1. Overview
Forming refers to a group of manufacturing processes that create the desired shape by applying external force to a material without removing material. While material removal processes create geometry by cutting away material, Forming uses the plastic deformation of the material to create shape.
Forming can be applied to various material forms such as metal sheets, bars, billets, slabs, tubes, and wires. It changes the shape of material by compressing, pulling, pushing, bending, or pressing it.
Representative Forming processes include the following.
Forging
Rolling
Extrusion
Press forming
Sheet metal bending
Deep drawing
Roll forming
Spinning
Drawing
Bending
Tube forming
The key feature of Forming is that material is not removed. Therefore, material utilization is high, productivity is good, and the process is suitable for mass production. In the case of metals, the grain flow formed during deformation can also improve strength and fatigue properties.
However, Forming is not simply a process of “changing shape by applying force.” It is a design-driven manufacturing process that requires consideration of material ductility, yield strength, work hardening, springback, cracking, wrinkling, die load, lubrication conditions, residual stress, and dimensional change after forming.
2. Role of Forming
The core role of Forming is to change shape while maintaining material continuity.
Material Removal creates shape by removing material. In contrast, Forming changes shape while preserving as much material as possible. As a result, material waste is low, production speed is high, and economic efficiency is strong in repeated production.
The role of Forming can be summarized as follows.
Creates shape without removing material.
Improves material utilization.
Secures productivity in mass production.
Improves strength by controlling metal grain flow.
Efficiently produces thin sheet structures, constant cross-sections, and high-strength structures.
Reduces the amount of machining required.
Secures dimensional consistency for repeated shapes.
Optimizes strength, stiffness, weight, and cost at the same time.
For example, automobile body panels, machine covers, brackets, frame parts, shafts, gear blanks, aluminum profiles, stainless steel covers, and chutes for food machinery can be efficiently produced through Forming.
Forming is especially important in the following cases.
Material loss must be reduced.
Production volume is high.
Sheet-metal or constant cross-section parts are required.
High strength and fatigue life are required.
Repeated production using dies, molds, or rolls is possible.
A faster and more economical process than machining is required.
3. Basic Principle of Forming
Forming is a process in which external force is applied to a material so that deformation exceeds the elastic range and enters the plastic deformation range. Once plastic deformation occurs, the material maintains the deformed shape even after the external force is removed.
The basic process flow is as follows.
Important material behaviors in Forming are as follows.
Material Behavior | Description | Design Impact |
|---|---|---|
Elastic Deformation | Deformation that returns to the original state when force is removed | Cause of springback |
Plastic Deformation | Permanent deformation that remains after force is removed | Basic principle of Forming |
Work Hardening | Material becomes harder as deformation progresses | Reduced additional formability, increased strength |
Elongation | Material stretches during forming | Affects cracking risk and thickness reduction |
Compression | Material flows under compressive force | Important in forging, rolling, and extrusion |
Residual Stress | Stress remaining inside the part after forming | Affects distortion, dimensional stability, and fatigue life |
The common core principles of Forming are as follows.
The material must have sufficient ductility.
Cracking must not occur during forming.
The die, mold, or forming tool must withstand the required load.
Springback must be predicted and compensated.
Residual stress and dimensional change after forming must be considered.
Stabilization through heat treatment or post-processing may be required.
4. Classification of Representative Processes
Forming can be divided into several processes depending on material form and deformation method.
Process | Applicable Materials | Main Characteristics |
|---|---|---|
Forging | Metal billets, bars | Secures high strength and fatigue life |
Rolling | Slabs, sheets, bars | Suitable for producing sheets, structural sections, and bars |
Extrusion | Aluminum, copper alloys, plastics | Suitable for producing constant cross-section shapes |
Press Forming | Sheet metal | Suitable for high-speed repeated production |
Sheet Metal Bending | Sheet metal | Suitable for covers, brackets, and frames |
Deep Drawing | Sheet metal | Produces cups, containers, and casing shapes |
Roll Forming | Sheet coils | Produces long constant cross-section structures |
Drawing | Bars, wires, tubes | Reduces cross-section and improves dimensional accuracy |
Spinning | Discs, tubes | Produces axisymmetric hollow shapes |
Tube Forming | Tubes | Produces piping, frames, and flow-path structures |
All of these processes use material deformation, but their design criteria differ. In sheet metal bending, bend radius and springback are important. In forging, material flow and die filling are important. In extrusion, cross-sectional geometry and extrusion ratio are important. In deep drawing, wrinkling and cracking control are important.
