How each process cuts
A laser focuses a beam onto a spot small enough to melt the metal beneath it, and an assist gas blows the melt out of the slot it leaves, the kerf. Nitrogen keeps a stainless or aluminium edge bright; oxygen cuts carbon steel faster and leaves an oxidised edge. The path comes straight from the CAD file, so the tenth part matches the first and there is no tooling to amortise, which is why most custom sheet metalwork starts at the laser cutting service. A tube laser rotates section under the same beam, so holes, slots, mitres and saddle copes come out in one pass.
A waterjet cuts cold. A hairline stream of water at very high pressure carries a fine abrasive through the material, eroding rather than melting it. Nothing is heated, so there is no burnt edge, no distortion and no change to the structure of the metal. The same nozzle cuts stainless steel, aluminium, brass, copper, stone, glass and composites, which is what the waterjet cutting service is for.
Plasma is an electric arc. Gas forced through a narrow nozzle is ionised into a jet hot enough to melt any conductive metal, and the jet's own velocity blows the melt clear. It is the fastest of the three through thick carbon steel. Hidayath runs it on a rotating pipe axis for round pipe plasma cutting, and on a multi-axis arm for robotic plasma cutting of beams, channels, angles and tube.
Edge quality and the heat-affected zone
A laser edge on sheet is narrow, near vertical and usually needs no rework. As thickness rises the striations on the cut face coarsen and a bead of re-solidified metal, dross, can cling to the bottom edge. The heat-affected zone is narrow but it exists: on stainless it shows as a thin band of heat tint beside the cut, on hardenable carbon steel as a hardened skin.
A plasma edge is wider, carries a slight bevel from the shape of the arc, and leaves dross that is knocked off before the part moves on. On a beam cope or pipe saddle that will be welded none of that matters. On stainless pipe the discolouration is removed by pickling or polishing where the finish matters.
A waterjet edge is a uniform matte with a sand-blasted texture, no heat tint and no burr. On thick material the lower edge shows a slight taper or striation. There is no heat-affected zone at all, which is the whole argument for the process.
ISO 9013 classifies the quality of thermally cut edges, laser and plasma among them, by perpendicularity and surface roughness; a drawing can call up a class from it instead of the word clean.
The Saudi consequence is on stainless. A heat-tinted edge is an oxide over metal that has given up chromium to form it, and in the humid, chloride-bearing air of Jeddah or Dammam that band is where a 304 part starts to stain and pit. Exposed coastal stainless is cut cold, or its heat-cut edges are pickled and passivated before the part leaves the shop.
Which thickness and material suits each process
Thickness and material sort the three processes more than anything else, as engineering practice rather than any one machine's range.
Laser owns thin and medium sheet in stainless, aluminium and carbon steel. It is fastest there and its edge is best there. As plate thickens the cut slows, dross appears and nitrogen consumption on stainless climbs. Copper and brass throw the beam back and are cut thin or not at all, so C26000 brass and C11000 copper sheet are usually waterjet work.
Plasma cuts only what conducts, and its economics improve as carbon steel plate and section thicken. Its natural work is ASTM A36 and S355 plate, beams, channels and pipe wall, where speed and a weld-ready edge are what the fabricator needs.
Waterjet cuts anything that can be clamped flat, at thicknesses beyond where the thermal processes give a usable edge, and it is the only choice for non-metals and for metal that must not see heat. It is slower on everything, so on thin sheet in quantity it loses to laser.
