Lear Training program Thomas Marcum and Larry Bruck

Lear Training program Thomas Marcum and Larry Bruck 2017/05/27

Agenda § Tuesday: – Introduction – Confirm tools talk is functional on all PC’s – Class Room § § § § Fastening Curve Definitions Tightening strategies Failure Modes Post View Lear Standards Wednesday: – Class room § § – Post View Tools Talk review One safety critical fastener to be reviewed live as a class and optimized Review data from class modified safety critical fastener/ any issues- fall out Production Floor § § § Basics of Fastening 101 Break into teams , each team to collect data on a safety critical fastener and analysis Review findings with instructors Thursday: – Class Room § § § Present results to the class/ original set points – optimized set points- fall out rate Open discussion for other applications, multi stage, issue joints, plastic Next steps

Objectives § Acquire a basic knowledge of the bolted joint as a system. § Understand the definition of terms. § Gain a basic knowledge of guidelines to follow during design. § Become aware of both product design and assembly issues.

Goal of the Fastening Process § What is the goal of the fastening process? – Meeting torque specifications? – Getting a green light? – Putting as much torque as possible into the joint? § ACHIEVING CLAMP LOAD TO HOLD PARTS TOGETHER!!!!!!!

Advantages of Properly Designed Joints § Optimize size and quantities of fasteners. § Eliminate need for ‘fixes’. § Simplify assembly, thereby reducing assembly errors.

Function of the Threaded Fastener § To keep two or more joint members from slipping relative to each other. § To act as a heavy spring to clamp two or more pieces together. In either case, the joint must be fastened properly to perform its intended function.

Basic Definitions • Bolt • Screw • Nut • Head • Bearing Surface • Shank • Body • Thread Point Head Bearing Surface Body Shank Thread Point

Thread Definitions § Root § Crest § Flank § Pitch § Major Diameter § Pitch Diameter § Minor Diameter Pitch Diameter Major Diameter

Thread Designation Metric Thread Designation Nominal size Pitch Length (bolt Only) M 8 X 1. 5 x 20 - 5 g 6 g Flank Dimensional Displacement Tolerance (Allowance) Tolerance Grade Tolerance Position Crest Diameter Tolerance Grade Tolerance Position

Preferred External Thread Designations M 8 X 1. 5 x 20 - 5 g 6 g § 6 g is the default and standard thread designation for metric externally threaded fasteners. § Critical fasteners, such as Cylinder Head, Main Bearing, and Flywheel bolts often call out tighter thread designations, such as 4 g. Connecting Rod bolts often call out the 4 g or 4 h thread designation.

Preferred Internal Thread Designations § 6 h is the default and standard thread designation for metric internal threads. § 4 h 6 h is often called out on critical engine block applications such at Cylinder Head bolt and Main Bearing bolt holes. This designation has a smaller tolerance on the pitch diameter, but allows normal minor diameter tolerances.

Bolted Joint Definitions Bearing surface • Preload • Grip length Bolted joint Preload/ or Clampload Grip Length

Torque Definitions § Torque – the twisting moment, product of force and wrench length, applied to a nut or bolt. § Dynamic (or applied) torque – the torque measured while the fastener is being installed.

• Tensile Strength Yield Strength Torque/ or Tension Strength of Fastener Definitions ultimate plastic yield elastic Angle/ or Time

Property Classes § Increasing numbers generally represent increasing tensile strengths § Two parts to the designation symbol: – first numeral(s) approximates 1/100 of the minimum tensile strength in MPa – last numeral approximates 1/10 of the ratio expressed as a percentage between minimum yield stress and minimum tensile stress

Property Class Example § Property Class 9. 8: – The minimum tensile strength requirement is 900 MPa. – The minimum yield strength requirement is 720 MPa. § 1/100 of 900 = 9 § ratio of yield strengths = 720/900 * 100 = 80% § 1/10 of 80% = 8 – Hence. . 9. 8

Failure Modes § Bolt fracture § Bolt stripping § Nut member stripping

Thread Engagement § Optimize bolt length and hold depth. § Avoid stripping of internal/external threads at assembly or service. § Bolt fracture is the preferred failure mode.

