Tutorial no. 1: Clearance and undercut

Tutorial no. 1: Clearance and undercut

The presence or absence of clearance and/or undercut within a part is an important point to think about when designing it. The presence of the clearance and/or undercut has a major influence on the price of production.

What is the clearance?

A clearance means that the shape of the part allows for easy demolding. The part has an angle of at least 0.5 degrees on its faces. As the shape of the mold follows that of the part, it is easy to extract it. An absence of clearance is equivalent to the absence of an angle greater than 0.5 degrees.

And an undercut?

In contrast to the clearance, the undercut is characterized by difficulty or impossibility of demolding the part by vacuum casting and may require the destruction of the mold. It is caused by problematic shapes such as cavities and retentions. These types of shapes cause blockage when extracting the part.

Concerning machining, it relates to all parts that the milling cutter cannot access and therefore cannot machine.

If the part is made of ABS, however, it is possible to obtain the desired finish despite the presence of undercuts by successive bonding of the machined parts to each other.