An organization needed to ensure the safe delivery of their product in its own packaging. To control its process improvement regarding seal strength, they used tools like poka-yoke and realistic tolerancing. The company targeted to reduce the percentage of improperly sealed products.
A simple experiment made it clear that a tight range of acceptable values for the pressure was needed to get the desired sealing results. The company used the poka-yoke technique to establish that when the hydraulic pressure is beyond the acceptable range, defects do not flow further in the process as the seal process shuts down. The experiment also identified that the seal integrity was majorly affected by the temperature of the air forced across the materials that have been sealed. The supply of heated air varied immensely because of the extensively varying temperature. It was suggested to use the poka-yoke technique as its implementation would terminate the sealing process and the partly sealed package would be discarded if temperature of the heated air varied. For this purpose, the acceptable range of air temperatures was to be determined, which was done by using the approach of realistic tolerancing. Realistic tolerancing was a method to control the process by using regression analysis.
A regression analysis was performed with 95 percent prediction bands and realistic tolerancing used the bands along with seal strength specification to figure out the range of air temperature permissible for successful seals. The data showed that to attain the optimized seal strength levels, the temperature must be maintained between 189 degrees Fahrenheit and 231 degrees Fahrenheit. The data also made it clear that noise affected the process and with less noise, the acceptable range of hot air temperatures broadens considerably.
The implementation of poka-yoke and realistic tolerancing resulted in zeroing customer complaints for unsealed products. The company encouraged the teams to use these techniques to sustain the changes and identify the areas which can be mistake-proofed.