Four Phases of Tightening § Phase I - Rundown – no contact between under head and part

Four Phases of Tightening § Phase II - Draw-Down (seating) – contact, joint seated

Four Phases of Tightening § Phase III - Elastic – elastic deformation, clamp load build-up

Four Phases of Tightening § Phase IV - Plastic – yield

Where does torque go? 23

WHERE DOES TORQUE GO? § 90% of Assembly torque varies with friction § Other clamp load scatter variables – strength of bolt/joint – tightening accuracy – operating environment – relaxation – service loads

3. JOINT RATE & TORQUE

3. JOINT RATE & TORQUE § PURPOSE : Be able to define a “hard” or “soft” joint. § EXAMPLE: § Tightening a metal bracket to an engine block = hard joint § Tightening an oil pan to the same block using a rubber gasket = soft joint § Two identical joints with the only difference being the length of fastener. The shorter fastener will be a harder joint and the longer bolt will be softer.

ANGLE DISPLACEMENT § HARD JOINT: § The torque required to achieve clamp force occurs after turning a few degrees < 30 § SOFT JOINT: § For the same torque a much larger angle displacement will occur >720 deg

CLASSIFICATION CHART: § HARD 0 -30 degrees § MEDIUM HARD 30 -90 degrees § MEDIUM 91 -240 degrees § MEDIUM-SOFT 241 -720 degrees § SOFT 720 and above

What is…. OVERSHOOT ? § DEFINED: § Increase in torque that occurs during the time it takes the tool to stop. § The magnitude of overshoot depends on the rate at which torque is increasing as a function of time at the point the stop signal is received

3 B. STATIC VS. DYNAMIC § STATIC TORQUE DEFINED: § The torque required to break a fastener away from a static or stationary position. § Static torque data acquisition: § Acquired through use of a beam, dial or digital torque wrench.

STATIC VS. DYNAMIC § DYNAMIC TORQUE DEFINED: § Monitored while the fastener is moving or in a dynamic state. § Dynamic torque data acquisition: § Acquired with an inboard transducer and electric monitoring device.

Which is higher: the Static or Dynamic torque? § If the joint relaxes severely, the static torque will be lower. § If the joint is tightened very fast, the static may be higher. § If it is a normal joint, the static is normally higher due to the physics and difference between static and dynamic friction.

3 C. RELAXATION § Occurs to some extent in all joints over a period of time. § Caused by the surfaces of the part embedding or by soft parts. § On a hard joint 70%-90% of relaxation occurs in the first 10 -30 msec

Clamp Force vs. Torque

Nut Factor (or K Factor) § An experimental constant used to evaluate or describe the ratio between the torque applied to a fastener and the preload achieved as a result. § It is not the coefficient of friction, it includes effects such as: – friction, torsion, bending, plastic deformation of the threads, phases of the moon, etc.

Torque Vs. Preload § T = F * K * D -- or -- F = T / (K * D) where:

Torque Vs. Preload § T = F * K * D -- or -- F = T / (K * D) where: – T = input torque – F = achieved preload – D = nominal diameter – K = nut factor

Variables Affecting Friction § Hardness of all parts § Surface finishes § Type of materials § Thickness, condition, and type of plating, if present § Fit between threads § Type, amount, condition, temperature, of any lubricants involved

Friction § Friction will always be present. § Without any friction, bolts would not stay in a bolted joint. § The most important thing to do is to evaluate the friction in the joint and maintain consistency.

5. PREVAILING TORQUE § DEFINED: Existing torque during rundown and before parts are seated or clamped together. § Prevailing torque can be intentional or unintentional:

Intentional prevailing torque: § Used to keep parts together even if clamp load is lost. § Self tapping or self threading joints. It must be present to cut / form threads.

Unintentional prevailing torque § Undesired material in threads. Paint, undercoating, weld spots. § Wrong dimensions. If either the fastener is too large or the hole is too small. § Coating of fastener. Coating material is too thick or too thin.

Effects on power tools § Tool will show decrease in rundown RPM i. e. the overall time to tighten increases. § Reduced ergonomics. Lower RPM will increase the reaction of the tool. § Overall wear of the tool. Gears, motor, angle head.

Current Issue § Unseated fasteners are not detected with torque monitoring only. Unseated fasteners have escaped our plants because angle monitoring is not used or used properly. This impacts all groups that complete safety critical fasteners JIT, Structures, Trim. § Plant staff not properly trained on programming controls and using advanced features § Same joint over multiple plants have different pass/fail ranges.

Example § Seats were found at the customer with the marriage fasteners not seated. – Fasteners were at torque – Angle settings in torque controller were min 6 and Max 9999 degrees. § Corrective actions – Angle settings changed to min 6 and Max 100 degrees. – Post View was implemented to verify there was a minimum of 200 degrees prior to the 16 NM cycle complete target. Prevailing torque NOK OK rundown with post view

Example § Many times these issues arise due to parts being out of tolerance Recliner weld nuts on cushion pan out of tolerance Recliner weld nuts not parallel, creates bind when marriage fasteners are torqued.

