Ask the Expert: Lean

The meaning of lean

Q: How does the Institute of Industrial Engineers define “lean manufacturing?”


The right count 

Q: I work as an industrial engineer and am leading an improvement that changes our strategy for product fulfillment from what we produce to how much we produce to where and how we inventory the finished goods. One of the goals is to increase our inventory accuracy through the reduction of inventory moves and transactions. Is there any data that supports the idea when your transactions and movements decrease, your inventory accuracy will increase? 


Batch vs. flow

Q: This is a very elementary question, but I need to ask it. I have read about batch vs. flow in several texts, learned about it in school, and I still cannot fully grasp the idea that flow is preferable to batch operations.

They say that with one-piece flows, cycle time is lower because once a piece finishes one operation it moves on to the next immediately. By contrast, a batch operation requires that pieces sit idle before moving to the next operation until the batch is completed. I agree that this is true when you are looking at the cycle time for a single piece.

However, in industry, we build to fulfill orders. If we have an order for 100 pieces, it doesn't matter how long it takes one piece to come through because the order can't be shipped until there are 100 pieces completed, which takes us back to a batch system. Now we are waiting for 100 pieces to be finished before shipping; therefore, the time it takes before shipping a product for flow vs. batch operations is the same, making the choice of systems inconsequential.

Another example: When mailing 100 letters, is it better to fold the letter, lick the stamp, and seal the envelope one after another in a flow environment or do all the folding for 100 letters before passing them on to have all the licking done, etc.? Shouldn't the time to complete the project be the same no matter how you do it? In fact, I would say that batching would be quicker because you get in a rhythm and are able to do it faster. Again, if the customer wants letters as soon as they are available, then I can see how the flow method would be better, but if the customer wants two or more letters at any particular time, would you be better off creating a batch size to match the demand?


Cell simulation

Q: My company is designing a manufacturing cell. It will be the first of its kind in this facility that is completely dedicated to one job. The cell is going to contain all of the necessary functions to manufacture the product from beginning to end. To design the cell properly, it is essential to know some key factors, including staffing, capital equipment capabilities, efficiency, bottle necks, output, etc. I have created a simulation model to obtain some vital information that will allow me to make decisions on capital equipment and staffing. The success of this manufacturing cell will depend on keeping the number of operators down to one person for cost purposes. I would like to know at what level I should be concerned with utilization of my resource.


Keep lean fair

Q: How often should you have a mass update of labor standards after you have measured improvements? Since the standards are used to calculate productivity, when do you establish a new baseline after the improvements have been achieved? Or do you continue to measure from the same baseline until something negatively affects productivity?


Lean changes

Q: I'm interested in the changing role of the industrial engineer in a lean environment. Are there any behaviors, skills, or projects that are different for an IE transitioning from a traditional role to one that supports a lean manufacturing environment? What does a typical job description look like for an IE in a lean environment?


Lean energy

Q: What are the trade-offs between energy costs and lean manufacturing?


Managing VSM

Q: I am new to value stream mapping. How do I manage machine centers that are members of several value streams? Our primary business is custom metal fabrication, so our cell layouts can’t necessarily be built around one value stream because different parts might require different processing. How can we approach value stream mapping with flexibility to accommodate different custom products?


Retail distribution

Q: I am an industrial engineer for a retail distribution center. I have been asked to calculate the savings of using palletized loads versus floor loads when making deliveries to our stores. Do palletized loads save money over floor loads?


Service takt time

Q: How do you apply takt time to a service industry?


Work imbalance

Q: We are converting some processes to lean. We have a high manual labor content in our processes and all work is done with pneumatic guns. We have combined the following three processes: one person on the first process (with work-in-process in between), two people on the second process (with WIP in between), and two people on the third process. The new process is as follows: Two people complete the first and second process on one table (with no inventory in between), and two people complete the third process.

The new process is somewhat imbalanced, and the output is down about 20 percent since the change to lean. We are discussing putting a small length of conveyor between the processes or moving work content around to balance the tables. Any suggestions?


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