Strip Layout in Progressive Dies: Why It Decides Your Part Cost

Before a progressive die is designed, the toolmaker draws the strip layout. It shows how the part will be pierced, formed and cut from a coil strip, station by station. It is a one-page drawing, but it largely fixes the piece cost for the life of the part. Material is often the biggest share of that cost.

What a strip layout shows

• The sequence of operations: which features are cut or formed at which station.
• Pitch: how far the strip moves on each press stroke.
• Strip width: the coil width you will need to buy.
• Web and bridge widths: the material left between parts and at the edges.
• Pilots: the holes used to locate the strip accurately at every station.
• Carrier: how the part stays attached to the strip until the final cut-off.

Material utilisation

Utilisation is the share of the strip that ends up in the finished part. Everything else is scrap. Small changes add up:

• Tighter nesting. Rotating or interlocking parts on the strip can save a large share of the material.
• Smaller pitch. Every millimetre saved on pitch is saved on every part, for millions of parts.
• Minimum web width. Webs that are too narrow cause distortion and feeding problems, so there is a limit. As a rough guide, webs are kept at least about the material thickness, and usually more for thin or soft material.

Our article 5 Ways to Reduce Sheet Metal Component Cost shows how part design affects nesting.

Quality decisions made in the layout

• Pilot holes first. Piercing pilots in the first station and locating on them at every station keeps features accurate to each other.
• Grain direction. Coil material has a rolling direction. Bends parallel to the grain are more likely to crack, so the layout should orient critical bends across the grain where possible.
• Idle stations. Empty stations give the die steel room to stay strong, and make it easier to add operations later.
• Carrier design. A solid carrier is the most stable. Side or centre carriers allow forming that a solid carrier would block. The right choice depends on the part shape.
• Burr direction. The layout decides which side of the part carries the burr. This matters for electrical and mating parts.

What to check before you approve

1. Strip width and pitch, and therefore material cost per part
2. Material utilisation percentage
3. Location of pilots
4. Bend orientation relative to grain
5. Burr side on critical edges
6. Number of stations, which drives tool cost (see what decides progressive die cost)

At Atharva Engineers we share the strip layout with every customer for approval before tool design starts. See our progressive tool manufacturing process, or send a drawing and we'll propose a layout.