For any manufacturer, idle time in production is lost money. Work stoppages affect productivity rates, increase cycle times, drive up costs and affect gross profit. If it continues unabated, the end result is lost jobs. With competition from overseas manufacturers, rising material costs, decreased demand, in addition to the constant pressures to be price competitive, it seems almost impossible for smaller manufacturers to compete. However, there are solutions.
Tracking Cycle Times for Individual Operations and the Finished Good
Cycle times are the time it takes to perform a work operation. There is a time for each operation and a total time for the finished good. A number of manufacturers will concentrate on lowering times in one work cell, without completely understanding the implications for the next cell in the process. Improving cycle times is all about capturing lost time, documenting its causes, and eliminating them altogether. Success means you'll increase throughput by eliminating waste.
The first step is to determine the productivity rates emerging from individual work cells. The second step involves capturing the causes of downtime. The third step is to take a new set of times. The fourth and final step includes tracking variances in order to determine your benchmark cycle time. However, this isn't an exercise that is only done once. Instead, it's a continuous process where you constantly try and improve upon results.
Step1: Calculating Productivity Rates
In order to properly calculate the productivity rate, we must know what the actual number of hours are available in production. While your company pays employees for an 8 hour work day, your employees don’t work that full 8 hours. For instance, you must subtract lunch time and breaks. Take that time away from the 8 hours, and that should provide you with a basis for how many hours of actual time is available.
After taking away lunch and breaks, your employees will likely have about 7 hours of available work time. However, they still don’t work that full 7 hours. If they did, they would be 100% efficient, and nobody is 100% efficient. What you need now is to determine their actual productivity rate. This process requires an in-depth analysis of the work station under which the employee operates.
What are the Steps Needed to Determine the Manufacturing Productivity Rate?
The steps needed to find the productivity rate include, 1) Determining total available work time, 2) documenting lost time, 3) adding up all the lost time and removing it from the 7 hours of work time, and finally, 4) taking that new total and dividing it by the 7 hours. Here is an example of how one might find the productivity rate.
- Total minutes available in 7 hours: 420 minutes
- Total lost or idle time: 120 minutes
- Actual time worked: 300 minutes (420-120)
- Productivity rate: 71% (300/420)
The above video shows how to design lean manufacturing work cells and work stations. It also provides a summary of how to calculate the productivity rate emerging from individual cells in addition to summarizing production volumes. To read more, please go to: Manufacturing Work Cell Optimization: Design, Layout and Analysis
Step 2: Eliminate Work Stoppages
Ultimately, you must be able to isolate why work stoppages are occurring. It isn't something that can be accomplished by simply relying upon the information emerging from your manufacturing software. It means seeing production happen in person. Software can only tell you what your times are - they can't tell you what they should be. The sheet below allows you to track the times within an individual cell, while also capturing the root causes of idle time.
The table is taken from the post: Small Manufacturer’s Sample Excel Sheet for Cycle Time Analysis. The sheet allows you to track the times emerging from individual work cells, while isolating any obvious issues inhibiting the operator from completing his or her tasks.
Step 3: Take New Cycle Times
After the second step you should have a list of issues to confront. These issues could pertain to machinery downtime, unclear and incomplete work orders, bill of materials or assembly drawings, or they could be related to how the work cell itself is laid out. Regardless of what these issues are, it's your job to eliminate as many of them as possible. Once you've done away with these issues, you'll take a whole new set of times.
Step 4: Tracking Cycle Time Variances
The table above, and the graph below, are taken from the article: Cycle Time Tracking & Variance Analysis in Excel for Small Manufacturers. The sample sheet allows you to track your times and then determine your mean, mode and median times within individual cells and larger work stations. The sheet will then graph these times for you. Tracking the variances between operations will help you determine your benchmark cycle time.
Again, this is a continuous process, one where you determine your current productivity rate, capture downtime within the work cell, track cycle times and then determine the variances between those times.
Taking the time to calculate your productivity rate, coupled with documenting all the lost and idle time, will provide you with the foundation to begin your analysis on improving your manufacturing cycle times. Make sure to welcome lost time during this analysis. Finding lost time provides you with the opportunity to correct the errors, and increase your production throughput. In this case, encountering issues is a good thing in the first step.
When doing this exercise, make sure to explain to your employees why this action is being taken. It is not to time them, but to help them make their job easier and more productive. It's common for production employees to be apprehensive when it comes to someone performing this kind of review.
Your production employees need to operate like surgeons.
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