Complete Guide & Technical Overview: What is a Press Brake Punch?
Q&A: What is a press brake upper die?
Also called punch or top blade, the ALAS upper die is installed on the press brake ram. It moves downward with the ram to press metal sheets into the V-slot of the lower die, creating permanent bends. It is the key part that decides the final bending angle and overall bending precision.
Main Types of ALAS Press Brake Upper Dies
Upper dies are mainly categorized by shape into straight dies, acute angle dies, gooseneck dies, radius dies and forming dies. Structurally, they fall into two types: solid dies and segmented dies.
Comparison of Common ALAS Upper Dies
| Die Type | Angle Range | Main Usage | Typical Application |
| Straight Die | 90° | Standard 90-degree right angle bending | Regular sheet metal parts |
| Acute Angle Die | 15° ~ 30° | Sharp angle bending and pre-bending before hemming | Sharp angled parts, pre-forming for full hemming |
| Gooseneck Die | 86° ~ 88° | Avoid collision for box and deep profile bending | Box parts and workpieces with return flanges |
| Radius Die | Based on required R value | Smooth curved bending | Decorative panels and rounded components |
| Forming Die | Custom made | One-step forming for special shapes | Irregular and complex bent parts |
| Window Frame Die | Custom made | Narrow space bending | Door and window frame production |
Straight dies work well for small standard bent parts. Gooseneck dies are ideal for complex workpieces where tool collision is likely during multiple bending steps. Acute angle dies are widely used for 30-degree pre-bending before full hemming.
Materials, Hardness and Heat Treatment Standards for ALAS Upper Dies
Most press brake upper dies are made of 42CrMo alloy steel (AISI 4140), with overall hardness controlled at HRC 47~52. The upper die must be harder than the lower die to guarantee good wear resistance and impact resistance. The die tip is usually treated with local induction hardening to extend service life.
Material Performance Comparison
| Material | Hardness (HRC) | Features | Application |
| 42CrMo | 47~52 | High strength, good toughness and wear resistance | Mass production and heavy-duty bending |
| Cr12MoV | 50~58 | Excellent wear resistance | High precision and high frequency bending work |
| T7/T8/T10 | 45~50 | Cost effective | General light-duty bending and occasional use |
| 55SiCr | 46~50 | Good elasticity | Working conditions requiring high toughness |
42CrMo features high strength and good hardenability. After tempering, it delivers improved fatigue resistance and impact resistance, which makes it a top choice for ALAS press brake dies and other heavy mechanical components. Upper dies are required to have hard wear-resistant surfaces, strong anti-fracture performance and high tensile strength.
Recommended Heat Treatment Process
Standard hardness match: Upper die HRC 48~52, Lower die HRC 42~45. The upper die is always kept harder than the lower die.
Solid Upper Die vs Segmented ALAS Upper Die
Solid upper dies are one-piece tools for long straight bending. Segmented upper dies consist of multiple short sections in standard sizes, easy to assemble for box parts and short workpieces with great flexibility.
| Features | Solid Upper Die | Segmented Upper Die |
| Standard Sizes | 835mm, 415mm | 10, 15, 20, 40, 50, 100, 200, 300mm |
| Max Length | Up to 6000mm (custom) | Unlimited by free combination |
| Application | Long straight bending, mass production | Box parts, short workpieces, mixed small-batch production |
| Flexibility for Die Change | Low | High |
| Bending Marks | Even across the whole length | Slight joint marks at segment connections |
| Storage | Occupies large space | Stackable to save storage area |
ALAS Segmented dies are essential for box bending. When processing closed box parts, gaps between segments allow flanges to pass through and avoid collision.
ALAS 835mm segmented set includes: 300mm, 200mm, 100mm (left), 100mm (right), 50mm, 40mm, 20mm, 15mm and 10mm sections.
Always use dies longer than 300mm to calibrate machine origin. Never use short segmented dies for this work.
Do not install upper dies with different heights on the same press brake.
Why ALAS Gooseneck Dies Are Indispensable for Box Bending
Gooseneck dies are designed with deep recessed clearance on the back. When bending the third and fourth sides of box parts, this space prevents pre-bent flanges from hitting the die body, namely flange interference. Deep box parts can hardly be processed without gooseneck dies.
Interference Principle
Digital models show perfect folding in CAD software, but in actual operation, pre-bent side flanges will rise while the ram moves down. A straight die thickens gradually from tip to body, so tall flanges will crash into the die. The recessed area of gooseneck dies reserves enough space for flanges to move.
This clearance design sacrifices part of structural strength. For reference, a standard straight die can bear 50 tons per foot, while an 88° gooseneck die only supports around 15 tons per foot. Never exceed the rated load of gooseneck dies during use.
Gooseneck Die Selection Tips
The throat depth of the die must be greater than the maximum height of work piece flanges, otherwise the workpiece will be damaged.
Larger throat depth means lower load capacity.
Segmented gooseneck dies with left and right end sections are recommended for better flange clearance.
How to Select Proper ALAS Die Angle and Tip Radius
Bending metal will produce springback. As a general rule, choose an upper die with angle 2°~3° smaller than the target bending angle to compensate springback. The tip radius directly decides the inner corner of finished workpieces. Too small radius causes obvious indentations, while oversize radius leads to unstable bending position.
