APPENDIX 1 ONE POINT LESSON

Transcription

1 131 APPENDIX 1 ONE POINT LESSON Table A1.1 One point lesson-2 Peening coverage No. 02 Coverage Less Check : Visual Good Coverage : 98 % to 100 % desired Coverage - Good

2 132 Table A1.2 One point lesson-3 Shot size No. 03 The shot size should be selected such that it is 10 % to 25 % of the wire diameter of the spring. Shot sizes will be 0.35 to 0.45 mm

3 133 Table A1.3 One point lesson-4 Shot type No. 04 The shot type used are Conditioned cut wire steel shots Wrong method Right method Do not use : AS CUT Shots

4 134 Table A1.4 One point lesson-5 Peening intensity No. 05 This is specified in terms of the Almen arc rise which is selected to suit the shot size. Example: 0.4 shot Arc Rise 0.16 to 0.20 A mm.

5 135 Table A1.5 One point lesson-6 What is conditioned shots? Cut wire No. 06

6 136 Table A1.6 One point lesson-7 Why conditioned shots? Cut wire No. 07 Because as cut shots have sharp edges and produce sharp notches on the spring surface which act as stress raisers leading to crack and break. It is observed, shown figure the failure of spring will take place because of cut shots. Always use conditioned shots only.

7 137 Table A1.7 One point lesson-8 Conditioned cut wire shots (0.4mm) - Information No Shape : Round ( cylindrical Squares Corners Rounded ) 2. Size : 0.35 to 0.45 mm 3. Chemical Analysis ( Is: 4454-ii ) : C , Si , Mn S: 0.05 Max. P: Max. 4. Average Mean Hardness : Hv : 650 to Length of 10 shots : 4.0 ± 0.50 mm 6. Height of 50 shots : 0.02 to 0.03 gms. 7. Specific height of 1 litter shots : kg. 8. Inventory : 800 kg 9. Packing : 25 Kg / Bag 10. Source : Bakul Castings Dewas (MP) 11. Accepting Authority : Inwards Inspection SSS 12. Procurement Time : 4 Weeks.

8 138 Table A1.8 One point lesson-9 Sieving of shots No Remove shots from machine. 2. Pass through Sieve 1 3. What remains on top is Scrap. 4. Pass again through Sieve What remains on top is good shots 6. Bottom is scrap. We get good shots of 0.6 mm Range : 0.45 to 0.6 ( Presently seiving is manual )

9 139 Table A1.9 One point lesson-10 Conditioned cut wire shots (0.4mm) - Information No. 10 Shot size is a parameter in the peening process. Shots degrade during peening. 1. Natural wear 2. Shots break 3. Contamination. To maintain acceptable quality of shots sieving is necessary.

10 140 Table A1.10 One point lesson-11 How often is sieving No Sample test : Visual Every 8 hours of running. 2. Sieving : Every 24 - hours of running.

11 141 Table A1.11 One point lesson-12 Sl No 1 Shot peening : Process control No. 12 Controlled Purpose Method Frequency Sieving 2 Amperage 3 Arc height 4 Coverage Shot Condition : Size, wear broken shots, contamination dust, fines Shots flow kg/min Level of shots in hopper Peening in intensity Velocity of shots 98% to 100 % peened surface Exposer time Visual & magnifier 10X Sieving 1&2 Ammeter current in amps Almen strip Fixture Test gauge Visual magnifier x 10x Mat.Lab if in doubt Every 8 hours Every 24 hours of running Daily Weekly Daily

12 142 Table A1.12 One point lesson-13 Belt specification No. 13 Belt specification : Part no : Length : 8730 MM Width : 100 mm Thickness : 8 mm No. of Buckets: 52 No s. The elevator belt conveys peened Shots from bottom hopper to top hopper. The belt is fitted with 52 buckets. ½ of the buckets 26 carry shots. The belt runs (7.5 X 52) / 2 = 195 Buckets. Carry 230 kgf shots per minute.

13 143 Table A1.13 One point lesson-14 Shots level in hooper No. 14 Minimum level of shots in hopper is marked. After each sieving and loading the shots: Check the level of hopper. Add new shots if necessary. Ideally, the hopper should be ¾ full of shots. Maintain it.