5. Forging
Forging is a process that deforms metal into the desired shape by applying compressive force. The material is shaped by hammering or pressing, and the process is widely used for high-strength components.
Representative forging methods include the following.
Open-die forging
Closed-die forging
Cold forging
Hot forging
Warm forging
Impression-die forging
Free forging
The advantages of forging are as follows.
High strength and toughness can be obtained.
Metal grain flow can be aligned with the shape direction.
Fatigue life is excellent.
Internal defects are relatively low.
Suitable for high-load components.
The limitations of forging are as follows.
Die cost is high.
Complex detailed features require post-machining.
High forming load is required.
Large equipment may be required.
Design changes are costly.
Designers should consider the following items.
Forgeability of the material
Direction of metal grain flow
Forging draft
Fillets and radii
Flash generation
Die parting line
Machining allowance
Need for heat treatment
Residual stress
Dimensional accuracy
Forged parts are suitable for components subjected to repeated loads and impact loads, such as shafts, connecting rods, gear blanks, crankshafts, high-load links, clamps, and hooks.
In forging design, sharp corners should be avoided and sufficient radii should be applied. Abrupt cross-sectional changes can disturb material flow and create defects. In addition, areas requiring precision dimensions are usually finished by machining or grinding after forging.
6. Rolling
Rolling is a process in which material passes between rotating rolls to reduce thickness or create a cross-sectional shape. It is widely used to produce sheets, bars, and structural sections from steel, aluminum, copper alloys, and other materials.
Representative rolling methods include the following.
Hot rolling
Cold rolling
Sheet rolling
Bar rolling
Structural shape rolling
Ring rolling
The advantages of rolling are as follows.
Continuous productivity is high.
Sheets and structural sections can be mass-produced.
Thickness and cross-section can be made uniform.
Cold rolling can improve surface quality and dimensional accuracy.
Material structure can be improved.
The limitations of rolling are as follows.
Available shapes are limited.
Initial equipment scale is large.
Residual stress may occur.
Material properties may vary depending on rolling direction.
Cutting or post-processing is required.
Designers should consider the following items.
Sheet thickness
Rolling direction
Surface quality
Flatness
Residual stress
Cutting direction
Formability
Material anisotropy
Subsequent bending or press forming
In designs using rolled material, rolling direction is important. The bending direction, tensile direction, and possibility of cracking can be related to rolling direction. In particular, when bending stainless steel or aluminum sheets, material directionality and minimum bend radius should be reviewed together.
7. Extrusion
Extrusion is a process that creates a constant cross-section by pushing material through a die opening. It is widely used for aluminum profiles, plastic profiles, tubes, rails, and frame structures.
Representative extrusion methods include the following.
Direct extrusion
Indirect extrusion
Hot extrusion
Cold extrusion
Impact extrusion
Plastic extrusion
The advantages of extrusion are as follows.
Long constant cross-sections can be produced.
Complex cross-sectional shapes can be created.
Suitable for aluminum frame structures.
Material utilization is high.
The extruded shape can be cut to various lengths.
The limitations of extrusion are as follows.
The cross-sectional shape must be constant along the extrusion direction.
Extrusion die cost is required.
Large differences in wall thickness make forming difficult.
Internal stress and bending may occur.
Precision mounting surfaces may require post-machining.
Designers should consider the following items.
Cross-sectional shape
Extrusion direction
Uniform wall thickness
Corner radius
Hollow section geometry
Die manufacturability
Extrusion ratio
Bending and twisting
Machining after cutting
Fastening slots and mounting structures
Aluminum extrusions are widely used for frames, guide rails, equipment covers, and structural profiles. Designers should make functional use of the extrusion cross-section and can integrate fastening grooves, locating surfaces, cover insertion areas, and wiring space into the section.
However, reference surfaces requiring high precision may not be sufficiently accurate in the as-extruded state, so additional machining may be required.
8. Press Forming
Press forming is a process in which sheet metal is placed between a punch and die, and pressure is applied to cut, bend, or form it. It is a very important process for mass production of sheet-metal parts.
