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Bend allowance workflowEstimate flat length from thickness, inside radius, bend angle, leg lengths, and K factor before preparing a cutting blank.
Cone and cylinder layoutsDevelop reducer sectors, truncated cones, sleeves, and rolling rectangles with scaled drawings that help communicate the shape.
Production review notesCompare calculator results with material behavior, press brake tooling, springback, grain direction, and first-article measurements.

⚙️ Bend Allowance Calculator

Professional Sheet Metal Unfolding · K‑Factor, Cone, Cylinder · Metric/Imperial · Export PNG/PDF

Unit System:
✨ Flat Length ✨
-- mm
Bend Deduction: -- mm
※ Formula: L = A + B - 2·(T+R)·tan(θ/2) + (θ·π/180)·(R + K·T)

📐 Bend Sketch & Flat Length Indicator

Adaptive scaling | Export includes all parameters & graphics
📐 Sector Development
--
Large radius: -- mm   Small radius: -- mm
Central angle: -- °
※ Radial line method for frustum. Inner/outer arcs correspond to perimeters.

🌀 Sector Flat Pattern (Frustum)

Sector automatically scales to fit canvas
📄 Rectangle Blank Size
-- × -- mm
Area ≈ -- cm²
※ Blank length = π × D, width = cylinder height.

📄 Rectangle Development (Rolling Blank)

Automatically centered & scaled

📘 How to Use ▼

1. Bend Unfolding (K-Factor)
Enter thickness, inside radius, bend angle, leg lengths, and K-factor (steel 0.44, aluminum 0.5, stainless 0.4). The flat length appears instantly. The sketch shows the bent shape and a bar representing relative flat length.

2. Cone / Truncated Cone
Input top radius, bottom radius, and height. If radii are equal, it switches to cylinder rectangle. Results show sector radii and central angle, plus a scaled drawing.

3. Cylinder Shell
Enter diameter and length. The rectangle blank (length = π×D, width = height) is displayed with area.

Unit Switch: Top bar lets you toggle between Metric (mm) and Imperial (inch). All inputs and results convert automatically.
Export: “Save as PNG” captures the current panel with margins; “Export PDF” generates a complete report.
Adaptive Drawing: Shapes always fit the canvas, scaled up/down as needed.

All calculations follow industry-standard formulas. Always verify with physical tests before production.

🤝 Trusted Partners Recommendation

Precision Manufacturing · Craftsmanship Excellence
📋 Company Profile One-Stop Solution
WAHI specializes in plastic injection molding, silicone rubber part production, and high-precision CNC machining. With a professional R&D team and a 3,000m² facility equipped with advanced injection molding machines, CNC centers, EDM, and CMM, WAHI provides integrated support from product development to mass production.
🎯 Core Business
Injection MoldingSilicone Rubber PartsCNC MachiningMold Design & ManufacturingRapid PrototypingAutomotive & Medical Components
60+
Advanced Machines
50
CNC Units
3,000m²
Facility
📧 info@wahimold.com  |👤 Max Huang
🌐 Visit Website →Get a Quote
📋 Company Profile Shenzhen Based
Shenzhen Huateng Zhenye Industrial Co., Ltd. is a professional custom precision machining parts manufacturer. Since 2016, specialized in CNC turning, milling, Swiss-style lathe. Advanced inspection equipment including Zeiss CMM and Mitutoyo CMM ensures micron-level accuracy for complex geometries and high-volume production.
🛠️ CNC Service Matrix
CNC MillingCNC TurningSwiss‑Style LatheWire Cutting5‑Axis MachiningRapid PrototypingVolume Production
Zeiss·Mitutoyo
CMM Inspection
±0.005mm
Tolerance
2016
Founded
📧 anna@huatengcnc.com  |👤 Anna
🌐 Visit Website →Request a Quote

Sheet Metal Bend Allowance Guides

Original tutorials for flat pattern planning, K factor, cone development, and shop communication

Use the calculator first

Start with the tool above, then read the guide library to understand the assumptions behind K factor, bend deduction, cone sectors, and cylinder blanks.

Open all guides

Keep production context

Material, tooling, bend method, grain direction, springback, and inspection tolerance can all change a real-world blank size.

Calculation notes

Shop communication

Use the drawings and exported reports to keep blank dimensions, assumptions, and forming notes clear for production review.

Read reporting guide
⏳ Generating report, please wait...