Roll forming is a continuous bending operation in which sheet or strip metal is gradually formed into a desired cross-sectional shape through a series of consecutive roller stations. Roll forming machines are widely used to produce consistent, high-quality profiles for metal building components.
Properly designing a roll forming system requires careful consideration of many parameters to create an optimal set-up for the desired profile shape, material type, and production volume. This guide provides a comprehensive overview of key factors in roll forming machine design and selection.
Overview of Roll Forming Process
Roll forming shapes metal profiles through an incremental, continuous bending process with a series of stands holding forming rollers. As the material passes through each stand, it is gradually shaped until the final cross-section is obtained.
The major components of a basic roll forming line include:
- Uncoiler or decoiler to hold the raw coil and feed metal strip into the roll form station
- Feed or pre-bend rolls to start gradual bending
- Forming roll stations with top and bottom rolls to progressively shape the profile
- Cutoff saws to cut finished parts to length
- Exit tables for collecting finished products
Additional ancillary equipment like straighteners, perforators, punching units, and upcoilers can be integrated into the roll form line for secondary processing steps. Correctly sizing and setting up the roll forming mill is critical for producing high-quality rolled metal parts efficiently.
How Roll Forming Process Works
The incremental bending in roll forming occurs due to the longitudinal position and contour shape of top and bottom rolls at each stand. As the strip engages progressively with the rolls, stresses are induced gradually to shape the profile.
The major steps are:
- Strip unwinding and feeding into the mill
- Gradual bending through a series of roll stations
- Final shaping and stabilization of profile
- Cutting formed profile into required lengths
Roll forming relies on precise control of material flow and roll design to make the desired shape accurately. The rolls must be ground and set accurately based on the material thickness and properties.
Advantages of Roll Forming
- Highly productive continuous process with fast metal forming
- Consistent and repeatable with uniform profile dimensions
- Applicable to wide range of metals including steel, aluminum, copper, brass
- Simpler tooling compared to stamping or press braking
- Lower setup costs for rapid changeovers between profiles
- Flexible production volumes from single pieces upwards
- Compact equipment with small footprint compared to press brakes
Roll Forming Process Parameters
Successfully designing a roll forming system requires proper selection of key process parameters based on the desired profile, material specifications, and production requirements.
Profile Shape Factors
The shape of the final profile is a primary factor determining the roll forming process design. Key considerations include:
- Profile geometry – overall dimensions, angles, radii, open vs closed shapes
- Section modulus – resistance to bending and deflection
- Wall thickness – thicker materials may need pre-conditioning
- Inside bend radius – affects force required for bending
- Flat pattern shape – optimized for bending sequence
More complex profiles require additional rolls, forming stages, and inline operations compared to simple shapes like standard tubes or structural channels.
Material Considerations
Roll forming equipment must be matched to the yield strength, hardness, and ductility of the specified material. Key material factors include:
- Alloy type – carbon steel, stainless steel, aluminum alloys, etc.
- Hardness – harder materials require higher roll forces
- Thickness – force required increases with thickness
- Coating – presence of coatings affects friction and wear
- Ductility – more ductile metals withstand bending better
- Stiffness – high stiffness may need pre-conditioning
Material testing is required to determine forming forces and select appropriate rolls. Lubrication between contact surfaces is essential.
Production Parameters
The desired production speed, volume, and batch size influences roll forming machine design considerations such as:
- Forming speed – max speed capability required
- Volume – overall capacity and runtime
- Batch size – roll reset time for changeovers
- Secondary operations – integrated perforating, punching, etc.
- Profile length – cutoff saw frequency
Determining these production targets is necessary to properly size the roll forming mill for optimal efficiency.
Roll Forming Equipment Components
The main equipment components of a complete roll forming line are outlined below. Correct selection and sizing of each component is crucial for an efficient roll forming system.
Coil Handling Equipment
Coil handling equipment unwinds raw material coil stock and feeds it into the roll forming section.