Representative press processes include the following.
Blanking
Piercing
Bending
Embossing
Flanging
Drawing
Coining
Progressive die forming
The advantages of press forming are as follows.
Production speed is very high.
Repeatability is good.
Suitable for thin sheet-metal parts.
Unit cost is low in mass production.
Cutting, holes, bending, and forming can be combined into continuous processes.
The limitations of press forming are as follows.
Die cost is high.
Design changes are difficult.
Material forming limits exist.
Springback occurs.
Cracking, wrinkling, and tearing may occur.
Designers should consider the following items.
Sheet thickness
Minimum bend radius
Distance between holes and bend lines
Material elongation
Forming depth
Springback
Die segmentation
Burr direction
Flat pattern dimensions
Production volume
In press part design, the positional relationship between holes, slots, and bends is important. Holes located too close to a bend line may deform, and holes that are too small compared with sheet thickness may cause punch damage or burr problems.
Press forming is very efficient for mass production, but design verification in the early stage is important because design changes are difficult after die production.
9. Sheet Metal Bending
Sheet metal bending is a process that creates a desired structure by bending sheet material to a specified angle. It is widely used for industrial machines, food machinery, electrical boxes, covers, brackets, chutes, and frame reinforcement parts.
The advantages of sheet metal bending are as follows.
Parts can be produced relatively quickly.
Suitable for both low-volume and medium-volume production.
Economical for producing covers and brackets.
Structural stiffness can be improved without welding.
Repeated production is possible through flat pattern design.
The limitations of sheet metal bending are as follows.
Bend radius is required.
Springback occurs.
Complex bending sequences can create interference.
Holes or slots near bends may deform.
There are limits to very high positional accuracy.
Designers should consider the following items.
Sheet thickness
Bend radius
Bend direction
Bending sequence
K-factor
Flat pattern length
Springback
Distance between bend and hole
Tool interference
Edge treatment
Welding or fastening method
In sheet metal design, the flat pattern is very important. Bend allowance and K-factor must be considered to achieve the final dimensions after bending. In addition, depending on the bending sequence, the tool and part may interfere, so designers must check whether the structure can actually be bent.
In food machinery, sheet metal bending can reduce gaps and improve cleanability. However, drainage direction and welded-area treatment must be considered together so that closed gaps or water-retaining structures are not created.
10. Deep Drawing
Deep drawing is a process that creates deep hollow shapes such as cups, cases, and containers by pushing sheet metal into a die with a punch.
Representative applications include the following.
Metal cups
Cases
Tanks
Cans
Covers
Sink bowls
Housings
The advantages of deep drawing are as follows.
Seamless hollow shapes can be produced.
Suitable for mass production.
Thin and lightweight structures can be created.
Material utilization is good.
The limitations of deep drawing are as follows.
Material elongation is important.
Wrinkling may occur.
Cracking or tearing may occur.
Forming depth is limited.
Multiple forming stages may be required.
Designers should consider the following items.
Drawing ratio
Material elongation
Blank holder pressure
Lubrication conditions
Corner radius
Wall thickness reduction
Wrinkling
Cracking
Number of forming stages
Trimming allowance
In deep drawing, if the corner radius is too small, cracking is likely to occur. If blank holder pressure is not appropriate, wrinkling or tearing may occur. Deep shapes are difficult to form in a single step, so multiple drawing stages may be required.
11. Roll Forming
Roll forming is a continuous forming process in which a long sheet coil passes through multiple roll stages and is gradually formed into the desired cross-sectional shape.
Representative applications include the following.
Rails
Frame members
Channels
Guides
Reinforcement parts
Cable trays
Structural profiles
The advantages of roll forming are as follows.
Long constant cross-section parts can be continuously produced.
Mass productivity is high.
Material utilization is good.
Repeated cross-section quality is stable.
Stiff structures can be made from thin sheet material.
The limitations of roll forming are as follows.
The cross-sectional shape must be constant along the length.
Initial roll tooling cost is required.
Cross-section changes are difficult.
Integration with punching, cutting, and hole-making processes is required.
It may be uneconomical for low-volume production.
Designers should consider the following items.
