Press Brake Die Examples AutoCAD: Designing Custom Tooling Profiles for Precision

 A custom press brake die designed in AutoCAD requires four critical parameters: die opening width $W$W (typically 8× material thickness for air bending), shoulder radius $R_s$Rs (0.5–1.5 mm for general use), relief angle (1–3° per side to reduce friction), and tonnage rating per foot. For a V‑die, the profile is defined by $W$W, the V‑angle (usually 85° or 90°), and the bottom radius (0.5–2 mm). For a gooseneck die, the critical dimension is the throat depth (clearance for already‑formed flanges). For a radius die, the profile is a circular arc with a center offset equal to the desired inside bend radius. AutoCAD’s parametric constraints ensure that the die profile matches the press brake’s clamping system (European style with 20° tangent angle or American style with straight shoulders).

Standard V‑dies cover 80% of bending tasks. The remaining 20% — deep channels, hemming, radius bends, or parts with complex flange geometry — require custom tooling. Designing a custom die in AutoCAD is a systematic process: define the material, thickness, bend radius, and required clearance; calculate the tonnage; draw the profile with proper relief angles; assign tolerances; and specify heat treatment. This article provides three complete design examples with dimensioned AutoCAD‑ready parameters, plus the mathematical validation steps to ensure the die will not crack under load.

Anatomy of a Press Brake Die – Key Parameters

Any press brake die, whether standard or custom, has these five essential features:

Parameter	Symbol	Typical range	Function
Die opening width	$W$W	6×T to 12×T	Determines tonnage and inside bend radius
V‑angle (included)	$\theta$θ	85°, 88°, 90°	Controls final bend angle after springback
Shoulder radius	$R_s$Rs	0.5–2 mm	Reduces stress concentration on the workpiece
Bottom radius	$R_b$Rb	0.5–2 mm	Prevents cracking at the die tip
Relief angle	$\varphi$ϕ	1–3° per side	Reduces friction and wear during bending

For air bending, the die opening is the most important variable. The recommended value is $W=8\times T$W=8×T for mild steel, $W=10\times T$W=10×T for stainless, and $W=6\times T$W=6×T for aluminum. Custom dies may deviate from these rules to achieve specific inside radii.

The die must also match the press brake’s tooling system. Two common systems exist:

• European (Wila) style: Die has a 20° tangent angle on the upper shoulders and a central slot for clamping. The die height is standardized (e.g., 50 mm, 60 mm).
• American (Amada, Cincinnati) style: Die has straight vertical shoulders and a through‑hole for a key or bolt. Height varies by tonnage rating.

AutoCAD drawings for custom dies must include the mounting interface exactly as specified by the press brake manufacturer. A die that fits the machine correctly is safe; a die that does not fit can slip, crack, or damage the ram.

Example 1 – Custom V‑Die for 4 mm Stainless Steel

Requirement: Bend 4 mm 304 stainless steel to 90°, inside radius $R_i=6$Ri=6 mm (1.5×T is typical for stainless). Production run of 10,000 parts. A standard 8× die would give $W=32$W=32 mm, $R_i\approx 4$Ri≈4 mm, which is too sharp for stainless. A larger die is needed.

Design steps:

1 Determine Die Opening

For stainless, $W=10\times T=40$W=10×T=40 mm. This produces $R_i\approx W\mathrm{/}8=5$Ri≈W/8=5 mm, close to the target 6 mm. Use $W=44$W=44 mm to get $R_i=5.5$Ri=5.5 mm.

2 Calculate Tonnage

Using the air bending formula (mild steel baseline, then multiply by 1.5 for stainless):$$P=\frac{1.42\times TS\times T^2\times L}{W}$$P=W1.42×TS×T2×L

For 304 stainless: $TS=90$TS=90 ksi, $T=0.157$T=0.157 in (4 mm), $L=1$L=1 ft, $W=1.73$W=1.73 in (44 mm).$$P=\frac{1.42\times 90\times 0.0246\times 1}{1.73}=\frac{3.14}{1.73}=1.82\text{ tons per foot}$$P=1.731.42×90×0.0246×1=1.733.14=1.82 tons per foot

A 4‑foot die will see 7.3 tons, well within a 50‑ton press brake. The die can be made from 42CrMo4 steel hardened to 45–50 HRC.

