Laser-Cut and Welded Assemblies

Laser-cut blanks as weldment parts: tabs, slots, gussets and base plates

A weldment can be drawn from laser-cut blanks that locate each other. A tab on one plate drops into a slot in the next, so the parts set their own angle and spacing before the first weld. Gussets cut from the same sheet triangulate a corner, a base plate carries the mounting holes, and an upright carries the slot pattern, all from one DXF nest. The tab-and-slot clearance is drawn on the print, wide enough to assemble by hand and tight enough to close for the weld; the quote flags a slot that will not assemble as drawn.

The blanks arrive with a laser edge, and the print decides what happens to it before welding. Hot-rolled steel carries mill scale, the flaky iron-oxide skin left by rolling. Wikipedia’s mill scale page says it becomes a nuisance when the steel is to be processed, that it is removed by flame cleaning, pickling or abrasive blasting, and that mills can supply steel with the scale removed and coated with a shop primer that can be welded or painted over (source 5). A print for mild steel therefore says whether the scale is ground back at the joint or the blanks are ordered with it already off. The stainless spoke covers the stainless grades. Where a leg of a weldment is bent rather than welded, the bent brackets spoke covers the bend callout. The inside radius is quoted as drawn, with a note if it won’t form. A formed corner and a welded corner can sit on the same part.

MIG and TIG are named on the print, with AWS A2.4 symbols

The print names the process and the weld, and AWS A2.4 is the language for it. AWS A2.4:2020, Standard Symbols for Welding, Brazing, and Nondestructive Examination (pubs.aws.org/p/1999/a242020-standard-symbols-for-welding-brazing-and-nondestructive-examination), "establishes a method for specifying certain welding, brazing, and nondestructive examination information by means of symbols" (source 1). Wikipedia’s page on welding documentation (source 2) describes the same conventions: a reference line with an arrow to the joint, the weld symbol placed on the arrow side or the other side, a circle at the junction of the reference line and the arrow for weld all around, and the process abbreviation in the tail.

MIG (gas metal arc welding) uses a consumable wire electrode with shielding gas fed through the gun, and Wikipedia’s GMAW page (en.wikipedia.org/wiki/Gas_metal_arc_welding) calls it "the most common industrial welding process" (source 4). TIG (gas tungsten arc welding) uses a non-consumable tungsten electrode under an inert shielding gas; Wikipedia’s GTAW page (en.wikipedia.org/wiki/Gas_tungsten_arc_welding) states it "is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminium, magnesium, and copper alloys", gives the operator "greater control over the weld" than competing processes such as MIG, and "is significantly slower than most other welding techniques" (source 3). The process is named on the print for each joint, and the weldment is welded to the print and quoted as one job with the cut blanks.

Material pairings: mild steel, 304L and 316L, 5052 aluminum

Common weldment materials are mild steel (A36 plate, 1008 cold-rolled sheet, A1011 hot-rolled sheet), 304L or 316L stainless, and 5052 aluminum. Name the material and thickness on the print, and say whether the blanks are hot-rolled or cold-rolled. The custom CNC brackets page covers the machined alternative for a bracket that mounts a motor or a guard on a frame. On aluminum, Wikipedia’s 5052 page rates its arc and resistance weldability "Very Good" and says it is not heat treatable but can be hardened by cold working (source 7). 6061 is also highly weldable, but Wikipedia’s 6061 page says that, typically, the properties near the weld are those of 6061-T4, a loss of strength of around 40% (source 6), so a welded 6061 print should not lean on T6 properties at the joint.

Welded stainless is drawn in the L grade. The British Stainless Steel Association (source 8) gives carbon at 0.08% maximum for 304 and 316 and 0.030% maximum for 304L and 316L, and says that below 0.030% carbon the intercrystalline corrosion does not take place after exposure to 450-850 °C for the times normally seen in the heat-affected zone of welds. Wikipedia’s 304 page (en.wikipedia.org/wiki/SAE_304_stainless_steel) puts sensitization, chromium carbides forming along grain boundaries, at roughly 480-820 °C (900-1,500 °F), with intergranular corrosion the result, and says 304L "is preferred" for corrosive applications where welding is required (source 9). Wikipedia’s 316L page (en.wikipedia.org/wiki/SAE_316L_stainless_steel) calls 316L "the low carbon version of 316 stainless steel", with 2-3% molybdenum against chlorides and marine use among its applications (source 10). Write 304L or 316L on laser-cut stainless that will be welded.

Distortion, and why machined features come after welding

Welding moves metal. The Australian Welding Institute, reproducing an article from TWI, says the localised heating of welding sets up non-uniform stresses from expansion and contraction, calls shrinkage and distortion "an inevitable result of welding" and says the amount of shrinking is almost impossible to predict accurately (source 12). Machine Design says eliminating thermal distortion is impossible, given the physics of welding (source 11). That is why a weldment print puts its critical dimensions on the finished assembly and marks machined features "after welding": a bearing bore, a pair of dowel holes, a flat mounting face, a tapped pattern that has to match a mating part. The blanks are laser cut with the bore undersize or the face proud, the assembly is welded, and the feature is then machined to the print on the welded part.

