Study on Uniformity Force Variations in PCR & UVR 16" & 17" Tyre Sizes

Study on Uniformity Force Variations in PCR/UVR 16” & 17” Sizes Halol Plant Syed Mohammed Sajl 90201039 DPS&RT, CUSAT CONTENTS 1. Tyre Uniformity - An Introduction 2. Scope of Study 3. Studies – Results and Discussions 4. Conclusions 5. Recommendations 6. The Way Forward 7. References 1. Tyre Uniformity – An Introduction 1.1 INTRODUCTION • Tyre Uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers. • These measurement standards include the parameters of Radial Force Variation, Lateral Force Variation, Conicity, Ply Steer, Radial Run Out, Lateral Run Out and Sidewall Bulge. Axes of Measurement Axes of Measurement • Tire forces are divided into three axes: Radial, Lateral, and Tangential. • The Radial axis runs from the tire center toward the tread, and is the vertical axis running from the roadway through the tire center toward the vehicle. This axis supports the vehicle’s weight. • The Lateral axis runs sideways across the tread. This axis is parallel to the tire-mounting axle on the vehicle. • The Tangential axis is the one in the direction of the tire travel. 1.2 TYRE UNIFORMITY PARAMETERS • Radial Force Variation (RFV) • Radial Force Harmonic Analysis (RFHx) • Lateral Force Variation (LFV) • Conicity • Ply Steer • Radial Run Out (RRO) • Lateral Run Out (LRO) • Sidewall Bulge and Depression • Static Imbalance • Dynamic Imbalance FORCE VARIATIONS GEOMETRY VARIATIONS WEIGHT VARIATIONS 1.21 Radial Force Variation (RFV) • Radial force acts upward to support the vehicle, radial force variation describes the change in this force as the tire rotates under load. • As the tire rotates and spring elements with different spring constants enter and exit the contact area, the force will change. • Tyres are made from a number of separate components, in order to achieve the requirements of comfort, performance etc. • As the components increases the various splices also increases. • The splices can cause a particular portion of the tyre to have more stiffness, which on running shows radial force to show a peak point. • The vice versa occurs in the area of tyre where there is no or relatively low splice. The presence of these two areas results in variation in the radial force. 1.21 Radial Force Variation (RFV) • Consider a tire supporting a 1,000 load running on a perfectly smooth roadway. It would be typical for the force to vary up and down from this value. • RFV can be expressed as a peak-to-peak value (RFPP), which is the maximum minus minimum value. Ｂ 1 cycle of tyreLoad Ａ Ｂ Opposing Force Ａ ＲＦＶOpposing force of the spring 1.22 Radial Force Harmonic Analysis • RFV, as well as all other force variation measurements, can be shown as a complex waveform. • This waveform can be expressed according to its harmonics by applying Fourier Transform (FT). • The first harmonic expressed as RFH1 (Radial Force First Harmonic) describes the force variation magnitude that exerts a pulse into the vehicle one time for each rotation. • RFH2 expresses the magnitude of the radial force that exerts a pulse twice per revolution, and so on. • High harmonics are less problematic because the rotating speed of the tire at highway speeds times the harmonic value makes disturbances at such high frequencies that overcome by other vehicle dynamic conditions. 