Delta PLC Wiring Guide for Roll Forming Machines (DVP Series & AS Series)

Delta PLC Wiring Guide

DVP & AS Series Wiring Architecture for Roll Forming & Coil Processing Machines

Delta PLCs are widely used in roll forming machines, especially in:

• Roofing panel lines

• AG and PBR machines

• Structural C/Z purlin systems

• Entry-level to mid-range automated lines

• Export-oriented machines

Delta’s DVP Series and AS Series PLCs are popular because they are:

• Cost-effective

• Compact

• Reliable when wired correctly

• Compatible with Delta VFDs and servo systems

However, many instability issues in roll forming lines using Delta PLCs are not software-related.

They are caused by:

• Incorrect I/O wiring

• Improper sourcing/sinking configuration

• Poor encoder shielding

• Mixed commons

• Inadequate 24V power distribution

• Noise from VFD motor cables

This guide explains how to wire Delta PLC systems properly for industrial roll forming environments.

1) Typical Delta PLC Architecture in Roll Forming

Common Delta configurations:

• DVP Series (DVP-SS2, DVP-SX2, etc.)

• AS Series (higher performance)

• Digital Input expansion modules

• Digital Output modules

• High-speed counter inputs

• Communication modules (RS-485 / Ethernet)

Word-Based System Flow:

Sensors → Delta DI → CPU → DO → Relays / Solenoids / Drives

Encoder → High-Speed Input → CPU → Shear Logic

2) Control Voltage Standard (24VDC)

Delta PLC systems typically operate at:

24VDC control voltage.

Word-Based Power Flow:

• AC Supply → SMPS (24VDC) →
• • PLC CPU
• • I/O modules
• • Sensors
• • Safety Relay

Key rule:

Use a stable, properly sized 24V power supply.

Undersized PSU causes:

• PLC resets

• Input instability

• Random faults

3) Delta Digital Input Wiring (Sourcing vs Sinking)

Delta PLCs may support:

• Sinking inputs

• Sourcing inputs

You must check model specification.

Most roll forming systems use PNP (sourcing) sensors.

Word-Based PNP Wiring (Typical)

+24V → Sensor → PLC Input (X0, X1, etc.)
0V → PLC COM

When sensor activates, PLC input sees +24V.

Incorrect selection between sourcing/sinking is a common fault.

4) Input Common Configuration

Delta inputs often grouped by common terminals.

Engineering discipline:

All sensors connected to that input group must share the same 0V reference.

Do not mix separate power supplies without tying commons correctly.

Floating commons cause false triggering.

5) Digital Output Wiring (Relay vs Transistor)

Delta outputs may be:

• Relay type (R models)

• Transistor type (T models)

Relay Output Example

PLC Relay Contact → Contactor Coil → Neutral

Advantages:

• Can switch AC

• Electrical isolation

Disadvantages:

• Slower

• Mechanical wear

Transistor Output Example (PNP Type)

PLC Output (Y0) → Solenoid → 0V

Advantages:

• Faster switching

• Ideal for shear trigger signals

Transistor outputs preferred for high-speed roofing lines.

6) Inductive Load Protection (Critical)

Hydraulic solenoids and relays generate voltage spikes.

Install:

Flyback diode across DC solenoid coils.

Word-Based:

PLC Output → Fuse → Solenoid → 0V
Diode across solenoid terminals.

Without suppression:

Output transistor may fail.

7) Encoder Wiring (Critical for Length Accuracy)

Delta DVP PLCs support high-speed inputs for encoder counting.

Word-Based Encoder Wiring:

• Encoder A → High-Speed Input X0
• Encoder B → High-Speed Input X1
• 0V → Common
• Shield → Earth bar

Use:

• Twisted pair shielded cable

• Separate routing from motor cables

• Proper shield clamp termination

Running encoder cable with VFD motor cable causes:

• Pulse loss

• Cut length variation

• Mistimed shear

8) High-Speed Counter Configuration

For roofing lines running 40–60 m/min:

High-Speed Counter (HSC) must be used instead of standard input scan.

Word-Based Shear Flow:

Encoder → HSC → PLC Logic → Y Output → Servo / Shear

Using standard digital input instead of HSC leads to:

• Delayed shear trigger

• Inconsistent cut length

9) Analog Wiring (If Used)

Delta PLC analog modules support:

• 4–20mA

• 0–10V

Preferred for industrial roll forming:

4–20mA.

