What is standard work?
Standard work is the documented best-known method for a job, defined by three elements: takt time, the work sequence and standard work in process. Taiichi Ohno called it the foundation of kaizen: once work is standardized, every deviation is visible and every improvement can be locked in as the new standard. Standard work is written by the people who do the work, with their supervisors, and is reviewed regularly.
The standard work documents
| Document | Purpose |
|---|---|
| Process capacity sheet | Capacity of each machine, including changeovers |
| Standard work combination sheet | Manual, machine and walking time per element against takt (this tool) |
| Standard work sheet | Layout of the cell with the operator's path, quality checks, safety points and standard WIP |
| Job instruction sheet | Major steps, key points and reasons, used to train operators |
Standard work combination sheet example
One operator runs a machining cell with a lathe, a mill and a washer at a takt time of 90 seconds. The seven elements take 57 seconds of manual work and 21 seconds of walking, a cycle of 78 seconds. The lathe (45 s) and the mill (52 s) finish before the operator returns, so there is no waiting, and the cycle fits takt with 12 seconds to spare. Two elements carry safety points and the gauge check is the quality check. Standard WIP is four parts: one in each machine and one being deburred.
Improving with standard work
- Cut walking first. Walking adds no value; rearrange the cell so machines are close together. A spaghetti diagram shows the path.
- Balance to takt. If the cycle exceeds takt, move work to another operator; see line balancing.
- Separate the operator from the machine. Automatic cycles with auto-eject let the operator move on instead of waiting.
- Measure, do not guess. Take element times from a time study.
- Update the standard after every kaizen, then retrain.
How to use this Standard Work tool
- Set takt time and WIP. Enter the takt time from customer demand and the standard work in process.
- List the work elements. Click + to add each element in the sequence the operator performs it.
- Enter the times. Click an element to enter its manual, machine and walking time. The combination sheet draws the timeline.
- Mark key points. Add the key point for each element and mark quality checks and safety points.
- Check against takt. See whether the cycle fits takt, how much time is walking and whether the operator waits for a machine.
- Export and post. Export the combination sheet to PDF or PNG and post it at the workstation.
Frequently asked questions
What is standard work?
Standard work is the current best way to do a job safely, with the required quality, at the pace of customer demand. In lean it has three elements: takt time, the work sequence, and standard work in process (WIP). It is the baseline for improvement: without a standard there is nothing to improve.
What is a standard work combination sheet?
A standard work combination sheet (SWCT) shows, for one operator, each work element with its manual time, automatic machine time and walking time on a timeline against takt time. It reveals whether the operator can keep pace, where they wait for machines and how much time is spent walking.
What are the three elements of standard work?
Takt time (the pace set by customer demand), the work sequence (the order of elements the operator performs) and standard work in process (the minimum parts needed in the cell to keep work flowing). All three are recorded on the standard work documents.
What is the difference between standard work and a work instruction?
A work instruction tells an operator how to do a task, often in detail. Standard work also defines the timing (takt, cycle time), the sequence across machines and the WIP, and is used by supervisors to check that the process runs as designed and to find improvements.
What is standard WIP?
Standard work in process is the minimum number of units within the cell needed for the operator to complete the work sequence without waiting: typically one part in each machine, plus any parts required for cooling or curing. Too little causes waiting; too much hides problems.
How do I find the times for standard work?
Observe the process and time each element over several cycles with a time study. Use the lowest repeatable time for manual work, the machine cycle for automatic time, and the walking time between stations.