- Decoilers hold the coil and provide controlled unwinding and tensioning
- Straighteners remove coil curvature and align strip before forming
- Feed rolls drive the strip into the forming section
Decoiler capacity, straightener rolls, and feed roll drive must match the strip width and production speed.
Roll Forming Stands
The roll forming section has a series of stands holding top and bottom rolls that shape the strip.
- Forming rolls progressively bend metal through each stand
- Roll contours ground to required shapes
- Roll materials chosen for hardness and durability
- Roll rotation speed matched to strip speed
- Roll force capacity rated for adequate forming
- Roll drives provide synchronized rotation control
- Roll support bearings handle roll station loads
The number of stands, roll sets per stand, and type of rolls selected depend on the profile shape complexity.
Secondary Processing Equipment
Inline secondary processing equipment may be integrated in the roll line:
- Perforators puncture holes in the profiled strip
- Punching units cut out shaped holes
- Embossing rolls deform sheet surface with patterns
- Specialized rolls for complex forming steps
Secondary operations are strategically positioned at optimal locations in the forming sequence.
Exit Equipment
Exit equipment cuts and collects finished roll formed products:
- Cutoff saws slice profiled strip into required lengths
- Exit tables collect and stack cut parts
- Bundlers group pieces into bundles
- Upcoilers re-roll formed strips into coils
High-speed saws and exit conveyors must be synchronized with the forming speed.
Roll Forming Machine Types
There are two main machine types used in roll forming process:
Fixed Configuration Roll Forming Machines
The roll forming stands in fixed set-up machines have a stationary horizontal layout with predefined sequences and positions. Forming rolls are fixed in position over the passes through the machine.
Advantages:
- Lower equipment cost
- Simplercontrols
- Faster set-up
Limitations:
- Only one profile shape possible per machine set-up
- Requires roll changeover for new profiles
Flexible Roll Forming Machines
Flexible or modular roll forming mills have moveable roll forming stands that can be re-positioned to create different stations and sequences. This allows changing the forming passes quickly to make different profiles.
Advantages:
- Allows frequent profile changes
- Reduces roll changing time
- Requires less inventory of roll sets
Limitations:
- Higher initial cost
- Complex programming required
- Potential alignment issues
Choosing between fixed and flexible roll forming machines depends on the production volumes, variability, and changeover needs for the required profiles.
Roll Forming Machine Design Considerations
Properly designing a roll forming system requires optimizing multiple parameters. The key factors to consider are summarized below:
| Design Aspect | Factors to Consider |
|---|---|
| Profile shape | Complexity, dimensions, bend radius, deviations |
| Material | Type, thickness, strength, ductility |
| Speed | Maximum production rate needed |
| Rolls | Contour design, diameter, surface finish and hardness |
| Drives | Synchronized speed control and reversing |
| Roll stations | Number, flexibility, minimum center distance |
| Guides | Strategic positioning to support material through forming path |
| Secondary operations | Adding perforating, punching, twisting units |
| Exit equipment | Speed and automation level of cutoff saws and tables |
| Controls | PLC programming sophistication |
| Changeover | Roll changeout method and time |
| Quality assurance | Inspection systems, troubleshooting guides |
Considering these key factors holistically will result in an optimized roll forming system for the production needs.
Roll Design and Engineering
Roll design is a critical step in the overall forming layout engineering. The objective is to design roll contours that gradually form the required profile shape at an optimal bend sequence without defects.
Roll Design Factors
The key considerations in roll design are:
- Target profile dimensions and tolerances
- Metal thickness and properties
- Required bending forces calculations
- Number and sequence of forming stations
- Positioning of rolls for correct grain flow
- Optimization of flat pattern shape
- Surface finishing and hardness
- Roll support bearing selection
- Deflection compensation
- Roll contour machining methods
Advanced 3D CAD, FEA, and virtual simulations empower accurate roll design.
