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In a progressive die, strip layout design (排樣設計) is the foundational blueprint that determines the sequence of stamping operations, the number of stations, material yield, die strength, and operational stability as the strip advances through the press12.
Designing a strip layout involves a systematic, step-by-step engineering process:
1. Flat Blank Unfolding and Calculation
Before laying out stations, any 3D formed features (such as bends, flanges, or drawn cups) must be mathematically unfolded into a 2D flat blank profile23.
- Bend Allowances: Neutral-axis shifts are calculated to determine exact developed blank lengths3.
- Multi-Stage Development: For drawn shells, intermediate drawing step diameters and reduction ratios are calculated to establish the required number of drawing stations4more_horiz.
2. Determining Feed Pitch ($P$) and Strip Width ($W$)
- Feed Pitch (Step Distance): The pitch ($P$) is the exact distance the strip advances between strokes78. It equals the part dimension parallel to the feed direction plus the required scrap margin (bridge width) between adjacent blanks7more_horiz.
- Strip Width ($W$): Calculated based on the part dimensions perpendicular to the feed direction, plus the necessary side margins for strip edge-trimming, pilot hole placement, or carrier webs7more_horiz.
3. Material Nesting and Layout Orientation
Engineers analyze different nesting orientations (such as straight single-row, double-row, inclined/angled, or interlocking layouts) to optimize material utilization ($\eta$) and maintain balanced cutting forces6more_horiz.
- Grain Direction: Bending operations are oriented across or at an angle to the material grain direction whenever possible to prevent cracking3.
4. Selecting the Carrier Web Type
Because parts remain connected to the continuous strip until the final station, selecting a suitable carrier web is essential for stable transport1012:
- Solid / Side Carriers: Attached along one or both edges of the strip, providing high stiffness for piercing and bending operations1012.
- Center / Bridge Carriers: Attached along the center line of the strip, allowing operations to be performed on both sides1012.
- Stretch / Spiral Webs: Incorporate flex loops or spiral cuts around the part profile, allowing material to flex vertically during deep-drawing stations without distorting the main carrier strip13more_horiz.
5. Station Sequencing and Operation Layout
The sequential arrangement of stations follows strict engineering rules216:
- Station 1 (Pitch Control & Pilot Piercing): Pierce pilot holes (導正孔) in the scrap web and notch side edge stops (pitch notches / 側刃) to establish initial feed distance2more_horiz.
- Station 2 (Precision Registration): Engage pilot pins (導正銷) into the pre-pierced pilot holes to lock the strip into micro-level alignment2more_horiz.
- Intermediate Stations (Piercing, Notching & Forming): Perform internal hole piercing, edge trimming/lancing, and sequential bending or drawing operations216.
- Idle Stations (空工位): Insert empty stations between active operations where necessary to preserve die block wall strength, accommodate spring lifters, or leave space for complex side-cams2more_horiz.
- Final Station (Cutoff / Blanking): Cut off, sever, or blank the finished component from the carrier web to drop it clear of the die212.
Core Principles for Strip Layout Success
- First Pierce, Then Form, Then Cut Off: Internal holes are pierced first while the strip is completely flat; forming and bending occur in the middle; final separation occurs at the last station216.
- Distribute Heavy Deformations: Complex profiles or large bend angles are split across multiple stations to avoid over-stressing punches, reduce wear, and control springback216.
- Ensure Tooling Strength: Cutting areas are separated across stations so that individual die inserts and stripper plates retain sufficient wall thickness to resist fracturing2more_horiz.
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