Error proofing technique - Poka Yoke

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT SENSOR INFORMATION: BASIC TYPES OF SENSORS Discrete sensors Analog sensors TYPES OF PRESENCE SENSORS Physical contact No physical contact TYPES OF NON-CONTACT SENSORS Reed relays Inductive Capacitive Photoelectric sensors ADVANTAGES OF THE VARIOUS TYPES Functionality Costs Areas of application

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT BASIC TYPES OF SENSORS: ANALOG SENSORS Answer the question: “Where is the part?” or “ To what level have we filled the container?” DISCRETE SENSORS The part is present or is not present. Most frequently asked question in a manufacturing operation.

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF PRESENCE SENSORS: PHYSICAL CONTACT e.g. Limit switches Advantages - Can carry more current - Gap between terminals NO PHYSICAL CONTACT Advantages - No physical contact - Better for counting sensitive surfaces, e.g. painted or polished surfaces - No moving parts - Faster

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: REED RELAYS Target is magnetic Will not respond to non-magnetic targets with reliability. INDUCTIVE Based on metal targets; will not respond to non-metallic targets with high reliability. CAPACITIVE Cannot distinguish between the real target and something else in the target region. Must control what comes close to the target. PHOTOELECTRIC Can be fooled by a non-target.

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: REED RELAYS Typical range: Up to 1.5 in. (approx. 4 cm) Two hermetically sealed metal foil reeds which make contact with each other to close the circuit, when in the vicinity of a magnet (permanent or electro-magnet). The differential is determined by differencing the point of first contact from the point of last contact. Magnet approach must be in a direction parallel to the direction of the line connecting the tow reeds. Best applications for magnetically actuated switches in general: Security and safety to avoid false tripping security door interlock for heavy machinery; end of travel for elevators, cranes, and the like. Sensing through walls (non-ferrous, e.g. Aluminum and Magnesium). Pallet identification in synchronous automated assembly lines. Relative dirty environments (e.g. dust, dirt, sand, oil, or coolant fluids). Whenever high response speeds are required. Disadvantages - poor long-term reliability (moving parts)

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: INDUCTIVE SENSORS Principle of Operation: Eddy currents are induced in the target (metallic) by the electromagnetic. The target reacts with the Eddy currents as a function of the distance from the field. Inside the field, the target attenuates the magnitude of the Eddy currents. Outside the field, the target does not impede the Eddy currents. This type of oscillator is referred to as a ECKO (Eddy Current Killed Oscillator).

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: CAPACITIVE SENSORS Principle of Operation: Senses all materials Contain a high frequency oscillator with one of its capacitor plates built into the sensor. Method of Application: All materials are sensed through a change on the dielectric characteristics. Ideal applications include bulk materials and liquids in containers of glass and plastic. Characteristics: Poor choice for metal targets. Is very sensitive to environmental factors. Sensing range depends greatly on the material being sensed. Can be misled and therefore it is important to control the material which is presented to the sensor.

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: PHOTOELECTRIC SENSORS Photoelectric controls need no physical contact and are ideal where sensed objects must remain untouched. Photoelectric controls respond rapidly to parts moving quickly and in varying positions along a conveyor, yet operate dependably if actuated only infrequently. There are controls for indoor or outdoor use, for varying ambient light conditions, for high vibration, for areas restrictive in space, and even for explosive locations. Typical applications include: Counting Labeling Conveyor control Bin level control Parts inspection Feed and/or fill control Package handling Thread break detection Edge guide Web break detection Regristration control Food processing Parts monitoring and sorting Batch counting Robotics Parts handling

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: PHOTOELECTRIC SENSORS Conveyor Control This application involves sorting brown cardboard boxes which are coded with up to four black marks per box. The application is to sense the number of marks on each box. Package Handling A diffuse scan photoelectric control is used to detect the light reflected from the object in this application. The control detects the light reflected off the box, turning ON and OFF the gluing machine. Labeling This application is designed to detect the leading edge of a black bar code on a read and write label. The labels are edge to edge on a spool. When the bar code is detected the sensor output triggers a laser bar code reader which reads the bar code. Food Processing This application monitors the level of an accumulator in a meat processing facility. A photoelectric control detects a fill level of hot-dogs in the accumulator then turns on the conveyor for a preset time period. Side walls of the accumulator are polished stainless steel. The equipment is subject to daily washdown. Fill Level Control This application inspects the fill level of various jars of food products. The photoelectric system produces an output when either an under or over fill condition is detected. Parts Handling Fiber optics are ideal for areas too small for a standard photoelectric control. The fiber optic cables direct the light from the base to where the sensing is needed.