Angle Selection Guide
| Target Bending Angle | Recommended Upper Die Angle | Matching Lower Die V-slot Angle | Notes |
| 90° | 86° ~ 88° | 88° | Standard right angle bending for springback compensation |
| Below 90° (Sharp Angle) | 30° | 30° | Sharp angle bending and pre-bending for hemming |
| Curved Bending | Matched with workpiece arc | Matched with upper die | Upper and lower dies must be supporting sets |
| Full Hemming | 30° (Pre-bend) | 30° | Bend to 30° first, then flatten with dedicated hemming die |
For bending angles equal to or above 88°, select 88° or 30° lower dies. For angles below 88°, use 30° lower dies only. Poor die angle accuracy will result in out-of-tolerance bending angles.
Tip Radius Selection & Surface Indentation
Use tip radius from 0.2mm to 1mm for regular work, adjust according to surface appearance requirements.
For workpieces with specified inner R values, adopt dedicated radius dies such as R0.3, R1, R4, R8 and R10.
For positioning line marking during bending, use sharp tip dies. Keep upper and lower dies flat without steps.
Installation & Safety Operation Rules for Upper Dies
Check the machine stroke before installation. Make sure it is longer than the total height of assembled dies to avoid damage and accidents.
Fasten dies firmly after installation, and check the straightness of cutting edges.
Align upper die with lower die during adjustment. Do not use short segmented dies to calibrate origin.
Test run before formal production. Reserve a gap equal to sheet thickness when the ram moves to the lowest position.
Never put hands between upper and lower dies during operation. Do not wear gloves when bending small parts. Assign two operators for long workpieces.
Do not work with single-side or single-point load. Avoid bending extra thick plates or hardened steel.
After work, align upper die with lower die before shutting down. Clean iron scraps and dirt on die surfaces.
Die Precision Tolerance & Why Upper Die Matters More
The final bending angle is mainly controlled by the upper die, so its precision requirement is stricter than the lower die. The accuracy of die tip affects bending angle; tip radius decides inner corner size; cavity profile influences clearance performance; mounting shank precision ensures stable installation.
| Die Part | Problems Caused by Low Precision | Recommended Tolerance |
| Cutting Edge | Out-of-tolerance bending angle | ≤ ±0.2° |
| Tip Radius | Irregular inner corner, poor appearance | ≤ ±0.05mm |
| Cavity | Flange jam and workpiece deformation | Custom as per drawing |
| Mounting Shank | Loose installation and parallelism error | ≤ 0.02mm |
| Overall Straightness | Inconsistent angles on long workpieces | ≤ 0.1mm/m |
High precision upper dies paired with CNC press brakes (ram repeat accuracy ≤±0.01mm) deliver stable bending results. Manual press brakes normally have an angle deviation of ±2°~3° in daily use.
Daily Maintenance for Upper Dies
Daily: Clean iron scraps and dirt. Inspect edges for cracks and chipping.
Weekly: Check tightness of fastening bolts and wear condition of cutting edges.
Monthly: Measure wear of tip radius and check gaps between segmented sections.
Quarterly: Test straightness and parallelism. Grind working surfaces when necessary.
Yearly: Full precision inspection. Replace severely worn dies.
Die tips wear fastest. Do not regrind the die more than 3 times. Excessive grinding will change tip radius and die height, leading to dimensional errors.
Cut off power, activate emergency stop and hang warning signs before any maintenance work.
Apply anti-rust oil on dies for long-term storage.
FAQ
Q1: What is the proper hardness ratio between upper die and lower die?
A: The upper die must be harder. Standard setting: Upper die HRC 48~52, Lower die HRC 42~45. As the active working part, the upper die bears more friction, so higher hardness ensures longer service life.
Q2: Why can’t we use upper dies with different heights together?
A: Different die heights make the ram stroke unable to match all dies properly. Some dies will be overloaded and damaged, while others cannot reach the working position. It causes defective products and safety risks.
Q3: What is the throat depth of a gooseneck die?
A: It refers to the horizontal depth of the recessed clearance behind the die tip. For box bending, the throat depth must be larger than the flange height of workpieces. Larger throat depth means lower load capacity of the die.
Q4: How to read the rated tonnage of upper dies?
A: Die load is marked in tons per meter. When using combined segmented dies, the maximum allowable tonnage follows the weakest single section.
Q5: Are your upper dies compatible with my press brake?
A: Our dies adopt 13mm Euro standard holders compatible with Wila, Trumpf, Amada, LVD, Durma and other mainstream press brake brands. Send us your machine model and existing holder dimensions for full confirmation.
Why Choose ALAS Press Brake Upper Dies
Material: 42CrMo alloy steel, overall tempering plus tip induction hardening, hardness HRC 48~52.
Precision: CNC precision grinding, angle tolerance ≤±0.2°, overall straightness ≤0.1mm/m.
Full product range: Straight dies, acute angle dies, gooseneck dies, radius dies and forming dies available.
Structure options: Solid dies in standard lengths and segmented die sets for flexible use.
Wide compatibility: 13mm Euro standard holders fit most mainstream press brakes.
Custom service: Special angles, tip radii and customized profiles are available per drawings.
Standard Specifications
| Parameter | Details |
| Material | 42CrMo (AISI 4140) |
| Hardness | HRC 48~52 (Tip induction hardened) |
| Standard Angles | 86°, 88°, 90°, 30° (Custom available) |
| Standard Tip Radius | 0.2mm ~ 1mm (Custom available) |
| Solid Die Length | 835mm, 1000mm, 2000mm, max 6000mm (custom) |
| Segmented Die Sizes | 10, 15, 20, 40, 50, 100, 200, 300mm |
| Holder Type | 13mm Euro standard (Wila/Trumpf), custom holders supported |
| Surface Finish | CNC ground, Ra ≤ 0.8µm |
Looking to improve your bending accuracy?
Contact ALAS for the perfect upper die match for your press brake. We deliver durable, high-quality dies—standard or custom—to keep your production running efficiently.
