Metal Forming technology – Expanding, Shrinking, Expanding-Shrinking and Roll-Forming technology

Shrinking Process – when the outside Diameter is of Importance

The shrinking process is, as expanding, the most economical means of forming and / or sizing a wide range of parts having a continuous cross-section.

Shrinking is the opposite of expanding, with the product being formed or sized from the outside diameter by exceeding the material yield stress during compression. This compression is used to reduce diameters. Forces act radially inward toward the machine centerline. The force required is higher than for the expanding process.  The advantage is that improvements of the material properties are generated by a lower deformation.

Shrinking is preferred over other forming methods when the diameter of the part is relatively small and/or outside diameter accuracy of the finished part is critical.

Shrinking can eliminate or reduce machining operations and therefore reduce cost per part, especially when the outside diameter is of importance.

The Expanding-Shrinking Process – when contoured transitional Areas are required

The expanding-shrinking process is an unique and economical means of forming a wide range of parts. For some applications, the principles of both expanding and shrinking are combined in a single machine. The center of such machine is an Expander. In principle, there are two methods to combine the processes:

1. With an expander as the center of the machine and with a collapsible outer die, the outer die will have a predefined diameter and act as a compression tool. The part is then expanded into the outer die.
2. With an expander as the center of the machine and a full shrinker around the expander, both the expander and shrinker can move to any given diameter.

This process is used for applications requiring the formation of localized embossments, beads, offsets, or other contoured transitional areas along the surface of the product.

Very complex curves or corrugations with high accuracy can be made. The process combines both motions so that the workpiece can be initially expanded and then shrunk. The cycle sequence can be reversed to provide shrinking first and then expanding.

This process can replace many other expensive forming processes.

The Roll-Forming Process – when Forming complex Profiles is needed

SizTech roll-formers can be widely used in most industries to form a variety of complex materials, such as Steel, Inconel, Titanium, and Aluminum based alloys. Rotary roll-formers apply an unique metal forming technology that generates complex profiles to straight sided and conical shape hollow cylinders. This process produces accurately dimensioned parts with essentially uniform cross section.

The tooling design and process parameters control the material thickness. It is typically preferred that the material thickness does not change. The Roll-Former forming rolls are mounted on two driven spindles. The lower spindle can be moved vertically toward or away from the upper spindle to provide the rotary motion during the roll forming process. The spindles are controlled by different forming process steps. When necessary, the part will be guided by side guides which help guide the part during the forming process.

Another successful benefit of roll-formers is the “near net shape” roll-forming process. The principle is the same; however, because of the special design, the roll-former has specific forces to allow material to displace in radial and axial directions. All kinds of shapes can be formed to reduce or to eliminate additional machining.

Roll-formers are commonly used for making parts in automotive, aerospace, power generation and other industries.