Bend Sequence
The order of bends distributed across stations along the roll former is optimized based on:
- Geometry constraints of the profile
- Material properties and forming forces
- Grain flow and splitting avoidance
- Minimizing stations and roll cost
The optimal bend sequence gradually forms the shape avoiding defects.
Roll Contour Design
The roll contour profiles are designed to match the geometry of the bend at each station. Design techniques include:
- 2D development through neutral axis
- Incremental 3D CAD modeling
- Discrete position calculations
- Interpolation and serialization
- FEA analysis and optimization
Rolls are CNC machined to precise contours for consistent forming.
Defects in Roll Forming
Roll forming depends on systematic corrective measures to avoid defects. Potential defects, causes, and remedies are listed below:
| Defect | Root Causes | Corrective Measures |
|---|---|---|
| Springback | Elastic recovery of metal after bending | Optimize roll design, overbend compensation |
| Bow and twist | Non-uniform stress during forming | Strategic guide placement, edge rolling |
| Flaring | Improper roll contours | Refine roll geometry design |
| Wavy edges | Non-uniform edge stresses | Edge rolling, stabilize material flow |
| Surface marks | Roll indentation | Use larger roll radii, lubrication |
| Splitting | Excessive tensile stresses | Reduce force, increase bend radius |
| Thinning | Metal stretching in bends | Account for elastic recovery and flow |
Continuously monitoring and controlling the roll forming process is necessary to minimize defects.
Roll Forming Standards
To ensure optimal design and quality control, roll forming equipment is designed in accordance with relevant standards published by organizations such as:
- ASTM International
- American Iron and Steel Institute (AISI)
- European Committee for Standardization (CEN)
- International Organization for Standardization (ISO)
Key standards include:
| Standard | Description |
|---|---|
| ASTM A1008 | Steel sheet specifications |
| AISI D100 | Cold-formed steel design |
| EN 10149 | Hot-rolled steel strip requirements |
| ISO 6520-1 | Roll forming vocabulary standards |
Compliance with applicable standards ensures the roll forming system meets accepted criteria.
Roll Forming Machine Suppliers
Many equipment manufacturers provide roll forming mills and components for various production needs:
| Company | Location | Product Range |
|---|---|---|
| Formtek | USA | Complete roll form lines |
| Metform | Canada | Flexible roll formers |
| Samco Machinery | USA | Custom roll forming machines |
| Bradbury Group | UK | Roll forming equipment |
| Shanghai Haoyin | China | Roll forming machines |
| Botou Xianxian | China | Roll forming tooling |
| Form Process Engineering | Italy | Roll forming lines |
This table presents some leading global suppliers catering to both standard and custom roll forming equipment requirements.
Roll Forming System Costs
The overall capital cost of a roll forming system varies based on:
- Level of automation and speeds
- Type of equipment – fixed vs flexible
- Amount of tooling and stations
- Additional secondary processing units
- Material of construction
- Production volume requirements
Typical roll forming equipment costs are:
| Equipment | Cost Range |
|---|---|
| Decoiler | $8,000 – $15,000 |
| Strip feeding section | $5,000 – $10,000 |
| Roll forming stands | $2,000 upwards per stand |
| Secondary processing stations | $3,000 upwards each |
| Exit tables | $4,000 – $8,000 |
| Cutoff saws | $6,000 upwards |
| PLC and controls | $15,000 upwards |
Total system cost can range from under $100,000 for simpler mills up to $500,000 for high-end flexible roll forming lines.
Choosing a Roll Forming Machine Supplier
To select the right roll forming equipment supplier, here are important factors to consider:
- Experience designing and building roll forming systems
- Capability to engineer customized solutions
- Range of equipment offered – decoilers, forming stands, secondary processing, exit tables
- Roll tooling design expertise and quality control
- Integration services for controls and automation
- Manufacturing standards and quality certifications followed
- Lead time and delivery reliability
- Installation assistance and after-sales technical support
- Local representation for servicing if needed
- Pricing and payment terms
Visiting existing installations and checking references is recommended before final supplier selection.
