How to Design a Lean Operation at a One Day Takt

Steve C asked:

I have just moved from a role where the takt was 55 seconds into a new role where the customer requirement is one part every day. Does anyone have experience running to this kind of timescale?

This is a fairly common challenge. For example the Boeing 737 line ran at a rate of between 19 and 22 units per month when I visited a few years ago. That is basically a one day takt. They had tried a moving line but found the line stops to be too disruptive and went to a pulse line. I am sure it evolved many times since that point towards a truly lean operation. Machine tool manufacturers, semiconductor equipment manufacturers, vehicle maintenance operations and various other business that have 22 units of customer demand per month run at this timescale.

When we say “one part every day” timescale, we first need to clarify whether that means a 24 hour takt, a two-shift 16 hour takt, an 8 hour takt for a one-shift operation or something else. For the sake of simplicity let’s take a one-shift, 8-hour operation with 1 unit of customer demand per shift and set the “one day” takt at 8 hours.

If the total work content of the unit is less than 8 hours then the design of the lean operation is a fairly straightforward “start the day, finish the day” flow of work. If the time to complete one unit is more than 8 hours, the flow line or workstation be they paced or non-moving lines, simply need to be visibly divided into the first 8 hour (takt) section of work, the second 8 hours of work and so forth until completion. However many such sections there are, that is the lead time for that process. These work pieces represent something called standard in-process stock. Define the repeatable work sequence within these takt sections and we have standardized work for a one day takt operation.

My experience with lean for products that have a demand of one unit per day has mostly been with large pieces of capital equipment containing hundreds of parts and sub assemblies. Most of the technical aspects of lean work involved laying out the workstation properly, designing the parts presentation and material logistics to the line, using the yamazumi to balance the work on the main line as well as the off-line sub assemblies, and problem solving rapidly. The essential human aspects of lean operation design are no different regardless of takt length.

If the product is a small, simple item that can be built in a few hours it is best just to have one person finish it at a work station, or incorporate the demand for this one unit into a mixed model line. But there are other types of situations, products and demand profiles within a one-day takt operation no doubt.

Who would like to share their experiences with lean operations in a “one per day” demand setting?

3 Comments

  1. ericmo

    August 25, 2010 - 2:04 pm

    This is a type 3 Standardized Work: non-repetitive kind of work and is analysed through use of operation analysis (classifying it to setup,main work,aux work,irregular work or muda). You measure the efficiency of work against the takt which is for this sample is one-day takt. When you have grouped the work elements into these classifications, the next thing you need to do is to eliminate the contents that fall under the “irregular work” category, shorten the elements falling under the “aux work”. You just apply what you know about the 7 waste and you will not be lost.

  2. Joseph

    August 26, 2010 - 2:52 pm

    Steve C.
    All production systems are just “Sausage machines.”
    I would approach this by firstly ensuring that what ever system designs you come up with are flexable. That is to say try to make a system that can increase production from current 100% (1 per/day ) to future 250%. With the least investment and disruption as possible.
    Establish a VSM of the current state. This will allow you to see where the value stream should be questioned. To Quote Peter Drucker, ” There is nothing so wasteful as doing efficiently that witch should not be done at all.”
    Calculate the total number of man hours work required to produce 1 complete assembly. This will be your base line.
    Break the work down into small pieces ( Sub-assemblies )that should be completed in a set time. The work should be PACED moving or static.
    Apply the 7 Wastes to the work / design. This should reduce your base line hours to complete 1 assembly.
    Please note I have never worked on a one per day build so these are only my thoughts.
    Ps. ericmo. Yours was an excellent post many thanks.