3 AutoCAD Profile – V‑Die Parameters

Feature	Value
Die opening $W$W	44 mm
V‑angle	88° (compensates for springback)
Shoulder radius $R_s$Rs	1.0 mm
Bottom radius $R_b$Rb	1.5 mm
Relief angle	2° per side (starting 2 mm below shoulder)
Total height	50 mm
Mounting slot (European)	20° taper, 20 mm deep, 30 mm wide at top

Drawing instructions in AutoCAD:

1. Draw the vertical centerline.
2. Construct the V‑angle: line at 44° from vertical (half of 88° included angle).
3. Offset the line by $W\mathrm{/}2=22$W/2=22 mm to create the right shoulder.
4. Add shoulder radius $R_s=1$Rs=1 mm at the top edge.
5. Add a bottom radius $R_b=1.5$Rb=1.5 mm at the V‑tip.
6. Add relief angle: from a point 2 mm below the shoulder, rotate the outer wall outward by 2°.
7. Mirror the profile across the centerline.
8. Add the mounting slot according to the press brake’s clamp specifications.

Tolerance notes:

• Die opening tolerance: ±0.1 mm
• V‑angle tolerance: ±0.5°
• Surface finish: Ra ≤ 1.6 µm on all working surfaces

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Example 2 – Gooseneck Die for Deep Flanges

Requirement: Form a 50 mm tall flange on a 3 mm mild steel part. The flange has a 90° bend at the top, and the part already has a previous bend 20 mm from the edge. Standard V‑die would collide with the existing flange. A gooseneck die provides clearance.

1 Critical Dimensions

A gooseneck die has a recessed profile that creates a “neck” — the die surface drops away from the shoulder, allowing the previously formed flange to pass through.

Dimension	Value	Calculation
Die opening $W$W	24 mm (8×3 mm)	Standard for mild steel
Throat depth	55 mm	Must exceed flange height (50 mm) + clearance (5 mm)
Throat width	30 mm	Must exceed material thickness (3 mm) + 27 mm for movement
Neck radius	5 mm	Prevents stress concentration
Shoulder to throat drop	15 mm	Transition height

2 AutoCAD Profile Steps

1. Start with a standard V‑die profile ($W=24$W=24 mm, 88° V‑angle).
2. From the shoulder, draw a vertical line down 15 mm.
3. At that point, draw a horizontal line (the throat floor) extending 25 mm inward from the shoulder.
4. Add a 5 mm fillet at the corner where the vertical meets the horizontal.
5. From the end of the throat floor, draw a vertical line up 15 mm to form the back wall.
6. Continue the V‑angle profile from the top of the back wall down to the V‑tip.
7. Ensure that the throat depth (distance from the shoulder to the back wall) is at least 55 mm.

The resulting profile has a “gooseneck” shape. The working surfaces (shoulders and V‑tip) must be hardened to 50–55 HRC. The recessed area can be left softer (35–40 HRC) to save cost.

3 Clearance Verification

After drawing, check for interference:

• Place a 2D representation of the workpiece with the existing flange at the correct height.
• Simulate the bending motion by rotating the part around the V‑tip.
• The existing flange must not contact any part of the die during the 0–90° bending range.

If interference occurs, increase the throat depth or throat width. Every 10 mm of additional throat depth adds approximately 5 kg of extra die weight (for a 500 mm die).

 Example 3 – Radius Die for Large Inside Bend Radius

Requirement: Create a 90° bend with a 15 mm inside radius on 2 mm mild steel. A standard V‑die produces $R_i\approx 3$Ri≈3 mm (too sharp). A radius die — a die with a concave cylindrical surface instead of a V‑groove — is required.

1 Radius Die Geometry

The radius die has a semi‑circular profile with radius $R_d$Rd. The workpiece wraps around this die surface. To achieve an inside radius $R_i=15$Ri=15 mm on the part, the die radius must be slightly smaller to account for springback: $$R_d=R_i\times (1-0.01\times \alpha )$$Rd=Ri×(1−0.01×α)

For mild steel, springback is approximately 1° per 90°, so $R_d=15\times (1-0.01)=14.85$Rd=15×(1−0.01)=14.85 mm. Use $R_d=15$Rd=15 mm for simplicity, and adjust with a urethane pad if needed.

