Manufacturing processes / methods
& Technical Drawing Differences
Manufacturing processes are controlled methods used to transform raw materials into finished components by altering shape, structure, or properties through mechanical, thermal, chemical, or energy-based means. These processes are selected based on geometry requirements, material behavior, production scale, and functional performance constraints.
Machining (CNC Milling / Turning)
Machining is a subtractive manufacturing process where material is removed from a solid workpiece using cutting tools to achieve the final geometry with high precision. Examples are:
- CNC milling:
Material is removed using rotating cutting tools along multiple axes to create prismatic and complex geometries - CNC turning:
Workpiece rotates while a stationary cutting tool removes material, mainly for cylindrical parts - Drilling:
Creates cylindrical holes using a rotating drill bit - Grinding (precision finishing):
Uses abrasive wheels to achieve very tight tolerances and surface finishes - EDM (Electrical Discharge Machining):
Removes material using electrical discharges, suitable for hard or complex materials
What the drawing looks like?
- Clean orthographic views (front/top/side)
- Dense dimensions everywhere
- Datum symbols (A, B, C)
- GD&T feature control frames
Typical visual signs of machining technical drawing:
- Everything is dimension-driven
- No “manufacturing process hints”
- Very geometric and precise
Key recognition rule ➡️ If you see datums + GD&T everywhere ➡️ machining drawing
Sheet Metal Forming
Sheet metal forming is a manufacturing process where flat metal sheets are plastically deformed into final shapes using bending, stamping, or drawing, without material removal. Examples are:
- Bending:
Plastic deformation of sheet along a straight axis to create angles - Stamping:
Pressing sheet metal into a die to create shapes or cut features - Deep drawing:
Forming sheet into deep hollow shapes using tensile forces - Punching / blanking:
Cutting or removing material using a punch and die system - Rolling (sheet production stage):
Reducing thickness and producing sheet stock through rollers
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What the drawing looks like
- Flat, unfolded 2D shape
- Bend lines clearly marked (dashed)
- Bend angles annotated
- Sometimes two views: flat + formed
Typical visual signs of sheet metal forming technical drawing:
- Looks “unfolded” or “spread out”
- Geometry looks unnatural in 2D (because it is flattened)
- Bend table often present
Key recognition rule ➡️ If it looks like a flattened 3D object ➡️ sheet metal drawing
Injection Molding (Plastics)
Injection molding is a manufacturing process where molten plastic is injected into a mold cavity, cooled, and ejected as a solid part with repeatable geometry. Examples are:
- Injection molding: molten polymer is injected into a closed mold cavity under pressure and solidified
- Overmolding: a second material is molded over an existing part for grip or multi-material functionality
- Insert molding: inserts (metal or other components) are placed into the mold and encapsulated by plastic
- Multi-cavity molding: multiple identical parts are produced in a single mold cycle for high-volume production
What the drawing looks like:
- Clean plastic part outline
- Draft angles marked on vertical walls
- Wall thickness controlled
- Parting line sometimes shown
Typical visual signs of injection molding technical drawing:
- Slightly “industrial product design” look
- Less GD&T everywhere
- Focus on mold behavior, not machining precision
Key recognition rule ➡️ If you see draft angles + plastic housing features ➡️ injection molding
Casting (Sand / Die Casting)
Casting is a manufacturing process where molten material is poured into a mold cavity and solidifies into a near-net-shape component. Examples are:
- Sand casting: molten metal is poured into a sand mold that is broken after solidification
- Die casting: molten metal is injected under pressure into a reusable steel mold for high-volume production
- Investment casting (lost wax): a wax pattern is coated with ceramic, melted out, and replaced with metal
- Gravity casting: molten metal fills a mold under gravity without applied pressure
What the drawing looks like:
- Rough shape + final machined surfaces
- Extra allowances marked
- Internal cavities shown via cores
- Less geometric precision on raw surfaces
Typical visual signs of casting technical drawing:
- “Raw + finished hybrid” drawing
- Machining symbols only on key faces
- More complex internal geometry indicators
Key recognition rule ➡️ If you see machining + rough cast geometry combined ➡️ casting drawing
Welding and Fabrication
Welding is a manufacturing and assembly process where parts are permanently joined using heat, pressure, or both, often causing material fusion at the joint. Examples are:
- MIG welding:
Uses a continuously fed wire electrode and shielding gas for fast industrial welding - TIG welding:
Uses a non-consumable tungsten electrode for high precision welds - Spot welding:
Joins sheet metal by applying localized heat and pressure at points - Arc welding:
General category of welding using electric arc heat for fusion - Riveting (often in hybrid fabrication):
Mechanical fastening using deformable rivets instead of fusion - Bolted assembly fabrication:
Structural assembly using threaded fasteners for disassembly capability
What the drawing looks like
- Assembly views of multiple parts
- Weld symbols everywhere (triangles, lines, notes)
- Minimal part geometry detail
- Focus on joints, not surfaces
Typical visual signs of welding technical drawing:
- Symbol-heavy instead of dimension-heavy. Especially with welding symbols!
