Tuesday, March 25, 2014

Assembly of Rim and Tyre of Tractors - Problem of Batch Manufacturing

Problems in the Current System at Mahindra and Mahindra Plant, Nagpur

1. More handling during shifting is involved in existing process.
2. Haphazard inwarding of tyres & rims without considering arrival of vehicles, available space & requirement for assembly.
3. Distance travelled by the worker & vehicle is more from storage to assembly & from assembly to production line.
4. Inventory of Tyres & Rims is the major concerns as it is “A” class material.
5. Limited space availability for storage & mixing of tyres & rims.
6. Vehicle turnaround time is very high up to 18 hours from inwarding in plant to outward.
7. Waiting time of direct vehicles is extended up to 8 days due to nonavailability of space for unloading.
8. Paying high vehicle detentation charges due to vehicle detentation
9. Non availability of space for unloading of Tyres & Rims which are urgent for production due to limited space for unloading.
10. Damages of Tyres & Tubes due to wrong storage & internal handling.
11. Damage of Tyres & Rims during assembly.
12. Production loss due to wrong tyre- rim assembly fitment.
13. Location specific Tyre fitment controlling is also major concern.
14. Obselence of Tyres due to end of shelf life.
15. Lack of SOPs


Total shift 3
Total hour per shift 8
Lunch and tea break per shift 40 min
Maintenance time per shift 10 min

A. Throughput time
1. Process time=214 sec
2. Inspection time=22 min, 5 sec
3. Move time=19 min, 16 sec
4. Queue time=40days, 8 hrs, 3 min,48 sec
Throughput time= (process time +inspection time+ move time +queue time)
= 40 days, 8 hrs, 3 min, 48 sec

B.Overall Equipment Efficiency

Planned production time = (1440-120)
 = 1320

Operating production time = (1320-30)
 = 1290

Availability = (Operating time/ planned Production time)

Performance = (Ideal Cycle Time * Pieces  Produced) / Operating Time
 = (2.5*500)/1290

Performance = (Ideal Cycle Time * Pieces
 Produced) / Operating Time
 = (2.5*500)/1290
 = 0.9689

Quality = (Good Pieces / Pieces
 = 0.95

0EE = (Availability* Performance
 = 0.899

C.Takt time
Takt time = (operating time/customer
= 1290/500
= 2.58min/piece

D.From Current state VSM

Value Added Time =84 Min.
Production Lead Time =40 day,54 hrs,20 min.

Critical: Against as value added time of 84 minutes, the lead time is 40 days, 54 hrs, 20 min

The system can be redesigned using the lean tools such as layout modification, visual factory, multiskilled labour, kaizen, kanban and 5S as appropriate.

Source for the Observations

International Conference on Emerging Frontiers in Technology for Rural Area (EFITRA) 2012
Proceedings published in International Journal of Computer Applications® (IJCA)
Value Stream Mapping Tool for Waste Identification in
Tyre-Rim Assembly of Tractor Manufacturing

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