Press Brake for Thick Plate Bending: Full Buyer's Guide
Choosing a press brake for thick plate bending starts with a tonnage calculation — not a product catalog. Thick plate (10mm and above) behaves fundamentally differently from sheet metal. It demands more force, specific tooling, and beam deflection compensation that most general-purpose machines simply cannot deliver. Get the spec wrong and you face angle errors, tooling failure, and machine damage. This guide gives you the exact formula to calculate your required tonnage, a V-die selection rule, a crowning system decision guide, and a material-specific thickness limits table — everything you need to specify the right machine. For application context, see our ボイラープレート曲げガイド for real-world thick plate use cases.
How Much Tonnage Does Thick Plate Bending Actually Require?
For thick plate, tonnage is the first number to confirm — and the most commonly underestimated. The standard formula for mild steel (metric) is:
P (kN) = 650 × S² × L / V
Where: S = plate thickness (mm), L = bend length (m), V = V-die opening width (mm).
| 板厚(mm) | Bend Length (m) | V-Die Opening (mm) | Required Tonnage (kN) | Required Tonnage (tons) |
|---|---|---|---|---|
| 10 | 3 | 100 | 1,950 | ~195 |
| 20 | 3 | 200 | 3,900 | ~390 |
| 25 | 3 | 250 | 4,875 | ~488 |
| 30 | 3 | 300 | 5,850 | ~585 |
For stainless steel, multiply the result by 1.5–2×. For aluminum, the multiplier is approximately 0.5×. Always add a 20% safety buffer to the calculated figure.
厚いプレートは予想以上のものを要求する理由
A 10% increase in plate thickness requires approximately 20% more bending pressure. This means moving from 18mm to 20mm plate is not a minor adjustment — it is a 23% force increase. Before selecting your machine, also confirm your bending method. Coining requires roughly 10× the force of air bending at the same thickness. Bottom bending requires about 4×. Specify your method first — then calculate.
厚板用V型ダイ開口部と金型選定
The V-die opening directly controls required tonnage, bend radius, and surface finish. For thick plate, the rule is: V-die opening = 8–10× the plate thickness.
| 板厚(mm) | Recommended V-Die Opening (mm) | トン数への影響 |
|---|---|---|
| 10 | 80–100 | 標準計算 |
| 15 | 120–150 | 標準計算 |
| 20 | 160–200 | 標準計算 |
| 25 | 200–250 | Reduces required tonnage vs. narrower die |
| 30 | 240–300 | ワイダーダイ=トン数は少ないが曲げ半径は大きい |
Using a die opening that is too narrow increases required tonnage, risks tooling fracture, and leaves pressure marks on the plate surface. Using one that is too wide reduces accuracy and produces a larger inside bend radius than specified.
Springback also increases with plate thickness. Plan for 2–5° of overbend compensation depending on the material grade. High-yield structural steels (550 MPa+) springback more aggressively than standard mild steel. The punch nose radius should not be smaller than the plate thickness — a smaller radius causes surface cracking on high-tensile materials.
油圧クラウディング — 厚手プレート購入者が省略できない特徴
For any press brake bending thick plate at 80+ tons or on a bed longer than 2.5 meters, a crowning system is not optional. Without it, the beam deflects downward at center under load, and bend angles vary across the part length.
This is why a machine rated at 400 tons can still produce inconsistent angles on a 4-meter thick plate job — the rating tells you force, not rigidity.
Mechanical vs. Hydraulic Crowning
| クラウニングタイプ | 調整方法 | ベスト・フォー | 相対コスト |
|---|---|---|---|
| Mechanical (wedge) | Manual/preset, not adjustable under load | Repetitive jobs, consistent plate thickness | 下げる |
| 水力の | CNC-adjusted, static compensation | General production, varied thicknesses | 中盤 |
| ダイナミック・ハイドロリック | ストローク中のリアルタイム調整 | Mixed production, high-precision requirements | 高い |
For machines 200T and above running mixed plate thicknesses, dynamic hydraulic crowning is the correct specification. It compensates in real time for material variations — thickness tolerances, tensile strength variation, and hardness differences — that static crowning systems cannot address. For CNC axis control of the back-gauge for positional accuracy on thick plate, see our 4-axis vs 8-axis back-gauge guide.
混合厚板生産のための動的クラウニング
Dynamic crowning monitors resistance during bending and adjusts the compensation cylinder pressure mid-stroke. This is critical when running 15mm and 25mm plate on the same shift — each requires different crowning compensation, and a static system can only be preset for one.
トン数クラス別の材料特異的厚さ制限
This table shows maximum plate thickness by machine tonnage for air bending at standard bed lengths. Values are based on industry-standard formulas.
| トンネージクラス | Max Mild Steel (mm) | Max Stainless Steel (mm) | Max Aluminum (mm) |
|---|---|---|---|
| 100T | 6 | 3–4 | 10–12 |
| 160T | 8 | 4–5 | 14–16 |
| 200T | 10–12 | 5–6 | 18–20 |
| 400T | 18–20 | 9–10 | 30–35 |
| 600T | 25–28 | 12–15 | 40–45 |
| 800T+ | 30–40 | 18–20 | 50+ |
For stainless steel at any thickness, select the next tonnage class up from your mild steel calculation. For our 600-ton model specifications, see the 600-ton CNC press brake page. These are air bending values. Bottom bending or coining the same material requires 4–10× the tonnage listed.
