Ed Hill

Synchronous Solutions

It is always best to know where you are now before you start an improvement How long does it take you to change a tire on your vehicle?  Fifteen or twenty minutes; maybe more. A NASCAR Pit Crew can change all four tires, fill the car with fuel and clean the windshield in less than one minute. That is a perfect example of the ultimate changeover time. In the real world, that is an example of the dramatic accomplishments that can be realized with a disciplined approach to operations management.

In the countertop fabrication industry, most shops would accept a CNC router changeover in twenty minutes. Commonly those changeovers can consume thirty minutes or more. We often see significant idle time during the changeover because the next material is not staged and ready at the machine, or when the DXF and program files are unavailable, or when assigned workers are not there when the changeover is needed. All of that is wasted time. 

The actual time to complete the changeover, if all materials, files and people are ready when the current changeover is completed can be dramatically improved if the task is properly planned and executed.

Single Minute Exchange of Die (SMED) is one of the many Lean Manufacturing methods for reducing waste in a production process. This approach provides a rapid methodology for converting automated equipment from running the current product to running the next product (aka Changeover time).

The phrase “single minute” does not mean that all changeovers should take only one minute, but that they can take less than 10 minutes (i.e., 9 minutes or less). The changeover time begins upon completion of the last piece on the current production run and ends at the start of the first piece on the next production run.

Work Sampling Study

A waterjet saw and a CNC router are expensive equipment installations. As a result, you should assure that you are getting the most productivity per hour of needed runtime out of these machines. A good first step toward process improvement is to know how much runtime is now being realized in your shop. A realistic expectation is that these machines should be running at least 80 percent of the required work time each day. The other 20 percent would be consumed with changeovers, rework on defective pieces and maintenance. Much of this idle time is an opportunity for improvement.

At any time, a machine can be running or not running. Those times can be consumed within several possible categories:

  •  It can be running on a new job (not a rework job).

  •  It can be running on a rework job. You don’t get paid again to do rework jobs.

  •  It can be idle (i.e., not running):

°During a changeover on a new job. This is a necessary task but should be streamlined to the minimum time actually required.

°During a changeover on a rework job. While this is occasionally required, the occasions should be mini- mized. Again, you don’t get paid twice to do rework jobs.

°It can be down for maintenance. Again, this is occasionally required, but good preventive maintenance practices will minimize the down times. You should identify the core causes of these maintenance delays, including:

— Mechanical.

— Electrical.

— Water.

° It can be idle while waiting on material for the next change-over. This should always be avoided.

° It can be idle while waiting on DXF or program codes. This should always be avoided.

°It can be idle while waiting on worker(s). This should always be avoided.

results of a recent Work Sampling study at one of our clientsOne way to learn how much time is spent on all the activities would be to conduct a detailed “all activity” time study over several days to document the time spent on each possibility. This is very time-consuming and expensive. The data provided by the equipment, while valuable and useful, does not identify all the reasons for the machine being idle, nor does it identify run time on rework. To properly know what is really happening, you will need to know the true reasons for every run time and idle time.

We have developed a simple statistical sampling program that will allow you to know how much time is occupied in all these possible categories. “Statistical Sampling” simply means that we can study the activities of a machine(s) over an entire work week by observing a statistically correct sample of randomly selected observations.

Our program divides the work week for each shift into 15-minute segments and numbers each of them. In a forty-hour work week, there are 175 15-minute segments. The program produces a random sampling of 30 of these segments, which is necessary to achieve a statistically correct study. 

results of a recent Work Sampling study at one of our clientsAn observer is then assigned to simply walk the floor at the appointed times and record exactly what each machine being studied is doing. Only 30 “snapshot” observations over an entire week at about ten minutes per observation is needed to produce reliable statistics on what is happening at each of the machines being studied during the entire work week.

The two charts show the results of a recent Work Sampling study at one of our clients. Note that the client estimated that their run time would be at least 75 percent. They were surprised and disappointed learning of the true situation.