Laser-cut holes that do not locate anything can stay as cut, and the print says which are which: bolt clearance holes carry the laser tolerance, and the bore and the mounting face carry a tighter tolerance and the note "after welding". The secondary machining spoke covers the machined features themselves; the ordering how-to is on laser-cut, tapped and machined as one order. Machining after welding is quoted when the whole job is one order: the parts are made, welded, then machined. A weldment you built and send in is not machined. Shops that weld their own assemblies can order the machined details that go into them on machined parts for fabrication and welding shops.

Finishing after welding: powder coat, passivation, and the weld bead

Finish comes last, after the weld and after any machining, and the print says so. For a steel weldment going to powder coat, the print says whether the bead is left as welded or ground flush and which threads and machined faces are masked. For a stainless weldment, name passivation per ASTM A967 on the print; name citric or nitric only if your spec requires one. ASTM A967/A967M-25 covers chemical passivation treatments for stainless steel parts, including nitric acid and citric acid immersion and electrochemical treatment (source 13).

A finish called out on the print is quoted with the part; the whole weldment comes back finished and inspected. If a part doesn’t match the print, it’s remade or credited. Which finish suits which weldment is covered on the finishing spoke, and the weld-in bungs page covers machined fittings welded into a laser-cut plate in the same order. A set of frames, guards and mounts for custom machinery can be quoted as one order.

What the print needs, and what to send

A weldment print that quotes cleanly carries: the material and thickness of every blank, the weld symbol at each joint with process (MIG or TIG), size, length and pitch, all-around or intermittent, the finish and any masked areas, and the critical dimensions of the finished assembly with "after welding" where they apply. A flat pattern DXF per blank plus an assembly PDF, or a STEP of the weldment with a PDF that carries the symbols and tolerances, is ideal. Any file type is accepted; if a symbol or a dimension is missing, the quote lists it rather than guessing. A fully dimensioned 2D PDF is quoted without a CAD line; a job that starts from a sketch, a new sample part or photos gets a quoted CAD line. What file to send for laser cutting covers the DXF side.

If a symbol, a size or a dimension on the print cannot be checked as drawn, the quote says so before you order. There is no minimum, and lead time is quoted per job with rush available, starting at the quote form or the laser-cut parts hub.

Sources

All accessed 4 October 2026. Where a figure here differs from your print, the print governs.

1. American Welding Society, AWS A2.4:2020, “Standard Symbols for Welding, Brazing, and Nondestructive Examination”: pubs.aws.org (the scope sentence quoted above).

2. Wikipedia, “Symbols and conventions used in welding documentation”, last edited 26 April 2026: en.wikipedia.org (arrow side and other side, the all-around circle, the process in the tail).

3. Wikipedia, “Gas tungsten arc welding”, last edited 20 September 2026: en.wikipedia.org (thin sections of stainless and non-ferrous metals, operator control, speed).

4. Wikipedia, “Gas metal arc welding”, last edited 30 September 2026: en.wikipedia.org (consumable wire electrode and shielding gas; the most common industrial welding process).

5. Wikipedia, “Mill scale”, last edited 11 June 2026: en.wikipedia.org (the flaky surface of hot-rolled steel; removal by flame cleaning, pickling or abrasive blasting).

6. Wikipedia, “6061 aluminium alloy”, last edited 4 July 2026: en.wikipedia.org (highly weldable; properties near the weld those of 6061-T4, a loss of strength of around 40%).

7. Wikipedia, “5052 aluminium alloy”, last edited 14 August 2026: en.wikipedia.org (weldability ratings; not heat treatable, hardened by cold working).

8. British Stainless Steel Association, “Comparison of 304 or 316 and 304L or 316L type compositions and effect on corrosion resistance”, undated: bssa.org.uk/bssa_articles/2-comparison-of-304-or-316-and-304l-or-316l-type-compositions-and-effect-on-corrosion-resistance/ (carbon maximums; intercrystalline corrosion after 450-850 °C).

9. Wikipedia, “SAE 304 stainless steel”, last edited 3 August 2026: en.wikipedia.org (sensitization range; 304L preferred where welding is required).

10. Wikipedia, “SAE 316L stainless steel”, last edited 22 August 2026: en.wikipedia.org (low carbon version of 316; 2-3% molybdenum; chlorides and marine use).

11. Emily Newton, “What are the Best Strategies for Reducing Thermal Distortion in Welding?”, Machine Design, 23 June 2026: machinedesign.com (eliminating thermal distortion is impossible).

12. Australian Welding Institute, “Distortion” (article reproduced with permission from TWI), undated: welding.org.au (non-uniform stresses from expansion and contraction; distortion an inevitable result of welding).

13. ASTM International, A967/A967M-25, “Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts”: store.astm.org (Active, last updated 24 January 2025; nitric acid, citric acid and electrochemical treatments).