In contrast to tube laser cutting and machining, CNC rotary draw bending is very tooling-oriented. As many as six types of tooling components may be needed for a project, based on its size and scope. Of these, the three most important types are the bend die, pressure die and clamp die. Depending on the bend radius and wall thickness, a mandrel and wiper may also be needed to achieve an acceptable bend. For parts requiring multiple bends, a collet is needed to grip the tube or pipe and rotate it to the proper location.
Types and Uses
The bend die is central to the tube forming process, as it rotates to form the center line radius. A concave channel on the die mates with the outside diameter of the tube or pipe, helping to hold the material while it is being bent.
The pressure die mates up with the tube, adding stability as the tube wraps around the bend die. The clamp die works in tandem with the pressure die, holding the tube against the straight section of the bend die as it turns.
When needed, the wiper die is used. Riding toward the end of the bend die, this tooling helps to smooth out the surface along the inside radius as the tube or pipe moves through the bend, preventing wrinkles and supporting the tube wall.
A mandrel is a bronze alloy or chrome plated steel insert that supports the pipe or tube on its inside. Its purpose is to prevent the tube from collapsing and minimize ovality. Learn about ovality here.
The collet grips onto the tube during the bend process, rotating it into position for the next bend. It softly closes onto the outside of the tube, guiding and moving it into place.
Availability and Costs
Depending on the size of the material being bent, the cost to create a bend die can range from 2K to 20K. This one-time charge covers material and production time needed to create the tooling, which can then be used on subsequent projects.
We have over 600 bending dies in our tooling inventory. If not available, most tooling can be produced by our tool and die shop on premises, which can help to control costs, lead time and quality.
If there is flexibility to adjust the part’s specifications, an alternative is to consider using an existing bend die with a similar radius to the original part design, thus saving on tooling costs and lead time to produce.
Whether for a small or large project, tooling must be carefully chosen to ensure quality and accuracy. When evaluating the parameters of a bending project, it may be beneficial to review our list of available tooling. This list is updated periodically, so please inquire about what may be needed for your specific project.