Sync Loss After Restart in Roll Forming Machines – Causes, Encoder Reset Errors, Inspection & Repair Guide
Sync Loss After Restart
Roll Forming Machine Control System Failure Guide
Sync loss after restart is a control system problem in roll forming machines where the machine loses synchronization between the strip position and the cutting or punching operations after the machine has been stopped and restarted.
Modern roll forming machines rely on precise synchronization between several components, including:
strip feed system
rotary encoders
PLC control systems
servo drives
cut-off systems
punching stations
During normal production, the control system continuously tracks the movement of the metal strip using encoder feedback. This information allows the machine to perform operations such as cutting or punching at precise positions along the strip.
However, when the machine stops—whether due to a planned shutdown, emergency stop, or power interruption—the control system may lose its position reference.
When the machine is restarted, the controller may no longer accurately know the position of the strip relative to the cutting or punching stations.
This condition is referred to as synchronization loss after restart.
Sync loss after restart commonly affects roll forming machines producing:
metal roofing panels
metal wall cladding panels
standing seam roofing systems
structural deck profiles
C and Z purlins
light gauge steel framing components
Typical production symptoms associated with sync loss after restart include:
cuts occurring in the wrong location
punch holes misaligned with panel ends
incorrect panel lengths immediately after restart
machine requiring manual recalibration
control system alarms related to position tracking
initial production scrap after restarting the machine
Once the machine re-establishes correct synchronization, normal production may resume.
Maintaining reliable position tracking and proper restart procedures helps prevent this issue.
Causes of Wear or Failure
Sync loss after restart usually occurs due to control system position tracking problems.
Several factors may contribute to this condition.
Encoder Position Reset
Encoders may reset when power is lost.
PLC Memory Loss
Certain position values may be cleared after restart.
Servo Drive Initialization Errors
Servo systems may not reinitialize correctly.
Manual Strip Movement
The strip may move during machine shutdown.
Sensor Initialization Failure
Sensors may not detect the correct starting position.
Improper Restart Procedure
Operators may restart the machine without resetting synchronization.
Why It Happened and What Caused It
From a control systems engineering perspective, roll forming machines rely on continuous position tracking to synchronize operations along the moving metal strip.
Encoders generate position data as the strip moves through the machine.
The PLC uses this information to determine the exact location of the strip relative to punching and cutting stations.
However, if the machine loses power or stops unexpectedly, the control system may lose the stored position data.
Additionally, if the strip moves while the machine is stopped—due to tension release or manual adjustment—the actual strip position may no longer match the recorded position in the control system.
When the machine restarts, the PLC may continue operating based on incorrect position data.
This causes punching and cutting operations to occur at incorrect positions until the system is recalibrated.
Maintaining reliable reference sensors and proper restart procedures helps prevent this synchronization loss.
How to Inspect the Problem
Inspection Procedure
Diagnosing sync loss after restart requires inspecting both the control system and strip position tracking.
Step 1 – Check Encoder Status
Verify whether encoder position values reset after restart.
Step 2 – Inspect PLC Memory Settings
Ensure position data is retained in memory.
Step 3 – Inspect Reference Sensors
Verify that sensors detect the correct strip position.
Step 4 – Observe Initial Production After Restart
Check whether the first panels are incorrectly positioned.
Step 5 – Inspect Strip Movement During Shutdown
Ensure the strip remains stationary when the machine stops.
Step-by-Step Technician Guide – How to Fix
Correcting sync loss after restart usually requires restoring proper position referencing procedures.
Method 1 – Reinitialize Encoder Position
Reset encoder reference values after restart.
Method 2 – Install Reference Sensors
Sensors may detect the strip position automatically.
Method 3 – Update PLC Restart Logic
Modify control programs to reestablish synchronization.
Method 4 – Lock Strip Position During Shutdown
Prevent strip movement while the machine is stopped.
Method 5 – Train Operators on Restart Procedures
Proper procedures ensure synchronization is restored.
Preventative Maintenance Tips
Preventing sync loss after restart requires maintaining accurate position tracking and restart procedures.
Use Absolute Encoders
Absolute encoders retain position data after power loss.
Maintain Reference Sensors
Sensors help restore position reference automatically.
Secure Strip During Shutdown
Prevent strip movement while the machine is idle.
Maintain Control System Configuration
Ensure PLC memory settings retain critical data.
Implement Restart Check Procedures
Operators should verify synchronization before production resumes.
FAQ Section
What is sync loss after restart in roll forming machines?
It occurs when the machine loses position synchronization after stopping and restarting.
Why does synchronization get lost after restart?
Power loss or encoder reset may cause the control system to lose strip position data.
Can strip movement during shutdown cause sync loss?
Yes. If the strip moves while the machine is stopped, the control system may lose track of position.
How can sync loss be detected?
Incorrect cuts or punch positions may occur immediately after restarting the machine.
Can absolute encoders prevent sync loss?
Yes. Absolute encoders retain position data even after power loss.
How can sync loss after restart be prevented?
Using reference sensors, absolute encoders, and proper restart procedures helps maintain synchronization.