Roll Forming Machine Operation
Correct operation procedures are necessary to achieve high productivity and quality roll formed parts.
Machine Setup
Proper machine setup involves:
- Loading roll tooling matched to profile design
- Threading strip through all forming stations
- Adjusting roll pressures and guides
- Setting equipment speeds, limits, controls
- Checking lubrication levels
- Testing run to validate settings
Operation
During production:
- Maintain consistent strip tension and alignment
- Control line speed within design limits
- Monitor roll pressures and tooling condition
- Inspect quality of formed profiles
- Ensure adequate lubrication
- Clear jams or misfed strips immediately
- Follow safety procedures for working around equipment
Changeovers
For roll set changeover:
- Safely stop equipment and unload strip
- Remove existing roll tooling from stations
- Insert new matched roll sets as per setup guides
- Adjust stations and test run to confirm clearances
- Restart production after okaying trial profile
Efficient equipment changeover is key for flexible roll forming.
Roll Forming Machine Maintenance
Regular maintenance activities are required to sustain optimal performance of roll forming systems:
- Cleaning – Remove strip debris, lubricant residues, dirt from equipment
- Inspection – Check roll and guide wear, look for damaged/cracked components
- Lubrication – Top up oil levels, grease bearings
- Adjustments – Realign forming rolls and guides periodically
- Roll replacement – Resurface or harden rolls if worn or reskin if damaged
- Bearing checks – Confirm tightness, check for wear or damage
- Drive servicing – inspect chains, sprockets, couplings, motors
- Safety checks – Ensure guards, doors, covers are functioning
- Electrical – Check wires, connections, panels for issues
Adhering to maintenance schedules and protocols preserves machine life.
Proper training for machine operators and maintenance personnel is essential.
Roll Forming Process Troubleshooting
During roll forming operations, some common issues that may appear include:
| Problem | Potential Causes | Troubleshooting Tips |
|---|---|---|
| Profile distortion | Worn or damaged rolls, improper lubrication, misaligned guides | Routinely inspect roll condition and replace if needed. Check strip lubrication. Inspect guides. |
| Thinning at bends | Excessive roll pressure, poor flat pattern design | Adjust roll pressure. Optimize roll design to account for material flow. |
| Flaring or spreading | Worn rolls, high roll force, edge waviness | Resurface forming rolls. Reduce roll pressure. Use edge rolls to control edge flow. |
| Surface marks | Debris buildup on rolls, lack of lubrication | Clean rolls and apply lubricant. |
| Scrap pieces | Roll speed mismatch, strip curving, feed issues | Ensure synchronized roll speeds. Check strip alignment at entry. Inspect feed rolls grip. |
Following forming troubleshooting guides helps resolve quality issues.
Roll Forming Safety
As with all industrial equipment, safe working practices should be implemented:
- Enclose moving parts in protective guards
- Ensure proper machine guarding around roll stations
- Use control relays and emergency stops
- Follow lockout/tagout procedures during maintenance
- Provide staff training on procedures
- Mandate personal protective equipment (PPE) for operators
- Regularly inspect machine condition
- Maintain adequate workspace around equipment
Prioritizing worker safety improves roll forming performance.
Roll Forming Machine Advantages
Key benefits of roll forming process:
- Highly productive continuous forming
- Consistent and repeatable profiles
- Applicable to high strength materials
- Lower tooling cost than press brakes
- Compact equipment footprint
- Flexible production scale
- Integrates with secondary processes
Roll forming is ideal for producing metal structural parts like columns, studs, joists, panels, racks, rails, solar module frames, highway crash barriers, enclosures and more.
