I’ve written several posts on the importance of increasing production throughput by minimizing cycles times in work cells. Lower these times and you'll reduce the effects of lost & idle time in manufacturing. It also means you'll lower costs and increase your gross profit. However, there is one aspect of cycle times I’ve yet to cover. What is it you ask? It's the transit time from one work cell to the next. To be successful in lowering cycle times means you must lower these transit times.
When looking at a product's overall cycle time, it's important to note that there are cycle times for individual operations and a transit time to move parts from one production work cell to the next. Reducing these transit times is an essential part of increasing your manufacturing productivity rates and lowering costs.
Adopting Lean Manufacturing Principles
Each work operation has a cycle time. For instance, a product may go through several stages in production before it’s finished and shipped to the customer. It might start out as a raw material and go through cutting, then move to drilling and tapping, CNC (Computer Numerical Control) programming, then onto soldering, assembly, painting and labeling, quality control & final inspection, and finally packaging and out to the customer.
In each of these operations, there are separate cycle times. However, once that specific operation is finished, there is an additional portion of the cycle time most companies ignore – and that is the transit time to move the product to the next chain in the process.
The cycle time for the finished product takes into consideration the time it takes to move that part from drilling and tapping to CNC to soldering to assembly and so forth. Too much time in transit and the cycle time for the finished product increases and costs rise. The following chart shows what the transit times might look like from one production work cell to the next.
Now, this might be a rudimentary flow chart, and I am well aware of how often parts are checked during large scale production. However, the basic principle applies. Each of these work operations above has a cycle time. Each of the red arrows indicated the transit time from one production work cell to the next. In every case, minimizing that transit time reduces the overall cycle time, increases production throughput, increases gross profit and saves money.
The video above is taken from a more recent post entitled: Manufacturing Work Cell Optimization: Design, Layout and Analysis
To drive this point home, I recently did a simple project for a manufacturer in Montreal, Canada. I was provided with their work flow in production, an outline of their production floor and a summary of each and every cycle time in all their production work cells. They were looking for any simple advantage they could get. They properly managed their cycle times through an MRP (Materials Resource Planning) production software package, and had done all their research on their individual cycle times in every operation. However, they ignored their transit time and couldn’t figure out why their cycle times were high.
It’s Not About a “Couple of Seconds Here and There”
When I asked for the transit times between the work cells, the answers were less than accurate. In addition, I could immediately see from the work flow chart, with its arrows all over the place, that they needed to better manage their transit times. Upon further investigation, I was told that “…a couple of seconds here and there doesn’t make a difference”. Well, it does, and here is an example of how the transit times between the work cells cost this company money.
The times above include the workers going from one production cell to another and returning. While the overall cycle times of the products manufactured at this plant were quite high – approximately 27 minutes – the impact of this 2 minutes and 36 seconds in transit time could easily be reduced, and was to 45 seconds overall.
The video above shows how to set up the ideal lean work cell and is taken from the post: Manufacturing Capacity Planning: The Perfect Manufacturing Work Station
We made a couple of changes here and there, and as a result, we increased their production throughput, reduced their total cycle times and increased their gross profit. It also helped the company reduce the incidence of damage to parts moving from one location to another.
When it comes to improving cycle times, don't ignore the transit time between production work cells. In many instances, these transit times hold the keys to increasing manufacturing productivity and eliminating the root causes of work stoppages.
Remember, a product's cycle times include its over all time and the individual times in each work cell and work station. Reducing the time it takes to move parts from one chain to the next, will reduce the product's overall cycle time and improve your bottom line.
The above table and graph are taken from the article: Cycle Time Tracking & Variance Analysis in Excel for Small Manufacturers. The article includes a sample excel sheet that allows you to track your cycle times within a given work cell and then plot them on a graph - similar to the one above. It will help isolate those issues that are causing high cycle times on your shop floor.
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