Department of Industrial and Engineering Technology College of Science and Technology Morehead State University IET 317 Group 5 Project

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Department of Industrial and Engineering
Technology College of Science and Technology
Morehead State University IET 317Group 5
Project
Steel Wheel Assembly Work Cell

• Group Members
• James Forrest, Lowell Outland, Evan Scott,
• Donald Snyder, Matt Wells

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Central Motor Wheel of America(CMWA)

• CMWA was established in 1987.
• Location Paris, Kentucky
• Employs approximately 500 people.

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CMWA Products

• OEM supplier of Steel and Aluminum Wheels.
• Steel Wheel Customers
• Toyota, Honda, and Hyundai
• Aluminum Wheel Customers
• Toyota and Lexus.

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Rationale for selecting the Steel Wheel Assembly
Station

• The rationale for our chosen process is simple
• A work cell is a collection of equipment required
  to make a single complex part
• The part being produced is the steel wheel
• The Steel Wheel Assembly Station itself has many
  parts. (Including the operators, robotic
  loaders, punch press, date stamp device, welders,
  grinders and inspection)
• Multiple factors can lead to the occurrence of
  waste

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Rationale cont.

• If diligent lean techniques arent practiced in
  this work environment, the efficiency of the work
  cell could easily deteriorate, wasting valuable
  company time and money
• In our efforts to make improvements we analyzed
  the processes of the Steel Wheel Assembly Station
• Identified areas that can be improved
• Made suggestions on how to improve them to make
  it a more lean and efficient process

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Description of Steel Wheel Assembly Station

•   The cell is used to assemble two main
  components of a steel wheel. The two components
  are the center disk (wheel center) and the Rim
  (outer part of the wheel). These parts are placed
  near an operator at the beginning of the assembly
  line. At the beginning of the wheel assembly
  machine there is one operator. This individual is
  responsible for loading the center disk onto the
  conveyor belt and loading the rim into a small
  punch press. This punch press is responsible for
  punching out the valve stem hole.
• The punch press side of the line will be
  discussed first. The operator grabs a rim (6sec.)
  and places it onto the punch press (3sec.), he
  then activates the press which locks the rim into
  place and almost simultaneously punches the hole
  for the valve stem (2 sec.). Once this operation
  is finished a mechanical arm pulls the rim onto a
  conveyor belt directly in front of the punch
  press (Note as the mechanical arm is pulling the
  rim on to the conveyor the operator is loading a
  center disk onto the other line). The rim
  continues down the conveyor to the stamp station
  which automatically positions and clamps the rim
  (2sec.). This station stamps a date (2sec.) onto
  the rim so that when the two parts are welded
  together the company has a record for quality
  assurance purposes. On the wheel center side of
  the line, the operator has to just load the part
  so that it travels down and stops near the two
  weld fixtures. Please note that the operator is
  responsible for keeping both conveyor lines full.
  
• At this point two additional operators are
  simultaneously grabbing a rim or a center disk
  and loading it into a weld jig. They then
  retrieve the opposing part and place it into the
  jig (20 sec per operator). The operators then
  activate the hydraulic clamps (2sec. per
  operator) to hold the parts together during
  welding. The welding process automatically starts
  as soon as the parts are clamped together. The
  welding robot is equipped with four MIG (Metal
  Inert Gas) guns that feed the wire continuously
  to create a seamless weld. The pallet that the
  parts are clamped to only has to rotate
  approximately 92 degrees to create the finished
  weld. The welding process takes about (30sec per
  assembly.). Once the parts have been full welded
  the newly formed wheels are removed by mechanical
  arms and placed (8sec.) onto another conveyor
  belt. The wheels then travel to an automated
  grinder that grinds/polishes the welded seam
  (15sec per wheel).
• The wheels then travel on to an inspection
  station where they are checked for visual and
  mechanical defects by a fourth individual. This
  takes approximately 15-25sec per wheel. There are
  time variances due to anomalies in the weld or
  grind finish that occurs from time to time and
  also indicated run out noticed on the inspection
  gage.
• The total amount of allowed run out is 0.3mm.
  This is the end of the journey for the newly
  minted wheel. The wheels next stop will be the
  powder coat/paint booth which is another work
  cell. Please note that the work cell is full of
  parts at all times so conveyor length is not a
  factor. As it was explained to our group the
  work cell is not timed linearly due to the fact
  that mechanical breakdowns are anticipated
  especially where the welders and grinders are
  concerned. Also, the nozzles must be cleaned and
  guides replaced after X-amount of wheels are
  welded.

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Work Cell Layout Steel Wheel Assembly Machine
Wheel Rim Rack
Punch Press (Valve Stem Hole)
Finish Grinder/ Polisher
Date Produced Stamped on Rim
Manual Load/1 person
Wheel Welder 1
Manual Load/1 Person
Inspection Gage
Wheel Welder 2
Manual Load/1 Person
Wheel Centers Rack
Manual offload/ 1 person
Note Four Person Work Cell
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Time Study Analysis
Step Time (in seconds)
Acquiring materials 6
Loading Punch Press 3
Small Punch Press (valve stem hole punch) 2
Stamp Station Load 2
Date Stamp (for quality assurance) 2
Loading Weld Jig 20
Activate Hydraulic Clamp 2 (per operator)
Welding Process Approx. 30 (per operator)
Remove wheels 8
Grind weld seam 15
Visual inspection 15-25


Total cycle time 110-120 per assembly



Time anomalies due to defects found on assembly during inspection. Time anomalies due to defects found on assembly during inspection.



Times inaccurate due to required maintenance i.e. cleaning nozzle and replacing guards



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Suggested Improvements

• Improve /Eliminate Finish Grinder
• Electric motors breaks down frequently
• Change to more reliable air motors
• Rotate conveyor belt 180 degrees
• Will help make the process more
  linear(Refer to layout)
• Move wok cell closer to punch press
• Use conveyor between punch press and work
  cell
• Help speed up production
• Add robot to place parts onto conveyor at
  beginning of work cell
• Eliminates need for manpower at this
  position
• Helps speed up production

• Consider adding a third welder(identified choke
  point)
• Move worker from first station to
  third welder
• Helps to alleviate choke point
• Move closer to paint booth
• Reduces travel time to paint
• Condense entire wheel making operation
• Help speed up production
• cost prohibitive

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• Group Recommendations
• Recommend changing electric motors to pneumatic
  motors for more reliability
• Recommend moving work cell closer to paint booth
  to reduce part travel time after assembly
• Recommend adding a third welding machine to
  eliminate bottleneck in production
• Recommend rotating welding machines 180 degrees
  to create a more linier product flow as shown by
  recommended layout

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Recommended /Revised Work Cell Layout Wheel
Assembly Machine
Wheel Rim Rack
Punch Press (Valve Stem Hole)
Finish Grinder/ Polisher
Date Produced Stamped on Rim
Manual Load 1st Person
Wheel Welder 1
Manual Load/1 person
Inspection Gage
Manual Load 2nd Person
Wheel Welder 2
Wheel Centers Rack
Manual offload/ 1 person
Note Four Person Work Cell
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Conclusion

• Using Time and Motion Studies are very useful
• The assembly cell can be improved
• The entire wheel production operation should be
  reexamined
• Room for cycle time improvements