Where I work, we have a full-service tool and die shop where we can produce hard tooling (blanking dies), as well as steel-rule and pierce dies in-house. In working with designers and engineers, we often receive questions regarding dies and tooling tolerances. Following is a quick reference.
Steel-rule die is best when you:
Have ±0.015 tolerance;
Have slight flexibility within your dimensions;
Need quicker turnaround for die production;
Want low production costs.
Blanking die is best when you:
Have ±0.005 tolerance;
Have use for heavy substrates;
Demand tight tolerance;
Have products used by the medical or engineering industries.
The advice of one of our tool and die makers is when you’re designing new nameplates and labels, try not to over-engineer the part. Put yourself in the place of the person building the tool, be realistic, and don’t get too crazy. Provide as much tolerance as possible to minimize the time needed to set up each phase of production, thereby reducing costs.
Another important element to consider is the placement of any holes, cutouts, or slots along the outside edges. When possible, try not to get too close to the outside edges, especially when using thicker materials. For functional parts that require multiple holes, consider using one oblong hole versus two separate holes.
Depending on the complexity of your part and your needs, several tooling options are available. Work closely with your industrial printer supplier to find a solution that meets your needs in the most cost-effective manner available.
Dave Wittenberg joined Mcloone in 1978 as a tool and die maker. With a degree in Mechanical Design Technology, he uses his skills in building tooling that meets customer demands and satisfies all product design requirements.
This author should make a tour of some of his local colleges and talk to engineering students who are overloaded with theoretical mechanics classes and don't get ANY exposure to manufacturing. As a result, too many new engineers don't know how to design for manufacturability. This kind if insight is invaluable.
Thanks for the article. I have seen otherwise capable engineers specify ridiculous tolerances over and over again without realizing the cost attached to those tolerances or the assembly problems they produce. I had one engineer that specified a 7.000" part to fit into a 7.000" slot. Not only was the part in no way not critical, but the parts wouldn't fit if one came from the cold warehouse. No matter how hard I tried, he just couldn't understand why it was a problem.
I tried to explain to a mechanical engineer that a dimension of 1.000 mm was wrong. I couldn't get him to understand that the default tolerance was +/- 0.0005 mm ! and the proper dimension should have been 1 mm, since it was not a critical part. This engineer also dimensioned a 14 foot long square tube frame as 168.000 inches !
T J McDermott; CAD is a tool for a draftsman (or draughtsman) to create a drawing. Computer hackers create garbage. In my AutoCAD course I was taught what the most frequent mistakes made in CAD were. On my first job in CAD, they were all there. The most common mistake = all drawinga are drawn full size, but they are scaled to fit the paper size to be printed on. The first drawing that I worked on would have needed a 300 ft sheet of paper.
And mechanical engineers (in my experience) do not understand that emergency stop and end-of-travel sensors are normally closed circuits.
Charles, I completely agree with you. I'm mentoring and managing several young engineers now and unfortunately they were not taught basic tolerance capabilities for each manufacturing process. I also agree that these basic manufacturing tolerances should be taught in all engineering colleges.
Thanks for your post Charles! We have 4 colleges/universities in the immediate La Crosse, Wisconsin area. While we are actively involved with these institutions through internships and other programs we have not considered a manufacturing focused engineering lecture series. Great idea...thank you for your suggestion.
I have to say Amen, Greg. Improper tolerancing is expensive and too few mechanical engineers really learn that in school. Unfortunately, often the young engineer learns tolerancing by doing it incorrectly.
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