Fastening Curve Definitions § § § Run down – Running down of the fastener before prior to pulling the joint together – Prevailing torque- the initial torque to run down the fastener First target – First target is a parameter when the tool will shift speed from step 1 to step 2 – Same target should be used for START FINAL ANGLE Start final angle target – Start Final angle is a parameter that is used as a starting point to start reading angle, – Same target should be used for FIRST TARGET to shift speeds Final angle – Recorded angle from start final angle target to gun shutoff – This is completed during pulling the joint together and the stretch of the fastener phase. Final Target – The torque final target value defined in the parameter set. Torque First Target Start final angle Final Target Final Rundown Angle

JOINT TYPES Free running Joint Note: Very low or no torque prior to seating. Prevailing Torque Joint Note: Substantial torque prior to seating.

TIGHTENING STRATEGIES § One stage – One speed thru the complete run down / torque of the fastener – Very slow speed is required to reduce overshoot of the final target § Two stage – Two speeds § Run down speed up to first target § 50 ms delay to relax joint § Ramped speed for final torque § Ergo ramp – Monitors torque rate of the fastener during second stage to control reaction. – Easily missed program/ miss understood not needed with torque reaction arms. § Quick step – Designed to simulate an air tool on medium to soft joints. – Two speeds without 50 ms delay or ramp in second stage. – Less adaptive for varying joints, reduce accuracy no relaxation first target Lear will be standardizing with Two Stage only

FAILURE MODES COMMON CAUSES § High torques – Tool programming § Low torques – Operator pre-releasing trigger – Socket slip offs – High angle § Low Angles – Re-hit of fastener – Missing components – Poor lubrication on Fastener – Cross threaded fastener – Joint out of design specifications § High Angles – Stripped threads – Improper angle threshold – Cross threaded fastener § Not seated fasteners. – High friction in joint.

Methods of Detecting Failures § Final Angle – Advantages § Detects if the elastic properties of the joint change. § Typically if a fastener cross threads it will exhibit a large angle deviation. – Disadvantages § If the cross thread follows the same characteristics as a standard fastening it may not catch the failure. § Tool must be fixtured/torque reaction arm to prevent improper data. § Designs with high prevailing torque during the rundown will be difficult to set limits. This is due to the angle threshold needing to be set above the prevailing torque. – Implementation § Determine Final angle threshold. § Gather data and perform statistics to establish range § Set limits. § Test failure modes § Review data regularly until limits are optimized

RUNDOWN EXAMPLE Common variation in Prevailing torque Angle Graph shown with multiple torque run downs synchronized at peak torque

STANDARDS § Final Angle – First Target and Final angle target to be the same § Maximum Specified Angle Range/Starting point – < 200 Max – > 5 MIN – If this range is not capable, Product Engineering, AME to be contacted § All FMVSS fasteners to be monitored for torque and angle with pass/fail ranges. § All FMVSS fasteners require a torque reaction arm to correctly monitor angle. § If the FMVSS torque count is >2 in station spatial positioning must be used. § Hand start fasteners with “T” handle tool or with the use of pneumatic clutch gun with runoff tool. § Post view or similar to be used on all FMVSS fasteners Note: Some joints will be impossible to control with these general guidelines. These joints need to be identified for further investigation.

STANDARDS § Hand Start Palm Ratchet – When hand starting these devices to be used to reduce ergonomic risk factors. § Runoff tool with pneumatic clutch gun. – This method will consistently start the fastener to a specified length and eliminate ergonomic risk factors.

Additional Methods of detecting failures § An advanced strategy that allows the PF controller the ability to monitor and react to a bad tightening during the rundown phase (prior to first target) § Makes it possible to monitor torque values during 2 specific angle intervals prior to first target (from Rundown Complete) § If rundown does not fit the tightening “road map”, the tightening cycle will abort before the final tightening phase begins 55

RUNDOWN EXAMPLE Upper Post View box Rundown complete First target Start final angle Lower Post View box

Post View Torque Function Defined Post View Torque concentrates on process during rundown phase Rundown/Drawdown Phase

Post View Torque Function Defined Run Down Complete Post View is initiated by the run down complete set point Post View is completed before the final torque of the fastener. In example above final torque stage is not completed because this fastener failed Post View.

