1. Overview
Manufacturing Process Classification is a section that systematically classifies manufacturing processes according to their common principles and purposes. If Manufacturing Fundamentals explains the basic way of thinking about manufacturing, Manufacturing Process Classification organizes how actual manufacturing processes should be divided and understood.
In mechanical design, classifying manufacturing processes is not simply a matter of listing process names. Designers must select an appropriate manufacturing process by considering part geometry, material, required accuracy, surface quality, production volume, cost, assembly method, and maintenance conditions.
Even for the same part, the design structure can change significantly depending on the manufacturing method. For example, a housing can be produced by casting followed by machining, by a welded sheet-metal structure, or by CNC machining from an aluminum block. If production volume is low, material removal may be suitable. If the part is produced repeatedly in large quantities, casting or forming may be more economical.
Therefore, manufacturing process classification provides a framework for answering the following questions.
By what manufacturing principle is this part made?
Is the material removed, deformed, or melted and shaped?
Are parts joined, is the surface improved, or is precision enhanced?
Is this process suitable for the required geometry, tolerance, cost, and production volume?
Manufacturing Process Classification is a structural map of manufacturing knowledge that connects the later topics of Primary Shaping, Forming, Material Removal, Joining, Additive Manufacturing, Heat Treatment, Surface Engineering, and Finishing and Precision Processing.
2. Purpose of Classifying Manufacturing Processes
The purpose of classifying manufacturing processes is to help designers understand manufacturing methods systematically and make appropriate process decisions during the design stage.
There are many manufacturing processes, including turning, milling, drilling, grinding, casting, forging, extrusion, injection molding, welding, bonding, plating, heat treatment, polishing, and additive manufacturing. If these processes are memorized only as names, they are difficult to apply effectively in design.
What matters is understanding the manufacturing principle behind each process.
The purposes of manufacturing process classification are as follows.
Systematize manufacturing processes by principle.
Clarify the relationship between design geometry and manufacturing method.
Provide process selection criteria suitable for material properties.
Distinguish processes according to tolerance and surface quality requirements.
Determine economical manufacturing methods according to production volume.
Understand connections with post-processing, assembly, and inspection.
Reflect the difference between prototyping and mass production.
In other words, manufacturing process classification is not a simple list. It is a decision-making framework that helps designers convert products into structures that can actually be manufactured.
3. Basic Viewpoint of Manufacturing Process Classification
Manufacturing processes can be classified by various criteria. In the Design-OS Manufacturing Track, processes are classified based on how the material changes, so that designers can judge manufacturing methods more easily.
The basic viewpoints are as follows.
Based on this viewpoint, manufacturing processes can be classified as follows.
Classification | Core Principle | Representative Items |
|---|---|---|
Primary Shaping | Creates a basic shape from raw material | Casting, injection molding, powder forming |
Forming | Deforms material without removing it | Forging, rolling, extrusion, pressing, bending |
Material Removal | Removes material to create the shape | Turning, milling, drilling, grinding, EDM |
Joining | Connects multiple parts into one structure | Welding, brazing, bonding, riveting, bolted fastening |
Additive Manufacturing | Builds the shape by adding material layer by layer | FDM, SLA, SLS, DMLS |
Heat Treatment and Property Modification | Changes the internal properties of the material | Quenching, tempering, annealing, carburizing, nitriding |
Surface Engineering | Improves surface function | Plating, coating, anodizing, passivation |
Finishing and Precision Processing | Improves precision and surface quality | Grinding, lapping, honing, polishing |
These classifications are not completely independent from one another. In actual manufacturing, several processes are usually combined in sequence. For example, a cast part may first receive its basic shape through Primary Shaping, then have reference surfaces and holes machined through Material Removal, then receive surface protection through Surface Engineering, and finally be joined with other parts during the Joining or Assembly stage.
4. Primary Shaping
Primary Shaping is a group of processes that create the basic shape of a part from raw material. Materials such as liquid, molten metal, powder, or resin are shaped through molds or dies.
Representative processes include the following.
Casting
Injection molding
Die casting
Powder forming
Compression molding
Blow molding
Initial extrusion shaping
The main characteristic of Primary Shaping is that complex shapes can often be produced in a single process. Casting and injection molding are especially economical in mass production. However, they require molds or dies, so the initial investment is high and design changes are difficult.
Designers should consider the following items.
