December 2005

Cellular Manufacturing: Part 2 - Cells Are for You, Too!

Savings in space, time and profits are just a few of the things cellular manufacturing concepts have going for them.

By Tom Dossenbach

Last month I presented an introduction to work cells by looking back at how woodworking machines were scheduled individually "in the old days" and some of the inefficiencies and waste that resulted. I also pointed out how that old methodology actually works against lean manufacturing and can result in a competitive disadvantage.

This month, I take a closer look at cellular manufacturing and discuss why you should be utilizing this simple concept wherever possible.

Basic Cell Design

To paraphrase from last month's column, a manufacturing cell is a grouping of machines, workstations or a combination thereof placed in close proximity to each other. Usually, they are arranged in a tight "U" shape with the machines close enough to eliminate, or at least minimize, steps that might be required to move parts from one operation to another. An additional reason for the U configuration is that individual team members within the cell only have to take a step or two to cross over to another workstation to quickly assist when the flow of materials through the cell is constrained for any reason. Also, the required aisle usually takes up less floor space because it is within the cell and is shared by other work cells around the U instead of being stretched out in a straight line.

8 Benefits of Cellular Manufacturing
  1. Simpler production scheduling and control
  2. Less material handling
  3. Less work in process
  4. At least 40% less floor space required
  5. Better quality control
  6. No over or under production
  7. Lower cost for products
  8. Good gateway into lean manufacturing

The flow within the cell is usually counterclockwise. I have been asked many times why this is and the reason is actually very practical. For the 80 percent of us who are right-handed, it is easier to pick up or handle things with our right hand and move right to left or counterclockwise within a U-shaped cell. Lefties, as so often required in a right-handed world, have learned to adapt, so this is not a big issue.

Note: If there is a compelling reason for your company to create cells that go clockwise, it is not the end of the world. Regardless of the direction of flow, the workstations are in such close proximity that little (one to six pieces) or no work is stored in between them.

To illustrate a basic cell concept, let's look at one designed to manufacture and assemble drawer boxes. Ideally, this cell is located close to where the drawers would be installed into the assembled cabinet or piece of furniture. For the purposes of this example, let's assume we are dealing with a small plant and there is just one operator in this drawer box assembly cell. The company buys cut-to-size drawer box fronts, sides, backs and bottoms made from plywood with the drawer bottom grooves already machined. Drawer fronts are screwed onto the box face from inside the drawer box.

The machines for this operation are located in a tight U shape with the operator in the middle (see illustration above). Drawer parts are organized on a rack, neatly separated in bins by size. The operator takes two drawer sides and the front and back from the cart and places them in the dovetail machine to make the necessary cuts. He takes a drawer bottom and uses it as a tray for the other parts. In this manner he is able to process a complete drawer box "kit" through the cell.

Note that this cell could contain more machines if operations are not combined or parts are not pre-cut, such as when preparing for the drawer bottoms (as in this case) or cutting drawer sides to length. In this example, some lengths are custom dimensioned from stock on a chop saw located in a different cell. The drawer glides are also put on there, but they could be applied within the drawer box assembly cell, if so designed.

This is just one simple illustration of how a cell can be designed to accommodate a family of parts and complete various levels of processing with fewer non-value-added activities. At the same time, it requires much less floor space than if each machine is set up by itself and space is set aside for carts of work in process as is the case in many plants today. I have mentioned before that a furniture plant utilizing work cells and continuous product flow can enjoy better productivity than the traditional woodworking plant, with almost half the space, and with much less lead time.

There is another characteristic of a cell that anyone who considers setting one up must not overlook. All operators must be cross-trained to be able to efficiently set up and operate each and every machine within the cell. Otherwise, if one person phones in sick, productivity is disrupted throughout the entire cell.

20 Steps for Setting Up Your First Cell

If you have no cells in your woodworking plant, it is high time to form your first. Following are some of the basic steps necessary to successfully create an effective cell.

  1. Select the project team that will lead your effort. You must have representatives of plant and department management, maintenance, quality, and, above all, a production worker on the team. All team members must be extremely receptive to change.
  2. Select the part or product family that is to be processed in the cell. Do not make the product family so broad as to over complicate the cell. Instead, strike a balance for efficient flow.
  3. Determine the production requirements and the process machines and operational sequence necessary to meet your goals and to meet the product family demand. Use machines and equipment that you already have, if appropriate, in order to utilize existing assets.
  4. Review tooling and the current state of all equipment and machines within the cell and have a preventive maintenance schedule developed for each. This will be critical to keep the cell running without unnecessary downtime.
  5. Review the quality requirements that must be met by the cell and make sure steps 3 and 4 will facilitate them.
  6. Eliminate any large or unusual parts in the family that will cause unnecessary delays in changeover, as well as other potential constraints within the cell.
  7. Have maintenance and operations personnel draft standard set-up procedures. This should include changes in methods and modifications to the machines to significantly reduce changeover times. Lengthy setups are unacceptable if you are to fully benefit from grouping process machines in one continuous-flow cell. This effort should continue after the cell is fully operational. (See the May 2005 installment of Management Matters, "Lean Set-Ups the NASCAR Way!")
  8. Select the area in the plant where the team feels the cell should be located. Consider short- and long-term issues as you try to look ahead to a cellular plant.
  9. Clear and clean the factory floor and outline the location of every workstation in tape to guarantee the best use of space. Remember to make space for material flow to and from the cell, plus any supplies needed within.
  10. Identify where and how air, electrical and lighting will be located. Do not hard wire or pipe in case the equipment must be moved in certain circumstances. It is possible that a product family may require moving a couple of machines from time to time and placing locking casters on these machines can make a cell more flexible.
  11. Create a timeline for the changeover. This is important to avoid interruptions in production in the plant during the movement of machinery and the startup of the cell.
  12. Finalize a production plan and schedule for the cell. Start with a simple schedule and move to more difficult ones as operators become proficient.
  13. Prepare for production to suffer setbacks before becoming more efficient than ever before.
  14. Crosstrain all operators on the concept of cellular manufacturing and on operating within this cell.
  15. Implement the change and move the machinery in place, incorporating any new fixtures, tooling or quick set-up features.
  16. Start running the cell and support it with training and technical support. Do not throw the operators to the lions and expect them to go it alone. They will need plenty of support as they make the transition to cellular manufacturing.
  17. Obtain feedback from the operators and make the changes necessary to allow the cell to run smoothly and meet the goals outlined in steps 3, 5 and 6.
  18. On a regular basis, measure the results and provide feedback to the cell and plant in order to show the progress and benefits the cell has provided.
  19. Do not get discouraged with slow progress; keep working to make the cell function as planned and success will follow.
  20. Compliment cell operators and team members on progress and share their successes with the rest of the plant.

This list of 20 steps may not cover every issue that you may face but it can still serve as a checklist to get started. The changeover should take hours instead of days if proper planning is done. Thus, a new cell could be set up at night or on Saturday without disrupting production flow.

Cells Are for You, Too!

Most plants already have cells in place, but often are not recognized by employees as such. If you are assembling furniture case goods or kitchen cabinets in a tight workstation with several operators doing different jobs, this could be considered an assembly cell.

Even the smallest cabinet shop can utilize the concept of cellular manufacturing. I urge you to take time to discuss this with your production management team and begin making plans to form a new cell, post haste. Let me know how it goes.

Tom Dossenbach is managing director of Dossenbach Associates LLC, a Sanford, NC-based international consulting and research firm. Contact him at (919) 775-5017 or tfd@dossenbach.com. Visit his Web site at www.dossenbach.com.

                                                                                                                                                                                           

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