Roll Forming Machine Limitations
Limitations to consider:
- Significant initial design engineering
- Fixed tooling restricts profile changes
- Limited to simple bend geometries
- Not suitable for small batches
- Large floor space needed for equipment
- Noise and safety considerations
Roll forming excels at high-volume production runs but has reduced flexibility for job shop environments.
Roll Forming vs Other Metal Forming Processes
| Process | Description | Typical Applications | Advantages | Limitations |
|---|---|---|---|---|
| Roll forming | Continuous bending of strips through successive roller stations | Panels, racks, rails, structural profiles | Highly productive, repeatable, low tooling cost | Only simple profiles, high engineering design needs |
| Press braking | Sheet metal bent at discrete positions in press brake machine | Enclosures, brackets, chassis, signs | High flexibility, complex geometries possible | Lower production rate, higher tooling cost |
| Stamping | Sheet blank pressed into 3D shapes between matched dies | Automotive panels, appliance housings, electronics enclosures | Complex 3D forms possible in one hit | Very high tooling cost, only mass production |
| Hydroforming | Tube pressing into shape with internal high pressure | Automotive space frames, aerospace structures | Complex tube geometries, enhanced properties | Slow cycle times, high pressure equipment |
| Laser cutting | Profile cutting of sheet using a high power laser | Cutting flat profiles and 2D shapes | High precision, cuts complex contours, no tooling | Limited thickness, higher operating costs |
Roll forming is ideal for continuous production of metal structural sections and is complementary to other processes like laser cutting and press braking in many applications.
The choice depends on the geometry, batch sizes, tooling cost factors, and overall manufacturing logistics. Using a combination of processes provides flexibility to balance productivity, quality, and costs.
Roll Forming Applications
Roll formed components are very widely used across industries to create metal structures. Typical applications include:
Building Construction: Columns, wall studs, trusses, cladding panels, roofing, doors, railings, lighting fixtures
Storage Equipment: Racks, shelving, lockers, conveyors
Automotive: Cabin structural parts, roof bows, rails, bumpers
Rail Transport: Passenger car sections, freight wagon frames
Solar Energy: Photovoltaic module mounting structures
HVAC: Air conditioning ducts and housings
Furniture: Frames, storage systems, enclosures
Electrical: Busbars, distribution boxes, cable trays
Transportation: Road barriers, guard rails, signage posts
Roll formed sections provide lightweight but strong structural support in many products.
FAQ
Here are some commonly asked questions about roll forming machines:
Q: What thickness of metal sheet can be roll formed?
A: Roll forming can work for sheet thickness ranging from 0.15 mm to about 3 mm for steel. Maximum thickness depends on material strength.
Q: How fast can roll forming produce profiles?
A: Production rates can range from 10 to 100 meters per minute depending on machine capability and profile complexity. High-end roll formers can go up to 200 m/min.
Q: What is the tolerance that can be achieved?
A: Roll formed parts can achieve dimensional tolerance similar to press brakes, around +/- 0.5 mm over 3 m lengths. Tighter tolerances are possible with proper precision equipment.
Q: What is the maximum profile length that can be formed?
A: There is no inherent maximum length – profiles are cutoff by saws into required sizes. The limiting factors are handling longer sheets and sagging under self-weight.
Q: How quick are roll changeovers?
A: On fixed roll formers, changeovers take 2-4 hours depending on number of stations. Modular or flexible roll changers can reduce this to under an hour in optimal cases.
Q: What expertise is needed for roll forming operation?
A: Roll forming operators require 1-2 weeks training depending on prior experience. Engineering staff need specialized roll design knowledge.
Q: What safety aspects are important?
A: Enclosing nip points, interlocks on doors, emergency stops, guards around rolls, personal protective equipment. Proper training in procedures is critical.
Conclusion
Roll forming is an efficient process for continuous production of metal profiles widely used in industrial and commercial applications. With proper engineering design of the roll contours and bending sequence matched to the desired profile, high-quality roll formed components can be manufactured at optimal cost and productivity.