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Target Thru: Light source (emitter) and receiver are placed opposite each other. The object to be detected passes between the two. Advantages: 1. Most reliable when target is opaque 2. Long range scanning, most excess gain 3. Use in high contamination areas, dirt, mist, condensation, oil film, etc. 4. Precise positioning or edge-guiding of opaque material 5. Parts counting Types of Non-Contact Sensors Photoelectric Sensors Emitter Receiver THRU

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Diffuse: Light beam is directed at the object to be detected. Light will be reflected off the object in many directions. Some of the light reflected from the object will be sensed by the receiver. Advantages: 1. No reflector required. 2. Convenient for installation. 3. One sided scanning. 4. Senses clear materials when distance is not fixed. 5. Ease of alignment Types of Non-Contact Sensors Photoelectric Sensors Target

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: PHOTOELECTRIC SENSORS Proximity (diffuse) Background Suppression Background suppression utilizes 2 receivers behind the receiving lens. They are aimed at a precise point in front of the unit and sense the presence of a target when the output of both receives are equal . Applications: Material handling - conveying systems Collision detection for AGV’s (Automatic Guided Vehicles) Car / truck wash Level sensing

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Retroreflective: Light beam is directed at a reflective target (reflector, tape or other reflective object) - one which returns light along the same path it was sent. The object to be detected passes between photoelectric control and reflective target. Advantages: 1. One-sided scanning 2. Ease of alignment 3. Immune to vibration Types of Non-Contact Sensors Photoelectric Sensors Target Retroreflective Reflector

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Convergent: Light beam is directed at object to be detected (ignores background surfaces) Object must be at a given distance in relationship to photoelectric control before light will be reflected to receiver Advantages: 1. First choice for detecting clear materials 2. Ignores unwanted background surface reflection 3. Detects objects with low reflectivity 4. Detects height differential Types of Non-Contact Sensors Photoelectric Sensors Target Convergent Beam Fixed Distance

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT TYPES OF NON-CONTACT SENSORS: PHOTOELECTRIC SENSORS Fiber Optic Sensors What do you do when the physical constraints of the application don’t allow for installing regular, self-contained sensors? Maybe the target is in a high temperature or chemically aggressive environment. Perhaps the target is small or very fast-moving. Fiber-optics, applied to photoelectric scanning, solves these problems. Fiber Optics and Sensing All fiber optic sensing mode are implemented using one type of amplifier which contains both emitter and receiver in one housing. Fiber Optic Thru-beam Scanning Using two opposed, individual fiber optic cables, the object to be detected breaks the beam. The target must be at least the same dimension as the effective beam, which in this case, is the bundle diameter. Because the beam is very small, the detection can be very precise. A typical application might be edge detection for a web printing press. Needle tips reduce the beam dimension for use with extremely small targets, typical for application in semiconductors and pharmaceutical industries. Typical application: Small parts detection Edge detection High temperature environment (600 degrees F+)

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Fiber Optic: Not a scanning technique but rather another way of transmitting light beam. Advantages: 1. High temperature applications 4. Corrosive areas 2. Where space is limited 5. Noise immunity 3. Size and flexibility of fiber leads 6. Color sensing Types of Non-Contact Sensors Photoelectric Sensors Target or Reflector Thru

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT Polarized: Will work only with comercube reflector or special polarized reflective tape. Will not false trigger when sensing shiny object. Advantages: 1. One-sided sensing 2. Does not false trigger off highly reflective object 3. Senses clear materials 4. Ease of alignment 5. Immune to vibration Types of Non-Contact Sensors Photoelectric Sensors Target Polarized Special Reflector

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT APPLICATIONS FOR PHOTOELECTRIC SENSORS

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT NEW APPLICATIONS: Pressure sensing Shape sensing Weight sensing Presence sensing Color sensing (dark vs light) Torque sensing (Piezo-electric) Position sensing Custom / adaptive size parts Vacuum sensing Flow sensing (e.g. gallon / minute)

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT POKA-YOKE Sensors at a Deming Prize Winner 1. Mechanical 9. Heat Sensor 2. Magnetic 10. Gas Sensor 3. Beam Cut 11. Force Sensor 4. Super Sonic 12. Torque Sensor 5. Image Sensor 13. Meter Relay 6. Counter 14. Vibration Sensor 7. Beam Reflector 15. Automatic Measurement 8. Pressure Sensor

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT THE MOST EFFECTIVE TYPES OF ERROR NOTIFICATION MEANS Getting the Operator’s Attention: Visual Signal (flashing light is best) Audio Signal (loud and persistent, e.g. burglar alarm) Protective Barrier (to prevent defect or operator injury) When used: low defect occurrence rate and when repairs can be made. Shutting Down the Operation: Upon detecting a “non-conformance” the operation is simply shut down, i.e. the next part will not be processed. When used: relatively higher occurrence rates and when repairs are not possible.

