How to quote a weldment without losing the fit-up

The request is a welded frame. Fourteen pieces of rectangular tube and plate, 2 machined faces after welding, 3 sheets of print and 40 dimensions. The estimator counts the welds, multiplies by a rate, adds material and sends it.

That quote is wrong and it will not be obviously wrong for 4 months. Weldment estimating fails at the fixture and the fit-up, and both of them sit outside the arc time everybody counts. Every figure below is illustrative and one frame carries through the post. The line by line discipline is the same one a machined part quote uses.

Where the hours actually go on a weldment

Arc time is rarely more than a quarter of the labour on a fabricated assembly. On the frame, an illustrative split across the 6 stages runs cut and prep 2.1 hours, fit-up 3.4, welding 2.6, straightening 1.2, post-weld machining 1.8 and inspection 0.9.

That is 12 hours, of which welding is 2.6. An estimator who prices the welds and adds a percentage for everything else is pricing 22 percent of the job accurately and guessing at the rest.

The reason the guess is usually low is that the stages nobody counts are the ones that scale with part count and complexity rather than with weld length. Fourteen pieces means 14 things to cut, deburr, locate and hold, and none of that appears anywhere on a weld symbol.

Cut and prep, before anything gets held

Every piece in the assembly needs cutting to length, squaring, and usually edge preparation before it can be welded. On the frame, the 14 pieces come off a saw at an illustrative 4 minutes each including handling, which is under an hour.

Prep is where it grows. Any joint calling for full penetration needs a bevel, and bevelling 8 joints by grinder is slow and unpleasant work that lands at an illustrative 1.2 hours on its own. If the print calls for a specific groove angle, that is a machining operation rather than a grinder job.

Hole and slot work in the members belongs here too, before assembly, because locating a hole after welding is a fixture problem rather than a drilling problem. Estimators who leave these to the machining stage price them at the wrong rate and in the wrong sequence.

Fourteen pieces, 14 handlings.

Material on a weldment is also a different exercise from material on a machined part. You are buying lengths of tube and sheets of plate, cutting into them, and living with the remnant, which is the same yield problem a sheet metal part has. A frame using 11 feet of a 24 foot length either finds a home for the rest or pays for all 24.

Fit-up and the fixture nobody costs

The fixture is the largest uncosted item on most weldment quotes. Fourteen pieces have to be held in the right relationship to each other while somebody welds them, and something has to do the holding.

On a one-off, that something is a welder with clamps, a square and a surface table, and the cost sits in the 3.4 fit-up hours. On a repeat program it is a built fixture, and a fixture for a frame like this is an illustrative $4,200 of design, material and build.

Something has to hold it.

Neither of those is free and neither appears on the print. The quoting error is to assume the fixture exists, because it did on the last similar job, and then to discover during the first article that the last one was 40mm shorter and the locators do not reach.

Fixture cost also decides the volume math. Spread over 6 frames the fixture is $700 a piece and dominates the quote. Spread over 200 it is $21 and the fit-up hours drop by half because the fixture does the locating. Quote the volume you were given and state the assumption on the quote.

Weld length against deposition rate

Welding is priced from length, thickness and process, and the number that converts them is deposition rate. Measure the total weld length off the print, work out the fillet size each joint calls for, and the deposit volume follows from geometry.

On the frame, an illustrative 84 inches of 1/4 inch fillet at a deposition rate typical for the process gives an arc time near 1.4 hours. Arc time is not welder time. Repositioning, tacking, slag and spatter cleanup, and the simple fact that nobody welds continuously push the 1.4 to the 2.6 in the split above.

The ratio between arc time and welder time is worth knowing for your own floor, because it varies with the work and it is the single most useful number in weldment estimating. It comes from your record rather than from a handbook.

Process choice moves it. A job that runs on a wire process in the flat position behaves nothing like the same joints run out of position with stick, and if the fixture cannot rotate the assembly then some of those joints are out of position by definition.

Arc time is not welder time.

Weld symbols are worth reading properly rather than counting. A symbol carrying a field weld flag, a specific groove angle, or a requirement that the joint be inspected changes the cost of that joint by more than its length does. Two symbols on the frame call for full penetration, and those 2 drive the bevelling in the prep stage above.

Weld quality requirements sit here too. If the print references a welding code, or asks for certified welders on a particular joint, that is a constraint on who can run the job and it belongs in the rate rather than in the hours.

Distortion and the straightening nobody quotes

Weld metal shrinks as it cools and the assembly moves, and somebody has to put it back. On a frame with 84 inches of weld across 14 pieces, movement is certain. The only question is how much and whether the print tolerances allow it.

Straightening is 1.2 hours in the illustrative split and it is almost never on a routing. It is done by a welder with a torch and a press, it is skilled, and on a bad day it takes 3 times the estimate.

Sequence controls it more than anything else. A weld sequence designed to balance shrinkage can halve the straightening, and that sequence is engineering work that happens once and belongs in the first article cost rather than in every piece.

If the print carries flatness or a hole pattern tolerance across the welded assembly, the first article will find out whether the sequence works. Quoting a tight tolerance across a welded frame without carrying straightening hours is the most common way this part loses money.

Post-weld machining and the inspection at the end

Two machined faces after welding means a setup on an assembly that is now large, heavy and slightly not where the model says it is. Work holding on a weldment is its own problem, and the setup is longer than the same faces on a solid part.

The illustrative 1.8 machining hours assume the fixture locates off features that survived welding. If they did not, the operator is indicating the part in, and that is 40 minutes before any metal moves. The burdened rate on the machine applies to all of it.

There is a sequencing decision buried here that changes the quote. Machining before welding is cheaper per operation and risks the features moving. Machining after welding is more expensive and gives the tolerance. The print usually implies which, and where it does not, the assumption belongs on the quote in writing, the same way a machined part quote states its stock condition.

Inspection closes the job. A welded assembly with 40 dimensions and a tolerance across the frame needs more than a caliper, and if the customer wants a report the measuring time is real. On the frame that is 0.9 hours, and on a first article it is several times that.

Add it up and the frame carries 12 labour hours, a fixture, material and 2 outside operations, against an arc time of 1.4 hours. Anyone quoting from the weld symbols alone is looking at a ninth of the job.