1.23 Lateral Force Variation (LFV) • The Lateral Force acts side-to-side along the tyre axle; lateral force variation describes the change in this force as the tire rotates under load. • Consider the various components of the tyre as individual spring elements. • As the tire rotates and spring elements with different spring constants enter and exit the contact area, the lateral force will change. • As the tire rotates it may exert a lateral force on the order of 10 Kg, causing steering pull in one direction. • It would be typical for the force to vary up and down from this value. A variation between 10 Kg and 12 Kg would be characterized as a 2 Kg lateral force variation or LFV. 1.23 Lateral Force Variation • LFV can be expressed as a peak-to-peak value (LFPP), which is the maximum minus minimum value, or any harmonic value as described below. Ａ Ｂ Ｃ Ｄ Ａ ＬＦＶ Opposing force of lateral direction 1 cycle of tyre Ａ Ｃ Ｂ Ｄ 1.24 Conicity • Conicity is a parameter based on lateral force behavior. • It is the characteristic that describes the tire’s tendency to roll like a cone. • This tendency affects the steering performance of the vehicle. • In order to determine Conicity, Lateral Force must be measured in both Clockwise (LFCW) and Counterclockwise direction (LFCCW). 1.24 Conicity • Conicity is calculated as one-half the difference of the values, keeping in mind that CW and CCW values have opposite signs. Conicity = Lateral Shift (CW) + Lateral Shift (CCW) 2 • Conicity is an important parameter in production testing. 1.3 TIRE UNIFORMITY MACHINES • Tire Uniformity Machines are special-purpose machines that automatically inspect tires for the tire uniformity parameters described above. • They consist of several subsystems, including tire handling, chucking, measurement rims, bead lubrication, inflation, load wheel, spindle drive, force measurement, and geometry measurement. • It contains following parts: - Feed Conveyor - Test Zone - Exit Conveyor 2. Scope of Study 2.1 OBJECTIVE • To study the factors responsible for the various parameters those affect the Uniformity Yield of Tyres. • To conduct a study on the Uniformity Force Variations in PCR/UVR Sizes in CEAT Halol Plant. 2.2 BACKGROUND • The SUV Segment in India is on the rapid rise and this leads the need of more UVR tyres. • The company had identified the need to improve the uniformity yield of PCR/UVR Sizes (16” & 17”) in order to meet the Original Equipment Manufacturer (OEM) Requirements considering the future prospect of the company. 2.3 PARAMETERS SELECTED FOR STUDY 1. Radial Force Variation (RFV) 2. Radial Force First Harmonic (RFH1) 3. Conicity (CON) The selection of the above parameters was based on the following criteria-: • The Trend of the Uniformity Yield of 16” and 17” Tyres occurring of the past 6 months was studied and the parameters causing them were then selected looking at the deviation. • The parameters were selected looking to the magnitude of the variation and the frequency of the occurrence. 2.3 PARAMETERS SELECTED FOR STUDY 1. Radial Force Variation (RFV) 2. Radial Force First Harmonic (RFH1) 3. Conicity (CON) With Original Specifications With 50% Tightened Specifications # SIZE RFV RFH1 LFV CON # SIZE RFV RFH1 LFV CON 1 16” – Type A 97.6 96.1 97.1 98.4 1 16” – Type A 84.8 78.8 94.6 95.0 2 17” – Type A 85.5 85.5 95.0 93.0 2 17” – Type A 82.6 77.2 94.0 92.7 3 16” – Type B 94.9 93.3 96.7 97.9 3 16” – Type B 69.1 82.7 94.6 93.6 4 17” – Type B 93.4 95.6 97.0 97.4 4 17” – Type B 76.5 82.3 94.6 85.9 5 16” – Type C 93.0 93.6 97.4 95.3 5 16” – Type C 61.1 58.2 93.2 87.4 Table: Deviation of Uniformity Yield Parameters after tightening the specifications by 50% in 16” & 17” Tyres 2.3 PARAMETERS SELECTED FOR STUDY RFV, RFH1 & CONICITY MATERIAL MAN MACHINE S/W spotting on the Carcass Shaping