How is the number of passes calculated?

The tool finds the weld cross-sectional area from the groove geometry, adds a cap allowance, then divides by the deposited area per pass and rounds up. More fill area or smaller passes means more passes.

How is the groove cross-section found?

For a single-V groove it sums a rectangular root channel, root gap times depth, with the triangular bevel area, depth squared times the tangent of the half-angle. Wider angles and deeper grooves both raise the area sharply.

What is a backstep sequence and why use it?

In a backstep sequence you weld short segments in the direction opposite overall travel. Each segment shrinks toward the previous one, so the accumulated pulling distributes evenly and angular distortion drops on thicker joints.

Why split passes into root, fill, and cap?

The root pass fuses the joint and sets penetration, fill passes build the bulk, and the cap shapes the reinforcement and finish. Planning the split helps you choose technique, amperage, and interpass cleaning for each stage.

How accurate is the deposited area per pass?

It is an estimate scaled from process and wire diameter, since real deposition depends on amperage, travel speed, and deposition efficiency. Override it with your measured bead area for a tighter pass count.

What is the Multi-Pass Weld Sequence Planner?

Estimates how many weld passes fill a V-groove or U-groove joint from its cross-sectional area, weld process (SMAW, GMAW, FCAW), and electrode or wire diameter. Breaks the result into root, fill, and cap passes and suggests a backstep or balanced sequence to control distortion. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Multi-Pass Weld Sequence Planner

Name: Multi-Pass Weld Sequence Planner
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Fill a thick groove one stringer at a time and the pass count drives your time, consumable cost, and heat input. This planner estimates how many passes a V- or U-groove needs, splits them into root, fill, and cap, and recommends a sequence that keeps the plate from bowing.

How it works

The weld cross-section is built from the groove geometry, then the pass count follows from the deposited area each bead lays down:

groove area = root_gap × depth + depth² × tan(angle / 2)
total area  = groove area × (1 + cap allowance)
pass area   ≈ process_factor × wire_diameter   (or your override)
passes      = ceil(total area / pass area)

The included groove angle is halved because the bevel is a triangle on each face. The process factor reflects that flux-cored deposits more per pass than stick, with MIG in between. For thick joints or high pass counts the planner recommends a balanced, backstep technique to spread shrinkage and limit angular distortion.

Example and tips

A 16 mm plate with a 60° single-V groove and a 2 mm root gap has a fill area near 100 mm². At roughly 8 mm² per MIG pass with 1.2 mm wire that is about a dozen passes — one root, the bulk as fill, and a final cap. Keep interpass temperature in spec, clean slag between every pass, and alternate fill beads side-to-side on heavy sections to pull the joint straight rather than letting it close on one face.

Why pass count matters beyond time

The number of passes has knock-on effects that go beyond simply “how long does this take”:

Heat input accumulates. Each pass puts energy into the joint and the surrounding heat-affected zone. More passes at the same heat input per pass means more total heat — which affects grain growth, mechanical properties, and distortion. On structural steel, codes often set a maximum cumulative heat input or a minimum cooling time between passes (the interpass temperature ceiling) precisely to limit this.

Interpass cleaning. Every SMAW and FCAW pass leaves slag. If you underestimate the pass count you may also underestimate the cleaning time — grinding or chipping slag before the next pass. On a 20-pass SMAW joint, cleaning is a significant fraction of total labour.

Root pass technique differs. The root pass must achieve full fusion at the back of the groove, often a tight space, and is usually run at lower travel speed or with a different technique (keyhole TIG for pipe, or a root pass rod for SMAW) than the fill passes. The planner flags this as a separate phase so you choose the right approach for each stage.

Code compliance. Welding procedures qualified under AWS D1.1, ASME IX, or ISO 15614 specify the approved range of heat inputs, electrode diameters, and positions. If your pass count implies a deposited area per pass outside the qualified range, the procedure may not cover it. Check the WPS before committing to a wire size.

Distortion control: backstep in practice

A backstep sequence breaks a long joint into short segments (typically 50–150 mm) and welds each one in the direction opposite the overall direction of progress. For example, to weld left-to-right along a 600 mm seam, you might weld six 100 mm segments from right-to-left, starting each one where the previous one ended, but working backward.

The result: each segment tries to pull the plate toward itself as it cools, but because the segments alternate sides of the previous bead, the pulls roughly cancel rather than accumulating. The technique adds setup time but can halve angular distortion on thicker joints where a balanced double-V prep is not practical.