14 144 Table A1.14 One point lesson-15 Classificatio n Shots flow information No. 15 The maximum shot flow this machine can give is 230 kgs / mins. The shot flow depends on current amperage. The no load current is 5.5 amps. ( 10 HP motor ) The maximum amps is 14.5 A. The operating amperage is 9 amps. Hence each amperage raise gives 25.5 kgs of shots. It is ideal to run the machine at 14.0 amps but not exceeding amps. The shot flow can be adjusted by abrasive control valve.

15 145 Table A1.15 One point lesson-16 Classificatio n Blast pattern: How to check/test? No. 16 Use a 3mm thick, 300 mm x 900 mm plate. Place it on the work conveyor (Mill). Do not run the work conveyor (Mill). Shot peen for 30 seconds. Take out the plate. The blast pattern shows the distribution of shots. The area which receives the max. shots is called the hot spot (warm to touch and deformed ) The location of hot spot is about 8 from the center of rotor. Adjust the pattern by control cage.

16 146 Table A1.16 One point lesson-17 How much load on work conveyor No. 17 If too much weight, Belt sags gap between belt and side plate Springs struck. Belt tears at holes Break downs. Belt shifts The right quantity: by volume: 1/3, by weight: 180 kgs. Do not overload.

17 147 Table A1.17 One point lesson-18 Set up of control cage through blast pattern No. 18 Fig. shows the warping of thin (3 mm) plate during the setting of hot spot. Test the plate for blast pattern. Determine the hot spot. Adjust the control cage for current hot spot location. Repeat the test for verification. Mark the location of control cage. This helps in future replacements

18 148 Table A1.18 One point lesson-19 Work conveyor information No. 19 Work conveyor consists of vulcanized endless rubber belt, multiple ply construction with 8.0 ø diameter drain holes. Work conveyor speed : 6.1 m/min, mill drive motor : 1400 rpm / 1 hp

19 149 Table A1.19 One point lesson-20 Dust collector data No. 20 Capacity : 1250 to 1700 CFM. Type : Motorized shanker type dust collector bag filters 3. Make : Vi-Ku Engineers. Efficiency : 99 % for 100 microns and above. Filter bags : 2 Nos Filter Area : 547 Sq.Ft. Bag size : 127 ø mm 1778 mm long. Shanker motor : 0.5 Hp, 1400 rpm Dust discharge : Manual gate

20 150 Table A1.20 One point lesson-21 V- Belts, always use correct V- belts No. 21

21 151 Table A1.21 One point lesson-22 Plant maintenance No. 22 Two important reasons for plant maintenance 1. Condition of the plant. 2. Performance of the plant. 1. Condition of the Plant: Due to peening action, not only the work but also other parts of the plant like peening cabinet, wheel housing also Receive peening, o o Through protection is provided, still they wear. If unchecked, they may cause holes and leakage of shots from unprotected parts which are not easy to replace. 2. Performance of the plant: Due to peening action, liners blades, impeller & control cage will wear. o If not checked they will affect the blast pattern, intensity and coverage. o For these two reasons, regular and periodic checks must be made immediately.

22 152 Table A1.22 One point lesson-23 Amperage and wheel efficiency- Importance No The ammeter reading of the motor (rotor) indicates the volume of shots thrown. 2. Therefore the correct amperage should be maintained 3. The Operating range of our 10hp rotor motor is 9 amps i.e., (Max. current A- No load current 5.5 A) 4. For maximum efficiency, it is necessary to run the machine at almost 14 amps, but not exceeding 14.5 amps (relay provided to cut off). 4. Less amperage indicates low shot flow or less shot in hopper. 5. This results in poor peening and low wheel efficiency. 6. Wheel efficiency is calculated as under : (Running load Amps No load Amps) ή = X 100 (Rated Max. Amps - No load Amps)

23 153 Table A1.23 One point lesson-24 Housing keeping No. 24 It is necessary to accept the fact that spillage of shots around the machine is inevitable. It is a self-detective machine. Shots may escape through unloading or holes and recess in the machine. These holes not only risk the personnel but also damage other machine. Even if a small problem is noticed, rectify it immediately. So, It is necessary to take Immediate corrective actions A STICH IN TIME SAVES NINE

24 154 Table A1.24 One point lesson-25 Adjusting and checking blast pattern No. 25

25 155 Table A1.25 One point lesson-26 Principle and effect of shot peening No. 26