厚板作業で指定すべき主要な機械機能
Before contacting any supplier, confirm these features are included in the specification:
- 油圧駆動 — electric press brakes lack the sustained force output for repeated thick plate bending cycles; hydraulic remains the correct choice for heavy plate work
- Rated tonnage with 20% buffer — calculate your peak job requirement first, then add 20% before selecting a tonnage class
- 油圧クラウニングシステム — dynamic crowning for mixed production; mechanical for dedicated repetitive jobs
- ベッド長は最大パーツ長にマッチング — 平均作業期間ではありません
- CNC back-gauge with minimum 4 axes — positional accuracy is critical when handling heavy plate; human error on manual machines costs material
- 角度補正を用いたCNC制御 — Delem DA66S, DA66T, or ESA S860 are proven systems for thick plate work with springback compensation built in
- 材料引張強度に適合したヘビーデューティ型工具 — structural steel can reach 550 MPa; confirm tooling grade with your supplier
For ESA controller specifications and features, see our ESAコントローラーのページでブレーキを踏みます.
RAGOS製の厚板プレスブレーキ
RAGOS heavy-duty hydraulic press brakes cover the 100T to 600T+ range — all equipped with Rexroth hydraulic systems and Delem CNC controls as standard. Dynamic hydraulic crowning is included on all models at 200T and above. In our experience, the most common mistake buyers make is selecting tonnage based on their average job, not their thickest plate requirement. A machine purchased for 10mm work cannot be stretched to handle 20mm reliably, even occasionally.
When clients share their plate specs — material type, thickness, bend length, and bending method — our technical team provides a written tonnage and machine recommendation before any purchase commitment. For general-purpose heavy plate work, our 100T CNC press brake for steel is a proven starting point. For structural and offshore applications, the ヘビーデューティプレスブレーキのレンジ covers 200T to 600T+.
Ready to specify your machine? Share your plate thickness, material, and bend length — we will confirm the tonnage and machine class in writing.
よくある質問
Q1: What tonnage press brake do I need for thick plate bending?
Use the formula P (kN) = 650 × S² × L / V to calculate required tonnage for mild steel. For 20mm plate at 3m with a 200mm V-die, you need ~390 tons. Add 20% safety buffer before selecting a machine class. For stainless steel, multiply the result by 1.5–2×. For a detailed reference, see our ダイの開きとトン数ガイド.
Q2: What is the minimum V-die opening for thick plate?
V-die opening should be 8–10× the plate thickness. For 20mm plate, use a 160–200mm opening. A die that is too narrow increases required force, risks tooling damage, and marks the plate surface. Wider dies lower required tonnage but increase the inside bend radius. For thick plate application context, see our ボイラープレート曲げガイド.
Q3: Why is hydraulic crowning required for thick plate press brakes?
Under heavy load, the press brake beam deflects downward at the center. This produces an open angle at mid-length and a closed angle at the ends of a long workpiece. Hydraulic crowning applies a compensating upward force to the bed, maintaining uniform bend angle from end to end. It is essential on beds over 2.5m or machines at 80+ tons. To understand how CNC axis control further improves accuracy, see our 4-axis vs 8-axis back-gauge comparison.
Q4: Can a 200-ton press brake bend 20mm mild steel plate?
A 200-ton press brake can bend 20mm mild steel at approximately 1–1.5m bend length using air bending with a 200mm V-die. At 3m length, the required force is ~390 tons — beyond a 200-ton machine's safe capacity. Always calculate using P = 650 × S² × L / V before committing to a tonnage class. For heavy-gauge applications, view our 600-ton CNC press brake specifications.
Q5: What is the maximum plate thickness a press brake can handle?
High-tonnage press brakes at 3,000 tons and above can bend steel plate up to 150mm thick in offshore and structural applications. For most fabrication shops, machines in the 400–800 ton range handle plate from 20–50mm reliably. The practical limit depends on rated tonnage, bed rigidity, and tooling specification. CNC hydraulic press brakes handle thick metals from 10mm to 20mm+ in the 300–1,000 ton class. View our ヘビーデューティプレスブレーキのレンジ for full capacity specifications.
Spec It Right. Bend It Right.
Three decisions determine success with thick plate bending. First, calculate your required tonnage using P = 650 × S² × L / V — then add a 20% buffer before selecting a machine class. Second, specify a hydraulic crowning system matched to your bed length and production mix. Third, set your V-die opening at 8–10× your plate thickness and confirm your punch nose radius is not smaller than the plate thickness. These three steps eliminate the most common sources of angle error, deflection, and tooling failure on thick plate jobs. Your next step: share your plate specification — material, thickness, and bend length — with the RAGOS technical team and get a written machine recommendation before purchase.