Shrinkage rate
Draft angle
Mold parting line
Gate location
Cooling conditions
Porosity or shrinkage defects
Machining allowance
Uniform wall thickness
Rib and boss structure
Mold manufacturing cost
For example, when designing a cast part, machining every surface reduces the advantages of casting. It is preferable to define only the functionally necessary areas as post-machining targets, such as reference surfaces, bearing mounting areas, bolt seating surfaces, and locating surfaces.
In injection-molded parts, non-uniform wall thickness can cause sink marks, warpage, or incomplete filling. Therefore, uniform thickness, appropriate ribs, draft angles, and gate locations must be considered.
Primary Shaping is suitable under the following conditions.
Complex three-dimensional geometry is required.
Production volume is sufficiently high.
Material waste must be reduced.
Mold investment is economically justified.
Post-machining areas can be limited.
5. Forming
Forming is a group of processes that change the shape of material by applying external force without removing material. It uses plastic deformation to create the desired shape.
Representative processes include the following.
Forging
Rolling
Extrusion
Press forming
Sheet metal bending
Deep drawing
Spinning
Roll forming
The key point of Forming is that material is not removed. Therefore, material utilization is high, productivity is good, and the metal grain structure can be strengthened along the direction of deformation. Forged parts are especially suitable for components requiring high strength and fatigue resistance.
Designers should consider the following items.
Material ductility
Forming limit
Springback
Minimum bend radius
Die load
Lubrication conditions
Risk of cracking
Residual stress
Dimensional change after forming
Need for post-machining
In sheet metal bending, the relationship between bend radius and sheet thickness is important. If the bend radius is too small, cracking may occur. If holes are located too close to the bend, they may deform. In addition, due to springback, the actual bend angle may differ from the die angle.
In forging, the direction of metal flow is important. Parts that receive repeated loads, such as shafts, gear blanks, and high-load links, can gain improved strength and durability through forging.
Forming is suitable under the following conditions.
High productivity is required.
Material waste must be reduced.
Strength and fatigue life are important.
A constant cross-section or repeated geometry is required.
Tooling cost can be recovered through production volume.
6. Material Removal
Material Removal is a group of processes that create the desired shape and precision by removing unnecessary material. It is one of the most common methods for manufacturing machine parts and provides high precision and flexibility.
Representative processes include the following.
Turning
Milling
Drilling
Boring
Reaming
Tapping
Broaching
Grinding
EDM
Waterjet cutting
Laser cutting
The advantage of Material Removal is that it can produce various shapes with high precision. Since it can be performed without molds, it is suitable for prototypes, low-volume production, and precision parts. However, because it removes material, material loss occurs, and machining time increases as the geometry becomes more complex.
Designers should consider the following items.
Tool access
Machining reference surface
Clamping direction
Number of setups
Cutting conditions
Tool deflection
Internal corner radius
Machinability of deep pockets
Surface roughness
Chip evacuation
Machining distortion
In CNC milling, an internal sharp right-angle corner cannot be produced with a rotating tool. Therefore, internal corners should be designed with a radius equal to or larger than the tool radius. Deep and narrow grooves require long tools, which can cause tool chatter and dimensional error.
In turned parts, designers must consider chucking reference, center support, tool access direction, undercuts, and threading allowance. In ground parts, thermal distortion, grinding burn, surface roughness, and geometric accuracy are important.
Material Removal is suitable under the following conditions.
Precision is important.
The part is a prototype or low-volume production item.
Mold manufacturing is not economical.
Post-machining reference surfaces are required.
Complex assembly reference surfaces or holes are required.
7. Joining
Joining is a group of processes that connect two or more parts into one structure. It is used to integrate parts or to create structures that can be disassembled.
Representative processes include the following.
Arc welding
TIG welding
MIG welding
Spot welding
Laser welding
Brazing
Soldering
Adhesive bonding
Riveting
Bolted fastening
Pin fastening
Clamp fastening
Joining is widely used for large structures, frames, tanks, piping, covers, sheet-metal structures, and module connections. Welding can create strong joints, but it also causes thermal distortion and residual stress. Bolted fastening allows disassembly and maintenance, but it requires fastening space, anti-loosening measures, and assembly time.
Designers should consider the following items.
Joint strength
Thermal distortion
Residual stress
Welding torch access
Fastening tool access
Disassembly
Corrosion risk
Fatigue strength
Sealing performance
Post-processing feasibility
Inspection feasibility
In welded structures, welding sequence and heat input are very important. If precision reference surfaces are required, the design should assume machining after welding. In food machinery, welded areas must also consider polishability and cleanability, and should avoid gaps or areas where contamination can accumulate.
