IE 408: Quality Assurance. Helicopter Project TPR 3 5/6/2015

Transcription

1 IE 408: Quality Assurance Helicopter Project TPR 3 5/6/2015 John Balzani, Aloysia Beaulieu, Chris Diaz, Kyle Jiron, Nick Kreuter

2 Work Instruction: Purpose: The purpose of this section of the project is to create work instructions for manufacturing the helicopter with the longest flight time from TPR 2. These work instructions will be used for all members of the project and on every step in the assembly line. To perform this task, the operators will need to be aware of what helicopter is being used, the material that is being used, and how many they need to make. This section of the project needs to be fully read and understood before the manufacturing process can begin. Scope: These work instructions are intended for use by the members of this project. To begin manufacturing, the materials that are going to be used are helicopter ID 12 from TPR 2, plain white computer paper, and one paper clip. Quality needs to stay at a high level while manufacturing these helicopters in order to keep the helicopters as similar as possible. All 250 helicopters will be made to the same specifications. Responsibilities: All members of the project are going to be placed at one part of the assembly line, and one production run is going to be performed. The assembly line is going to consist of cutting the exterior material off the helicopter, then passing it to station two where the tail is cut out, then station three where the wings are cut in half, station four where the wings are folded, and station five where the paperclip will be added. Due to the helicopter dimensions being identical, in stations one and two multiple helicopters were cut at a time. Instruction: Station 1: 1. Reach for three helicopter prints and square them to each other. 2. Lay stacks of paper on cutting board and square to top line on board. 3. Hold stack firmly. 4. Cut excess material off helicopter. 5. Rotate 90 degrees, square to top line on cutting board, hold firmly, and cut again. 6. Repeat step 5 until all excess material is cut off from helicopter design. 7. Pass design to station 2. Station 2: 1. Reach for stack of trimmed helicopters and prep scissors in dominant hand. 2. Cut excess material away from tail on all three sides. 3. Pass to station 3.

3 Station 3: 1. Reach for the fully trimmed helicopters and separate them from each other. 2. Pick up scissors with dominant hand and cut helicopter wings in half 3. Once cut, pass to station 4. Station 4: 1. Reach for cut helicopters. 2. Fold the wings on the helicopter on the dotted line, right wing back and left wing forward to ensure clockwise rotation of the helicopter. 3. Pass to station 5 when completed. Station 5: 1. Reach for helicopter and paper clip. 2. Place paper clip on bottom of tail where indicator mark is. 3. Stack in finished pile when completed. Conclusion: Safety requirements for this project include taking care to avoid paper cuts, and ensuring proper handling of scissors and cutting board. In theory, all helicopters will look identical to each other. Takt time from start to end should be 27 seconds. Total production time for all 250 helicopters will take 1 hour and 52.5 minutes. Manufacturing Process: In order to create an SPC Chart, it is required to make a large amount of paper helicopters. In order to complete this, a manufacturing process is developed in order to finish this task in a small and efficient amount of time. First off, the helicopter that performed with the maximum flight time was used. This helicopter has the wing length of 115, the wing width of 45mm, body height of 25mm, tail width of 30mm, and total length of 255mm. In order to come up with significant information, 250 of these helicopters needed to be created. After entering these dimensions, 250 copies were printed. Once printed, an assembly line is created to efficiently cut out each helicopter. Efficiency and quality need to be kept to a maximum for this part of the project to obtain consistency and keep the time needed to make all 250 helicopters to a reasonable time.

4 Manufacturing Process Flow: SPC Control System: After all 250 helicopters were manufactured, drop testing began. As in TPR 1 and TPR 2, the helicopters were dropped from six feet. Since random sampling was used, half of the helicopters flight times were recorded. Three different operators were used to drop the helicopters. Each operator would drop a total of 40 helicopters at a time. The timer would time each drop, but every other five drops would be recorded. Once the operator dropped 40 helicopters, the operator would switch. This would repeat until all 250 helicopters were dropped.the reason for changing operators after every 40 drops was to incorporate assignable variability along with the recording of times every other 5 drops. Process Control Report: Control Chart for our process: From our SPC control system, we assembled an Xbar R chart based on the times of the helicopter drops from 6 feet. Using this chart, we were able to get a glimpse of whether or not the process was in control for our manufacturing system. The result of our time samples and its Xbar R chart can be seen below.

5 From the chart, we can see that the short term variability was in control for the sample groups of 5 that we selected. We had a mean short term variability or R bar of about.245 seconds, meaning the difference from the longest and shortest helicopter drop times was about.25 seconds. None of the groups saw an outlying range, where the largest drop and the smallest drop had a large difference. From this chart we believe that we can use the Xbar chart above to measure the long term variability. Looking at the Xbar chart we can see that the grand mean of the samples we measured was about 3.2 seconds. The process stayed within the control limits throughout all of the samples that we took, and none of the samples had an average that was smaller than the lower specification limit of 3 seconds. From analysis of these charts, we believe that this manufacturing process is in control. We next look at the capability analysis of the manufacturing process to see if the process is capable and fit to be used. Process Capability: In order to measure the capability of our process, we used the capability sixpack tool in Minitab to analyze the data for our manufacturing process. We use the sixpack because it allows us to verify the assumptions for using a normal capability report. First we look to make sure that the process is stable and in control. From the control charts on the sixpack and above, we see that there is not a single sample that lands outside of the control limits that have been set. This shows that the stability assumption has been verified. Next we check to make sure the data is distributed normally, which we verify by analyzing the probability plot on the sixpack. Looking at the sixpack output shown below, we verify that the data is distributed normally as the data points fall mostly on the normal distribution line. Also we have a p value of.129 from the Anderson Darling test, meaning that we cannot reject the assumption that the

6 data is normally distributed. Last we check to make sure the data is independent, and that samples do not depend on the ones measured before them. Looking at the output of the samples below, there is no trend or anything else that would suggest that the data is dependent, verifying the assumption of independence between samples. Since we have verified all of our assumptions, we can look at the output and see our process capability and potential. Since there was only a lower specification limit of 3 seconds, there is no C U, C P, P U, or P P calculated. These require an upper specification limit to calculate, which is not applicable to our situation since we are trying to maximize the flight time and it does not matter how far above 3 seconds the flight time is.

7 From the capability sixpack output seen above, we find our C pk and our P pk which are equal to the C L and P L respectively. For the C L we are given an output of.64, which is not a stellar number. It means that the process is outputting more variation than what is considered allowable. In other words, our process is not capable. The P L is.62, which is very close to the C pk, meaning that the process as it is cannot get too much closer to the capability (only a difference of.02). If we wanted to increase the capability and potential of our process, we would probably need to create the helicopters with tools allowing for a greater amount of accuracy. The design of the helicopter could also be a contributing factor. The process is putting out a lot of helicopters close to the specification limit, and this was known since the design had a mean time of just above 3 seconds when we tested them in the last part of the project. Conclusion: We designed a process to produce 250 helicopters to the same dimensions, and we produced all these helicopters. We dropped these helicopters and measured their flight times, the mean flight time being above the lower specification limit of 3 seconds. To determine whether or not our process was in control, we created an Xbar and R chart of the flight times. From analysis of these charts, we determined that our process is in control. After determining that our process was in control, we looked at whether or not our process was capable. We created a process capability sixpack in Minitab to analyze the capability of our process, and we determined that our process is not capable. However, we believe that our process could be improved in the future by using tools that allow us to create helicopters with a greater degree of accuracy.