Incremental sheet forming (or ISF) is a sheet metal forming technique where a sheet is formed into the final workpiece by a series of small incremental deformations. Generally, the sheet metal is formed by a round tipped tool, typically 5 to 20mm in diameter. The tool, which can be attached to a CNC machine, a robot arm or similar, indents into the sheet by about 1 mm and follows a contour for the desired part. It then indents further and draws the next contour for the part into the sheet and continues to do this until the full part is formed.

Uses in manufacturing

Because the process can be controlled entirely by CNC processes no die is required as is in traditional sheet metal forming. The elimination of the die in the manufacturing process reduces the cost per piece and increases turnaround time for low production runs because the need to manufacture a die is eliminated. However, for high production run the time and cost to produce a die is absorbed by the higher per piece speed and lower per piece cost. In addition there is a loss of accuracy with the ISF process.

Implementation

The ISF process is generally implemented by clamping a sheet in the XY plane, which is free to move along the Z axis. The tool, usually a sphere, moves in the XY plane and is coordinated with movements in the Z axis to create the desired part. It is often convenient to retrofit a CNC milling machine

Milling machine

A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...

 to accommodate the process.

The machine employs a combination of stretch forming by drawing the sheet incrementally down over a die, with the CNC tool approach described above. This is said to produce a more even distribution of thickness of the material. The process is well suited to one off manufacture though difficulties in simulating the process mean that toolpaths are complex and time consuming to determine.

Current research

Research is underway at several universities. The most common implementation is to outfit a traditional milling machine with the spherical tool used in the ISF process. Key research areas include

• Developing rolling tools to decrease friction.
• Eliminate springback
• Increase accuracy
• Develop novel uses

External links

• Production Processes - Single point incremental forming