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Customers are demanding higher quality, lower cost products, delivered faster with more variety. More and more, manufacturers are increasingly responding to these pressures by incorporating lean manufacturing strategies into their product's value stream, allowing them to compete in global markets. The Japanese capitalized early using lean concepts post-WWII, and are celebrated for having created them, you may be familiar with the Toyota Production System.
Alzatex has a large selection of timers, counters, displays, and annunciators that can be combined into an almost countless arrangement of Andon displays. Following is background information on lean manufacturing, monitoring techniques, and some common examples of how production control systems are used in lean manufacturing operations. Follow the link below to view some of our popular production control and lean manufacturing packages, but remember, if one of our popular packages doesn't quite fit your needs, contact Alzatex and let us customize our flexible technology to your application needs.
Lean manufacturing is not a process; a process is the series of operations one executes to create a product. Instead, lean manufacturing is a series of operations strategies aimed at reducing product lead-time by eliminating waste during production. One may ask the valid question of how does eliminating waste reduce product lead-time? One may also ask what can one do to eliminate waste? The answer lies in the lean definition of waste, what that waste does to the manufacturing time, and what tools and techniques are available to eliminate waste.
For manufacturing purposes waste is defined as any action that consumes resources (i.e. time, money, space, or material) without adding value to the final product. Therefore waste in a manufacturing process comes in many forms. Traditionally there are the seven wastes identified in lean thinking, these are:
A systematic approach to eliminating waste from a production line begins by determining how the line currently operates. Some organizations map their value stream to determine the state of their process. A value stream is all of the steps and processes required to transform raw materials into a product that you deliver into the hands of your customer. Other organizations may hold a series of kaizen events or blitzes to focus on specific areas of the manufacturing process. These events use a cross-functional team made up of the stakeholders to target those specific areas and quickly plan ways to improve them.
Whatever approach is used, whether by formal value stream mapping, or by a series of Kaizen events, or even by a blended approach, chances are that work cell layouts will be affected by the plan. Work cells at their best are compact arrangements of people and machinery made up of multiple workstations executing related steps in the process. Before optimizing a production line, possibly rearranging many work cells, some manufacturers follow the 5S technique to prepare their facility.
The goal of the 5S technique is to create a working environment that is organized, simple, clean, and safe. The underlying philosophy of 5S is that efficient and quality work requires a clean and safe environment. The traditional terms of 5S are of Japanese origin, to which English translations have been added:
Once the 5S technique has been utilized on the production line, further optimizing the work cells require knowing how long it takes for the product to get through the steps of the process. Knowing this entails production monitoring.
Production monitoring can be as simple as taking a stopwatch or video camera with time and date stamping out onto the production floor and timing the steps of the process. Introducing a rate counter into the process can gather more precise data over a longer period of time. Rate counting can be accomplished manually with a hand held counter, counting each product as it leaves the work cell or workstation, and at the end of the shift dividing the count by the number of hours worked, minus any downtime hours. But a manual approach isn't very feasible on short-cycle process steps where the time to toggle the counter makes up a significant percent of the overall process time. More sophisticated rate counters incorporate an electronic timer and counter activated by mechanical or optical switches. At the beginning of a shift the counter is reset and the timer is started. As product flows through the line and gets counted, the rate counter automatically divides the count by the elapsed time to come up with a completion rate, usually measured per hour, or per minute. With rate information one can begin calculating the product lead-time and planning ways of making it shorter. Rate information for the work cells in a production line is an important statistic if one wants to balance their work cells.
Work cells are balanced when the time it takes for a product to flow through each work cell is the same or as close as feasible. This is an important concept in lean manufacturing. When all of the work cells in a production line have the same rate there is no need to batch and queue product between them, this lessens the chance of excessive WIP or inventory, which is one of the seven wastes.
