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fab-dat/fab-product-dat/fab-sheet-metal-dat/fab-sheet-metal-dat.md
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- [[rivet-dat]] - [[rivet-nut-dat]]
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+- [[metal-dat]] - [[tube-dat]]
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## common to use sheet metal products
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@@ -50,13 +51,10 @@ flange hold line
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![](2026-01-01-01-13-20.png)
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-
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-hem
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-
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-![](2026-01-01-01-05-52.png)
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+- [[fab-sheet-metal-hem-dat]]
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tab
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-
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+![fab-sheet-metal-hem-dat/2026-01-01-01-05-52.png](fab-sheet-metal-hem-dat/2026-01-01-01-05-52.png)
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![](2026-01-01-01-23-07.png)
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![](2026-01-01-01-23-40.png)
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fab-dat/fab-product-dat/fab-sheet-metal-dat/fab-sheet-metal-hem-dat/fab-sheet-metal-hem-dat.md
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+# fab-sheet-metal-hem-dat
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+
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+![](2026-01-01-01-05-52.png)
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+
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+## Summary
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+
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+An integral-formed hem (one-piece hem) is essentially: using machine capability to trade for consistency and reliability.
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+
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+- Yes — the entry threshold is definitely higher.
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+- Not just slightly higher: it's a step up in difficulty and equipment requirements.
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+
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+## What is an integral-formed hem?
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+
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+An integral-formed hem means folding the edge of the same sheet material back to 180° so the hem is formed from a single piece without adding separate parts. This requires stable, repeatable forming on the original workpiece.
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+
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+## Why the equipment threshold is higher
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+
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+Forming a one-piece hem on the same blank imposes three hard requirements on the equipment:
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+
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+1. Progressive forming capability
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+2. High repeatability (precision)
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+3. Surface quality control
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+
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+### Quick comparison table
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+
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+| Requirement | Why it matters | What the machine must provide |
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+|---|---:|---|
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+| Progressive forming | A single aggressive bend will fail or be inconsistent | Multi-step forming with controllable angles and force
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+| High repeatability | Hem radius, thickness, and straightness must be consistent part-to-part | High rigidity, accurate guiding, and precise positioning
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+| Surface quality control | Avoid cracks, waviness, and tool marks on the hem and adjacent area | Dedicated forming tooling, smooth forming surfaces or rollers
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+
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+## Detailed requirements
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+
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+- Progressive forming capability
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+ - Do not form the hem in one hit. The process must be executed in multiple controlled passes with adjustable angles and loads.
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+ - Ordinary press brakes or simple presses typically cannot achieve stable, repeatable one-piece hems.
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+
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+- High repeatability (precision)
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+ - Every finished hem must match targets for:
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+ - Radius
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+ - Material thickness in the hem area
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+ - Straightness/flatness of the hem and adjacent panel
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+ - Equipment must be stiff, with precise guides and repeatable positioning.
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+
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+- Surface quality control
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+ - Defects to avoid:
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+ - Tearing or cracking
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+ - Waviness or buckling
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+ - Press marks or visible scoring
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+ - Achieve this with specially shaped forming faces, rollers, or tooling that distribute force and protect the surface.
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+
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+## Key metrics to control
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+
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+- Hem radius tolerance
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+- Hem cross-section thickness
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+- Local flatness / straightness near the hem
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+- Surface finish (no visible marks, scratches, or tears)
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+
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+## Common defects and causes
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+
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+- Crack / tear — too aggressive a single bend or insufficient material flow control
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+- Waviness / buckling — uneven compression or lack of progressive forming
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+- Press marks / indentations — improper tooling surface or excessive local pressure
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+
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+## Equipment and tooling checklist
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+
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+- Ability to program/perform multi-pass forming with controlled angles and loads
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+- High structural rigidity and accurate guides (for repeatability)
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+- Dedicated forming dies or rollers with smooth contact surfaces
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+- Means to control and measure part location consistently (fixturing, clamps)
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+- Process monitoring (force, stroke, angle) and ability to adjust on the fly
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+
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+## Process notes / best practices
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+
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+- Use gradual, multi-stage bends rather than a single full-angle stroke.
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+- Match tooling geometry to material thickness and desired hem radius.
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+- Validate process with sample parts; measure radius, thickness, and flatness across samples.
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+- Inspect surface after each forming stage to catch defects early.
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+
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+## References
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+
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+- [[fab-sheet-metal-dat]]
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+- [[AI]]
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\ No newline at end of file
mechanics-dat/mechanical-structure-dat/Shaft-dat/tube-dat/tube-bend-dat/tube-bend-dat.md
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+
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+# tube-bend-dat
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+
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+## R15
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+
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+Quick reference table (R = 15 mm)
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+
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+| Bend angle | Total bend length (mm) | Middle point (mm) |
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+| ---------- | ---------------------- | ----------------- |
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+| 45° | 11.78 | 5.89 |
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+| 60° | 15.71 | 7.85 |
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+| 90° | 23.56 | 11.78 |
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+
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+
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+
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+## ref
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+
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+- [[tube-dat]]
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\ No newline at end of file
mechanics-dat/mechanical-structure-dat/Shaft-dat/tube-dat/tube-dat.md
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@@ -6,6 +6,7 @@
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- [[tube-pvc-dat]]
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+- [[shaft-dat]]
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6mm 以下
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@@ -61,3 +62,9 @@ PA6尼龙管
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- 聚氨酯 空心棒材 减震 PU 空心管 弹性胶棒 橡胶棒 优力胶棒
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![](2025-12-30-14-29-07.png)
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+
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+
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+
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+## ref
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+
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+- [[shaft-dat]]
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\ No newline at end of file