It is always best to know where you are now before you start an improvement process. The Work Sampling Study is a relatively easy way to know what is really happening with your automated equipment. This fabricator engaged his staff in a SMED project and significantly improved the up time of his equipment. A planned purchase of a new CNC router was delayed until sales volume increased to justify it.

Lean Manufacturing Tactics

Overall, Lean Manufac-turing is a systematic approach to identifying and eliminating waste through continuous improvement efforts. It is ideally suited for continuous manufacturing processes that make hundreds or thousands of the same item. However, many of its elements, like SMED, can be useful in the custom fabrication industry.

Lean Manufacturing is essentially a set of process tools, each designed to accomplish a specific objective:

  • Value Stream Mapping – Effective design of plant layout for optimum flow.

  • Kaizen – Continuous improvement activities done in a rapid manner.

  • 5S – Workplace organization and cleanliness. Everything has a place and everything is in its place.

  • Total Productive Maintenance – Equipment Preventative Maintenance procedures.

  • Kanban – Pull Mentality and inventory control.

  •  SMED – Set-up/Changeover reduction activities.

Lean Thinking, By James Womack and Daniel JonesThese tools, among a few others, can be implemented together or separately and form the concepts of the Lean Manufacturing System. 

Lean is actually a derivative of the Toyota Production System (TPS) developed by the Japanese auto manufacturer in the 1970s. Lean Thinking, a book by Jim Womack published in 2003, describes an Americanized version of the TPS process.

SMED - Single Minute Exchange of Dies

This is a series of techniques designed to reduce complex set-up/changeovers to less than 10 minutes. That goal is entirely possible with the proper attention to the details of the SMED process. 

There are seven basic steps to reducing changeover using the SMED system:

  1. Observe and video record the current methodology from completion of the current changeover to the start of the next changeover.

  2.  Select a group of managers and workers involved in the changeover process to carefully review that video and identify the internal and external activities. Internal activities are those that can only be performed when the process is stopped, while external activities are those that can be done while the current production run is working. For example, internal activities would include:
    • Positioning PODS for the next run.
    • Placing the cut parts on the router.

External activities would include:

  • Transferring the DXF and program files to the equipment for the new run.

Staging and organizing the material for the new run.

  • Alerting the needed workers to be ready at the instant the current run is finished.

3. Convert (where possible) internal activities into external ones. Identify every activity that can be done before the current run is finished. Confirm a documented plan to assure that those activities are completed for every changeover during the current run. Make sure that all workers understand that these activities must be completed on every changeover.

4. Streamline the remaining internal activities, by simplifying them and assuring the necessary staffing is ready to complete the tasks.

5. Streamline the external activities, so that they are done routinely without delay to the changeover.

    • Assure that the needed DXF and/or program files for the new changeover are available BEFORE the machine stops.
    • Stage all the material needed for the next changeover BEFORE the machine stops.
    • Assure that the necessary workers are ready to perform their changeover duties immediately when the machine stops.

6. Document the new procedure, and train/practice multiple times. Video record each trial and analyze it to identify further opportunities for improvement. You must make changeover reduction important and a priority for your people.

7. Do it all again. All of it. For each iteration of the above process, a 45 percent to 50 percent improvement in changeover times can be expected, so it may take several iterations to cross the ten-minute line.

The countertop fabrication industry is blessed with amazing technology. Saw jets, robotic cutters and CNC routers have dramatically improved the productivity of fabrication shops and have reduced the reliability on manual workers, who are so difficult to find and retain. But the point is, before you spend several hundred thousand dollars on a new CNC router or other automated equipment, first make sure it is your system’s constraint and, if so, make sure you are getting the most out of the existing equipment. And when you do decide to invest in expensive automated equipment, make sure you operate it to its maximum capability. Effective reduction of changeover times, using the SMED process, is one way to do that.

For more information on utilizing Synchronous Flow and Lean Manufacturing, contact Ed Hill,  at 704-560-1536.