Drum Loading Sidewall Width, Length & Gauge Belt Width, Length & Gauge METHOD Heavy Component Splicing Bead Spotting on the GT GT not placed on the Trolley as per the centre Measuring Systems GT Loading Material Offset VCL Height Ring Down Height Turn-up Height Stretching of components to meet the splice I/L Width, Length & Gauge Bead Inner Circumference High Conicity Predictor Value in Tread Profile Tread Width, Length & Gauge Shaping Drum Wobbling Loose application of components wrt splice Incorrect Material Spotting Splice Correction as per the standards 2.4 EXPERIMENTAL • All the components required during the building operation were inspected during the building process and curing process; and the variation in them was induced by keeping the other component variables constant and under specification. • The green tyres were then inspected for any types of non-acceptable variation occurring. If so they were not included in the remaining follow-up. • The tyres were tested for the uniformity values over the tyre uniformity machine. It was ensured that the tyres are properly lubricated and was loaded perfectly over the load wheel in the uniformity machine. • The sample size for each study was 5 tyres each. • The following Machinery was utilized used for the study: Machine Name Purpose RMS Tyre Building Machine For building the green tyre L&T Curing Press – Segmented Mould Curing the tyre AKRON Standard Tyre Uniformity Machine Checking tyre uniformity 2.5 METHODOLOGY • The following approach was used for the study of the induced variations over the uniformity. Selection of Parameter Inducing the Variation in the Tyre Collection of Respective Force Values over the Tyre Uniformity Machine Analysis of the Data Results and Discussion Vector Effect Analysis Conclusion Recommendations 2.5 METHODOLOGY The variations were induced at the building stage of the tyre. The methodology used for inducing variations are described below: • Belt Offset • Inner Liner Offset: • Ply Offset • Belt Over-Splice • Inner Liner Over -Splice • Ply Over-Splice • Spotting Study  The spotting of the specific splice is changed with respect to the original position of the splice in the building stage.  This was done by calculating the total perimeter of the expanded drum and then shifting splice and entering the required angle of the splice into the Building Machine configuration panel. 2.5 METHODOLOGY Conicity Predicitor Study • The analysis presented by the Conicity Viewer option in the Profilometer, is printed on the lower right of the report of symmetric profile measurement. • The Conicity Predictor creates a left/right differential error map by graphically finding the halves of the tread together and calculating the difference between the left and right halves. • The sum of the Inner and Outer Conicity moment represents the Conicity Predictor. 2.5 METHADOLOGY Figure: A Typical Tread Profilometer 3. Studies – Results & Discussion 3.1 UNIFORMITY YIELD COMPARISON - UNIFORMITY MACHINES • Machine B has a better Bead Locking when compared to Machine A 40 50 60 70 80 90 100 1-Feb 2-Feb 3-Feb 4-Feb 5-Feb 6-Feb 7-Feb 8-Feb 9-Feb 10-Feb 11-Feb 12-Feb 13-Feb 14-Feb 15-Feb 16-Feb 17-Feb 18-Feb 19-Feb 20-Feb 21-Feb 22-Feb 23-Feb 24-Feb 25-Feb 26-Feb 27-Feb 28-Feb 1-Mar 2-Mar 3-Mar Type A – 15 Inches - Uniformity Machine A Vs Uniformity Machine B A B 3.1 UNIFORMITY YIELD COMPARISON - UNIFORMITY MACHINES 50 55 60 65 70 75 80 85 90 95 100 1-Feb 2-Feb 3-Feb 4-Feb 5-Feb 6-Feb 7-Feb 8-Feb 9-Feb 10-Feb 11-Feb 12-Feb 13-Feb 14-Feb 15-Feb 16-Feb 17-Feb 18-Feb 19-Feb 