FMS Insight Monthly Flexibility Analysis

FMS Insight supports continuous improvement by assisting with a monthly review. We suggest that approximately once a month, all stakeholders review the operation of the cell and decide on potential improvements. The improve an FMS documentation goes into more details about how to make the most of these efficiency calculations.

Screenshot of choosing analysis month

At the top of the page are two radio buttons allowing you to analyze either the last 30 days or a specific calendar month.

The best metric for continuous improvement of an FMS is not cost/piece but instead is the bottlenecks and utilization of system resources (the goal is to produce more stuff with the same machines and quality). The efficiency tab shows some charts and graphs for a monthly summary of the operation of the cell, displaying reports that in our experience are very helpful to find and fix bottlenecks. We suggest you review this data once a month and use these reports to gradually alter the flexibility or operation of the cell to improve the performance.

Buffer Occupancy

Screenshot of buffer occupancy chart

As material moves through the system, it buffers before various operations. It can buffer on a pallet waiting on the inbound rotary table, it can buffer on a pallet in the stocker waiting for either machining or unloading, or it can buffer between processes in a transfer queue. In general, material will buffer right in front of the bottleneck operation. The buffer occupancy chart can thus be used to determine which operation (machining, loading, unloading) is the current bottleneck and also how the bottleneck changes over time.

The buffer occupancy chart calculates a moving average of the quantity of material buffered in all these various places. The x-axis is the days of the month. For each time on the x-axis, a window around that point is used to calculate the average quantity of material in the buffer during the window of time. This average quantity is graphed on the y-axis.

Using a moving average window smooths out the jitter from individual pallet moves, for example when a pallet rotates into the machine and another pallet is quickly sent to the inbound rotary. The size of the window can be controlled by the slider in the top-right. The size of the window should be set so that the major trends are visible while short oscillations are smoothed out.

In an efficient, well-running system the bottleneck is always machining. This will be reflected in the buffer occupancy chart with the "Stocker[Waiting for unload]" line zero or almost zero, the "Rotary" for each machine always above zero, the "Stocker[Waiting for machining]" only positive if all rotary tables are full, and any in-process transfer queues small. If instead the load stations become the bottleneck, the buffer occupancy chart will show a rise either "Stocker[Waiting for unload]" or a rise in the in-process transfer queue between processes. Also, the rotary buffer occupancy will drop to zero.

Station Use

Screenshot of Station Use Heatmap

The Station Use heatmap shows the station usage over the month. On the x-axis are the days of the month and on the y-axis are the machines and load stations. There are three charts which can be selected in the top-right corner: "Standard OEE", "Planned OEE", and "Occupied".

  • The "Standard OEE" chart computes the actual overall equipment effectiveness (OEE) over the month. For each station and each day, FMS Insight uses the log of parts produced and adds up the expected operation time for each part cycle and then divides by 24 hours to obtain a percentage that the station was busy with productive work. (If station cycles were longer than expected, this extra time is not counted in the OEE.) For each grid cell in the chart, the OEE percentage is drawn with a color with darker colors higher OEE and lighter colors lower OEE. A grid cell can be moused over to obtain extra information in a tooltip.

  • The "Planned OEE" chart displays the simulated station usage for the downloaded jobs and is the prediction of what the OEE should look like based on all the schedules for the month.

  • The "Occupied" chart computes the total percentage of time that a pallet is occupying the station. For each station and each day, FMS Insight uses the log of events to determine when a pallet arrives and departs from each station. The total time a pallet is at the station is then divided by 24 hours to obtain a percentage that the station was occupied. These percentages are then charted with darker colors higher occupancy.

The Station Use heatmaps are useful for several observations. First, the Occupied heatmap can be used to determine the overall usage of the load station. If the load station occupied percentages are very high, it can indicate that the load station is a bottleneck and preventing the cell from performing useful work. In a healthy cell, the load stations should be faster than the machines, so the load stations should be empty at least part of the time waiting for machining to finish.

The difference between the Standard OEE and Occupied heatmaps can be useful to determine if there is a lot of cycle interruptions. For example, if a program is expected to take 25 minutes but spends 40 minutes at the machine, the Standard OEE heatmap will be credited with 25 minutes and the Occupied heatmap will be credited with 40 minutes, causing the Occupied heatmap to be darker in color for that day. Now, cycle interruptions do occasionally happen; comparing the Standard OEE and Occupied heatmaps allows you to determine if these are one-off events or a consistent problem. If most days are darker on the Occupied heatmap, the cycle interruptions should be investigated in more detail. (For example, look at individual parts on the machine cycle charts, ensure the expected time entered into the schedule is actually correct, investigate machine maintenance records, etc.)

Finally, the Standard OEE heatmap helps visualize how balanced the machines were loaded over the month. We want to see all the machines consistently roughly the same color. If you see that a machine has a lighter color for a couple days, that indicates either the machine was down or that the daily mix for that day did not have enough flexibility. You should then consider picking a part and extending that part to run on the lightly loaded machine. To find such a part, you can use the part production chart below to see which part mix was run on this day to help find a part that might be changed to run on the lightly loaded machine.

Part Production

Screenshot of Part Production Heatmap

The Part Production heatmap shows the distribution of completed parts over the month. On the x-axis are the days of the month and on the y-axis are the part types. For each part and each day, FMS Insight counts how many parts were produced that day. For each grid cell in the chart, the entry is drawn as a color with darker colors higher machine hours and lighter colors lower machine hours. A grid cell can be moused over to obtain extra information in a tooltip.

The part production OEE heatmap is mainly useful to visualize the part mix as it varies throughout the month, by comparing the relative color shades. Also, it can help find a part to change move onto a lightly loaded machine. For example, consider that a machine is found to be lightly loaded via the station OEE heatmap. That same day can be viewed on the part production OEE heatmap and the darkest colored part was the highest run that day and could be considered to be extended to be run on the lightly loaded machine.

Note that these heatmaps should only be used to brainstorm ideas. We would still to investigate if expanding yyy to include machine 2 would increase overall system performance. Are there enough pallets? How many extra inspections are required? Will this cause a traffic jam? These questions can be answered using simulation, SeedTactic: Designer, Little's Law, or a tool such as our SeedTactic: Planning.

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