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT EXAMPLES OF POKA-YOKE’S FOR THE THREE MOST COMMON PROBLEMS

ERROR-PROOFING TECHNIQUES (Poka-Yoke) CONCEPT What is the best method for sensing fluid levels for a machine? What is the best method for sensing magnets for electric motors? What are three possible methods for sensing burs on a cylinder bore? What is the best method for detecting the presence of an O-ring? BEST SENSING IDEAS

Four Categories of Errors - Questions to Ask???? Missing Parts Is there a model mix such that some models require a part while others require nothing at all in that location? Is the part assembled as a small part after some main activity? Is the part difficult to see after being assembled?

Missing Parts Is the part : Unseen or untouched in subsequent process steps? Difficult to see during assembly? Difficult to assemble? Difficult to see after assembly? Difficult to differentiate between pre and post assembly? Can anything be done to resolve this in design of product/process? Can the part be combined with another part? Can the part be eliminated? What can be done to detect whether the part has been assembled? Detection device - torque counter, photoelectric eye over container, limit switch at dispenser,.... Lock out subsequent operation if part is missing. Lock out device - limit switch, conductivity sensor... Implement operator instructions, visual aids and training as minimum requirement YES NO NO Implement Error Proofing (process/design change and/or detect/lock out device) Verify results YES

Brainstorm Error Proofing Mechanism Make visible/obvious if missing Color contrast Visible at numerous operations and pack Use mirrors Position of part as moves down line Visual aid/picture posted with part present and highlighted Redefine process Assemble early in process Successive check Rearrange multiple write-up to eliminate “sometimes do/sometimes don’t” Monitor part supply Only supply parts needed for that model (no questions-if there are parts present, use them) Lot control, count parts-must equal # pieces produced Sensors Photoelectric eyes to detect, lock out until corrected Limit switch to detect, lock out until corrected Modify design Eliminate part Missing Parts - Thought Starters

Misassembled Parts Is the operation difficult for the operator to see as they perform the job? Is there an assembly or positioning operation that can be completed incorrectly? Four Categories of Errors-Questions to Ask????

Misassembled Parts Is the part : Difficult to see during assembly? Difficult to assemble? Difficult to see after assembly? Difficult to differentiate between pre and post assembly? Lacking guides or fixtures for proper assembly or proper alignment? Can anything be done to resolve this in design of product/process? (guides, fixtures, automation) Can the part be combined with another part? Can the part be eliminated? What can be done to detect whether the part has been misassembled? Detection device - torque counter, photoelectric eye, limit switch Lock out subsequent operation if part is misassembled. Lock out device - limit switch, conductivity sensor... Implement operator instructions, visual aids and training as minimum requirement YES NO NO Implement Error Proofing (process/design change and/or detect/lock out device) Verify results YES

Brainstorm Error Proofing Mechanism Visual aids Visual aid/picture posted with correct position highlighted Redefine process Assemble early in process Successive check Workplace organization Organize for maximum ease and visibility Sensors Photoelectric eyes to detect, lock out until corrected Limit switch to detect, lock out until corrected Modify/design fixture Unable to assemble incorrectly Modify design Eliminate part Prevent misassembly - e.g. two sizes of studs Provide guides or references Misassembled Parts- Thought Starters

Incorrect Processing Is there an operation that requires a recognition of some characteristic to determine what to do with the part next? REJECTS GOOD Four Categories of Errors-Questions to Ask????

Incorrect Processing Does the operation require recognition of some characteristic to determine what to do with the part? (e.g. Red light indicates place in reject pile, visual inspection for pre-defined defects) Can anything be done to resolve this in design of product/process? (fixtures, automation) Can the part be combined with another part? Can the part be eliminated? What can be done to detect whether the part has been incorrectly processed? Detection device - reset button, photoelectric eye, limit switch Lock out subsequent operation if part is incorrectly processed. Lock out device - limit switch, conductivity sensor... Implement operator instructions, visual aids and training as minimum requirement YES NO NO Implement Error Proofing (process/design change and/or detect/lock out device) Verify results YES

Brainstorm Error Proofing Mechanism Visual aids Quality alert indicating high potential for error Fixture or template outlining pre-defined defects Bogey or sample boards for visual inspection Redefine process Reset or acknowledge but at the appropriate next operation Automate Workplace organization Separate and clearly label reject locations/containers Sensors Photoelectric eyes to detect, lock out until corrected Limit switch to detect, lock out until corrected Incorrect Processing- Thought Starters

Incorrect Parts Is there a selection of parts in front of the operator that would allow for the wrong part to be chosen and assembled? Four Categories of Errors-Questions to Ask????

