Well here it is, Labor Day 2010. I hope you are having (or had, by the time you read this) a very good holiday weekend. I am sending this out today because I have just been too busy to do so earlier. Isn’t it great to have a day off? Again, to those who have replied to these emails, I thank you. Sometimes I wonder if anyone is even reading them much less getting some valuable data to help them in designing their products or equipment. So, any and all feedback is greatly welcomed. By the way, if there is any particular design issue you have that is bugging you, please let me know. Others may be having a similar issue. I will be happy to discuss it in a general format so as not to disclose anything confidential. Of course if you need personal attention, well, that is what I do for a living.
Okay. In the last issue I began discussing DFA (Design For Assembly) concepts and started with a discussion of an apparently uniform pin. If you recall, it actually had a step in it that would not be discernable by a quick visual inspection. Now, let’s take a brief look at other ways to employ DFA concepts. Very often a part must be inserted into another one, usually by means of a rectangular tab. Please refer to the drawing shown below.
In both examples, the height of the cylinders on the top and bottom of the pieces with the tab are not the same height. They are close, but different. In Example 1, the tab and the hole it fits into are plain rectangles. The part with the tab could be inserted either way. Now refer to Example 2. You will see that a chamfer has been added to one corner of both the tab and the hole. Now, it can only be inserted one way; the correct way. So, it is really just a matter of making a feature different enough on the mating parts so they can only be assembled correctly. There are many ways to accomplish this. Very often, the method of manufacturing the parts will dictate the best way to accomplish this.
Once again, I am out of space and out of time. Hopefully, I can get out the next issue before the Thanksgiving Holiday. Stay tuned.