When designing a part or product, there are several things you can do to reduce the overall cost of manufacture. For years managing a machine shop, I have come across some terrible drawings. The ones on the napkins or scratch paper are sometimes the best. Often times, companies retain high level engineers that have never made anything. Of course this may not be their fault but designing parts that can actually be made with machine shop tools is a learned skill. Recently, we were machining a cover with an O-ring groove. The print had no flatness callout. When we asked the customer how flat the plate needed to be, their answer was, ” you know pretty flat, but don’t machine it flat.” Now the tolerance for the depth of the O-ring groove is +/- .005. There is absolutely no way that can be achieved with out machining the surface of the plate. Of course when the plate came in from the customer, it had a bow in it roughly 3/16″ or .190″ This required grinding and pressing before we could even touch it.
This type of problem is so common. Designers always forget the most important information, or just assume that the fabricator or machinist knows what the designer was thinking. We all see parts differently and seldom do I just guess correctly. There are two ways that engineers and designers can combat this expensive cycle; education, and experience. Experience- Even if an engineer doesn’t actually make a part, just having him or her in the shop while the machinist or fabricator is building the item drawn, can be a huge advantage. We have had our customer’s engineers call or stop by so they can really see some of the issues we deal with, and it cam be extremely helpful for all involved. Education- This is where my blog post may be most helpful… Last summer, I made a connection with a local shop that specializes in very high end complex parts made in difficult materials. They are a wonderful group of guys and gals ready and willing to help out when the parts get a little too fancy for our capabilities. Over the years, the CEO has developed an E-book that deals with these issues in a real world way. This e-book should be required reading for ALL designers and Mechanical engineers. Following these points will save an immense amount of time, money and frustration when the designs can be easily made. Most of the time small insignificant changes made to the drawing can save hours. Engineers, please read this short book and set yourself high above your competition.