As the size of the tube diameter is increased, the tube becomes weaker. Two factors that help prevent this from happening are a grooved bend die, which supports the tube along the centerline and the natural strength of the tube round or square (Figure 2).įigure 2 Little or no support is needed within the tube when the tube diameter is small and the wall is thick. The outside and inside of the bend tend to pull towards the centerline of the tube (flattening). Excessive flattening or wrinkling of the bend should not occur. Compressedįunction of Bend Die When the ratio of the tube diameter to wall thickness is small enough, the tube can be bent on a relatively small radius (Centerline Radius or CLR = 4 x Tube O.D.).
The material that forms the outside of the bend has further to travel and therefore is stretched the inside of the bend has less distance to travel and is compressed. The material actually is formed approximately about the centerline of the tube. The outside wall is reduced in thickness due to the stretching of the material and the inside wall becomes thicker due to the compressing of the material (Figure 1). Stretching and Compression Principles When a tube is bent, two things happen to metal (Figure 1-a). TROUBLESHOOTING Tube breakage Tube wrinkling Scratches/Marking on Tube Centerline Tube Collapses Either With or Without Wrinkling Through Bend Hump at the End of a Bend and Mandrel Ball Humps Tool Marks/Scratches Excessive Springback Possible Reasons for Link Failure Final Tips V. BENDING WITH BALL MANDREL AND WIPER DIE Bending Thin Wall Tubing IV.
BENDING TUBE WITH A PLUG MANDREL Balanced Pressures Unbalanced Pressures Mandrel Too Far Back Mandrel Too Far Forward III. BENDING TUBE WITHOUT A MANDREL Stretching and Compression Principles Function of Bend Die Basic Primary Tooling Control of Springback Kinked or Buckled Bends II. BASIC TUBE BENDING GUIDE 2710 Swamp Cabbage Court ٠ Fort Myers, FL 33901 23 ٠ 23 fax ٠ 80 US & Canada ٠email: