SMT Troubleshooting

SMT Line Blocking Caused by Unstable PCB Transfer – How to Fix It

Problem Description

Line blocking is a common issue in SMT production, especially in high-mix or semi-automatic lines.
PCBs accumulate at certain stations, causing upstream machines to stop and reducing overall efficiency.

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Why This Happens

Typical causes of line blocking include:

• No buffer or insufficient buffer capacity

• Inconsistent cycle time between processes

• Unstable PCB transfer signals

• Manual stations interrupting automated flow

• Poor coordination between inspection and production

Blocking is often a system imbalance problem, not a single equipment failure.

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Common Mistakes

Factories often respond by:

• Increasing operator workload

• Speeding up selected machines

• Removing inspection steps

• Accepting blocking as “normal”

These measures usually hide the problem instead of solving it.

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Practical Solutions

To reduce or eliminate line blocking:

• Identify bottleneck processes

• Introduce SMT buffer or NG buffer where appropriate

• Stabilize PCB transfer logic using SMEMA coordination

• Separate inspection flow from main production flow

• Balance manual and automated processes

The objective is to create predictable PCB movement, not maximum speed.

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When to Consider a System-Level Fix

If line blocking occurs daily or worsens with product changes, it often indicates the need for automation and process coordination improvements.

👉 For a structured approach, please refer to our SMEMA & Automation Solutions to improve line stability and PCB flow.

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This issue is part of a broader PCB transfer and line stability topic.
Please refer to our SMT Troubleshooting Hub.