In bolted structures, designers must consider fastening direction, tool space, washer use, anti-loosening measures, tightening torque, and thread engagement length. For parts that require maintenance, bolted or clamped structures may be more suitable than welding.
Joining is suitable under the following conditions.
Multiple parts must be connected into one structure.
Large structures must be fabricated in divided sections.
Different materials must be joined.
A disassemblable structure is required for maintenance.
Welding, fastening, or bonding must be selected according to function.
8. Additive Manufacturing
Additive Manufacturing is a group of processes that create the desired shape by adding material layer by layer. While conventional manufacturing methods remove or deform material, additive manufacturing builds geometry by adding material only where needed.
Representative processes include the following.
FDM
SLA
DLP
MSLA
SLS
DMLS
Binder Jetting
Material Jetting
The advantage of Additive Manufacturing is its high geometric freedom. It can easily create internal channels, lattice structures, lightweight structures, complex curved surfaces, and integrated structures. It is also useful for early-stage design verification because prototypes can be produced quickly without molds.
However, additive manufacturing has the following limitations.
Surface quality may be low.
Strength may vary depending on build direction.
Support removal may be required.
Dimensional accuracy is limited depending on the process.
Production speed may be slow.
Post-processing is often required.
Material choices may be limited.
Designers should consider the following items.
Build orientation
Need for support structures
Layer thickness
Surface roughness
Strength anisotropy
Thermal distortion
Shrinkage
Post-curing or heat treatment
Post-machining reference surfaces
Inspection feasibility of internal structures
In FDM, tensile strength and interlayer bonding vary depending on build direction. SLA and DLP provide good surface quality, but post-curing and resin shrinkage must be considered. SLS and DMLS are suitable for complex structures, but post-processing, powder removal, and internal stress management are required.
Additive Manufacturing is suitable under the following conditions.
Complex geometry is required.
Rapid prototyping is needed.
Low-volume production without molds is required.
Lightweight structures are needed.
Internal channels or integrated structures are needed.
Shapes that are difficult to produce with conventional processes must be realized.
9. Heat Treatment and Property Modification
Heat Treatment and Property Modification is a group of processes that change the internal structure and properties of a material. These processes do not directly create the shape, but they strongly affect strength, hardness, toughness, wear resistance, and fatigue life.
Representative processes include the following.
Quenching
Tempering
Annealing
Normalizing
Carburizing
Nitriding
Induction hardening
Precipitation hardening
Stress-relief heat treatment
Heat treatment is used to improve the mechanical properties of parts. For example, gears, shafts, cams, bearing contact areas, and wear parts may require hardness and wear resistance. However, heat treatment can cause distortion, dimensional change, and residual stress, so it must be considered during design.
Designers should consider the following items.
Required hardness
Hardening depth
Toughness
Wear conditions
Heat-treatment distortion
Need for post-machining
Risk of surface cracking
Residual stress
Material suitability for heat treatment
Inspection method
If precision dimensions are required after heat treatment, grinding or post-machining should be considered. Carburizing or nitriding can increase surface hardness while maintaining internal toughness, making them suitable for gears and shafts. Stress-relief heat treatment is used to reduce distortion in welded structures or large machined parts.
This process is suitable under the following conditions.
Hardness and wear resistance are required.
Fatigue life is important.
A hard surface and tough core structure are required.
Residual stress after welding or machining must be reduced.
Dimensional stability is required before or after precision machining.
10. Surface Engineering
Surface Engineering is a group of processes that improve the function of a part surface. Since the surface directly contacts the external environment, it greatly affects corrosion resistance, wear resistance, friction properties, cleanability, and appearance quality.
Representative processes include the following.
Plating
Anodizing
Coating
Passivation
Pickling
Electropolishing
Surface nitriding
Ceramic coating
Teflon coating
Shot peening
Surface Engineering is used to supplement surface functions that cannot be sufficiently achieved by the base material alone. For example, carbon steel parts have good strength but are vulnerable to corrosion, so painting or plating may be required. Aluminum parts can improve surface hardness and corrosion resistance through anodizing. Stainless steel food-contact parts can improve corrosion resistance and cleanability through passivation and electropolishing.
Designers should consider the following items.
