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Using Lean Manufacturing Tools

1. Introduction

1.2 Identification of causes that lead to low productivity in the manufacturing process of the M300 wheel hub

In order to identify the leakages and causes of low productivity, the 5MQS (methodology to identify waste related to machines, method, materials, man, management, safety, and quality) method was used. This was complimented with the use of an Ishikawa diagram to analyze root causes. The general findings were:

  • Machines: A flow diagrams and switch travel diagrams were used as analysis tools leading to the conclusion that there is a very poor distribution within the plant. On top of that, there are constant stoppages for machine maintenance. No preventive maintenance programs are in place.

  • Method: In accordance with the time studies, the critical activity (bottle neck) is the final lathing of the exterior, meaning that productivity needs to be increased at this work station.

  • Making human-machine and machine-machine diagrams showed a workload imbalance for the different machines and operators.

  • Constant time wasting was observed while tools and devices are sought since they are not kept in a specific place and are far away from the work station. A high level of loss is incurred due to movement of materials and people due to poor distribution of the machines in the plant.

  • A space for raw materials is not demarcated and as such it often gets in the way of people and the flow of material in the production process.

  • Checking the degree of compliance with the 5S. Check-lists were designed for the 5S that were then used to measure compliance. The results are presented in Table 2 and the diagram of Figure 1.

Operation Machine Standard time (seconds) Goal (pieces per hour)
Forging
Cutting raw material of wheel hubs Saw 49.5 73
Heating and forging of wheel hubs Furnace and press 50.79 71
Heat treatment: standardization Furnace 15.45 233
Cleaning Blasting machine 18.33 196
Inspection for cracks Magnaflux equipment 20.94 172
Machining
Pre-mechanized exterior of the flange Lathe-1 146.05 39
Roughing of interior diameter Lathe-2 for roughing 121 40
Broaching Broaching machine 61 59
Final lathing of exterior Lathe-3 for finishing 212 17
Boring and countersinking long holes for stay bolts Drill 1 79 46
Threading holes Tap drill 65 56

Table 1. Main data related to plan operation.


5S Maximum score Machining area
Result %
Sort 25 9 36
Set in order 35 16 46
Shine 20 8 40
Standardize 45 35 78
Sustain 35 20 57
Total 160 88 55

Table 2. Results of the 5S check-list applied at the plant.



Figure 1. Diagram of the 5S network at the production plant.


The 55% compliance level for the 5S at the production plant indicate the necessity of implementing the 5S methodology.

  • Material: There is a large accumulation of inventory at the bottle neck of the process, there is an imbalance in the line and lack of order for placing material.

  • Man: What is seen as weaknesses in the method leads to the conclusion that there are no operation standards at the plant resulting in a lack of structured training and formation for operators at the plant.

  • Management: Quality inspections were carried out on 100% of the finished products leading to a huge loss of time for the operator. In addition, there is low illumination in the inspection area where high visibility is needed to be able to read the instruments.

  • Safety: There is no established place to keep safety gear which is one of main the reasons why it is hardly used. The lack of order and standard procedures also contribute to unsafe conditions.

  • Quality: The level of defects found for the period under study (second semester of 2017) is 49,937 PPM (parts per million). Both the company and clients defined the goal as <15,000 PPM.