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When designing your parts, it is always important to keep in mind the impact your design has on the manufacturing process. Key points to consider are highlighted below:
A radius of 1 mm or less creates a corner in the steel rule die which is stronger than a square corner. Sharp corners require tooling to be joined at the corner, creating a weak point in the tool, which can cause deflection in the tool as a part with localized deformation.
Replace holes close to edge with U-slots or notches. When holes are attempted close to the edge of a part, localized distortion may be present, or the hole may tear out.
Leaving the default tolerances of +/- 0.005” on your drawing can be an expensive habit. Die cut parts cannot hold the same tolerances as machined parts. The design should reflect not only the tolerances of the tool, but include the cutting tolerances and the dimensional stability of the material.
Many materials require cutting tolerances much greater than the tolerance of the tool. For example, Nomex® aramid paper is hygroscopic and can expand up to 2% in the direction of the grain, due to changes in humidity. Therefore, a 10” part could expand up to 0.2”. Also, soft and dense foams and rubbers can have distorted edges when die cut. This distortion usually does not affect the fit of the part, but when measured, is shown to be out of tolerances. Tolerances should be designed with the material and application in mind. Please contact one of our technical representatives to determine the most suitable tolerance for your application. This will help us produce parts that perform as you expect, in the most economical fashion.
Graphics courtesy of ITW Formex Design Guide www.itwformex.com