Roll Forming Line Components

1. Definition

A roll forming line is a complete production system that transforms flat metal coil into finished profiles through a sequence of mechanically linked stations. While the roll forming machine itself — the section with progressive roller stations — is the core, it cannot operate without supporting equipment for coil handling, strip preparation, punching, cutting, product collection, and process control. A typical line comprises 8 to 14 functional modules, each contributing to feeding stability, forming accuracy, and output efficiency.

2. Component Overview

3. Coil Handling & Feeding

3.1 Decoiler (Uncoiler)

The decoiler holds the steel coil and feeds it into the line under controlled tension. Three types are common:

Standard decoiler specifications include: coil inner diameter 450–560 mm, maximum outer diameter 1,200–1,600 mm, motor power 4–11 kW, hydraulic power 5.5 kW, and speed range 0–80 m/min adjustable via frequency converter. A hold-down arm prevents coil loosening during unwinding, and a pneumatic brake system maintains stable strip tension.

3.2 Coil Car

For coils exceeding 3 tons, a coil car is recommended to load the coil onto the decoiler mandrel safely. The car typically supports up to 10,000 kg, with hydraulic cylinders for vertical lift and hydraulic motor for horizontal travel along guide rails. This reduces crane dependency, improves safety, and shortens coil change time.

3.3 Entry Guide

The entry guide aligns the strip laterally before it enters the first forming station. It typically consists of a steel plate platform, two pinch rollers, and adjustable side guides with positioning stops. Proper guide alignment prevents edge marking, camber, and feeding instability.

4. Strip Preparation

4.1 Leveler (Straightener)

After decoiling, the strip retains curvature from the coil (coil set) and may exhibit edge wave or camber. A leveler removes these defects by passing the strip through a series of alternating upper and lower rollers that apply progressive bending in the opposite direction of the coil set.

For high-precision applications such as metal deck or light gauge framing, multi-roll precision levelers with 11 or more rollers are preferred. Some advanced levelers, such as the Amada LCC SA series, feature Active Straightening Correction (ASC), which automatically adjusts roller pressure based on changes in coil outer diameter during production.

4.2 Servo Feeder

When the line includes punching, a servo feeder is essential. It controls the feed length of the strip before each punching cycle, ensuring hole positions are accurate and repeatable. Servo feeders typically achieve feed accuracy of ±0.15 mm over a single feed stroke. Common servo motor ratings range from 0.75 to 1.5 kW for standard roll forming applications.

5. Punching System

Many roll formed products require holes, slots, or notches for fastening or assembly. These features are created inline using punching units positioned before or after the roll forming section:

• Hydraulic punching press: Most common for medium to thick material (1.0–3.0 mm); typical capacity 30–80 tons; stroke rate up to 40 strokes/min
• Mechanical press: Used for high-speed lines requiring rapid cycle times; suitable for thin material (≤1.0 mm)
• Servo-driven punching: Allows variable hole patterns without mechanical adjustment; servo motor synchronizes with line speed and length control

Punching is synchronized with the main line PLC via encoder feedback. For products such as C and Z purlins, steel studs, and guardrails, punching is mandatory and directly affects downstream assembly compatibility.

6. Roll Forming Section

The roll forming section is the core of the line. It consists of a series of forming stations — typically 10 to 24 — each equipped with a pair of upper and lower rollers mounted on shafts. The rollers are machined to conjugate profiles that progressively bend the strip according to a predetermined flower pattern.

The machine frame is typically a welded steel structure with 25–30 mm side plates, stress-relieved after welding and machined by CNC gantry milling to ensure station-to-station alignment. For high-strength material lines, cast iron stands (140# grade) may be used for greater vibration damping.

7. Cut-Off System

Once the profile is fully formed, it is cut to the specified length. Two primary methods are used:

Servo-driven flying shear systems are increasingly standard on modern lines. Key specifications for a flying shear unit include:

• Blade material: Cr12MoV, SKD11, or D2 tool steel; hardness HRC 58–62
• Cut length tolerance: ±0.5 mm (flying shear), ±2 mm (hydraulic stop-cut)
• Squareness: ≤0.5 mm per 1,000 mm
• Repeatability: ±0.3 mm over 100 consecutive cuts
• Servo motor power: 7.5–11 kW (material ≤1.0 mm); 15–30 kW (1.0–3.0 mm); 30–55 kW (3.0–6.0 mm)
• Encoder resolution: 2048 PPR recommended for closed-loop position control
• Synchronization tolerance: ≤±0.3 mm positional deviation during cut

The flying shear carriage accelerates to match strip speed, performs the cut during synchronized motion, then decelerates and returns to the start position — all without interrupting the continuous flow of the forming line.

8. Product Handling

8.1 Run-Out Table

After cutting, finished profiles are supported by a run-out table — typically 3 to 6 meters in length, equipped with unpowered rollers for smooth product movement. The table prevents bending or surface damage to cut profiles and provides a collection point for manual or automated handling.

8.2 Automatic Stacker

For medium to high volume lines, an automatic stacker replaces manual product collection. Stackers can sort by length, count pieces, and form bundles for strapping. Automated handling significantly reduces labor cost and improves overall line productivity, particularly on high-speed roofing and deck lines running at 30–60 m/min.

9. Control System

Modern roll forming lines are managed by a PLC-based control system that integrates all functional modules:

• PLC controller: Siemens, Mitsubishi, or Delta; manages line speed, cut length, punching sequence, and production count
• HMI touchscreen: Operator interface for recipe management, length setting, batch counting, and fault diagnostics
• Encoder: Omron or equivalent; provides real-time length measurement and servo synchronization feedback
• Frequency inverter: Shihlin, Panasonic, or Schneider; controls main motor speed and decoiler rotation
• Safety interlocks: Emergency stop circuits, light curtains, and overtravel protection integrated into the PLC logic

Advanced lines may include remote diagnostics, production data logging, and ERP integration for factory-wide traceability.

10. Auxiliary Systems

• Hydraulic station: Gear pump-driven; supplies power for cutting and punching cylinders. Typical motor power 3–5.5 kW; closed oil tank with auto-off during idle to conserve energy.
• Air compressor: Required for pneumatic systems (punching, clamping, ejection). Industrial-grade compressor with clean, dry air supply.
• Lubrication system: Centralized lubrication for bearings and shafts; reduces wear and extends machine life, especially on high-duty-cycle lines.
• Safety systems: Full guarding, light curtain protection, servo motion interlocks, emergency stop circuits, and two-hand control for punching stations. Compliance with OSHA, CE, or local regulations is mandatory.
• Power infrastructure: 380V/415V/480V, 3-phase, 50/60 Hz; proper grounding and electrical panel compliance required before commissioning.