Stamping: Deburring
engineering fundamentals Stamping: Deburring
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Introduction

Burrs: Burrs are the normal by product of the stamping process. Burrs are often not acceptable, usually for safety reasons, either for handling or for product safety (burrs cutting into insulation, or mechanical chafing). Another reason could be to improve surface appearance-discoloration from welding/brazing, oxidation, scale from heat treatment etc.

Cosmetics requirements of finished parts sometimes require graining. Graining is used to hide surface defects by creating uniform scratches using an abrasive belt sander for example. This results in an even surface appearance. Like all finishing operations, this is to be avoided since it adds extra costs to the product. The grinding grit can range from #100 for removal of gross defects, to about #180 for materials that need silk screening. The abrasives used are dependant on the material. Aluminum oxide is used for steels and silicon carbide is used for softer materials such as aluminum.

A normal burr from well-maintained tools is usually less than 10% of material thickness. If burrs are not acceptable (burr-free requirement), then deburring needs to be done. Typically deburring results in a rounded edge with a radius of 0.05 to 0.075 mm (0.002 to 0.003 in).

Deburring: Deburring is done by tumbling parts in a barrel or a vibratory bowl, along with finishing media. Ceramic media is often used for steels. For softer materials, plastic media, walnut shells etc can be used. This type of deburring is usually confined to unfinished materials. For materials that are already finished, such as pre-plated or pre-painted materials bulk deburring operations are not suitable, because the deburring will remove the finish along with the burrs. For these materials, other forms of deburring such as belt sanding or hand filing will have to be done with the associated higher costs.

Deburring can be avoided by considering the direction of the burrs in the design of the parts. If the burrs will be in a non-accessible area or will be folded later, then deburring can be avoided.

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