26 APPENDIX 2 KAIZEN IMPLEMENTED Table A2.1 Kaizen case-1 Machine: Shot-peening Kaizen case - 1 Unit: Main plant Kaizen theme : Minimum shots level indicator/ sensor. Problem : - No minimum shots level indicator - Rotor runs even if shots are less - Poor peening quality - Rework Target: Counter measure : A visual shots level indicator and sensor provided and machine stops if shots level is low. Before counter measure : Benefits / results after implementation: - Shots level in hopper visual - Rotor stops if shots level is low. - Good peening quality - No rework Analysis: Rework, why? Poor peening quality, why? After counter measure : Scope and plan for horizontal deployment: Not noticed Root cause : Less shots in hopper Idea : Minimum shots level indicator/sensor provided 156

27 Table A2.2 Kaizen case-2 Machine: Shot-peening Kaizen case-2 Unit: Main plant Kaizen theme: Safety guards at 5 places. Problem : - All moving parts like rotor, drive, sprockets etc., have no guards. - Unsafe Target: Counter measure : Local safety guards provided Before counter measure : Benefits / results after implementation: - Safety Analysis : Unsafe, why? After counter measure : Scope and plan for horizontal deployment: No protective guards Local safety guards provided at 5 places Root cause : Unsafe Idea : Local guards 157

28 Table A2.3 Kaizen case-3 Machine: Shot-peening Kaizen case-3 Unit: Main plant Kaizen theme: Development of semi-automatic. electrical, control panel. Problem : - Manual controls. - Only trained person can operate. - No controls, timer, hour meter. - No separator switch for shaker and dust collector Target: Counter measure: New control panel with delay timer relay with all controls developed. Before counter measure : Benefits / results after implementation: - A single button press starts the operations in sequential manner with delay timer relay - Timer, buzzer and safety controls developed. - Easy to operate Analysis : Only trained persons, why? After counter measure : Scope and plan for horizontal deployment: Manual controls only Root cause : Manual controls Idea : Semi automatic controls 158

29 Table A2.4 Kaizen case-4 Machine: Shot-peening Kaizen case-4 Unit: Main plant Kaizen theme: Easy CLIT activities on top of machine. Problem : - No daily CLIT - Poor accessibility - Unsafe - Forced / accelerated deterioration. Target: Counter measure: Landing platform around the machine and aluminum ladder is provided Before counter measure : Benefits / results after implementation: - Easy CLIT activities - Easy accessibility - Safe ladder. - Forced deterioration prevented Analysis: No daily CLIT, why? Poor accessibility, why? After counter measure : Scope and plan for horizontal deployment: Can be deployed to all shot-peening machines Unsafe, why? Small straight fixed ladder Root cause : Poor accessibility for CLIT Idea : Landing around machine and safe ladder 159

30 Table A2.5 Kaizen case-5 Machine: Shot-peening Kaizen case-5 Unit: Main plant Kaizen theme: Arresting shot spilling from funnel. Problem : - During on/off operation shots spillage occurs from funnel - Shots fall on top of the machine and floor - Reclaiming Target: Counter measure: Funnel modified, so that shots do not spill out during on /off, operation Before counter measure : Benefits / results after implementation: - Spillage is arrested - Shots do not fall on the machine and floor - No reclaim Analysis: Shots spillage from on/off, why? After counter measure : Scope and plan for horizontal deployment: Funnel height not adequate Root cause : Funnel height Idea: Funnel height increased. 160

31 Table A2.6 Kaizen case-6 Machine: Shot-peening Kaizen case-6 Unit: Main plant Kaizen theme: Oil level indicator for reduction gear box. Problem : - No oil level indicator for reduction gear of mill drive - Gear / bearing may get damage Target: Counter measure: Tabular oil level indicator provided. Before counter measure : Benefits / results after implementation: - Prevents damage of gear box. - Inspection made easy. Analysis: Gears / bearing get damage, why? Oil level in gear box is low / not there why? After counter measure : Scope and plan for horizontal deployment: Can be adapted to all machines. No oil level indicator Root cause : Oil level inspection Idea: Visual control 161

32 Table A2.7 Kaizen case-7 Machine: Shot-peening Kaizen case-7 Unit: Main plant Kaizen theme: Emergency switch provided on machine. Problem : - No emergency switch - In case, of emergency, operator has to come out to stop the machine - No safety Target: Counter measure: Emergency switch is provided on the right side of the machine Before counter measure : Benefits / results after implementation: - Emergency stopping is possible. - Safety Analysis: Not safe, why? After counter measure : Scope and plan for horizontal deployment: Emergency stop of machine is not possible,why? No emergency switch Root cause : Emergency stopping is not possible Idea: Emergency switch 162