| Process | Cuts by | Heat input | Kerf | Edge | Materials | Typical use |
|---|---|---|---|---|---|---|
| Laser | Focused beam melts the metal; assist gas clears the kerf | Low; narrow heat-affected zone, heat tint on stainless | Narrowest | Fine, near vertical; dross as plate thickens | Stainless, aluminium, carbon steel; brass and copper only thin | Sheet parts, screens, brackets, signage; tube on a tube laser |
| Waterjet | High-pressure water carrying abrasive erodes the material | None; no heat-affected zone, no distortion | Fine, wider than laser | Uniform matte, no burr or tint; slight taper on thick material | Any material: metals, stone, glass, composites | Thick plate, reflective and heat-sensitive metals, blanks for machining |
| Plasma | Ionised gas arc melts conductive metal; jet velocity clears it | Highest; widest heat-affected zone, dross | Widest | Slight bevel, dross to remove; weld-ready after de-slagging | Conductive metals; carbon steel first | Thick carbon steel plate, beams, sections and pipe |
Kerf, tolerance and part geometry
The kerf is the material the process removes, and the program offsets the tool path by half of it so the part comes out to size. A narrow kerf decides how fine a feature can be cut and how tightly parts nest. The laser's is the narrowest, which is why a perforated pattern or mashrabiya screen is laser work; the perforated sheet open area calculator and the article on choosing hole size and pitch start from the same geometry.
Small holes tell the processes apart. A laser cuts a hole close to its own kerf width. A plasma arc struggles once the hole diameter approaches the plate thickness; it leaves a taper and an entry divot, which is why structural bolt holes are plasma-cut only where the specification allows and drilled where it does not. A waterjet cuts a small hole cleanly but pierces slowly, so a part with hundreds of holes costs more than its outline suggests.
Flatness follows heat. A long, narrow laser-cut part in thin stainless can bow as one edge heats before the other. Waterjet puts in no heat, so a large thin part stays flat, which is why decorative panels in mirror or PVD-coated sheet are cut face down under film on the waterjet when the face must arrive untouched, the same bar the V-grooving article sets for folding.
What drives the cost of each process
Cost per part is time on the machine, what the machine consumes, and what has to happen to the part afterwards.
Laser time is short on sheet and the consumables are gas and optics. Nitrogen is the one that counts: a bright stainless or aluminium edge is bought with a high flow of it, and the flow climbs with thickness. Nesting packs parts across the sheet to cut waste, and the sheet is the largest cost line on most stainless jobs; the sheet and plate weight calculator puts a figure on the blank before the enquiry goes in.
Waterjet time is long and the consumable is abrasive, garnet in the main, plus the power to hold the pressure. The slower a material cuts, the more abrasive each metre of edge consumes, so cost tracks thickness and hardness closely. Against that there is no afterwards: no dross, no heat tint, no pickling.
Plasma time is the shortest through thick carbon steel, and its consumables, electrodes and nozzles, are cheap against the metal removed. The afterwards is where its cost sits: de-slagging on every part, grinding or bevelling where the specification calls for a prepared edge, and on stainless the pickling or polishing that removes the heat tint.
Laser and waterjet carry no tooling, so the first part costs what the hundredth costs, and a short run is priced by the metre of cut and the pierce count rather than by a set-up charge.
Choosing between laser, waterjet and plasma
What is the material? Non-metals, copper, brass and heat-sensitive or hardened alloys go to the waterjet. Carbon steel section and pipe go to plasma. 304, 316L and 5052 aluminium sheet go to the laser unless thickness or the edge sends them elsewhere.
How thick is it? Sheet and light plate are laser work; thick plate is waterjet or plasma, split by the next question. The comparison of carbon steel and stainless steel for structural work makes the same point from the material side: carbon steel cuts by plasma without the surface concerns a thermal cut brings to stainless.
What happens to the edge? An edge that will be welded tolerates plasma. An edge that will be machined, polished, seen or exposed to coastal air wants a laser on sheet and a waterjet on plate. An edge that must not be hardened or softened wants the waterjet whatever the thickness.
How many, and how fine? Fine detail and small holes in quantity are laser work. A handful of thick, plain blanks is waterjet or plasma work, and the machine that is free.
Where Hidayath fits
Hidayath Metal Industries operates from three cities, ten locations and three factories in Saudi Arabia, with branches in Jeddah, Riyadh and Dammam; the group began in 1976. The service centre runs all three processes: flatbed laser cutting and tube laser cutting in stainless steel, aluminium and carbon steel; abrasive waterjet cutting of plate, brass, copper and non-metals; and plasma on a rotating pipe axis and on a robotic cell for structural sections. Material comes from Hidayath stock or is customer-supplied, subject to inspection on receipt, and the cut part can carry on to bending, V-grooving, welding, pickling, polishing or PVD on the same order.