I just completed a course where Statapults were used to improve process flow…. There were 4 teams using 4 different statapults. My team had the worst results in each of 3 exercises – where each exercise we were allowed to make additional changes to the statapult to remove variances. Each team seemed to use all the same techniques to reduce variances – yet our yield was 25% below the other teams. This is why I believe we were behind the other teams: our mean distance of each shot was 132″, the other teams means were 77″, 85″ and 93″. The other teams clearly had a different type of rubber band (yellow – ours was black). I believe added error is inherent with the extra distance. The instructors dismissed this, saying that using consistant stretch time (which we tried to do) of the rubber band with each shot would eliminate errors and make each team have the same results. I disagree and would like to know if there is a way to figure out if all other things are equal, than what error is created when a statapult shoots the ball up to 70% further (77″ vs 132″). thanks.
Were the balls used all the same? Was the placement of the pins all the same? Was the pull back angle all the same? How was the statapult kept from moving? Did everyone do it at the same level, not some on the floor and some on the table? How was the rubber band affixed? How was everything measured? Was your’s straight and the other’s off to the side? These are some of the variables I have seen in the exercise. When used for DOE, it has been a great exercise. By the time they are done understanding the process, I have them tell me how far to place a paper cup and then more often than not, they get it in or at least hit it. Amazes the heck out of them.
Thanks for the reply Darth,
1. We all used a different set of balls2. All settings of the statapults were the same (pins, pull back angle, level, rubber band affixed the same, statapults taped to the floor).3. Our statpult shot slightly to the left… not sure of the others – we were seperated in different rooms. But our shots were missing either short or long, not to the side.4. Having to shoot 80% further than some of the other teams must increase the failure rate, no?
We use the Statapault for our Green Belt Training (nearly a BB) and have conducted 11 full sessions. It is an Excellent tool. We bring it out at Process Mapping and use it 12 times in our sessions.
At the DOE state the purpose is to put the ball into the cup by “optimizing the process.” It does not matter if you have a different ball, different rubber band, and use differeent settings. If you have performed the Experiment (fraction factorial) correctly, it does not matter. You do have to use the same Statapult throughtout the session.
When we do our final shots to determine the winning team, we use two distances – short (about 40-60 in) and long (95-120 in). In our last class, at 42 inches one team put 5 of 5 into the cup!!!
We have conducted 11 classes, with more planned, and could not do it without the Statapult!! We use GBs as Team Leaders.
We have also performed statapult exercises with yellow and black rubber bands and seen a difference in total distance and variance.
It makes sense that the further you are shooting your statapult, the more of an effect your noise variables will have. Imagine that with pin and cup settings exactly the same that you have a super rubber band that shoots statapult balls an average of 1 mile, while your competitor’s shoots only 77″. Are you going to have just as good of a chance of hitting a paper cup 1 mile away as he does of hitting one 77″ away? I don’t think so.
One thing I have found wiht the statapult is to unload the elastic when not shooting, otherwise the stretch has an effect on the results.
SOP’s – Shooting Techniques: Grip – The operator should carefully grip the cup in the same way each time. Various grip methods have been used such as holding the edge of the cup, holding the arm, holding the wing nut behind the cup, or having one finger over the arm just below the cup. The grip we have found to be best is holding the sides of the arm between the thumb and index finger.
SOP’s – Rubber Bands: Heating – The shot rate also affects shot distance. Heat is produced if you shoot several shots per minute for an extended period. If you then stop for a while, the next few shots may be longer than before by several inches. Establish a warm-up procedure before shots begin.
SOP’s – Maintenance Hints: Alignment Techniques: Rubber band nicks/cracks – The team should inspect the rubber band frequently. Small nicks and cracks do influence the shot distance. Crack propagation occurs quite rapidly. Before the rubber band breaks, though, changes occur in the shot distances. If the rubber band is changed, shot distances will change significantly. Exercise the new rubber band by extending it fully 50 or more times before conducting your experiment.
These and other tips explain the issues you are having. There are subtle factors that must be considered. The Statapult in the hands of a knowledgeable instructor is able to be a very accurate tool.
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