Sharp Edges on Stamped Sheet Metal Parts and how to avoid them.

Stamped Sheet Metal Parts inherently have sharp edges at least on some edges unless measures are taken to prevent this.
Sharp edges occur on the side where the sheet metal part rests on the die plate opposing the punch direction. This is due to tearing as the punch pushes through the material the last section of the material thickness is thinned to the point where cutting force exceeds ultimate yield strength and the material snaps separating the scrap from the part, creating a tear. This tear area is typically ⅔ of the material thickness. This ratio is influenced by the material properties and the cutting clearance between punch and die, increasing the clearance also increases the tearing.
The edge is raised and sharp due to stretching and thinning of the material this sharp raised edge is also called burr. Keeping the tool sharp will minimize this.
The side where the punch entered will be slightly rounded as the material deforms before it offers enough resistance to allow the punch to cut.

If sharp edges are not acceptable additional steps can be taken to avoid sharp edges or their impact on function.
If not all edges are required to be burr free a punch direction can be indicated to take advantage of the rounded edge where the punch entered. Typically this is indicated with an arrow that points in the direction of the punch cutting the material.

After stamping vibration deburr using abrasive media is another possibility we offer. This will grind the sharp edges down and as a side effect provide a uniform surface finish.

Sharp edges can also be avoided by using an angled coin punch to add small chamfer this can be done in the progressive tool.
If you have any questions regarding this contact us here.