Incorrect Parts Is there a selection of parts available at the workstation? Are similar parts assembled onto the product at the same location? Can anything be done to resolve this in design of product/process? (Consolidation, separate operations) Can the part be combined with another part? Can the part be eliminated? What can be done to detect whether the incorrect part has been assembled? Detection device - bar code, photoelectric eye, limit switch Lock out subsequent operation if the incorrect part is detected Lock out device - limit switch, conductivity sensor... Implement operator instructions, visual aids and training as minimum requirement YES NO NO Implement Error Proofing (process/design change and/or detect/lock out device) Verify results YES

Brainstorm Error Proofing Mechanism Make visible/obvious if incorrect part Color code - match part to product Visible at numerous operations and pack Position of part as moves down line Visual aid/picture posted with correct part present and highlighted Redefine process Assemble early in process Successive check Rearrange multiple write-up to separate assembly of like parts Monitor part supply Only supply parts needed for that model Sensors Photoelectric eyes to detect, lock out until corrected Limit switch to detect, lock out until corrected Modify/design fixture Unable to assemble incorrect part Modify design Eliminate part Prevent assembly of incorrect part Incorrect Parts- Thought Starters

Error-Proofing Process The Error Proofing Process: Utilizes a multi-functional approach Is driven by Customer Satisfaction and allows for Quick response and implementation of solutions Is used to “Kill” problems Is documented in the ‘Problem Solving Document’ (PSD) Supports Continuous Improvement Methodology Is the ‘Contain’ step in the 5 Step Problem Solving Process People & Teamwork 5. Evaluate 1. Identify 2. Analyze 3. Plan 4. Implement “ Quick Response / Quick Implementation” Institutionalize the Solution and the Ongoing Control Problem Solving Documentation First Time Quality (F.T.Q.) at Operation Departmental Containment Station Network Internal Plant Audit Customer Rejects (PPM) Systematic Problem Solving Process Candidates for Error Proofing Warranty Information Prevent Select Contain Correct Institutionalize Continuous Improvement Opportunity

1% DEFECT RATE ( 99% YIELD ) OF ALL STATIONS RESULTS IN 78% CONFORMING PRODUCTS Cell 1 Cell 3 Cell 2 Cell 4 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate 1% Defect Rate

PROCESS FALLOUT TABLE Centered Process Process capability ratio Parts per million defective 0.50 133,600.00 0.75 24,400.00 1.00 2,700.00 1.10 967.00 1.20 318.00 1.30 96.00 1.40 26.00 1.50 6.80 1.60 1.60 1.70 0.34 1.80 0.06 2.00 0.0018

Implementation Procedure: Product Tooling Design Phase Predict Potential Quality Defects during Product Tooling Design Stage. Use DFM to modify Tooling Design to Prevent Potential Defects from Occurring in Production based on Potential Defects Identified. Build Poka-Yoke Devices into the Process where Design “Fixes” can not be Incorporated. ERROR PROOFING

ERROR PROOFING Production Phase Retro-fit Poka-Yoke Devices into Existing Tooling Use Quality History to Target Potential Error Proofing Application Sites Obtain Set-Up Operator Input as to Where to Apply “Error Proofing” Devices as well as the Type of Devices to Use. Implementation Procedure (Continued):

Some Error Proofing Guidelines: Standardize Press Shut Heights Utilize Digital Process Parameter Gages Apply Locating Devices to Dies, Fixtures, Etc. Gages Pre-calibrated prior to Start of Set-Up Utilize Common/”Quick Connect Fittings and Clamping Hardware “ One Way” Loading 100% Component Presence Check Verify “Machine Cycle Completed” Detected “Error” Stops Process ERROR PROOFING

CASUAL CONNECTIONS BETWEEN DEFECTS AND HUMAN ERRORS Strongly Connected Connected SOURCE: NKS/Factory Magazine “Poka-Yoke” Causes of Defects Omitted Processing Processing Errors Errors Setting Up Workpieces Missing Parts Wrong Parts Processing Wrong Workpiece Misoperation Adjustment Error Improper Equipment Setup Improper Tools and Jigs Human Errors International Misunderstanding Forgeful Misidentification Amateurs Willful Inadvertent Slowness Non-Supervision Surprise

Error proofing technique - Poka Yoke

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Error proofing technique - Poka Yoke