Six Sigma and Beyond: Design for Six Sigma, Volume VI

Figure 5.6 shows a schematic of a manufacturing system. There are four categories of manufacturing processes. They are:

1. Fabrication process ” which can be further categorized as basic process, secondary process, or finishing process. Typical types are:

   • Single station

   • Continuous production flow

   • Pace production line

   • Manufacturing cell approach

2. Assembly process ” which can be further categorized as manual assembly, mechanical assembly, automatic assembly, or computer-aided assembly. Typical types are:

   • Continuous transfer

   • Intermittent transfer

   • Indexing mechanisms

   • Operator-paced free-transfer machine

3. Inspection or quality control process

   • Inspection check point(s)

4. Material handling process

   • Conveyors

   • Tractors

   • Fork lifts

   • Parts/component feeding system:

     • Vibratory bowl feeder

     • Reciprocating tube hopper feeder

     • Centerboard hopper feeder

     • Reciprocating fork hopper feeder

     • External gate hopper feeder

     • Rotary disk feeder

     • Centrifugal hopper feeder

     • Revolving hook hopper feeder

     • Stationary hook hopper feeder

     • Bladed wheel hopper feeder

     • Tumbling barrel hopper feeder

     • Rotary centerboard hopper feeder

     • Magnetic disk feeder

     • Elevating hopper feeder

     • Magnetic elevating hopper feeder

Figure 5.6: Manufacturing system schematic.

Approaches to manufacturing processes include the job shop approach, the assembly line approach, and the one in, one out approach. Details of these processes are as follows :

• Singled station manufacturing process ” job shop approach

  • Definition: Single fixture with one or more operations performed

  • Advantages:

    • Capital investment ” low

    • Line balance ” not needed

    • Interference with other operations (downtime) ” minimum, if any

    • Flexibility ” easy to expand or rearrange

    • Employment fulfillment ” high

  • Disadvantages:

    • Multiple tooling/fixture investment ” high

    • Material handling ” high

    • Material flow ” easy to congest at in/out

    • Operation cycle time ” long

    • Operator skills ” moderate

• Continuous production flow manufacturing process ” assembly line approach

  • Definition: Continuous, sequential motion assembly/manufacturing approach

  • Advantages:

    • Work-in-process ” low

    • Manufacturing/assembly cycle time ” low

    • Material handling ” very low, if not eliminated

    • Material flow ” good

    • Operator skill/training ” only in specialized areas

  • Disadvantages:

    • Capital investment ” high

    • Preventative maintenance and corrective maintenance ” absolute necessity (If one part breaks down, the entire line is down.)

    • Engineering, technician, and flow disciplines ” absolute necessity

    • Flexibility ” low

    • Production changeover ” complicated

• Pace production line ” one in, one out

  • Definition: Same cycle time at all work stations , and likely all work pieces transfer at the same time

  • Advantages:

    • Work-in-process ” very low and can be calculated

    • Material handling ” automatic

    • Material flow ” good

    • Productivity ” best

  • Disadvantages:

    • Capital investment ” high

    • Preventative maintenance and corrective maintenance ” absolute necessity (If one part breaks down, the entire line is down.)

    • Engineering, technician, and flow disciplines ” absolute necessity

    • Flexibility ” very low

    • Production changeover ” difficult