Word-Based:

• Transmitter + → AI+
• Transmitter – → AI–
• Shield → Ground at cabinet end only

Analog cables must not share trunking with motor cables.

10) Communication Wiring (RS-485 / Ethernet)

Delta systems often use:

• Modbus RTU (RS-485)

• Ethernet (AS Series)

Requirements:

• Shielded twisted pair for RS-485

• Proper termination resistors

• Clear routing away from VFD cables

Communication dropouts often caused by poor cable routing.

11) Safety Integration with Delta PLC

Standard Delta PLC is not a safety-rated controller.

Proper architecture:

E-STOP Dual Channel → Safety Relay → Main Contactor

Safety Relay Auxiliary → Delta PLC Input

PLC monitors safety status only.

Never wire E-stop directly through Delta input as primary safety function.

12) Word-Based Safety Monitoring Example

Safety Relay AUX → PLC Input X10

PLC Logic:

IF X10 = ON
THEN Allow Motor Enable

If X10 OFF → Block Start

Safety function still controlled by relay hardware.

13) EMC & Shield Separation

Inside control panel:

Left duct → Power cables
Right duct → Signal cables

Rules:

• Encoder cables shielded

• Analog cables shielded

• Motor cables routed directly to gland exit

• Shield grounded at defined earth bar

Delta PLCs are sensitive to encoder noise if separation is ignored.

14) Common Delta PLC Wiring Mistakes in Roll Forming

1. Using wrong input type (sinking vs sourcing)

2. No suppression diode on solenoids

3. Shared commons between unrelated circuits

4. Encoder cable routed near VFD output

5. Mixed control and power trunking

6. Undersized 24V PSU

7. No fuse protection on output branches

8. No labeling of input/output terminals

Most downtime attributed to “PLC problem” is wiring error.

15) Commissioning Checklist (Delta)

Before full machine startup:

• Verify 24V supply stable

• Check DI LED indicators

• Confirm DO outputs energize correct device

• Monitor encoder count while rotating roll

• Confirm count direction

• Verify analog stability (if used)

Test under load with VFD running.

Noise problems often appear only during motor operation.

16) High-Speed Roofing Line Considerations

At high speeds:

• Transistor outputs preferred

• HSC required

• Encoder shield mandatory

• PSU must handle continuous load

• Scan time optimized

Small wiring mistakes create measurable cut deviation.

17) Export Considerations

Delta PLC systems are popular in:

• Asia

• Middle East

• Africa

• Latin America

Before exporting:

• Confirm PSU voltage compatibility

• Confirm spare part availability

• Provide WPLSoft or ISPSoft program backup

• Include full I/O list documentation

Backup file is critical for field recovery.

18) Buyer Strategy (30%)

Before purchasing a Delta PLC roll forming machine, ask:

1. Which Delta series is used (DVP or AS)?

2. Are outputs transistor or relay type?

3. Is high-speed counter used for encoder?

4. Is 4–20mA used for analog feedback?

5. Is safety relay properly integrated?

6. Are encoder cables shielded and segregated?

7. Is PLC program backup included?

8. Is I/O mapping documented?

Red flag:

“Encoder wired to normal input.”

That is not suitable for high-speed roll forming.

6 Frequently Asked Questions

1) Is Delta PLC suitable for roll forming?

Yes, especially for small to medium lines.

2) Should I choose relay or transistor outputs?

Transistor outputs are preferred for high-speed control.

3) Is encoder shielding necessary?

Yes, especially in VFD-heavy systems.

4) Can safety be handled directly by Delta PLC?

No. Use safety relay or safety PLC.

5) What is most common Delta wiring mistake?

Incorrect sourcing/sinking configuration.

6) Does Delta support high-speed counting?

Yes, if wired to designated HSC inputs.

Final Engineering Summary

Proper Delta PLC wiring in roll forming machines requires:

• Stable 24VDC distribution

• Correct input type configuration

• Proper output protection

• Shielded encoder integration

• Strict power/signal segregation

• Clear safety relay integration

• Documented I/O mapping

Delta PLC systems offer reliable automation when wiring architecture supports:

• EMC stability

• Accurate length control

• Hydraulic synchronization

• Global serviceability

In roll forming systems, electrical discipline determines whether the PLC performs reliably under vibration, heat, and VFD noise.