20-Feb 21-Feb 22-Feb 23-Feb 24-Feb 25-Feb 26-Feb 27-Feb 28-Feb 1-Mar 2-Mar 3-Mar Type B – 15 Inches – Uniformity Machine A Vs Uniformity Machine B A B 3.1 UNIFORMITY YIELD COMPARISON - UNIFORMITY MACHINES Table: Difference in Uniformity Yield - Uniformity Machines – K2 vs MP Type A – 15” Type B – 15” Difference in Yield M/c A M/c B M/c A M/c B Size A Size B MIN 47.00 65.62 55.60 71.00 MAX 93.00 88.34 96.20 94.14 AVG 69.42 79.76 77.83 81.20 10.34 3.37 STD DEV 12.82 6.33 9.15 6.55 -6.49 -2.60 3.2 VARIATIONS IN THE BUILDING MACHINES 3.2.1 Component Offset Variations 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50 9.00 01-Mar 02-Mar 03-Mar 04-Mar 05-Mar 06-Mar 07-Mar 08-Mar millimeters I/L Ply 1 Ply 2 3.3 VARIATIONS IN THE BUILDING MACHINES 3.2.2 Component Splice Variations 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 26-Mar 27-Mar 28-Mar millimetres I/L Ply 1 Ply 2 3.3 STUDY - COMPONENT VARIATION VS TYRE UNIFORMITY 3.3.1 Component Offset Variation vs Uniformity Parameters Date 08-Mar-14 Tyre Size 16” – Type C LOAD INF RFV (N) H1 (N) LFV LFH1 LFD CONICITY Centered 6048.57 200.19 77.66 40.78 48.35 39.79 376.17 -24.72 IL Off 6055.67 200.75 104.64 76.60 50.48 38.33 365.56 16.70 Ply 1 Off 6074.78 200.75 123.08 53.45 76.32 62.00 408.28 47.64 Ply 2 Off 6051.69 200.50 112.13 68.81 50.99 34.89 401.00 58.26 Belt Off 6016.78 199.33 144.55 86.16 23.88 44.68 354.08 -34.52 Date 14-Mar-14 Tyre Size 17” – Type A LOAD INF RFV (N) H1 (N) LFV LFH1 LFD CONICITY Centered 4369.21 199.47 64.67 23.29 40.06 16.07 376.17 12.9 IL Off 4366.47 199.33 85.50 43.7 18.49 7.98 202.14 -12.64 Ply 1 Off 4374.55 199.38 92.98 57.86 51.93 44.61 262.46 -1.4 Ply 2 Off 4362.06 199.32 89.89 58.34 30.66 17.61 238.46 -3.87 Belt Off 4343.06 198.92 142.09 88.07 29.12 13.42 225.78 -17.87 3.3 STUDY - COMPONENT VARIATION VS TYRE UNIFORMITY 3.3.2 Component Over-Splice Variation vs Uniformity Parameters Date 10-Mar-14 Tyre Size 16” – Type B LOAD INF RFV (N) H1 (N) LFV LFH1 LFD CONICITY Centered 5040.69 200.19 79.68 40.93 49.63 39.79 376.17 -24.72 IL Off 5022.78 199.84 99.53 45.16 40.23 14.51 335.85 -35.95 Ply 1 Off 5032.69 200.12 145.51 92.53 23.53 5.98 317.02 -32.94 Ply 2 Off 5045.21 200.2 146.76 94.6 26.95 11.2 362.18 44.48 Belt Off 5037.02 200.35 176.45 112.16 43.43 16.18 289 -74.94 Date 15-Mar-14 Tyre Size 17” – Type A LOAD INF RFV (N) H1 (N) LFV LFH1 LFD CONICITY Centered 4365.57 200.19 68.95 39.87 38.45 38.33 365.56 16.7 IL Off 4392.85 200.22 100.47 73.3 41.4 35.52 251.75 7.45 Ply 1 Off 4364.24 199.72 126.37 85.12 58.99 43.34 380.39 12.87 Ply 2 Off 4367.79 199.67 136.77 91.79 53.43 41.82 342.85 -1.02 Belt Off 4364.78 199.55 158.01 119.54 51.86 35.5 345.97 13.89 3.4 VARIATION IN CONICITY PARAMETER AND LEFT-RIGHT ERROR IN TREAD PROFILES Date 16” – Type A 16” – Type B 16” – Type C Conicity Prediction Left-Right Error Conicity Prediction Left-Right Error Conicity Prediction Left-Right Error 01-Mar-14 3457.742 54.58 -2328.134 -7.358 02-Mar-14 3231.278 55.945 1493.024 18.101 -71.906 -25.62 03-Mar-14 2082.991 32.397 -1801.348 -8.027 -2581.434 -17.228 04-Mar-14 -1925.877 -15.898 1568.57 -17.213 05-Mar-14 -4465.399 -57.994 -1877.286 16.782 -2425.13 -2.444 06-Mar-14 3455.215 23.373 -2071.733 -35.839 07-Mar-14 355.391 23.149 -3347.225 -10.987 08-Mar-14 -1337.675 -7.089 -54.895 16.246 -1866.619 29.906 09-Mar-14 2784.961 44.699 -1748.5 5.531 -2574.757 7.792 10-Mar-14 -3452.77 -18.019 -2224.106 17.402 MIN -4465.40 -57.99 -1925.88 -15.90 -3347.23 -35.84 MAX 3457.74 55.95 3455.22 23.37 1568.57 29.91 AVERAGE 328.73 14.93 -263.03 9.91 -1792.25 -6.16 STD DEV 3351.28 43.46 1974.07 14.73 1447.82 19.98 3.4 VARIATION IN CONICITY PARAMETER AND LEFT-RIGHT ERROR IN TREAD PROFILES 1. The Die is taken and it is centered. 