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RAS Know-how Knowledge in a nutshell

Was ist eigentlich Schwenkbiegen?

Bei welchen Biegeteilen eignet sich Schw...

Schnelles Rüsten

Einfaches Handling

UpDown-Schwenkbiegen mit Pendeln und Umf...

UpDown-Schwenkbiegen mit einer oder zwei...

Radien biegen

Schwenkbiegen von Edelstahl und beschich...

Schwenkbiegen von Lochblech, Streckgitte...

RAS Know-how

Knowledge in a nutshell

TECHNOLOGY
Bending process compared

Bending sequence

Folding

During the folding sequence the blank rests on the sheet support table. A gauging system positions the part to the bend line. The upper and lower beam clamp the blank. During the bending cycle the folding beam moves up around a pivot point. On up-down acting machines, the folding beam moves upwards or downwards, depending on the bending direction.

  • The part rests on the table (no fatigue, short cycle times)
  • The gauging system positions the part to the bend line (operator training finished in no-time)
  • Upright posture, easy operation (no health problems)
  • Usually one operator is sufficient even for large, cumbersome and heavy parts (low labor/parts costs)

Bending sequence

Press brake

During the bending sequence the blank is positioned outside the machine. The operator holds and supports the weight of the blank. For bending the upper ram moves down into the lower die. Both sides of the part move up and leave the plane. A linear ram movement results in the bend angle. Sequence requires experienced operators.

  • Operator needs to lift/support/hold the part (quality problems due to fatigue)
  • Experienced, well trained operator required (problem finding skilled operators)
  • Health (shoulder problems) and safety are critical
  • Large/cumbersome or heavy parts require multiple operators (high costs per part)
  • Slow cycle times (high costs per part)

Machine setup

Folding

Folding machines can bend all angles with a single set of tools. The machine automatically adjusts to the material thickness. Higher automated folding machines come with an automatic tool changer.

  • Universal tools (reduced setup effort)
  • Usually one set of tools sufficient for all customer parts
  • Low investment and operating costs
  • Low set-up times allow for small batch sizes (need-based production)

Machine setup

Press brake

Press brake bending typically requires a large number of punches and  different applications.

  • Different "V" dies for different sheet thicknesses
  • Small "V" dies required for short flanges
  • Usually a large variety of upper ram geometries are used
  • Investment in additional tools over time
  • Often long set-up times

Material thickness tolerances

Folding

During the folding sequence the folding beam tool contacts the outside of the material and moves exactly to the programmed angle.

  • The reference side is only the outside of the material
  • Exact movement to the programmed angle (high angle accuracy)
  • Sheet thickness tolerances do not affect the bend angle
  • No angle measuring system required

Material thickness tolerances

Press brake

On press brakes, the punch contacts the material from above and the "V" die from below.

  • Contact points on both sides of the material
  • The bend angle iresults from a linear upper tool movement
  • Sheet thickness tolerances lead to angle variances
  • Expensive, inflexible angle measuring system required for compensation

Gauging

Folding

On a folding machine the entire part is inside the machine. Only a short flange stands out of the upper and lower beam tool.

  • Gauging of the entire part
  • Blanks dimension tolerances show up in the first flange
  • The overall panel dimension as well as the opposite flanges are always accurate

Gauging

Press brake

Press brakes normally gauge the short flange. The long flange protrudes from the machine.

  • Gauging the short flange
  • Blanks tolerances show up in the overall dimensions of the finished part
  • These are usually the critical part dimensions for a perfect fit in the assembly

Sensitive material surfaces

Folding

Folding reduces the sliding area of tools on the material surfaces to a minimum, or completely eliminates it on some machines (Multibend-Center, ProfileCenter).

  • No scratches on the material surface
  • Ideal for stainless steel or coated sheets

Sensitive material surfaces

Press brake

Press brakes draw the material over the edges into the "V" die. The long sliding distance is shown results in scratches on the outside of the sheets.

  • Significantly visible scratches on the sheet
  • Not ideal for sensitive materials

Tool wear

Folding

As there are only very slight relative movements between the tool and the material surface, the tooling shows no abrasion wear even after years of use.

  • No wear on the tools
  • Low maintenance costs
  • Precision parts even after years of operation

Tool wear

Press brake

The long sliding distances over the "V" die edges lead to wear of the tools.

  • Tools must be replaced from time to time
  • Gradual deterioration of bend results
  • Programs need to be readjusted

Bending radii

Folding

On folding machines, a radius can be easily created of short bending segments. By using small steps the outside of the radius will be very smooth and the individual steps will not be visible.

  • Creation of any radius without special tools
  • Bending steps not visible on the outside
  • Part rests on the table
  • Fast bending cycles

Bending radii

Press brake

Creating a radius with bending steps on a press brake is quite difficult, as the sheet moves upwards at each step.

  • Gauing of the parts is difficult
  • Very well trained operators required
  • Very long cycle times

Bending hems

Folding

Folding does not require special tools for hemming.

  • Open, closed or tear-drop hems can be created
  • Applications: Increased stiffness, protective edges, part connections

Bending hems

Press brake

Press brakes use special tools for hemming.

  • Higher tool costs
  • Extensive lifting of the part during pre-bending
TECHNOLOGY
Cutting processes compared

Shears are machine tools used for straight cuts on sheet metal. On a swing beam shear the swing beam moves with the upper blade in a circular arc. On a guiottine shear the upper beam moves straight down.

Upper blade penetration

Swing beam

The upper blade penetrates the metal sheet above the lower blade

  • Clean, right-angled cuts with almost no burr

Upper blade penetration

Guillotine

Upper blade penetrates the material with an offset (blade clearance) to the lower blade

  • Oblique fractured cutting line
  • Bigger burr especially when the blades are not sharp

After the cut is made

Swing beam

The cut is made by a pivoting movement of the swing beam. After the cut is made the upper blade moves away from the lower blade.

  • Prevents the blank from jamming between the lower blade and the backstop

After the cut is made

Guillotine

On guillotine shears the cut is made by a linear motion of the upper beam

  • Part may get stuck between the lower blade and backstop
  • Higher wear

Sharp blades

Swing beam

The upper blade moves away from the lower blade after cutting. Upper and lower blade do not rub on each other.

  • Keeps blades sharp for a long time

Sharp blades

Guillotine

Upper and lower blade rub on each other when the blade clearance is low.

  • Blades go dull (burrs)
  • Frequent blade changes required

Blade clearance adjustment

Swing beam

The blade clearance can be easily adjusted by simply turning the cutting gap eccentric.

  • Short setup times
  • Automatic adjustment on higher capacity machines

Blade clearance adjustment

Guillotine

Tedious and costly clearance adjustment by repositioning the shear table

  • Long down times
  • Often compromises in the cutting quality

Twist-free cuts

Swing beam

Swing beam cutting requires a ridig shear design. The reasonis the low rake angle, which is fix for any material thickness.

  • Low rake angle results in twist-free parts starting at about 10-15 x sheet thickness

Twist-free cuts

Guillotine

Guillotine shears use a variable rake angle. Low rake angle for thin materials. High rake angles for thicker materials. Machines can be built lighter.

  • The results are twisted parts with narrow strips