After the work cells have been cleaned up, analyzed, and balanced; and the production line has been rearranged, practicing the 5S technique should embed a spirit of continuous improvement into an organization. The continued use of production monitoring equipment is essential because processes that can't be measured can't be improved or relied on. Some companies use Takt timers coupled with actual, deviation, or efficiency displays as more sophisticated production monitoring tools.
Takt is of German origin. Essentially takt time is associated with keeping in step, or keeping in time. In lean thinking takt time is another important concept. Takt time is the time it takes to fabricate and ship one product, and is established by dividing the number of orders in hand by the number of working hours in a day. As an idealized example, if an electronic display has a customer demand of 60 displays per day, which translates to 8.182 displays per hour, based on one shift of 7.33 hours, is one display, ready to ship every 7.33 minutes. One way to think of it is; every 7.33 minutes a customer is being made happy. Continuing with our ideal example, if there are three work cells in the production line, each work cell has 2.4+ minutes to process each display. Multiple workstations in each work cell would further divide the time each workstation has to process each display, but in our example each work cell will contain one workstation. If a company was using takt timers to calculate the rate of production, each work cell would have a counter that increments by one every 2.4+ minutes, or the end of the production line would have a counter that increments by one every 7.33 minutes. A timer/counter used this way calculates a running goal. It should be noted that if desired the work cell counter could be programmed to count by three every 7.33 minutes by changing the scale factor of the goal count to three instead of to one. A takt timer will set a pace, but how does one know if the production line is keeping up?
If the same company desires to track production actuals versus the goal count, there are a number of ways of achieving this. A simple production counter would work. A counter incremented every time a product passes through the work cell is the production actual. The goal would be to keep the actual count equal to or as close to the running goal as possible. A second variation would be to increment a counter as product passes through a work cell, just as before, but display the difference between the goal count and the actual count, which is the deviation of the production line. The goal in this scenario is to keep the deviation display at or near zero. A third variation is to again count the actual production as it passes through the line, but display the actual count divided by the goal count as a percentage, which is the efficiency of the line. The goal in this scenario is to keep the efficiency as close to 100 percent as possible. A fourth variation is to divide the elapsed work cell processing time by the total work cell processing time, and display this calculation as process percent complete. Some companies may want to track production in one of the ways described above, but instead of calculating a running goal they want to show the goal for the day, which is the shift goal. This doesn't present any issues, a display at each workstation would be dialed up to display the static goal, while a running goal would be calculated in the background by dividing the elapsed shift time by the total shift time and multiplying that result by the shift goal. This running goal calculation and the production actual counts are used to generate deviation and/or efficiency displays. If our hypothetical company managed to manufacture displays at 100 percent efficiency, one would see that there is little or no WIP, nor is there excess inventory space needed, as there are no buffers built. But running at 100 percent efficiency is not realistic, at least not for very long.
There are two basic areas that affect overall efficiency, time and numbers. A production line will not be productive one hundred percent of the time. Likewise, not all of the product will make it to the end of the line; there will be defects. And the sad thing is that as one moves further away from one hundred percent efficiency in either area, the faster overall efficiency decreases. For example, if a production line is 95 percent efficient in terms of both time and output, the resulting overall efficiency is 90.25 percent. But if that same line is 80 percent efficient in both measures, the overall efficiency is only 64 percent, not a passing mark by any body's measure. To improve uptime and output again requires analysis and monitoring. So in addition to pacing and tracking production, companies can track downtime and defects. In the past downtime may have been logged by hand, and defects may not have been counted at all. But with additional timers downtime can be tracked and displayed visually, giving a sense of urgency to get issues resolved. Likewise, counting defects with additional counters gives one the option to visually display raw defect counts, calculate percent defects, or even a defect rate.
Another concept in lean thinking is the use of visual displays to communicate production line status. The counter and timer displays can be arranged into andons to communicate status throughout the entire facility. Andon is derived from the Japanese "lantern" to mean signal. And some companies connect light stacks to the timers and counters to color code the various states of the line, or parts of the line. Typically the color green is used to denote that the line or an area is up, yellow is used to denote that there may be a problem, and red is used to denote that the line or an area is down. The overall effect is to communicate status very quickly.