- Looks like instructions for assembly, not machining
- Often multiple parts in one drawing
Key recognition rule ➡️ If you see weld symbols dominating ➡️ fabrication drawing
Additive Manufacturing (3D Printing)
Additive manufacturing is a process where parts are built layer-by-layer from digital models using materials such as polymers, resins, or metals. Examples are:
- FDM (Fused Deposition Modeling):
Extrudes thermoplastic filament layer by layer to build a part - SLA (Stereolithography):
Uses a laser to cure liquid resin layer by layer with high precision - SLS (Selective Laser Sintering):
Fuses powder material using a laser to form solid structures - SLM / DMLS (metal 3D printing:
Uses a laser to melt metal powder into fully dense metal parts
What the drawing looks like
- Orientation arrows (critical)
- Support structure regions marked
- Less traditional dimension density
- Sometimes shows print setup, not just part
Typical visual signs of welding technical drawing:
- Directionality matters (Z-axis emphasis)
- Geometry looks “manufacturable in layers”
- Supports sometimes explicitly drawn
Key recognition rule ➡️ If you see print direction + supports ➡️additive manufacturing drawing
Surface Treatment
Surface treatment is a manufacturing process category that modifies the surface properties of a component without significantly changing its bulk geometry, in order to improve performance such as wear resistance, corrosion resistance, hardness, or appearance.
- Heat treatment:
Controlled heating and cooling of metals to modify microstructure and mechanical properties (e.g., hardness, toughness) - Anodizing:
Electrochemical process that forms a protective oxide layer on aluminum surfaces for corrosion resistance and aesthetics - Plating (electroplating / galvanizing):
Deposition of a thin metallic layer (e.g., zinc, chrome) onto a substrate for protection or appearance - Painting / coating:
Application of organic or polymer-based layers for corrosion protection and visual finishing - Powder coating:
Electrostatically applied powder cured under heat to form a durable protective surface layer - Shot peening:
Surface bombardment with small spherical media to induce compressive stresses and improve fatigue resistance - Polishing / surface finishing:
Mechanical or chemical smoothing of surfaces to reduce roughness and improve appearance or friction behavior
What the drawing looks like
- Minimal geometric change to part shape
- Surface finish symbols (roughness Ra values)
- Coating thickness specifications
- Treatment notes applied globally or to selected surfaces
- Sometimes heat treatment tables or process callouts
Typical visual signs of surface treatment technical drawing:
- Geometry is unchanged compared to machining or forming drawings
- Focus shifts to surface notes rather than shape definition
- Often includes annotations like:
- “Anodized 20 µm”
- “Case hardened 58 HRC”
- “Ra 1.6 μm”
Key recognition rule ➡️ If you see surface notes dominating instead of geometry ➡️ surface treatment drawing
