How to quote a welded assembly: cost structure

How to quote a welded assembly is a matter of eight lines: material, cutting, forming, weld time, fixture amortisation, coating, inspection and packing, with overhead and margin applied on top. On a typical 12 kg frame with 1.8 m of 4 mm fillet, material is about 45% of the piece price and welding about 6%, which is the opposite of what most buyers assume when they ask "how much per metre of weld".

The quote is only comparable if those eight lines are visible. Two suppliers can be 20% apart on the same drawing and both be right, because one priced coating on one side, amortised the fixture over 5,000 pieces and excluded first article inspection.

This page sets out the structure, a worked example with every rate shown as an assumption, the weld length at which manual and robotic welding cross over, and the questions that turn two totals into a decision.

How to quote a welded assembly: the eight cost lines

Each line is driven by a different input, and each can move independently when the drawing changes.

Material is priced on gross weight, not finished weight, because the blank and the nest consume more than the part weighs. Cutting is priced on cut length and pierces. Forming is priced on the number of bends and the handling time. Welding is priced on arc time, which follows weld size and length, not part weight. The fixture is a one-time cost divided by the volume it will run. Coating is priced on developed area and the number of coats. Inspection follows the sampling plan and the tolerance class. Packing follows the handling risk.

A quote that collapses all of this into a rate per kilogram hides the two lines that a designer can actually change: weld length and coated area.

A worked example: 900 × 600 mm frame, 1.8 m of weld

The assembly is a 3 mm CRCA frame with four parts, six bends, 1.8 m of 4 mm fillet weld and a powder coat, released at 40 per month. The rates below are assumed shop rates used to show the structure; replace them with your supplier's actual figures before comparing anything.

• Material. 12.0 kg net at 78% utilisation is 15.4 kg gross. At ₹72/kg that is ₹1,109.
• Laser cutting. 4.6 m of cut and 14 pierces at ₹55/m and ₹3 each gives ₹295.
• Bending. Six bends at 45 s each is 4.5 minutes at ₹900/h, which is ₹68.
• Welding. 1.8 m at 0.30 m/min is 6.0 minutes of arc; with handling and cleaning at 1.8 times arc time, 10.8 minutes at ₹750/h gives ₹135.
• Fixture. ₹90,000 over 2,000 pieces is ₹45.
• Coating. 1.2 m² per side is 2.4 m² of coated surface at ₹140/m², which is ₹336.
• Inspection. Two minutes per part at ₹600/h is ₹20.
• Packing. ₹60.

The subtotal is ₹2,068, and overhead plus margin at 18% adds ₹372, for a piece price of ₹2,440.

The arithmetic matters less than the proportions. Material is the largest line at 45.5%, and coating at 13.8% is more than twice the welding cost. A 10% saving on material is worth 4.5% of the price; a 10% saving on welding is worth half a percent.

Where the money actually goes

Shares below are from the worked example, rounded to the nearest half point.

The weld length where manual becomes robotic

Welding cost scales with arc time, and arc time scales with length divided by travel speed. That gives a clean crossover.

Manual MIG on 4 mm fillet runs at about 0.30 m/min of arc, and paid time is roughly 1.8 times arc time once loading, cleaning and tacking are counted. At ₹750/h, which is ₹12.50 per minute, a metre costs 6 minutes of paid time, or ₹75.

A robotic cell runs the same fillet at about 0.60 m/min, adds about 1.5 minutes of load and unload per part, and costs more per hour: at ₹1,800/h, ₹30 per minute, a metre costs ₹50 plus ₹45 fixed per part.

Set the two equal: 75L = 50L + 45, so L = 1.8 m. Below 1.8 m of weld per assembly, manual welding is cheaper. Above it, the robot wins, and the gap widens quickly: at 4 m of weld, manual is ₹300 and robotic is ₹245 per part before the fixture is counted.

That is why a 40-per-month order with 1.8 m of weld sits exactly at the break-even and should be quoted on manual stations, while a genset base frame with 5 m of weld belongs in a cell. Robotic versus manual welding cost works through the same comparison with the capital cost included.

Tooling, fixtures and what amortised really means

Every welded assembly needs something to hold it: a fixture, a checking fixture, or both. The cost is real and it has to land somewhere.

The fixture for the worked example costs ₹90,000. Spread over 2,000 pieces it is ₹45, which is small. Spread over 500 pieces it is ₹180, which is larger than the welding cost and would change the sourcing decision. Spread over the 5,000 pieces in the business plan and it looks almost free, which is where quotes stop being honest.

