Most tube and pipe bending is done using a mandrel, an aluminum-bronze alloy or solid steel insert that supports the pipe or tube while it is being bent. This common technique keeps the tube from collapsing, flattening or wrinkling during the bending process. A mandrel also helps to ensure accuracy of the end product by maintaining the shape of the tube.
Three things help determine the use and variety of the mandrel: type of material, wall thickness and bend radius. A softer metal like copper or brass requires more support during bending than a stronger alloy like stainless steel. Similarly, tube with a thinner wall is more susceptible to kinking or breakage than one with a thicker wall. Bends with a tight radius need the extra support of a mandrel to withstand the pressure of the machine and hold a new shape.
Overall, a mandrel is key to achieving an accurate and precise bend. It also extends the life of the tooling and helps to minimize the wear and tear on the bending machine.
Not All Mandrels Are The Same
There are several different types of mandrels. The most common is the ball mandrel, which is used on bends with normal wall thickness. As the name implies, this type of mandrel can move in multiple directions, allowing flexibility to accomplish multi-radius bends. Ball mandrels are used in tandem with a wiper, clamp and pressure die, together adding the required pressure to hold, stabilize and smooth the bend.
A plug mandrel is a solid rod used on heavy walled tube with a larger radius, and does not require a wiper. And, a form mandrel is a solid rod with a curved end, and is also used with thicker walled tube or pipe with an average radius. The formed end provides additional support to the inside of the tube or pipe.
Things to Remember
When selecting a mandrel, it is important to know the type of material being bent and how the tube or pipe will be used in the application.
Use of the correct mandrel material also helps minimize wear inside of the tube, and reduces the incidence of pock marks, or galling, created from the movement of the mandrel against the tube during bending.
Overall, mandrels are considered “tooling”, along with dies and wipers. Having a wide variety of tooling available can help manage project costs and reduce lead times. Learn more about tooling here.
For additional information on tube and pipe bending, laser cutting or end forming, please feel free to contact us at 800-879-4418 or send your questions to estimating@sharpeproducts.com.
This blog was authored by Paul Krickeberg, President & CEO, Sharpe Products. Paul can be reached at paulk@sharpeproducts.com.