Cross-sectional shape
Sheet thickness
Number of bending stages
Roll interference
Springback
Straightness along the length
Punching position
Cutting method
Surface damage
Production volume
Roll forming is highly suitable for long, repeated cross-section structures. However, if the cross-section is complex, the number of roll stages increases and tooling cost becomes higher. Therefore, the cross-sectional shape should be designed with both function and productivity in mind.
12. Drawing
Drawing is a process in which metal bars, wires, or tubes are pulled through a die opening to reduce the cross-section and increase length. It provides high dimensional accuracy and good surface quality.
Representative applications include the following.
Wire
Precision bars
Tubes
Shaft stock
Spring wire
Conductors for cables
The advantages of drawing are as follows.
Dimensional accuracy is good.
Surface quality is excellent.
Material strength can increase.
Suitable for producing long linear materials.
Continuous productivity is high.
The limitations of drawing are as follows.
Cross-section reduction ratio is limited.
Material cracking may occur.
Lubrication and die wear must be managed.
Intermediate heat treatment may be required due to work hardening.
Designers should consider the following items.
Cross-section reduction ratio
Drawing direction
Material ductility
Surface quality
Lubrication conditions
Die wear
Residual stress
Straightness
Subsequent heat treatment
Final dimensional tolerance
Drawn materials are used as shaft, pin, wire, and tube stock, and they are often connected to subsequent cutting, machining, and heat treatment processes.
13. Main Design Criteria for Forming
In Forming design, the key question is whether the material can be deformed into the desired shape without cracking.
The main design criteria are as follows.
13.1 Minimum Bend Radius
If the bend radius is too small, the outer fibers stretch excessively and cracking may occur. The allowable minimum bend radius depends on the material, sheet thickness, and heat treatment condition.
13.2 Springback
Springback is the phenomenon in which material partially returns toward its original shape due to elastic recovery after forming. Higher-strength materials may show greater springback.
13.3 Forming Limit
Materials cannot stretch or deform infinitely. If the forming limit is exceeded, cracking, tearing, or wrinkling occurs. In deep drawing and press forming, the forming limit diagram should be considered.
13.4 Material Directionality
Rolled materials may have different mechanical properties depending on direction. The relationship between bending direction and rolling direction affects the possibility of cracking.
13.5 Residual Stress
After Forming, residual stress can remain inside the part. Residual stress can cause dimensional distortion, warpage, and reduced fatigue life.
13.6 Lubrication and Friction
Friction between the die and the material during forming affects material flow, surface damage, and die life. Lubrication conditions are especially important in deep forming and high-load forming.
14. Defects and Quality Issues
In Forming processes, various defects can occur during material deformation.
Representative defects include the following.
Defect | Main Processes | Cause |
|---|---|---|
Cracking | Bending, forging, deep drawing | Excessive tensile deformation, small radius, low ductility |
Wrinkling | Deep drawing, press forming | Compressive stress, insufficient blank holder pressure |
Springback | Bending, pressing, roll forming | Elastic recovery |
Tearing | Deep drawing | Excessive drawing ratio, insufficient lubrication |
Thickness reduction | Deep drawing, stretch forming | Material elongation |
Surface scratches | Extrusion, bending, pressing | Die friction, foreign matter, insufficient lubrication |
Warpage | All Forming processes | Residual stress, non-uniform deformation |
Dimensional defect | All Forming processes | Springback, die wear, material variation |
These defects are not only production problems. They are directly connected to design geometry, material selection, bend radius, forming depth, die structure, and lubrication conditions. Therefore, designers must review formability and defect risk during the early design stage.
15. Forming and Post-Processing
Parts produced by Forming may be used as-is, but functional areas may require post-processing.
Representative post-processing operations include the following.
Cutting
Trimming
Hole machining
Tapping
Reference surface machining
Grinding
Deburring
Heat treatment
Surface treatment
Cleaning
Inspection
For example, forged parts secure basic shape and strength first, and then shaft diameters, bearing mounting surfaces, and gear tooth profiles are finished by machining or grinding. Sheet-metal bent parts may go through welding, deburring, surface treatment, and assembly after bending.
In Forming design, the important point is not whether the final part can be made in one step. The important point is to distinguish which areas are created by forming and which areas require post-processing to secure precision.
16. Production Volume and Economic Feasibility
Forming often requires dies, rolls, press equipment, and dedicated tools. Therefore, initial cost is required, but as production volume increases, cost per part decreases.