2. The gap between the Preform - Cassette stopper is eliminated 3. The damaged Preform and Extruder Head Stopper was replaced 3.4 VARIATION IN CONICITY PARAMETER AND LEFT-RIGHT ERROR IN TREAD PROFILES Date 16” – Type A 16” – Type B 16” – Type C 16” – Type D Conicity Prediction Left-Right Error Conicity Prediction Left-Right Error Conicity Prediction Left-Right Error Conicity Prediction Left-Right Error 14-Apr-14 -40.77 19.721 1222.906 8.866 -665.19 -2.77 15-Apr-14 -622.088 10.334 144.652 -3.747 1288.756 14.769 -885.31 32.439 16-Apr-14 -296.533 14.516 1099.58 -11.742 483.24 17.086 17-Apr-14 -1225.667 -19.447 -599.799 7.944 18-Apr-14 -613.769 17.869 683.032 -2.04 973.162 19.814 19-Apr-14 -298.844 8.924 210.119 -11.027 MIN -1225.67 -19.45 144.65 -11.74 -599.80 7.94 -885.31 -2.77 MAX -40.77 19.72 1222.91 8.87 1288.76 19.81 -665.19 32.44 AVERAGE -516.28 8.65 672.06 -3.94 536.34 14.90 -775.25 14.83 STD DEV 411.24 14.38 494.44 8.35 826.76 5.08 155.65 24.90 • After corrective steps, the Conicity Predictor value has been minimized. 3.5 STUDY – SPOT ANALYSIS AVERAGE STD DEV RFV 117.02 49.25 RFH1 65.68 43.63 CON 49.48 25.54 AVERAGE STD DEV RFV 86.12 28.24 RFH1 62.32 26.80 CON 30.30 18.08 AVERAGE STD DEV RFV 74.05 24.16 RFH1 61.12 23.92 CON 25.12 18.35 3.6 STUDY – SPOT ANALYSIS Figure: A fine tuned, well balanced GT Spot 3.7 STUDY - VECTOR EFFECT ANALYSIS 4. CONCLUSIONS • The Drop in Tyre Uniformity Yield is due to the Force Variations. • The Major Force Variations are Radial Force Variations (RFV), Radial Force First Harmonic (RFH1) and Conicity (CON) as these parameter has abnormal deviations. • There is a difference in the yield obtained in Uniformity Machine A and Uniformity Machine B. • Material Offset and Heavy Component Splicing can be attributed to the variation in Radial Force Variations (RFV) and Radial Force First Harmonic (RFH1) due to magnitude of these variations and its frequency of occurrences. 4. CONCLUSIONS • The effect of each material splice on Radial Force Variations (RFV) is respectively; Belt, Ply 2, Ply 1 and Inner Liner. • The above trend is followed in case of component offset splices. • The Material Offset in Tyre Building which can be a reason of variation in conveyer speeds. • The Conicity Predictor Values in PCR/UVR Sizes were found to be consistently high and it was brought down by taking counter steps. • We can bring down the concentration of High Spots/Low Spots in a Tyre by following a well balanced fine tuned Spot Analysis. • A perfect tyre spot can be obtained by conducting a Vector Effect Analysis. 5. RECOMMENDATIONS • The Machine Tolerance Checks must be made on frequent basis. • Revalidation of GT Spotting (Splices) of all sizes. • Conicity Predictor value must be made to be a parameter in controlling the Conicity of the Tread with respect to the end tyres. 5. THE WAY FORWARD • Vector Effect Analysis with respect to Curing • Waveform Analysis with respect to each parameter. • Improvement in Tooling and Machineries 7. BIBLIOGRAPHY • The Pneumatic Tire - Akron University – NHTSA • Tyre Science and Technology - Tire Society, Inc.,– Journal • User & Product Manuals, Micro Poise & llinois Tool Works Company (ITW), Akron Standard • ASTECPLUS™ - Operators Manual - Micro Poise Measurement Systems • Profile Viewer User’s Guide – Profilometer SL – Bytewise Measurement Systems - Product Manual • SAE J332 - http://standards.sae.org • http:// www.wikipedia.com Thank You