Hydropiercing
At the end of the forming process holes may be pierced in the component. The forming pressure may be used to provide support against an advancing punch (Outside-In piercing) or to shear the material against a retracting support (Inside-Out). When a hole is pierced, it important to control what happens to the removed material (the slug). Slug-free and Slug-attached piercing are two alternatives that may be considered.
Outside-In
At the end of the forming process the punch is advanced using the internal pressure as a support. The punch shears the material to form the hole. It is important to understand that as the demands for surface flatness around the hole increases so does the internal pressure required to make the hole.
Inside-Out
The technique for hydropiercing uses the internal pressure at the end of the forming process and a retracting support to shear the material on the hole boundary. This method is particularly suitable for larger holes and gives good surface flatness around the hole.
Slug Free
Both Inside-Out and Outside-In operations may be used for slug-free piercing. With this method the slug is left to fall free from the component. During manufacturing it is important to account for all slugs since presence of slugs in the die will result in scrap parts.
Slug Attached
Slug-Attached piercing is only appropriate for the Outside-In method. A specially shaped punch is used to ensure that the hole is not completely sheared, leaving a small region where the slug remains attached to the component.
