From DDL Wiki

First Report

We received your report on the stapler and were very impressed with your work. Your analysis and conclusions are clear, and you have identified a number of opportunities for improvement. We can’t wait to see what you come up with in the next phase. Detailed comments follow:

• Your assembly picture was a big help in understanding the function, but can you label major parts? The description of function is great, but would be much more helpful if parts in the disassembly picture were labeled so that we can see what you mean. The video is a nice touch, but the low quality makes it difficult to see details. Your links to pictures of parts in the disassembly procedure section really helped us see what you were talking about.

A labeled picture of the dissassembly has been added to the report. We're glad the other pictures were helpful and hope that this one is more so now.

• Why is the bending spring composed of two metal bars instead of one? Also, you mentioned that the bending of the spring was below that which would cause failure, but I didn’t see the calculation – is it far below? Should we reduce the size?

There are two main reasons for having two bending springs instead of one. The first is that these two springs are much easier to bend than one thicker one. In order for an average user to be able to operate this product, it must be easy to use. The other reason is that it is optimal to use two bars is that it is easier to manufacture the parts this way. The stamp goes through a thinner piece of metal easier than a thicker one. As for your last question about reducing the size of the springs, we do not think this would be a wise decision because, although they may not need to be as thick to avoid failure, making them smaller would take away from the power the staple gun produces which, for some users, is already on the weak side.

• safety to prevent misuse, tight corners
• You have identified some good areas of improvement from your user study – the difficulty inserting staples, high required force to operate, difficulty working in tight corners, and difficult using the tension adjust lever. We are also surprised that the user fired the gun several times without realizing that there were no staples loaded. Doesn’t this model have a window for viewing the presence of staplers? Should we redesign it? Also, did you come across any issues with different sized staples?

This model has a very small window to view the staples, but it is meant to show the user what size staple they are using rather than whether or not there are staples left. We have thought of a few ideas to address this problem which appear in our next steps. We have yet to come across any issues wih different sized staples.

• Your FMEA seems a bit sparse. Do you think there might be other important failures? For example, is part 21 a wear part, since the springs appear to slap against it?

The FMEA was rather sparse because the staple gun was designed very well and most failures with regular use or even mis-use are very unlikely.

• Your DFMA analysis was insightful.
• Also, please include a free body diagram with numerical analysis of the input and output forces and the energy transfered to the staple. Can you be clear about why a spring is used in a two-part operation instead of applying the user's input force directly to the staple itself?

By using the two part operation we are able to give the staple a much greater and more consistant force than it would receive if the user were applying their force directly to the staple.

Additional Comments

It could be useful, if along with the various ways in which the product has been designed for X, you mentioned whether or not you found these design points to be sufficient, or lacking.

Revision

We received your response to our comments on the first report, and we are generally satisfied. It looks like you made some changes to the problem by rotating the beam for analysis – do these assumptions change your results? The Finput of 4.2 lbs appears to be the max force applied just before release – although that was not explained. Does this match your experience with the gun? Finally, your answer to the question of why energy is stored in the spring rather than applied directly to the staple is questionable – you may want to look at this again.