33 Table A2.8 Kaizen case-8 Machine: Shot-peening Kaizen case-8 Unit: Main plant Kaizen theme: Arresting of conveyor belt shifting Target: Counter measure: Split flange is provided at both the ends of the main roller. Problem : - Work conveyor belt shifts - To be realigned - Belt gets damaged Before counter measure : Benefits / results after implementation: - Belt shifting is arrested. - Belt damage eliminated. - Increased MTBF Analysis: Belt gets damaged, why? Belt shifting, why? After counter measure : Scope and plan for horizontal deployment: No guide Root cause : Belt shifting Idea: Flange to arrest shifting. 163

34 Table A2.9 Kaizen case-9 Machine: Shot-peening Kaizen case-9 Unit: Main plant Kaizen theme: Arresting shots falling on ground during unloading. Problem : - Shots leak out from door edges - Spread on floor. - Personnel risk ( unsafe ) Target : Counter measure: Door seating changed and toggle clamp closing provided. Before counter measure : Benefits / results after implementation: - Leakage arrested. - Shots do not spread on floor. - Safe working. Analysis: Leakage from door edges, why? Gaps between door and main frame, why? After counter measure : Scope and plan for horizontal deployment: Seating is not perfect, why? Poor seating system. Root cause : Seating is not perfect Idea: Modify/change the door seating 164

35 APPENDIX 3 POKA YOKE IMPLEMENTED Table A3.1 Poka yoke case-1 Machine: Shot-peening Poka - yoke case-1 Unit: Main plant Problem: If the door is open, blast motor / shots can still run * Prevent error Shut down Solution: Limit switch is provided to door. Key important : 1. Safety to operator 2. No leakage of shots Before Improvement Detect error * Control Alarm After Improvement Old control panel: - Independent control - If the door is opened blast /shots can still run - Risk to personnel (unsafe) - Shots leakage. New control panel: - Semi-auto mode - Limit switch provided at door that is connected to control circuit - If door is opened, blast motors / shots will stop automatically. - No risk and no shot leakage. 165

36 Table A3.2 Poka yoke case-2 Machine: Shot-peening Poka - yoke case-2 Unit: Main plant Problem: If shots level is low, blast motor / shots can still run Prevent error Shut down Solution: Proximity sensor provided at minimum shots level in * Control hopper Detect error Key important : No rework Alarm Before Improvement After Improvement No photo Old control panel: - If shots level is low, peening still takes place. - Poor quality - Rework. New control panel: - Proximity sensor provided at minimum shots level on hopper which gives indication to control circuit and the blast motor / shots will be automatically switch off - Good peening quality - Rework reduced 166

37 Table A3.3 Poka yoke case-3 Machine: Shot-peening Poka - yoke case-3 Unit: Main plant Problem: If the bottom mesh tray is opened, machine can Prevent error * Shut down still run Solution: Limit switch and toggle clamp provided at the * Control opening of tray. Detect error Key important : Prevent damage to machine parts Alarm Before Improvement After Improvement No photo Old control panel: - If the mesh tray is open, machine can still run. - Occasionally small springs can escape to hooper and damage the parts. - Also shots come out from the opening New control panel: - Limit switch and toggle clamp closing provided to the tray - If the tray is open by mistake the entire electrical system shutdown. - No damage to the machine parts - No leakage 167

38 Table A3.4 Poka yoke case-4 Machine: Shot-peening Poka - yoke case-4 Unit: Main plant Problem: Even after completion of peening cycle the rotor * Prevent error * Shot down and shots can still be on. Solution: Indicator and hooter is connected to output timer * Control * Detect error Key important : Quality Alarm Before Improvement After Improvement Old panel : - If the mesh tray is open, machine can still run - Occasionally small springs can escape to hooter and damage the parts. - Also shots come out from the opening New panel : - A timer, hooter and indicator provided. - Rotor and shots will switch off immediately after the completion of peening cycle. - No over shot-peening. - No scrap. 168

39 Table A3.5 Poka yoke case-5 Machine: Shot-peening Poka - yoke case-5 Unit: Main plant Problem: Sequential operation (manual) confusion. * Prevent error Shot down Solution: Automatic control panel. * Control Detect error Key important : No confusion Alarm Before Improvement After Improvement - All manual control. - Operation sequence confusion - In auto mode, one press of button starts the machine in sequential manner - No confusion. 169