Waterjet Cutting
Also: abrasive waterjet, water jet cutting, AWJ, waterjet machining, pure waterjet, garnet waterjet, waterjet profiling, water jet cut parts
Waterjet cutting slices any material with high-pressure water and garnet abrasive: no heat-affected zone, plate to 150 mm thick, ±0.13 mm, a 1 mm kerf and a slight taper.
472 waterjet cutting companies in the Noramark directory
Water pumped to 4,000-6,000 bar (60,000-90,000 psi) passes through a 0.25-0.35 mm diamond or sapphire orifice to form a jet at about three times the speed of sound. Garnet abrasive (80 mesh is typical) is drawn into a mixing chamber and focused by a 0.75-1.0 mm mixing tube, and the abrasive stream erodes the material. Pure water without abrasive cuts soft materials such as gaskets, foam, rubber and food. The head rides a gantry over a tank that catches the spent jet; tilting heads compensate taper and cut bevels, and 5-axis heads cut angled edges.
Because it erodes rather than melts, the process is indifferent to material and hardness and leaves no heat-affected zone, no recast, no hardened edge and no thermal distortion. That makes it the choice for hardened tool steel, tempered aluminum plate, titanium, pre-finished or laminated stock, composites, stone, glass and stacked sheet, and for plate thicker than a laser can manage. It holds ±0.13 mm (±0.005") as standard and ±0.05 mm (±0.002") with care on thinner material, with a kerf of about 1 mm and a sandblasted edge texture.
It is slower and dearer than a laser on thin sheet: a few hundred millimeters a minute in 12 mm steel and tens of millimeters a minute in 100 mm. Thick material cut at production speed shows a 1-2° V-taper and striations toward the bottom of the cut; slowing down or a tilting head fixes both at a price. Piercing laminates can delaminate, garnet embeds in soft materials and lingers in porous ones, and tempered glass shatters.
At a glance
| Typical tolerances | Standard ±0.13 mm (±0.005") on parts up to 25 mm (1") thick; ±0.05 mm (±0.002") with care on material under 12 mm (1/2") with a taper-compensating head and a slow, fine cut; ±0.25-0.5 mm (±0.010-0.020") on 50-150 mm (2-6") plate, where jet lag and taper dominate. Taper is 1-2° (about 0.1-0.2 mm per 10 mm of thickness) on a fixed head at production speed and near zero with a tilting head; the kerf is wider at the top than the bottom. |
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| Size limits | Tables of 1,500 x 3,000 mm (5 x 10 ft) and 2,000 x 4,000 mm (6.5 x 13 ft) are common, with 3,000 x 6,000 mm and larger at some shops. Most shops cut to 100-150 mm (4-6") in steel, aluminum and stone, and 200-300 mm (8-12") is possible on the slowest setting; the practical sweet spot is 3-75 mm (1/8-3"). The kerf is 0.75-1.3 mm (0.030-0.050"), so the smallest inside radius is about 0.5 mm (0.020") and the smallest hole about 1.5 mm (1/16"); small-orifice heads reach a 0.4 mm kerf on thin material. |
| Surface finish | A matte, sandblasted texture: about 3.2 µm Ra (125 µin) on a slow, fine (quality 5) cut, 6.3 µm Ra (250 µin) on a medium (quality 3) cut, and striated with visible lag lines toward the bottom on a fast separation cut (quality 1-2). No heat-affected zone, recast, hardened edge or dross; a light burr where the jet exits comes off with a hand deburr or a tumble. Bearing and sealing edges are machined afterwards. |
| Lead time | Parts in 2-5 business days from stocked plate; production in 1-3 weeks. Cutting time governs on thick material: a nest of 75 mm (3") stainless parts can run for hours, so large orders in thick plate add days. |
Typical of U.S. job shops; confirm with the shop for your part.
Materials
Practically anything. Aluminum in every temper, including 7075 and MIC-6 plate that must not warp; carbon and alloy steel plate (A36, A572, 4140 pre-hard); hardened tool steel (D2 at 60 HRC cuts at nearly the same rate as annealed); stainless 304, 316 and 2205 duplex; titanium, Inconel and Hastelloy; copper, brass and bronze plate. Plastics (UHMW, HDPE, polycarbonate, acrylic, PTFE, Delrin, nylon) cut without melting, and composites (G10/FR4, carbon fiber, Kevlar) cut without fumes, with care on the pierce. Stone, tile, glass (not tempered), rubber, foam and gasket material round it out.