2 Die Profile in AutoCAD

1. Draw a horizontal baseline representing the top of the die.
2. Draw a circle with radius $R_d=15$Rd=15 mm, centered below the baseline by exactly 15 mm (so the top of the circle is tangent to the baseline).
3. Trim the circle to leave only the upper 90° arc (from 45° left to 45° right of vertical).
4. Add vertical side walls extending downward from the arc ends to the die base.
5. Add a 2 mm radius at the transition between the arc and the side walls.

The die height is typically 50 mm. The width is $2\times R_d=30$2×Rd=30 mm plus side wall thickness (10 mm each side) = 50 mm total.

3 Tonnage for Radius Bending

A radius die requires significantly lower tonnage than a V‑die because the contact area is larger. Use the following approximation: $$P_{\text{radius}}=P_{\text{V-die}}\times \frac{W_{\text{V-die}}}{2\times R_d}$$Pradius=PV-die×2×RdWV-die

For 2 mm mild steel, standard V‑die $W=16$W=16 mm, $P_{\text{V-die}}=1.33$PV-die=1.33 tons/ft. Then:$$P_{\text{radius}}=1.33\times \frac{16}{30}=0.71\text{ tons per foot}$$Pradius=1.33×3016=0.71 tons per foot

A 4‑foot die requires 2.8 tons — easily within any press brake. The die can be made from 1045 steel or even aluminum bronze for non‑marring applications.

 Material Selection and Heat Treatment for Custom Dies

Die type	Recommended steel	Hardness (HRC)	Wear resistance	Cost
V‑die (general)	42CrMo4 (AISI 4140)	45–50	High	Moderate
V‑die (high volume)	1.2379 (D2)	58–60	Very high	High
Gooseneck (body)	42CrMo4	35–40 (body), 50–55 (working surfaces)	Moderate	Moderate
Radius die (steel)	1045 (AISI 1045)	40–45	Moderate	Low
Radius die (urethane)	Polyurethane 90A	N/A	Low	Low

For dies that will be used on stainless steel or high‑strength materials, specify D2 tool steel with cryogenic treatment. The extra cost (approximately 3×) is justified by tool life exceeding 500,000 cycles instead of 50,000.

Heat treatment must be performed after all machining. Distortion during heat treatment can close the die opening by 0.05–0.2 mm. For precision dies, leave 0.2 mm grinding stock and finish‑grind the working surfaces after hardening.

Tolerances and Dimensioning in AutoCAD

Use these default tolerances for custom press brake dies (per ISO 2768‑m):

Feature	Tolerance class	Value
Die opening width $W$W	±0.1 mm	Critical
V‑angle	±0.5°	Critical
Shoulder radius	±0.2 mm	Standard
Overall height	±0.5 mm	Standard
Mounting slot position	±0.1 mm	Critical
Flatness of bottom surface	0.05 mm over 300 mm	Critical

AutoCAD dimensioning tips:

• Use baseline dimensions for die opening and V‑angle to avoid cumulative errors.
• Apply geometric tolerances (GD&T) to the working surfaces: flatness, parallelism, and surface profile.
• Add a note: “Break all sharp edges 0.2–0.5 mm.”
• Include a surface finish symbol (Ra 1.6) on the V‑faces and shoulders.

Verifying Die Strength Against Calculated Tonnage

A custom die must be strong enough to withstand the bending force without permanent deformation. Use the bending stress formula for a V‑die:$$\sigma =\frac{P\times L}{2\times Z}$$σ=2×ZP×L

Where $Z$Z is the section modulus of the die cross‑section. For a simple V‑die, the weakest point is at the V‑tip. For a 50 mm tall die with a 24 mm opening, the section modulus is approximately 3000 mm³. For a 4‑foot die, $P=10$P=10 tons = 100,000 N. The stress at the tip is:$$\sigma =\frac{100,000\times 4\times 304.8}{2\times 3000}=\frac{121,920,000}{6000}=20,320\text{ kPa}=203\text{ MPa}$$σ=2×3000100,000×4×304.8=6000121,920,000=20,320 kPa=203 MPa

42CrMo4 has a yield strength of approximately 800 MPa after heat treatment. A safety factor of 4 is acceptable. If the calculated stress exceeds 50% of yield strength, increase the die height or add a backing plate.

