Sheet metal bending technology is the key technology that our sheet metal processing operator needs to grasp,and it is also an important process for sheet metal product forming

Always in the sheet metal processing, we need to cut and blank, punch, bend and form,In additional,it sometime happen to various uncontrollable factors (mechanical, material, manual)

The problems will occur inevitably. By consulting various masters of different sheet metal factories, some sheet metal bending technology problems and the methods (experience accumulation) of the masters were summarized.

Damage the surface of work piece after folding

Cause:

  • the surface of Raw material is not smooth
  • The Bending radius of press brake punch is too small
  • Bending clearance is too small

Solution:

  • Improve the finish of convex and concave dies
  • Increase the bending radius of the punch
  • Adjusting the bending gap

Q2.The bent edge is not straight and the size is unstable

Cause:

  • The design process does not arrange crimping or pre-bending
  • Material pressing force is not enough
  • Male and female die fillet asymmetric wear or bending force is uneven
  • The height is too small

Solution:

  • Design crimping or bending preparatory
  • Increase pressure
  • Rounded polished and Even clearance between male and female die
  • The height must not be smaller than the minimum limit size

Q3.Cracks in the corners

Cause:

  • Bending inner radius is too small
  • Material grain direction is parallel to the bending line
  • The burr of the blank faces outward
  • Poor metal plasticity

Solution:

  • Increase the bending radius of the punch
  • Change the blank layout
  • Burr changed to fillet of workpiece
  • Annealed the metal material or choose soft materials

Q4.Thin extrusions on curved surfaces

Cause:

  • The radius of female die is too small
  • The clearance of male and female dies is too small

Solution:

  • Increase the radius of female die
  • Amending clearance of male and female

Q5.Thin extrusions on curved surfaces

Cause:

  • The radius of female die is too small
  • The clearance of male and female dies is too small

Solution:

  • Increase the radius of female die
  • Amending clearance of male and female

Q6.The end face of the part is bulging or uneven

Cause:

When bending, the outer surface of the material is stretched in the circumferential direction to cause contraction and deformation, and the inner surface is compressed in the circumferential direction to cause elongation and deformation, so the flexed end surface in the bending direction cause to bulge

Solution:

  • The work piece should have sufficient pressure in the final stage of stamping
  • Make the fillet radius of the die corresponding to the external fillet of the part
  • Increase processing improvements

Q7.The bottom of the concave part is not flat

Cause:

  • The material is uneven
  • Small contact area between top plate and material or insufficient top material force
  • No top material device in the female die

Solution:

  • Leveling material
  • Adjust the jacking device to increase the jacking force
  • Adding top loading device or calibration
  • Plus shaping processing

Q8.The axis of the two holes opposite to each other after bending is misaligned

Cause:

  • Material rebound changes the bending angle and shifts the centerline

Solution:

  • Increase calibration process
  • Improved bending die structure reduces material spring back

Q9.Dimensional accuracy of hole position cannot be guaranteed after bending

Cause:

  • Part unfolded with bad size
  • Cause by material spring back
  • Unstable positioning

Solution:

  • Accurate calculate the raw material size
  • Plus correction process or improve bending mold forming structure
  • Change process method or increase process positioning

Q10.The curved line is not parallel to the center of the two holes

Cause:

  • When the bending height is less than the minimum bending limit height, swelling occurs in the bending part

Solution:

  • Increase the height of the bend
  • Improved bending process

Q11.Deformation in the width direction after bending, Bowed deflection in the width direction of the bent part

Cause:

  • Torsion and deflection due to inconsistent drawing and shrinkage in the width direction of the part

solution:

  • Increase bending pressure
  • Increase calibration process
  • Ensure that the material grain direction and the bending direction have a certain angle

Q12.The product surface crease is too deep

Cause :

  • Small V-groove in the lower die
  • The R angle of the V-groove in the lower die is small
  • The material is too soft.

Solutions:

  • Using large V-groove to process
  • Use mold processing with large R angle
  • Padding bending (pad with metal or casting polyurethane)

Q13.The two sides are not parallel after offset bending

Cause :

  • The mold is uncorrected.
  • The upper and lower die gaskets are not adjusted.
  • The upper and lower die faces are different.

Solutions:

  • Re-calibrate the mold.
  • Increase or decrease the gaskets.
  • The mold uses eccentric processing.
  • Change the surface and take the same surface of the upper and lower mold.

Q14.The overall size of the blanking (referring to the expansion) is too small or too large, which is not consistent with the round surface.

Cause :

  • Project deployment error.
  • The feeding size is wrong.

Solutions:

  • According to the total deviation and the number of bending times in the deviation direction,the deviation assigned to each fold is calculated.
  • If the calculated distribution tolerance is within the tolerance range, the work piece is acceptable.

– If the size is too large, you can use a small V-groove.

– If the size is too small, you can use a large V-groove.

Q15.Large-height draw bridge is easy to break

Cause :

  • Because the height of the draw bridge is too high, the material is severely stretched and fractured.
  • Special mold corners are not sharpened or not sharpened enough.
  • The toughness of the material is too poor or the bridge is too narrow.

Solutions:

  • Lengthen the process hole on one side of the fracture.
  • Increase width of the draw bridge.
  • Repair the special mold R angle and increase the arc transition.
  • Add lubricant to the draw bridge. (Therefore, this method will make the surface of the work piece dirty, so it cannot be used for AL parts, etc.)

Q16.The long flattening side rises after flattening

Cause :

  • Due to the long flattening edge, it does not stick tightly when flattened, which causes its ends to rise after flattening. This situation has a lot to do with the flattening position, so pay attention to the flattening position when flattening.

Solutions:

  • First bend the uplifting angle (see the diagram) before bending the dead edge, and then flatten it.
  • Flatten in multiple steps

– Press the end first to bend the dead side down.

– Flatten the roots part.

Precautions:

  • The flattening effect is related to the operator’s work skills, so please pay attention to the actual situation when flattening.