“They don’t have standard work,” I said. “Yes they do. I can show you,” replied the supervisor as he pointed toward the binder of work instructions. The supervisor and I were observing the operators loading containers of engines, and we were both right. The difference is in our definitions and expectations of what standard work is, and what it should look like.
The terms 'standard work' and 'standardized work' are interchangeable, but I prefer the shorter term because, well, it is shorter. The Lean Lexicon, published by LEI, defines standardized work as having three things:
- “Takt time, which is the rate at which products must be made in a process to meet customer demand.
- The precise work sequence in which an operator performs tasks within takt time.
- The standard inventory, including units in machines required to keep the process operating smoothly.”
The standard operations sheet (SOS), also known as the operator balance chart, records and displays all three of these elements.
The supervisor understands the term 'standard work' to mean work instructions, which he had, and which were available to the operators in their work area. Further, the operators had been trained on the work instructions, as evidenced by their signature on a training record. Takt time has not been calculated, but engineers had done a time study to create an average cycle time, which is mistaken as being the same as takt (which it is not). It is a simple task and they did have standard inventory using standard equipment.
While the value-adding task of transferring and packaging the engine for transcontinental shipment did have a standard sequence, the rest of the tasks performed by the operators did not, and they did not have a standard time, only an hourly target. Going to get required materials, moving materials around the area, and the tasks of the material handlers moving containers in and out of the area were not standardized. More than 20% of the operators' time was spent in these non-value adding tasks or waiting for the material handler.
The typical cycle was to load eight to 10 engines, then get more materials and move materials around the area. In minutes, the cycle would look like this: 2-2-2-2-2-10-2-2-2-2. The difference between two minutes and ten minutes is 500%. That is not very standard. Even the normal cycle had some variation in it. Besides the occasional 500% variation non-standard cycle, the times ranged from 1 minute, 48 seconds to 2 minutes, 15 seconds, with the average being 2 minutes.
Repeatability and Reproducibility
Like a gauge reliability and repeatability study (GRR), the cycle time should be measured in terms of variation when the same person does the same task (repeatability) and when different people do the same task (reproducibility). Standard work would have every cycle in a very narrow range, with no outliers like the 10 minutes. Most operations would be considered very good if they had every cycle in the time available with less than 10% variation, but world-class operations are striving for, and achieving, repeatability of 0.04% and reproducibility of 0.06%. If the cycle is 120 seconds, true world-class operations have a range of 120 +/- .05 seconds, or less, regardless of which trained operator performs the task.
To have a cycle time between 50 and 300 seconds with cycle-to-cycle variation less than 10% requires that operator movements be highly repeatable. Untangling parts in a box, removing dunnage, sealing a container every 24 cycles, periodically applying a label, and other simple tasks are variables that need to be removed or standardized. Material must be presented to the operator in precisely the same way and in the same orientation, every time. To minimize the variation of the operator cycle, the material handler and other support services must also be following detailed, repeatable and reproducible standard work.
Takt Time is Not Cycle Time
Takt time is a function of the customer demand and time available; it has nothing to do with cycle time or process time. Takt is not an abbreviation, but as a memory jogger you can remember the formula for takt using the definition Time Available divided by Kustomer Take (customer demand). When there is a lack of standard work, takt time is a theoretical number for use by consultants and academics without apparent practical application. Standard work starts with takt time, and designs the work sequence, support systems and repeatability into that work cycle. It requires detailed study and constant refinement. Sources of common cause and special cause variation are root caused and corrected. Creation, training, and improvement of standard work is constant and requires a people development system that creates well-trained and motivated team leaders that are continuously reducing variation and improving the standard work.
Without standard work based on standard time (takt), standard sequence, and standard work-in-process (SWIP), the focus becomes achieving a work standard by any means possible. The only method for improvement without standard work is to work harder or go faster. The supervisor got busy telling the employees to work harder and go faster.
We have very different definitions of standard work, indeed.
