- THE MAGAZINE
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Manufacturers who are serious about quality, those companies that actually want to find out why and where a problem occurs, have found process mapping an efficient way to track down production problems.
Process mapping is a technique that identifies the "world" of a process. It shows all of the inputs, such as subassemblies and materials, machining processes and machine operators -- basically anything that happens inside a process -- and all of the outputs of that process, including the finished product or the individual manufacturing or handling steps along the production line.
Too often, companies try to "inspect" quality into their products, finding problems in final inspection and fixing them on the spot. Quality people should not be solving problems this way; they should force the process back to where the problems originated. The best quality system is one in which, when problems in finished products are found, manufacturing is then charged with determining what went wrong and how to correct it, so that the process turns out products that are ready for shipment -- with no failures.
By viewing the route the finished product takes along the process map, quality personnel can determine where the potential problems lie, rather than catching it, or not, during final inspection.
Knowledge is key
The basic tenet of process mapping is to understand all of the influences that affect that part or product. To do so, information must be obtained from as many sources as possible, and that data must be organized to reflect how things are actually done in producing an item.
The most important part of the whole process is the interview. Interview people from as many different departments and operations as possible. Interview the operators of a particular machine and ask: What do you do? How do you do it? Why do you do it? They should be able to show documents that detail the process.
Think of a process as a living thing, with people and machines working to accomplish a manufacturing goal. Think about the materials that go into it. Does it use a piece of steel? If so, where did the steel come from? Why is it there? What materials will be used with the steel? Who are the people that bought the steel? Who sold the steel? Who handled it along the way?
As the interviews are completed, a huge amount of information is collected involving humans, machines and processes that needs to be organized. The flowchart is the best way to do that because it can be kept simple at first and then filled in later as more information is discovered.
Flowcharts should be layered, beginning with general information leading to specific information. For instance, an initial flowchart may have three components: obtain raw material; process raw material; ship the material. That is a three-step flowchart and it is complete. From there, dig down deeper and create more complex subflowcharts to show the process.
And this is not a one-time project. Quality personnel should continually ask questions and keep their ears open. Sometimes they may see something and not know if it is good, bad or indifferent. Then, later on, they may hear or see something else and may put two and two together to solve a problem, or identify an unnoticed or developing problem.
This was the case in the assembly area of a computer parts maker. The company sold a machine to other businesses for more than $50,000. The company installed a door on the machine over a shroud area, an area where crucial components that are susceptible to environmental contaminants are installed. The door has to move back and forth, and a door runner is used as a movable seal to the shroud area.
The problem was that sometimes the door would not shut or stay shut. Sometimes the problem would surface at a customer site, and here, as in the plant, it might be intermittent. Because it would come and go, field engineers had trouble finding a root cause.
One evening, the quality control manager heard an "unquality" sound. The sound was a hammer clanging away against metal. Because the company did not build houses, the use of a hammer was outside the needs of quality. Following the sounds, he found a mechanical assembly worker beating a door runner into specification. The man was pounding on an area near the very heart of the entire machine.
Through a short interview, it was discovered that the department manager had bought the 3/4-pound mallet in answer to a quality problem that had been discussed in a weekly meeting. The manager instructed workers on all three shifts in the correct use of the hammer.
The quality manager looked at all of the factors that were involved with the process. The rails of the doors, which were outsourced, were factors to be explored. The installation process included fastening two door runners to the frame of the machine and installing the door, and all of which had to mate. Those were factors as well. The initial process map (see Process Map of Shroud Area) showed the path these doors took before arriving at the assembly area.
Each step along the production path was noted, from identifying the top and bottom side of a door to removing the spacing tool and letting it air cure for an hour. While "interviewing" the door process, a couple of grievous quality problems were found. The problems were again the result of a lack of training and experience of the management team. Interviews with the manager and the assemblers led to the construction of the Flowchart of the Door Rail Assembly Process. This detailed flowchart shows how the initial flowchart was expanded as the quality manager got to know all of the things that went into the door assembly process.
The most significant error was that the spacing tool, which sets the distance between the rails and is paramount to sealing the shroud area, was not listed as a tool, and was not listed on any Tool Calibration Schedule. The aluminum tool had worn over time and was out of tolerance.
The lack of calibration on a tool used in production was a serious breach of basic engineering and caused the entire "hammer" incident. Changing out the tool and setting up a calibration schedule solved a pesky quality problem that was hurting the company's reputation and costing it money. But solving it once wasn't enough. The calibration of the tool had to become routine, so the quality manager incorporated it into the process maps for future reference. As can be seen in the flowchart, a note directs operators to consult the calibration schedule. The note, Specifications of a Spacing Tool, is now added to all flowcharts that refer to this production tool.
This production situation was resolved by the use of process mapping and process flowcharting. Process mapping gave the plant's quality assurance team an outline of the entire manufacturing floor. It described a trail that showed where the doors came from -- which provided enough information to identify which process was in need of further review.
In the end, the mechanical assembly manager was presented with process maps of all processes that served as inputs to his processes, and finally, he was given his hammer to take home.
- Process mapping shows the route that a finished product takes to get ready for shipping.
- Knowledge is key. Extensive interviews should be conducted.
- Inputs and outputs give clues as to where to search for answers to pesky production problems.
- Layered flowcharts of each individual process will narrow the possibilities for error and lead to the problem areas.