6.1 Digital Andon Systems

A traditional Andon system (lights on a pole) is a passive request for help; a Digital Andon system is an active command for intervention. When a line stops, the clock ticks against profitability. The system must convert physical downtime into digital tickets, forcing specific resources to respond within defined SLAs. Stop relying on "yelling across the floor"; use data to drive urgency.

Call Types & Taxonomy

Do not allow a generic "Red Light" to mean everything. Precise categorization drives the correct support team to the line immediately.

The "Three-Bucket" Logic

Classify every stop into one of three domains to prevent "alert fatigue" where maintenance ignores quality calls.

• Type A: Maintenance (Machine Down)
  • Trigger: Machine failure signal (PLC) or Operator "Repair" button.
  • Responder: Maintenance Technician.
  • Example: Nozzle jam, Feeder error, Conveyor motor fault.
• Type B: Material (Starved/Blocked)
  • Trigger: Sensor (Low Level) or Operator "Resupply" button.
  • Responder: "Water Spider" / Material Handler.
  • Example: Component Reel empty, PCB magazine full, Glue syringe low.
• Type C: Quality/Process (Validation Fail)
  • Trigger: Test failure loop or Operator "Inspect" button.
  • Responder: Process Engineer / Quality Tech.
  • Example: 3 consecutive test fails, component misalignment, visual defect.

The "Unknown Stop" Rule

• If Machine State = Stop AND Duration > 5 Minutes AND No Call Type selected → System Auto-Triggers "Management Escalation".
• Reasoning: An unclassified stop is invisible data. Force the operator to tag the downtime to stop the alarm.

The Escalation Matrix (Tiered Response)

Hope is not a strategy. Define exactly who is notified when a problem persists. The goal is to solve the issue at the lowest level, but escalate rapidly if the resolution stagnates.

Time-Based Tiers

• Tier 1 (Immediate):
  • Who: Line Lead / Local Support.
  • Trigger: T=0 min (Button Press).
  • Action: Line Dashboard flashes Red.
• Tier 2 (The Expert):
  • Who: Maintenance Engineer / Shift Supervisor.
  • Trigger: T=15 min (Unresolved).
  • Action: SMS/Microsoft Teams notification sent to specific individual.
• Tier 3 (The Manager):
  • Who: Production Manager / Plant Manager.
  • Trigger: T=60 min.
  • Action: Email sent to Management Group. This implies a "Loss of Shift" risk.

Escalation Logic

• If Tier 1 acknowledges the ticket → Reset Escalation Timer.
• If Tier 1 ignores the ticket → Accelerate to Tier 2.

Hardware vs. Software Interfaces

The interface determines the response speed. Do not bury the "Stop" button three menus deep on a touchscreen.

Physical Controls (Tactile)

• Best For: High-stress, high-frequency events (e.g., "Line Stop").
• Requirement: Hard-wired button or Physical Andon Cord.
• Reasoning: Muscle memory works faster than reading. In an emergency, an operator hits a big red button instantly; they fumble with a mouse.

Digital Interfaces (HMI)

• Best For: Detailed classification (e.g., "Select Reason Code: Feeder Jam").
• Requirement: Large touch targets (min 20mm x 20mm) on the station HMI.
• Logic: The Hard Button stops the line; the Digital Screen asks "Why?".

Pro-Tip: Integrate "Smart Watches" for Material Handlers. A vibrating wrist alert ("Line 4: Reel Needed") is 5x faster than a PA system announcement.

Key Performance Metrics (KPIs)

Data from the Andon system is the primary input for OEE (Overall Equipment Effectiveness) availability calculations.

Primary Metrics

• MTTA (Mean Time To Acknowledge): How long does the light stay red before support arrives?
  • Target: < 3 Minutes.
  • Insight: High MTTA = Understaffed support team or broken notification system.
• MTTR (Mean Time To Resolve): How long from "Arrived" to "Running"?
  • Target: Varies by Call Type (e.g., Material < 5 min; Repair < 30 min).
  • Insight: High MTTR = Lack of spare parts or training gap.

Availability Calculation Logic

• Availability % = (Scheduled Time - Andon Downtime) / Scheduled Time
• Rule: Exclude "Planned Downtime" (Lunch, PMs) from the calculation. Only count Unplanned Andon events.

Final Checklist

Category	Metric / Control	Threshold / Rule
Taxonomy	Call Types	distinct buttons for Maint, Material, Quality
Escalation	Auto-Alert	Tier 2 notified automatically after 15 mins
Hardware	Input	Emergency Stop must be a Physical Button
Response	MTTA	Support must "Badge In" to acknowledge (< 3 min)
Data	Downtime Reason	100% of stops > 5 min must have a Reason Code
Notification	Channels	SMS/Teams integration for Tier 2+ (No Email only)
Safety	Override	Andon Stop overrides all Production signals