Consistent Form Height Requires Stroke Control
Consistent, precise forming requires analysis of punch press stroke dynamics. When the upper unit meets material, several tons of force come into play. In applying this force, the frame of the punch press tends to move slightly in the opposite direction; to “yaw” in a manner that increases shut height. As the punch pierces the material, punching force reduces sharply and the frame springs back toward its original position. This causes the upper unit to lunge deeper into the lower unit.
The lunging motion typically occurs before the forming operation has taken place. If the motion is not controlled, forming is performed by spring back of the press frame and there is very little control over accuracy of depth.
Flatter Emboss Tops
A combination of material properties and emboss proportions may cause the flat top of an emboss to arch into a domed shape after it is formed. If a domed emboss shape is unacceptable, pre-punching a hole in the top of the dome will remove much of the stress that is causing the material to arch. The form will remain much flatter across the top.
Form down Last
When using forming tools, form-down operations are generally avoided because they take up so much vertical room and any additional operations tend to flatten them out or bend the sheet. They can also drop into dies, get caught and pull out of work holders. However, if a form-down operation is the only solution for a particular piece part, make it the last operation on the sheet.
Form Raised Beads in Any Configuration
With Mate’s beaded emboss tool, you can raise an embossed bead in virtually any configuration that fits on the sheet. This tool forms in 0.030(0.8) increments up to a height of 0.250(6.4) in materials 0.075(1.9) and thinner. It can be used for forming straight lines or curved lines.
Start Continuous Louvers in the Center
Continuous louver tools are now designed to produce smooth-edged, level-topped louvers when recommended procedures are followed. Start in the center and form to one side and then the other in 0.030(0.8) increments. If needed, complete the process by rehitting the center for ultimate flatness.
If Your Stainless Steel Extrusions Are Distorted…
Apply a good forming lubricant to the material before making the extrusion. Not only will the material release from the die better, it slides over the die surface smoothly when being formed. This gives the material a better opportunity to distribute the forces of bending and stretching, preventing distortion in the formed wall and tearing at the root of the extrusion.
Tearing or Splitting of Overstressed Metal Forms
Reduce these by placing the form on the sheet with the grain running perpendicular to the form. Corners of high louvers, high extrusions, complex lance-and-forms, and card guides are typically vulnerable to this effect. Liberal application of a forming lubricant is also recommended to let the metal slide more freely over the forming surface of the tool, especially in stainless steel.