What drives the cost
- Cut length divided by cut speed: thickness and hardness set the speed, which falls steeply above 25 mm (1")
- Edge quality: a fine (Q5) edge cuts at a third to a half the speed of a separation (Q1) cut
- Abrasive: garnet is consumed at 0.3-0.7 kg per minute of cutting and is a large share of the hourly rate
- Pierces: every hole needs a pierce, and pierces are slow in thick or laminated material
- Material cost and yield: thick plate and exotic alloys dominate the price, so nesting and common-line cutting help
- Taper compensation and tolerances below ±0.13 mm (±0.005"), which slow the cut
- Handling and secondaries: lifting thick plate, deburring and machining the datum surfaces
When to use it
- Plate thicker than a laser can cut or where a laser edge is too hard or rough: 25-150 mm (1-6") steel, stainless, aluminum and titanium
- Heat-sensitive material: hardened tool steel, tempered aluminum plate, pre-finished or laminated stock, where a heat-affected zone or warp is unacceptable
- Composites, glass, stone, rubber, foam and plastics that a laser burns or a plasma cannot touch
- Reflective metals in thicknesses a laser struggles with: copper, brass and bronze plate
- Blanks for machining: near-net profiles from expensive alloys with little waste and no edge damage
When not to
- Thin sheet under 3-6 mm (1/8-1/4") in steel, stainless or aluminum: a fiber laser is many times faster and cheaper
- Carbon steel plate over 25 mm (1") where edge quality is not critical: plasma cuts it for less
- Tolerances below ±0.05 mm (±0.002") or square, striation-free edges: wire EDM or machining
- Tempered glass, porous materials that trap garnet, and honeycomb or foam cores that flood
Design tips
- Give inside corners a radius of 0.5-1 mm (0.020-0.040") or more; the jet is about 1 mm wide.
- Keep holes larger than 1.5 times the thickness where possible and expect a slight taper in small holes; ream or drill afterwards for fits.
- Say which edge quality you need (fine, medium or separation) and where; a rough edge on a weld prep is free.
- Ask for taper compensation, or state a taper limit, on parts over 12 mm (1/2") thick that mate on their cut edges.
- Add 0.5-1 mm (0.020-0.040") of machining stock on surfaces that will be finish machined from a waterjet blank.
- Plan the pierce on laminates and composites: a pre-drilled start hole or a low-pressure pierce prevents delamination.
- Send a 1:1 DXF with thickness and material; send a STEP for 5-axis bevel cuts.
- Ask for tabs if the parts must stay in the sheet for handling, or for a drop-out cut if they must not.
Frequently asked questions
- How thick can a waterjet cut?
- Most shops cut steel, aluminum and stone to 100-150 mm (4-6"), and 200-300 mm (8-12") is possible on the slowest, highest-quality setting. Above about 75 mm (3") the cut slows to tens of millimeters a minute and taper and jet lag grow, so tolerances loosen and the price climbs.
- Waterjet or laser cutting?
- Laser for sheet and plate up to about 25 mm (1") in steel, stainless and aluminum: faster, cheaper and ±0.1 mm. Waterjet for thicker plate, for anything heat-sensitive or hardened, for composites, stone and glass, and for reflective metals in thickness. Many shops run both and split a job between them.
- What tolerance can waterjet cutting hold?
- ±0.13 mm (±0.005") is standard up to 25 mm (1") thick. With a taper-compensating head and a slow fine cut, ±0.05 mm (±0.002") is achievable under 12 mm. Thick plate of 50-150 mm loosens to ±0.25-0.5 mm (±0.010-0.020") because the jet lags and tapers.
- Does waterjet cutting have a heat-affected zone?
- No. The jet erodes the material at close to room temperature, so there is no melting, recast layer, hardened edge or thermal distortion. That is why hardened tool steel, tempered aluminum, titanium and pre-finished stock are waterjet cut, and why a waterjet blank machines like the parent plate.
- What materials can be waterjet cut?
- Nearly all of them: any metal at any hardness, plastics, rubber, foam, composites, stone, tile, glass and wood. The exceptions are tempered glass, which shatters, some porous materials that trap abrasive, and diamond. Pure water without abrasive cuts soft materials such as gaskets and food.
