Know-how (part 2)


Technology . Mandrel bending machine in practice: The right setting

You know the wide-ranging capabilities of a mandrel bending machine from the first part of the digression. This time, you learn how to recognise and correct errors in practical application – for optimal results.

Error analysis and remedy

1. Pipe breaks off

  • The material does not have the correct elastic limits and forming qualities. Non-annealed pipe quality.
  • Acquire a different material or possibly heat non-iron metal pipes in order to appropriately adapt the qualities.

2. Pipe slips in clamping section of the bending tool

  • Adjust the pressure on the clamping section.
  • The clamping section must be roughened, eroded or equipped with a sawtooth.
  • The clamping section must be longer.
  • On the initial bending a solid adapter can be pushed into the pipe end.
  • Too much pressure on the clamping section; the mandrel elements are clamped too hard. Air gap on the flanks too large; pressure too high.
  • Too much pressure on the pressure die; excessive counterforce to the wiper die is generated.
  • The mandrel is too far forward; readjust the mandrel behind the tangent.
  • Too few links on the mandrel; the pipe already catches in the clamping section at a low angular degree.

3. If only folds arise, it may be due to the following:

  • Mandrel and/or wiper die not in correct position.
  • Mandrel diameter too low in relation to the radius and the wall thickness.
  • If folds form, this can be caused by using the wrong mandrel section.This is especially the case when the folds form towards the inside of the bend area. Then a mandrel with smaller distances between the segments must be used (open pitch, closed pitch, ultra closed pitch). Use a mandrel with closely positioned segments.
  • Nicht ausreichende Schmierung oder falscher Schmierstoff oder Schmierung an falscher Stelle.
  • Dorn steht zu weit hinten, hinter der Tangente der Biegerolle.
  • Insufficient lubrication or incorrect lubricant or lubrication in the wrong place.


  • Mandrel too far to the rear, behind the tangent of the bending roll.
  • Wiper die not in the correct position.
  • Wiper die worn out.
  • Outside pipe diameter and tool are not precisely matched.
  • The flanks of the pressure die touch the flanks of the roller when closed.
  • Insufficient pressure on the pressure die.
  • Excessive lubrication.

The third and final part of our technology report for mandrel bending machines can be read in the upcoming edition of t time(s).