Tag Archives: Lean Manufacturing

Batch-and-Queue vs. One-Piece Flow: Quarter Activity

At Wednesday’s (7/9) Lean Implementation Leaders and Lean Facilitators meeting, Bob Hiltunen (Director, Auxiliary Services) provided a wonderful teach back activity on the advantages of one-piece flow processing vs. batch-and-queue processing.

Background

One-Piece flow is one of the most important principles of lean manufacturing. One-piece flow means that parts are moved through operations from step-to-step with no work in process in between; either one piece at a time or a small batch at a time. Once work on a product begins it never stops moving until it is a finished product.

As opposed to one-piece flow, batch-and-queue processing is the action of producing more than one piece of an item and then moving those items forward to the next operation before they are all actually needed there. Batching and queuing tends to drive up inventory and lead time, and creates inefficiency in an operation. It also increases the space needed for production.

Teach back Activity

LIL’s and Facilitators Participating in the Teach back Activity

To complete this activity, 2 “directors,” 4 “managers,” 4 “workers, and 1 “customer” are needed. Each worker is a “station” at the table (as seen in the photo). The first three workers are assigned the task of flipping quarters and passing them to the next worker and this process repeats until the quarters reach the last worker who is asked to “stamp” them, and pass them to the customer.

The activity begins by simulating a batch-and-queue system with the first worker flipping all 30 quarters before passing them, in a batch, to the next worker and so on until they reach the customer. The batch sizes that are passed between workers are reduced after each subsequent round until each worker is flipping and passing only one coin at a time, to represent a one-piece flow system.

To measure the effect of the transition to one-piece flow, time measurements are taken at many times during the process:

  • At the start of the process when the first coin is flipped
  • When each worker first receives a coin from the previous worker
  • When each worker flips and passes their last coin
  • When the customer receives the first coin
  • When the customer receives the last coin

As the activity progresses, the time each work station is active gradually increases, however, the time it takes for the coins to reach the customer dramatically decreases. In our simulation, the process time was reduced from 1 minute 30 seconds to 20 seconds.

The ideal state for a production process is continuous one-piece flow. If you can’t manage to get down to one-piece flow, always the question … can you get two-piece or three-piece? The most important thing to remember is the idea of continually moving closer to the ideal state.


Calumet Electronics Tour

Recently, Todd Brassard, Vice President/COO of Calumet Electronics, spent an afternoon giving our group a tour of their operations in Calumet, MI. During this tour, we were able to see the complex process (over 40 steps!) that it takes to produce a circuit board. In their manufacturing operations, there were several examples of Lean Manufacturing and Six Sigma in practice. I’ll talk about a few examples that we saw during our tour.

  • Many pieces of equipment had a three-color light (green, yellow, or red), that indicated the status of the machine, an example of andon.
  • Machines that drilled holes into the circuit boards automatically picked the necessary drill bit needed for the particular hole size it needed to drill, and tested the bit prior to drilling any holes into the circuit board. If a bit is damaged, then the red light on the machine comes on (andon!) so that a worker can come to the machine to inspect the bit and address the issue.
  • Workers that inspect the quality of each of the circuit boards worked in a left-to-right pattern in their work area to ensure that untested circuit boards don’t get mixed in with circuit boards that have either passed or failed the quality inspection (error proofing); only the boards that had passed the inspection made it into the stack on the far right of their work area. These workers also test the circuit boards in small batches of 25 that their computer confirms the count of; this ensures that the whole stack of 25 has been inspected before the next batch can be tested. The computer also says, in clear and large text, “Pass” in green or “Fail” in red (a visual control) when telling the worker the results of the inspection.
  • Todd also noted that for many of their process, they are tracking Cpk, which is the actualized process capability. As a rule of thumb, a Cpk of at least 1.33 indicates a capable process.
  • At the end of the tour, Todd showed our group some awesome data collection and metrics that they’ve begun keeping to track the “health” of their business. To the “data geeks” among us, this was pretty neat!