Surface treatment thickness
Dimensional change
Adhesion
Surface preparation condition
Corrosion resistance
Wear resistance
Food-contact suitability
Cleanability
Surface roughness after treatment
Need for masking
Drainage of treatment liquids
Surface treatment can affect dimensions. Plating or coating adds thickness to the surface, so treatment thickness must be reflected in the tolerance of fitted areas. In addition, treatment liquids may remain in blind holes or internal spaces, so drainage structures should be considered.
Surface Engineering is suitable under the following conditions.
The part is used in a corrosive environment.
Friction and wear must be reduced.
Cleanability is required in food, medical, or chemical environments.
Appearance quality is important.
The base material alone cannot provide the required surface function.
11. Finishing and Precision Processing
Finishing and Precision Processing is a group of processes that improve the final precision and surface quality of a part. These processes are applied when general machining cannot meet the required accuracy or surface roughness.
Representative processes include the following.
Grinding
Lapping
Honing
Polishing
Buffing
Superfinishing
Deburring
Precision polishing
Electropolishing
These processes are important for completing functional surfaces. Bearing mounting surfaces, sliding surfaces, sealing surfaces, gear tooth surfaces, hydraulic cylinder inner surfaces, and food-contact surfaces may require high surface quality and precision.
Designers should consider the following items.
Required surface roughness
Dimensional accuracy
Geometric accuracy
Grinding allowance
Thermal effect
Edge treatment
Burr removal
Cleanability
Measurement feasibility
Distinction between functional and non-functional surfaces
Grinding can achieve high dimensional accuracy and surface quality, but damage or distortion from grinding heat must be controlled. Lapping and honing are suitable for very high surface quality and geometric accuracy. Polishing and buffing are used to improve appearance and cleanability, but they can affect functional dimensions.
In food machinery, deburring and surface polishing are very important. Sharp edges, weld beads, small gaps, and rough surfaces can cause contamination accumulation and poor cleanability.
Finishing and Precision Processing is suitable under the following conditions.
High dimensional accuracy is required.
Low surface roughness is required.
Sealing performance is important.
Friction and wear must be reduced.
Cleanability of food-contact surfaces must be improved.
Final appearance quality is important.
12. Combined Structure of Manufacturing Processes
Actual products are rarely completed with only one manufacturing process. Most parts and products are made through a sequence of multiple processes.
For example, a machine frame may follow this process flow.
A cast housing may follow this process flow.
A stainless steel food-machinery part may follow this process flow.
In this way, manufacturing processes do not exist independently. They are connected within a complete manufacturing flow. Designers must understand not only individual processes but also the overall process sequence.
When reviewing process combinations, the following questions should be checked.
Which process must be performed first?
Will heat treatment or welding cause distortion?
Are reference surfaces secured for post-machining?
Are deburring and cleaning required before surface treatment?
At which stage should final inspection criteria be verified?
Which processes must be completed before assembly?
Good manufacturing design considers the entire process sequence, not only individual processes.
13. Manufacturing Process Selection Criteria
Manufacturing process selection is not determined by a single criterion. Designers must review several conditions at the same time.
The main selection criteria are as follows.
Selection Criterion | Review Items |
|---|---|
Geometric Complexity | Whether the shape is simple, has complex internal structures, or includes many curved surfaces |
Material | Whether the material is metal, plastic, rubber, ceramic, or composite |
Precision | Whether general tolerance, precision tolerance, or ultra-precision machining is required |
Surface Quality | Whether the surface is an appearance surface, sealing surface, sliding surface, or food-contact surface |
Production Volume | Whether the production is one-off, low-volume, medium-volume, or mass production |
Initial Investment | Whether molds, jigs, or dedicated equipment are required |
Unit Cost | Whether unit cost decreases as production volume increases |
Lead Time | Whether rapid prototyping or long-term mass production is required |
Post-processing | Whether heat treatment, surface treatment, polishing, or cleaning is required |
Assembly | Whether fastening, welding, alignment, and disassembly are easy |
Inspection | Whether the part can be verified with measuring equipment |
Maintainability | Whether disassembly and replacement are possible |
For example, a low-volume precision part may be suitable for CNC machining. In contrast, a mass-produced aluminum housing may be suitable for die casting followed by partial CNC finishing. A thin cover part is more economical when made by sheet metal cutting and bending than by machining from a solid block. A part requiring complex internal channels may be better suited for additive manufacturing.
