4.1 Digital Andon Systems

A traditional Andon system (lights on a pole) is a passive request for help; a Digital Andon system is an active commandsubpoena for intervention.support. WhenIn a linehigh-speed stops,line, thea clock"Red ticksLight" againstthat profitability.goes unnoticed for 10 minutes is 10 minutes of lost capacity that can never be recovered. The goal of Digital Andon is to convert "Line Down" events into Workflow Tickets with enforceable Service Level Agreements (SLAs).

The Taxonomy of Stops

Not all stops are equal. The system must convertclassify physicalthe downtime"Ask" into digital tickets, forcing specific resourcesimmediately to respondroute within defined SLAs. Stop relying on "yelling across the floor"; use datait to drive urgency.

Call Types & Taxonomy

Do not allow a generic "Red Light" to mean everything. Precise categorization drives the correct supportdepartment. teamDo not broadcast generic "Help" messages to the line immediately.everyone.

TheMaterial "Three-Bucket"Call Logic(Logistics)

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

• TypeTrigger: A:Operator scans "Low Level" or Machine throws "Feeder Empty" alarm.
• Routing: Warehouse / Water Spider.

Maintenance Call (MachineEquipment)

Down)

• Trigger: Machine failureError signalCode (PLC)e.g., "Motor Fault") or Operator "Repair"Broken Tool" button.
• Responder:Routing: Maintenance Technician.
• Example:

Nozzle

Quality jam, Feeder error, Conveyor motor fault.

Type B: MaterialCall (Starved/Blocked)Process)

• Trigger: SensorConsecutive (LowFailures Level)at AOI or Operator "Resupply"visual button.doubt.
• Responder:Routing: "WaterQuality Spider"Engineer / MaterialLine Handler.
• Example: Component Reel empty, PCB magazine full, Glue syringe low.Lead.

Type C: Quality/Process Call (ValidationBottleneck)

Fail)

• Trigger: TestCycle failuretime loopexceeds ortarget Operatorby "Inspect"> button.15%.
• Responder:Routing: ProcessShift 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.Supervisor.

The Escalation MatrixLogic (TieredThe Response)Timer)

HopeThe Digital Andon is a "Dead Man's Switch." If the primary responder does not react, the system automatically escalates to the next tier. This removes the social friction of "tattling" on a strategy. Define exactly who is notified when a problem persists. The goal is to solvecoworker; the issuesystem atcalls the lowestboss, level, but escalate rapidly ifnot the resolution stagnates.operator.

Time-BasedSeverity Tiers& SLA Matrix

Define these rules in your MES configuration:

• Tier 1 (Immediate)Responder): The Technician/Lead assigned to the line.
  • Who:Response SLA: Line5 Lead / Local Support.
  • Trigger: T=0 min (Button Press).Minutes.
  • Action: LineMust Dashboard"Acknowledge" flashes(Scan Red.Badge) at the station.
• Tier 2 (The Expert)Manager):
  • Who: MaintenanceThe EngineerArea Manager / Shift Supervisor.Engineer.
  • Trigger: T=If Tier 1 Status = "Open" > 15 min (Unresolved).Minutes.
  • Action: SMS/MicrosoftReceive TeamsPush notificationNotification sent/ to specific individual.SMS.
  • Tier 3 (The Manager)Executive):
    • Who: ProductionPlant Manager / Plant Manager.Director.
    • Trigger: T=If Tier 1 Status = "Open" > 60 min.Minutes.
    • Action: Receive Email sentReport. to Management Group. (This impliesis athe "Lossnuclear of Shift" risk.option").

    Pro-Tip: Do not count "Response Time" as "Fix Time." Measure two metrics: "Time to Acknowledge" (Reaction speed) and "Time to Resolve" (Technical capability).

    The Workflow State Machine

    An Andon event is a ticket. It must traverse a defined lifecycle.

    Open (Red State)

    • Start: Event Triggered.
    • Clock: Ticking. Line is likely Down.
    • Andon Board: Flashing Red.

    Acknowledged (Yellow State)

    • Action: Responder scans badge at the terminal.
    • Meaning: "I am here working on it."
    • Clock: Escalation Timer pauses; Resolution Timer continues.
    • Andon Board: Solid Yellow.

    Resolved (Green State)

    • Action: Responder selects Root Cause Code and closes ticket.
    • Meaning: Production has resumed.
    • Clock: Stopped.

    Closure Rules & Reason Codes

    You cannot improve what you do not categorize. Closing an Andon ticket requires a "Confession"—a mandatory data entry explaining why the line stopped.

    The "Other" Ban

    • Rule: Remove "Other" or "Misc" from the dropdown menu.
    • Why: "Other" is a data black hole. Force users to select a specific category (e.g., "Feeder Jam," "Software Crash," "Missing Part").

    Validation Logic

    • If TierDuration 1> acknowledges10 theMinutes ticketAND Comment Field is Empty → ResetThen EscalationBlock Timer.Closure. Force the technician to type a brief explanation.
    • If TierResponder 1ID ignores= theOperator ticketID → AccelerateThen toFlag Tierfor 2Review. (Operators should not be closing their own maintenance tickets).

    HardwareAutomatic vs. SoftwareManual InterfacesTriggers

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

    Physical Controls (Tactile)

    • BestAutomatic For:(Hard Down): High-stress,Connect high-frequencythe eventsmachine state (e.g., "Line Stop").
    • Requirement: Hard-wired buttonDI/O or PhysicalOPC-UA) Andondirectly 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) onto the station HMI.Andon.
    • 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):If HowMachine long does the light stay red before support arrives?
      • Target: < 3 Minutes.
      • Insight: High MTTAState = Understaffed"Error" support> team30 orSeconds broken→ notificationThen system.Auto-create Maintenance Ticket.
    • MTTRManual (MeanSoft Time To Resolve)Stop): HowTouchscreen longinterface fromfor "Arrived"the to "Running"?operator.
      • Target:Logic: VariesOperator bypresses Call"Quality TypeCheck." Line continues running (e.g.if safe), Materialbut <Quality 5Engineer min;is Repair < 30 min).
      • Insight: High MTTR = Lack of spare parts or training gap.summoned.

    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
    TaxonomyRouting	CallTargeted TypesAlerts	distinctAlerts buttonsgo foronly Maint,to Material,the Qualityrelevant department (Logistics vs. Maint).
    EscalationSLA	Auto-AlertEscalation	IfTier 2Ticket notified automatically after> 15 mins unacknowledged → Then Auto-alert Manager.
    HardwareStates	InputAcknowledgement	EmergencyDistinct Stopstates must be a Physical Button
    Response	MTTA	Support mustfor "BadgeHelp In" to acknowledgeRequested" (<Red) 3vs min)"Help Arrived" (Yellow).
    Data	Downtime ReasonTaxonomy	100%"Other" ofcategory stopsbanned. >Specific 5Root minCause mustrequired havefor a Reason Codeclosure.
    NotificationInput	ChannelsFriction	SMS/TeamsOne-touch integrationactivation for Tieroperators. 2+ (No Emailcomplex only)menus during a crisis.
    SafetyGovernance	OverrideGhost Calls	If Auto-Andon triggers but Operator clears it instantly → Log as "Micro-stop" for analysis.
    Visibility	Displays	AndonLarge Stopoverhead overridesscreens allmust Productionrefresh signalsstatus in < 5 seconds.