Two rules keep this visible. Ask what volume the tooling is amortised over, in writing. And where the programme is uncertain, buy the tooling separately and own it, so the piece price does not carry a bet on volume. Customer-owned tooling also has to be stored, maintained and controlled, which is a separate agreement rather than a line in the piece price.

What to ask when two quotes differ by 20%

Work down this list before arguing about the rate.

• Coating basis. One side or two, one coat or primer and topcoat, masking included or extra, and whether the price covers a 60–80 µm film.
• Weld map. The same drawing can be read as 1.8 m of intermittent fillet or 4 m of continuous weld. The symbol and the note decide.
• Tolerance class. A general tolerance of ISO 2768-1 class m and a weldment to ISO 13920 class B are not the same inspection load, and the tighter one costs time at first-off.
• Inspection. Sample size, dimensional report, first article, PPAP, and whether the report is a separate charge.
• Material source and grade. A substituted grade can save on the material line and cost at the weld line, because the weldability and the springback change.
• Freight and packing. Ex-works and delivered are different numbers, and export packing on a 900 mm frame is not trivial.
• Payment terms and price validity. A rate held for 30 days and a rate held for 12 months are not the same offer on a steel price that moves.

How to compare sheet metal manufacturing quotations turns this into a scoring sheet that procurement can defend.

What should move when the revision changes

A revision that adds a hole and a revision that changes a weld size look equally small on the change note and cost very different amounts.

Adding a 10 mm hole changes the laser line by about 0.1 m of cut and one pierce, which is a few rupees. Changing a 4 mm fillet to 5 mm increases the filler volume by (25 ÷ 16) − 1, or 56%, and slows the travel speed, so the weld line grows by roughly a fifth on the same length. Welding 1.8 m at 5 mm instead of 4 mm adds about ₹27 per assembly in the worked example, which is more than the bending line.

Three other changes move the price more than buyers expect: coating the inside face as well as the outside, which doubles the coated area; tightening the weldment to a finer tolerance class, which adds fixture time and inspection; and dropping the release volume by half, which doubles the fixture share per piece without changing a single manufacturing operation.

Where Ganesh prices a welded assembly

Fixtures, checking fixtures and press tooling are designed and built in our tool room, and tooling is quoted separately from the piece price so the amortisation volume is the buyer's decision rather than a hidden assumption.

Welding runs on three CLOOS robotic MIG cells and more than 30 manual MIG, MAG, spot and SPM stations, which is what makes the manual-versus-robotic crossover a real choice rather than a brochure line. Coating runs through seven-tank pretreatment, a 16 ft × 16 ft shot blast chamber and an 18 ft × 14 ft electrostatic powder booth, so the coated area is priced from the same drawing the welder works to.

Assemblies are held to ±0.5 mm general tolerance with tighter features by agreement, first article inspection is available, and PPAP documentation is provided where the programme requires it. The route covers elevator frames, genset base frames, rack frames and rail brackets for customers including TKE, Eros Elevators, Mahindra and Indian Railways. The welded assemblies capability page lists the cells and the stations, and the bending, welding and assemblies hub indexes the technical guides.

What to put in the RFQ so the quote comes back comparable

• The assembly drawing with the weld map to ISO 2553, and every weld marked structural or cosmetic.
• The general tolerance for the weldment, and the tolerance class for unwritten dimensions.
• Coating spec: system, colour, film thickness, masked areas, and whether the inside faces are coated.
• Release volume per month and total programme volume, so tooling can be amortised on a real number.
• Inspection requirements: first article, dimensional report, PPAP, and any customer-specific forms.
• Hardware, labels, serial marking and packaging, listed as included or excluded.
• Delivery basis and destination, because the landed cost is the only number procurement can compare.

The landed cost calculator adds freight, duty and inventory carrying to the piece price, and the RFQ checklist lists the file set that avoids a second round of questions.

When this cost model does not apply

The model assumes a fabricated assembly that stays fabricated. If the annual volume is above roughly 20,000 pieces, a stamped and spot-welded design may undercut it, and the comparison belongs in pressing versus fabrication rather than in a welding quote.

It also does not apply to one-off prototype frames, where the fixture and the set-up dominate and a piece-price model is meaningless. And it does not apply where the assembly is really a single formed part with two brackets welded on: that is a bending and laser quote with a small weld line, and pricing it as a fabrication overstates it.

Send the drawing, the weld map and the release volume, and the quotation comes back with the eight lines separated and the assumptions stated. The request a quote form takes the revision and the file set in one step.