A progressive die performs a part in stages: the strip of stock advances one progression at a time, and each station adds an operation — piercing, notching, forming, then finally cutting the part free. By the time the strip reaches the end, a finished part drops out with every press stroke.
The whole design hangs on one idea: the part is built incrementally as the strip travels, so the order of operations and the spacing between them is the heart of the work. Get the strip layout right and the rest of the die follows; get it wrong and no amount of good toolmaking saves it.
Strip layout is the plan that maps each operation to a station along the strip. The progression — the distance the strip advances per stroke — is set by the part geometry plus the web and scrap bridge you leave between parts for strength and carrying. The Simple Strip Layout and Advanced 3D Strip tools help you lay out stations and visualize the progression.
A good layout sequences operations so that earlier stations do not distort features needed later. As a rule, pierce holes that will serve as locating references early, perform forming after the cutting that defines the blank outline, and leave the part-off (cutoff) for last so the part stays carried as long as possible.
Idle stations — stations with no operation — are deliberately added to give room for tooling, to ease die construction, or to stagger punches so they do not crowd each other. They cost strip length but often buy reliability.
Pilots are pointed pins that enter previously pierced holes to pull the strip into exact registration before the working punches hit. The feed gets the strip close; the pilots make it precise. Pierce pilot holes early and protect them through the rest of the progression.
The carrier (or web) is the skeleton of stock that holds the developing parts together as they travel. Common forms are a single-side carrier, a center carrier, or a two-side (ladder) carrier. The carrier must be strong enough to feed without tearing yet light enough not to waste material — a balance the strip layout and stock allowance both inform.
Because the punches are spread along the strip, their combined forces rarely act through the center of the ram. The center of pressure is the point where the total punching force is balanced. If the die is mounted so this point is offset from the press centerline, the ram tips and tooling wears unevenly.
Calculate the center of pressure from each operation’s force and location, then position the die so that point sits under the ram centerline. The Center of Pressure tool does this summation; pair it with Punch Force to estimate each station’s contribution.
Sum the cutting and forming forces across all stations to size the press, and do not forget reverse (snap-through) tonnage — the rebound that occurs when the material fractures and the load suddenly releases. Reverse tonnage stresses the press in the opposite direction and is a real limit on many machines.
Stripper plates pull the strip off the punches on the upstroke and, in many dies, guide the punches and hold the stock flat during cutting. Sizing stripper force and travel is part of getting the strip to feed cleanly stroke after stroke.
Start from the finished part and work backward: list every feature, decide the operation that creates it, then sequence those operations into stations with pilots placed early. Set the progression, add idle stations where tooling needs room, balance the center of pressure, then total the tonnage including reverse tonnage. Only then detail the die. This content is a conceptual overview — validate any specific layout against your part, material, and press before cutting steel.
strip_layout calculator · strip_layout_3d calculator · center_pressure calculator · punch_force calculator · stock_allowance calculator