The relationship between production volume and Forming can be summarized as follows.
When selecting Forming, the following cost elements should be reviewed.
Die manufacturing cost
Die modification cost
Material cost
Press or forming equipment cost
Cycle time
Work speed
Defect rate
Post-processing cost
Surface treatment cost
Inspection cost
Possibility of design change
Expected production volume
Forming is a powerful manufacturing method in mass production, but caution is needed in early development stages where design changes are frequent. In such cases, it is preferable to verify shape and function using soft tooling, laser cutting and bending, CNC machining, or 3D printing before moving to production tooling.
17. Application of Forming in Food Machinery
In food machinery and meat-processing machinery, Forming is widely used to produce stainless steel sheet-metal parts, covers, chutes, hoppers, frame covers, guides, trays, and drainage structures.
Representative applications include the following.
Stainless steel covers
Food transfer chutes
Hoppers
Trays
Guide plates
Drain plates
Hygienic covers
Electrical boxes
Protective covers
Washable sheet-metal structures
When applying Forming to food machinery, the following should be considered.
The shape must be easy to clean.
Water pooling must be avoided.
Gaps and dead corners must be reduced.
Contamination must not accumulate inside bends.
Polishability of welded and bent areas must be considered.
Sharp edges and burrs must be removed.
Surface damage to stainless steel must be minimized.
Materials must withstand cleaning agents and temperature.
Parts requiring disassembly and cleaning must consider fastening structure.
For example, a food transfer chute made by sheet metal bending can reduce welded areas and improve cleanability. However, if the bent structure creates closed gaps, contamination may remain. Therefore, drainage direction and cleaning access must be reviewed together.
In food machinery, Forming is not simply a sheet-metal fabrication technique. It is an important manufacturing method that must satisfy both hygienic design and manufacturability.
18. Connection with Other Knowledge Tracks
Forming is closely connected with other Knowledge Tracks.
18.1 Connection with Material
Forming is strongly affected by material ductility, yield strength, tensile strength, work hardening, rolling direction, and heat treatment condition.
18.2 Connection with Mechanism & Motion
Formed parts can serve not only as covers and frames, but also as basic components of motion structures, such as links, levers, guides, and shaft blanks.
18.3 Connection with Assembly
Formed parts create assembly structures through bends, flanges, fastening surfaces, taps, inserts, and welded areas.
18.4 Connection with Manufacturing Quality
Forming can create quality issues such as cracking, springback, wrinkling, warpage, and dimensional variation. Therefore, process conditions and inspection criteria are important.
19. Core Thinking
The core thinking in Forming is as follows.
Material is not removed; it is deformed.
Formability is largely determined by material ductility.
If the bend radius is too small, cracking occurs.
After forming, the final shape may differ from the target shape due to elastic recovery.
Rolling direction affects bendability and cracking risk.
Deep forming must control wrinkling and tearing at the same time.
Friction between die and material affects quality and die life.
Residual stress can create warpage and dimensional change after forming.
Precision functional surfaces may require post-processing after forming.
Forming is powerful in mass production, but sensitive to design changes.
Good Forming design considers formability, strength, dimensional stability, assembly, and inspection together.
20. Conclusion
Forming is a group of manufacturing processes that deform material into the desired shape using external force without removing material. Processes such as forging, rolling, extrusion, press forming, sheet metal bending, deep drawing, roll forming, and drawing provide high material utilization and excellent productivity, and play a very important role in repeated production and mass production.
However, Forming is not simply a process of pressing or bending material. Designers must consider material ductility, forming limit, bend radius, springback, residual stress, cracking, wrinkling, die load, need for post-processing, and production volume.
From the mechanical design perspective, the key points of Forming are as follows.
Can this material be deformed into the desired shape without cracking?
Are the bend radius and forming depth appropriate?
Can springback be predicted and compensated?
Have rolling direction and material directionality been considered?
Will precision functional surfaces be secured through post-processing after forming?
Can tooling cost be recovered through production volume?
Can forming defects be inspected and controlled?
Is the structure suitable for assembly and maintenance?
Therefore, Forming is a core section in the Manufacturing Track for understanding material deformation processes. It is closely connected with Material, Mechanism & Motion, Assembly, and Manufacturing Quality.