One piece flow
14th April 2026
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Hi everyone, Imagine you have a factory that makes widgets. But in order to produce the widget there are 4 processes that need to be undertaken. Each process takes 1 minute per widget. If you process these in batches then you’d complete process 1 for all items before moving onto process 2 etc etc. |
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BATCH PROCESSING 25 units process 1 = 25 minutes 25 units process 2 = 25 minutes 25 units process 3 = 25 minutes 25 units process 4 = 25 minutes Total time to produce 25 completed widgets = 100 minutes If you batch in units of 100 then it becomes 400 minutes to produce 100 completed units. In lean though they look at one piece flow rather than work in batches. |
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ONE PIECE FLOW 1 unit through process 1, then straight into process 2, then process 3 then process 4. Total time to complete 1 unit = 4 minutes When the first unit is on process 2 the second unit can start on process 1 When the first unit is on process 3 the second unit is on process 2 and the third unit is starting process 1 When the first unit is on process 4 the second unit is on process 3 the third unit is on process 2 and the fourth unit is starting process 1 So to make 25 widgets takes 28 minutes If you batch in units of 100 then it becomes 103 minutes to produce 100 completed units. |
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In addition if there are any issues / defects then it would get picked up immediately. For example if there was an issue at process 3 then you’d typically notice this when you start process 4. Under batch processing there are 25 units that are now defective and may need to be scrapped entirely and also put through processes 1 and 2 again – so more wasted time. Under one piece flow you’ve only wasted 1 unit and you can fix the problem before you waste any more product / have to reprocess anything. Also, if you have another process that needs to be added in you only add 1 minute to the total time under one piece flow. i.e. it would only take 29 minutes to produce 29 units if there is 5 processes. (Under batch processing it would take 125 minutes – you need to add 25 minutes for every process you add in). |
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Check out this video of the Toyota factory where a car comes off the plant every 88 seconds – that’s because each step of the process takes 88 seconds (88 seconds to put in the dashboard, 88 seconds to put in the brakes etc etc). |
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Take care until the next time Russell + Russell |