm. Calculate C_p and C_pk, and interpret the result.
2. A machined part costs $18 per unit plus $24,000 tooling, while a molded part costs $7 per unit plus $112,000 tooling. Ignoring other costs, calculate the break-even quantity and explain which option is preferable above that quantity.
3. Propose a manufacturing route for a low-volume aluminum robotic gripper with complex internal channels, precision bearing locations, and a requirement for repairability. Justify the process sequence, inspection strategy, and sustainability considerations.

Multiple Choice Questions with Answers

Question 1

Which process is most directly associated with shaping a material through plastic deformation rather than removing material?

A. Forging

B. Turning

C. Investment casting

D. Electroplating

Correct Answer: A. Forging

Question 2

What is a principal advantage of die casting for suitable nonferrous alloys?

A. It requires no tooling

B. It provides high productivity and repeatable complex shapes

C. It produces only porous parts

D. It is limited to one-off prototypes

Correct Answer: B. It provides high productivity and repeatable complex shapes

Question 3

In the turning estimate v = πDN, what does v represent?

A. Feed per revolution

B. Radial depth of cut

C. Peripheral cutting speed

D. Material density

Correct Answer: C. Peripheral cutting speed

Question 4

Which heat-treatment operation generally follows quenching to reduce brittleness and adjust toughness?

A. Tempering

B. Casting

C. Blanking

D. Anodizing

Correct Answer: A. Tempering

Question 5

A process has availability 0.90, performance 0.80, and quality 0.95. What is its OEE?

A. 68.4%

B. 72.0%

C. 76.0%

D. 85.5%

Correct Answer: A. 68.4%

Question 6

If C_p is substantially higher than C_pk, what is the most likely interpretation?

A. The process spread is zero

B. The process is centered perfectly

C. The process has acceptable potential spread but is off-center

D. The specification limits are absent

Correct Answer: C. The process has acceptable potential spread but is off-center

Question 7

Which feature is most consistent with design for assembly?

A. Many unique fastener types

B. Parts that require several possible orientations

C. Keyed connectors and self-locating features

D. Hidden tools and inaccessible joints

Correct Answer: C. Keyed connectors and self-locating features

Question 8

Which additive-manufacturing issue is strongly affected by build orientation?

A. Anisotropy and support requirement

B. The atomic number of the material

C. The legal ownership of the CAD file

D. The nominal voltage of a sensor

Correct Answer: A. Anisotropy and support requirement

Question 9

What is the main purpose of a riser in many casting designs?

A. To supply liquid material during solidification shrinkage

B. To sharpen a cutting tool

C. To measure surface roughness

D. To provide electrical insulation

Correct Answer: A. To supply liquid material during solidification shrinkage

Question 10

Which statement best describes a stable process in quality control?

A. Its variation is predictable over time

B. Every part is identical with no variation

C. It always has a centered mean regardless of specifications

D. It requires inspection but no process control

Correct Answer: A. Its variation is predictable over time