Exporting from AutoCAD to Manufacturing

After completing the 2D profile in AutoCAD, follow these steps:

1. Extrude the profile to the required die length (e.g., 500 mm).
2. Export as STEP or IGES for CNC machining.
3. Create a 2D DXF of the profile for wire EDM or laser cutting of the blank.
4. Add machining notes: “Machine from solid 42CrMo4. Heat treat to 48–52 HRC. Grind working surfaces after heat treat.”

For wire EDM, the DXF must be a single closed polyline with no self‑intersections. Use the OVERKILL command in AutoCAD to remove duplicate entities.

Conclusion

Designing custom press brake dies in AutoCAD is a structured process. Start with the material thickness and desired bend radius, calculate the die opening using the 8× rule (or a modified rule for stainless or aluminum), determine the V‑angle (typically 88° to compensate for springback), add relief angles (2°), and specify the mounting interface according to your press brake’s clamping system.

The three examples — a heavy‑duty V‑die for 4 mm stainless, a gooseneck die for deep flanges, and a radius die for large inside radii — cover the most common custom tooling requirements. Each example includes dimensioned parameters, material recommendations, and tonnage verification.

AutoCAD’s precision (0.01 mm) ensures that the die opening and V‑angle match the calculated values. A die that is even 0.2 mm narrower than specified increases tonnage by 5% and accelerates wear. A die that is 0.5° too sharp produces inconsistent bend angles. Therefore, dimensioning and tolerance notes are as important as the geometry itself.

Custom tooling pays for itself when standard dies cannot produce the required part geometry. With the design methods in this article, a tooling engineer can create a press brake die in AutoCAD that will perform reliably for tens of thousands of cycles.

 Frequently Asked Questions

Q: What is the standard die angle for air bending?

A: Most air bending dies have an 85° or 88° included angle. The 2–5° under‑bend compensates for springback. For bottoming, use a 90° die because the material is forced to conform to the die angle.

Q: How do I determine the required die opening for a custom inside radius?

A: For air bending, the inside radius is approximately $R_i=W\mathrm{/}8$Ri=W/8. To achieve a specific $R_i$Ri, set $W=8\times R_i$W=8×Ri. For example, $R_i=5$Ri=5 mm requires $W=40$W=40 mm. Verify that $W$W is between 6×T and 12×T for the material.

Q: Can I use a standard die drawing from the internet and modify it in AutoCAD?

A: Yes, but verify all dimensions against your press brake’s clamping system. Many free drawings use generic dimensions that may not fit your machine. Always measure your existing tooling’s mounting slot, height, and shoulder angle before modifying.

Q: What is the maximum die opening before tonnage becomes too low to form the material?

A: If the die opening exceeds 12×T, the bending force becomes very low, but the inside radius becomes large, and springback increases significantly. The part may not hold the desired angle. For most materials, stay between 6×T and 10×T. For very soft materials (copper, soft aluminum), 12×T is acceptable.

Q: How do I prevent the die from cracking at the V‑tip?

A: The V‑tip must have a radius (0.5–2 mm), not a sharp corner. Sharp corners act as stress risers. Also, ensure the die material is heat‑treated to the correct hardness (45–50 HRC for 42CrMo4). Over‑hardening (above 55 HRC) makes the die brittle. Use a fillet radius of at least 1 mm.

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References

1. Wilson Tool International. (2019). Press Brake Die Design Guide. Wilson Tool Technical Publication.
2. ISO 2768‑1:1989. General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications.
3. ISO 16162:2012. Cold‑rolled steel sheet products — Dimensional and shape tolerances.
4. Amada America, Inc. (2020). Custom Tooling Design for Press Brakes. Amada Technical Bulletin TB‑2020‑07.
5. Machinery’s Handbook, 31st Edition. (Tool steel selection and heat treatment tables).
6. KETIV AVA. (n.d.). Sheet Metal Unfold Rule Equations. KETIV Virtual Academy. (Bend allowance and K‑factor derivations).