Therefore, manufacturing process selection is not about finding the “best” process in general. It is about finding the process most suitable for the product conditions.
14. Application of Manufacturing Process Classification in Food Machinery
In food machinery and meat-processing machinery, hygiene, cleanability, corrosion resistance, and foreign-material prevention are more important than in general industrial machinery when selecting manufacturing processes.
Manufacturing processes commonly used in food machinery include the following.
Stainless steel sheet metal cutting
Bending
TIG welding
Weld polishing
CNC machining
Electropolishing
Passivation
Deburring
Surface polishing
Hygienic pipe welding
Machining of food-grade plastics
In food machinery, it is not sufficient to simply make parts strong and accurate. Food residue must not remain on the surface, cleaning liquid must not be trapped, and welds and edges must not become contamination sources.
Designers should especially consider the following items.
Surface roughness of food-contact surfaces
Possibility of polishing welded areas
Removal of gaps and dead corners
Sloped surfaces to prevent water pooling
Disassembly for cleaning
Removal of sharp edges
Possibility of foreign-material generation
Corrosion resistance against cleaning agents and sanitizers
Food suitability of bearings and seals
Possibility of lubricant contact
For example, stainless steel frames must consider distortion after welding, and food-contact areas must be polished so that weld beads do not remain. Bent sheet-metal structures are useful for reducing gaps, but care must be taken not to create closed spaces that are difficult to clean.
In food machinery, manufacturing process classification is not simply a distinction between production methods. It is a design decision-making criterion for ensuring hygiene and quality.
15. Connection with Other Knowledge Tracks
Manufacturing Process Classification is closely connected with other Knowledge Tracks.
15.1 Connection with Material
Material directly affects manufacturing process selection. Stainless steel requires consideration of weldability and surface treatability. Aluminum requires consideration of machinability and anodizing conditions. Plastics require consideration of thermal deformation, creep, and machining burrs.
15.2 Connection with Mechanism & Motion
Moving parts depend heavily on precision and surface quality. Shafts, bearing housings, sliding guides, cams, and gears are directly affected by manufacturing process selection.
15.3 Connection with Control
Sensor brackets, actuator mounts, wiring holes, control boxes, and cover structures change depending on the manufacturing method. Control components require positional accuracy and maintenance accessibility.
15.4 Connection with Assembly
Manufactured parts must ultimately be assembled. Manufacturing process selection affects assembly references, fastening methods, assembly sequence, and tolerance stack-up.
15.5 Connection with Functional Module
Functional modules must be implemented as actual parts and processes. For example, transfer modules, cutting modules, cleaning modules, and drive modules each require suitable manufacturing processes and materials.
16. Core Thinking
The core thinking in Manufacturing Process Classification is as follows.
Manufacturing processes should not be memorized only by name. They should be understood by how the material changes.
Part geometry is the result of the selected manufacturing process.
Even parts with the same function can have completely different structures depending on the manufacturing method.
Precision is determined by process selection.
Surface quality is connected to post-processing.
Production volume is a key condition in selecting a manufacturing method.
Mold-based processes require high initial cost but are economical in mass production.
Material removal is flexible, but its cost can become high in mass production.
Welded structures are suitable for large structures, but thermal distortion must be considered.
Additive manufacturing is useful for free-form geometry, but strength, surface quality, and post-processing limits must be considered.
Good manufacturing process selection must satisfy function, material, geometry, tolerance, cost, lead time, and quality at the same time.
17. Conclusion
Manufacturing Process Classification is not a document that simply lists manufacturing processes. It is a structure of manufacturing knowledge that explains how designers should understand and select processes in order to actually make a product.
In mechanical design, manufacturing process selection is not a secondary issue decided at the end of design. The manufacturing process directly affects part geometry, material, tolerance, surface quality, cost, production volume, and assembly method.
Therefore, designers should understand manufacturing processes from the following viewpoints.
Processes that shape material from its initial state
Processes that deform material
Processes that remove material
Processes that join parts
Processes that add material layer by layer
Processes that change material properties
Processes that improve surface function
Processes that improve precision and surface quality
Understanding this classification system allows Primary Shaping, Forming, Material Removal, Joining, Additive Manufacturing, Heat Treatment, Surface Engineering, and Finishing and Precision Processing to be understood as one connected manufacturing system.
Manufacturing Process Classification is the second step in the Manufacturing Track and provides the structural foundation for studying each manufacturing process in detail.