Post View Torque Function Defined Run Down Complete Post View failed this run down because there was not enough Run down angle for post view to look back. Notice: how the upper Post view box is to the left of the start point.

Post View Torque Function Defined Cross Threaded Rundown These two traces show the difference in a good rundown vs a cross threaded rundown. These traces can be used to setup your post view settings Good Rundown

Post View Torque Good Rundown. Torque OK Tightening Target 1 3 Angle • Measurement looks back 300 degrees then forward 200 from rundown complete torque Point 1. • If torque falls within the Post View window it is reported as a not ok. • In the example above low lubrication was causing a buildup of friction during the rundown.

Post View Torque Angle Problem Detected Torque NOK reported. Target 1 3 Angle • Measurement looks back 300 degrees then forward 200 from rundown complete torque Point 1. • If torque falls within the Post View window it is reported as a not ok. • In the example above low lubrication was causing a buildup of friction during the rundown.

Post view implemented Back 360 deg. Rundown complete Max Post View torque Forward 300 deg Note Both of the failures did not have any rundown angle • If Post View is used the controller reads back from Rundown complete. • Then forward for a defined interval. • If there is not enough data or if the rundown enters the red box the tightening is aborted and NOK is given.

Good rundown with high prevailing torque. Zoomed view of final torque. Note: final torque is linear. Linear

Bad rundown high prevailing torque. You can see angle vs TQ is not linear. Non-linear

Benefits of Post View Torque § Post View Torque allows the PF controller to monitor for joint inconsistencies early in the tightening strategy (before First Target) § It can be used to verify proper seating of the fastener before reaching final target by detecting fastener material changes, lubrication changes or missing washers and other fastener parts. § It can help detect cross-threads of fasteners BEFORE reaching final target § In some cases, it can detect incomplete angle engagement of the fastener BEFORE entering into the final rundown phase (eg: short bolt used in long bolt application). 66

Post View Torque Function Hardware Requirements § PF 3100/4000 controller (graph or compact) § RBU types : Silver, Gold, ETX, Customer Specials (Silver or Gold) § Available with SL, S, STB, STR and ETX tool types Firmware Requirements § Minimum PF firmware – PF World 5 SR 2 (only Gold RBUs) § Minimum PF firmware – PF World 7. 2. 4 (Silver, Gold RBUs and Silver/Gold Customer Specials) § Latest version of Tools Talk PF General Requirements § Post View Torque can be added to any torque or angle control strategy § OK fasteners need to have consistent seating 67

Post View Torque Monitoring Specifications § Post View defines 2 separate angle intervals for monitoring torque prior to First Target. One monitors for a max torque limit and one monitors for a min torque limit § You can define or both of these limits and either can be used first (min then max, or max then min). § The monitoring of the intervals begins with the Rundown Complete parameter § Rundown Complete is the torque level when the rundown phase is finished. Only activated if Rundown Angle or any PVT options are enabled. (Default is Tool Max Torque x 0. 2) § Rundown Complete is a defined torque point between Cycle Start and First Target § From Rundown Complete, the PF reads back to specified angle intervals and compares torque data to specific torque min and max limits

Post View Torque - Fault Notification Overall status was a NOK 69

Summary of the Benefits of Post View Torque § Post View Torque allows the PF controller to monitor for joint inconsistencies early in the tightening strategy (before First Target) § It can be used to verify proper seating of the fastener before reaching final target by detecting fastener material changes, lubrication changes or missing washers and other fastener parts. § Post View Torque can help detect cross-threads of fasteners BEFORE reaching final target § In some cases, it can detect incomplete angle engagement of the fastener BEFORE entering into the final rundown phase (eg: short bolt used in long bolt application). 70

Take Away’s § Always save your current controller settings before making changes! § First target and Start Final angle to be the same § Cycle complete to be ½ of Cycle Start § Set Postview boxes to catch failures, don’t make too tight. 71

Terms & Definitions § Cycle Start- set point in Nm to wake up the controller § Run down complete- set point in Nm to initiate postview check § First target- set point in Nm to change speeds § Final angle- degree of rotation of the fastener in the elastic stage § Start final angle- set point in Nm to start recording Final Angle § Final target- set point in Nm for final torque target § Cycle Complete- set point in Nm to store/send data to LPS § End time- amount of time allowed under cycle complete set point before ending rundown and sending data § Ramp- this is the acceleration in speed, 100%= 10 seconds, 50%=5 seconds……… 72

73 Committed to sustainable productivity.