In today's global markets speed and efficiency is paramount, so using production monitoring tools to analyze, tune, monitor, and improve production line performance is essential.
A production counter increments every time a product passes through a work cell or workstation. If the counter were used in conjunction with a takt timer, the goal would be to keep the production count equal to or as close to the running goal as possible.
A production timer has two modes. Used to display elapsed time, the timer could be used to monitor a process step to determine its length. Used in a timer mode, one could use it to monitor curing, or soaking times in a production process.
Percent complete is calculated by dividing the elapsed work cell processing time by the total work cell processing time, and displaying the calculation as a percentage.
The actual counter increments every time a product passes through a work cell or workstation. The counter can count by more than one if the products are batched together going through the line.
The goal displays a running goal.
The takt timer calculates the rate of production as a running goal by typically incrementing once every takt time interval. The goal counter can increment more than once if the products are batched together going through the line.
Additional andons or annunciators can be connected to the takt timer to visually signal the amount of time left in a takt time interval, green during mid-interval, yellow during warning period, and red when interval has ended.
The goal is to keep the actual count equal to or as close to the goal count as possible.
The goal displays a static count.
The goal is to produce as many items as is displayed on the goal count by the end of the shift.
A disadvantage of this approach is that without additional timers or displays, one does not know if the pace of production is correct.
The actual counter increments every time a product passes through a work cell or workstation. The counter can count by more than one if the products are batched together going through the line. Likewise, if a defect is found the actual counter can decrement as necessary to keep a correct count.
The defects counter increments every time a defect is located. The counter can count by more than one if the products are batched together and the entire lot fails.
The goal is to keep the defect count at zero, or as low as possible.
The actual counter increments every time a product passes through a work cell or workstation. The counter can count by more than one if the products are batched together going through the line. Likewise, if a defect is found the actual counter can decrement as necessary to keep a correct count.
Defects are displayed as a percentage by incrementing a counter every time a product passes through a work cell or workstation, and dividing that count by the total (actual plus defects) count.
The goal is to keep the percentage at zero, or as low as possible.
The actual counter increments every time a product passes through a work cell or workstation. The counter can count by more than one if the products are batched together going through the line.
The deviation display is the difference between the goal and actual counts.
The efficiency display is the actual divided by the goal, displayed as a percentage.
The goal is to keep the deviation count at zero or as low as possible, and to keep the efficiency at 100 percent, or as high as possible.
The goal displays a running goal.
The takt timer calculates the rate of production as a running goal by typically incrementing once every takt time interval. The goal counter can increment more than once if the products are batched together going through the line.
Additional andons or annunciators can be connected to the takt timer to visually signal the amount of time left in a takt time interval, green during mid-interval, yellow during warning period, and red when interval has ended.
The goal is a static display.
The deviation and efficiency displays work the same as the counter with takt timer with the exception that they are created using a calculated running goal from the elapsed shift time divided by the total shift time, with that result multiplied by the shift goal.
The actual counter increments every time a product passes through a work cell or workstation. The counter can count by more than one if the products are batched together going through the line.
The deviation display is the difference between the goal and actual counts.
The downtime display is the total elapsed time production has stopped for downtime (typically not breaks, lunch, etc.).
The goal is to keep the deviation count at zero or as low as possible, and to keep the downtime at zero or as low as possible.
The goal displays a running goal.
The takt timer calculates the rate of production as a running goal by typically incrementing once every takt time interval. The goal counter can increment more than once if the products are batched together going through the line.
Additional andons or annunciators can be connected to the takt timer to visually signal the amount of time left in a takt time interval, green during mid-interval, yellow during warning period, and red when interval has ended.
The goal displays a static count.
The deviation display works the same as the counter with takt timer with the exception of deviation being created by using a calculated running goal from the elapsed shift time divided by the total shift time, with that result multiplied by the shift goal.
