Our CNC press brakes hold ±0.1 mm angle accuracy and ±0.05 mm bend-line positioning. Servo-hydraulic tonnage up to 400 tons. Programmable 6-axis backgauges with automatic angle measurement. For any part with bends — enclosures, brackets, chassis, panels — press brake bending is where sheet metal becomes structure.
A press brake is a hydraulic or servo-driven press that forces a sheet of metal into a V-shaped die using a matching punch. The angle of bend, radius, and springback are controlled by the combination of: die V-opening width, punch tip radius, material thickness, tonnage, and material yield strength.
Three bending methods:
Air bending (most common). The punch doesn't bottom out in the die. Angle is controlled by punch depth. Same tooling handles many angles — a 90° die can make 60° through 120° bends. Springback depends on material and must be compensated in the program. Forgiving, flexible, most cost-effective.
Bottom bending. The punch forces the sheet fully into the die, yielding the material against die geometry. Angle is fixed by tooling. More precise than air bending (no springback) but needs specific tools for each angle. Used for critical parts.
Coining. Overbending the material past yield to eliminate springback entirely. Requires high tonnage (3-5× air bending). Produces very accurate bends with tight inside radii. Rarely used — air bending with springback compensation achieves 99% of applications.
| Material | Max thickness (air bend) | Min inside radius | Springback typical | Notes |
|---|---|---|---|---|
| Mild steel (A36, 1018) | 12 mm | 1× thickness | 0-2° | Predictable, easy |
| Stainless 304 / 316 | 10 mm | 1.5× thickness | 3-5° | High springback, work-hardens |
| Aluminum 5052 | 8 mm | 1× thickness | 2-4° | Most forgiving aluminum grade |
| Aluminum 6061-T6 | 6 mm | 2-3× thickness | 3-6° | Hard to bend tight — cracks |
| Galvanized steel | 4 mm | 1.5× thickness | 0-2° | Watch zinc flaking on outside of bend |
| Copper C110 | 6 mm | 1× thickness | <1° | Excellent bending, anneal if work-hardened |
| Brass C260 | 6 mm | 1.5× thickness | 2-4° | Crack-prone if cold-rolled |
| Titanium Gr2 | 3 mm | 3-4× thickness | 5-10° | Heat to 200 °C for tighter bends |
Minimum inside radius depends on grain direction. Bending perpendicular to rolling direction allows tighter bends; parallel requires 2× more radius.
Shorter flanges won't clear the press brake die during bending. For 2 mm sheet with 3 mm inside radius, minimum flange is 11 mm.
Holes closer than this distort during bending (oval-shaped holes). For 3 mm steel with 3 mm bend radius, holes must be ≥10.5 mm from the bend.
The flat pattern length ≠ sum of leg lengths. K-factor (roughly 0.33-0.5 for sheet metal) corrects for material stretch during bending. Send STEP of folded part — we generate the flat pattern.
Bends perpendicular to rolling direction crack less than bends parallel. For minimum-radius bends, specify sheet orientation on the drawing. If unspecified, we bend perpendicular when possible.
Bending near a weld zone or previously-formed feature (hydroform, deep draw) may crack. Keep bends at least 3× thickness from weld lines and formed edges.
When two bend lines meet at 90°, add a relief cut at the intersection. Usually a small circle or slot — prevents tearing at the corner during bending.
Two acceptable workflows:
Best: 3D STEP of the folded part. We unfold it in-house using the correct K-factor for your material. You tell us the inside bend radius; we figure out the flat pattern. This eliminates the most common sheet metal mistake — sending a pattern with incorrect K-factor compensation.
Also acceptable: DXF of the flat pattern plus a drawing showing bend lines. Bend lines should be on a dedicated layer (typically named "BEND_UP" and "BEND_DOWN"). Include a table of bend angles and inside radii.
STEP of folded part is easiest — we unfold. DFM review flags any bend issues with.
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