Design for Waterjet Cutting — DFM Guide
Design rules for waterjet that maximize cut quality, minimize cost, and ensure manufacturable parts.
Kerf & Lead-Ins
Waterjet kerf is 0.030"–0.050" depending on orifice/nozzle combination. Compensation is automatic in the CAM software but designers should account for kerf when specifying inside features near edges — minimum web width should be 2x the kerf (0.060"+) to avoid breakthrough. Lead-in pierce points should be placed in waste material or on the scrap side of the cut.
Tab Design for Nested Parts
Small parts nested on a sheet need tabs to prevent them from falling into the tank and being damaged by the abrasive stream. Tabs are typically 0.020"–0.060" wide and are snapped or ground off after cutting. Design tab locations on non-critical edges. If the part cannot tolerate tab witness marks, specify tabless cutting (parts fall into a softcatch system — not all shops have this).
Nesting Efficiency
Waterjet parts are almost always nested — multiple parts arranged on a single sheet to minimize material waste and machine time. Design parts with nesting in mind: parallel straight edges that pack tightly, common-line cutting where adjacent parts share a cut line, and standardized material thicknesses. Good nesting can reduce material cost by 15–30%.
Stack Cutting
Thin materials (under 0.125") can be stacked and cut simultaneously — 4, 8, or even 16 layers at once. This multiplies throughput proportionally. Design for stack cutting by using locating features or a fixture frame. Material must lay flat without air gaps. Stack cutting is the key to making waterjet cost-competitive with stamping on thin parts at moderate volumes.
Pierce Sensitivity
The initial pierce creates a momentary burst of high-pressure water that can crack brittle materials (glass, ceramic, thin stone). Use low-pressure pierce or oscillating pierce for brittle materials. On metals, the pierce creates a small crater — locate pierce points in waste material, not on the finished edge. Avoid piercing closer than 0.250" to an edge on brittle materials.
Thickness Considerations
Design to the thinnest material that meets structural requirements — waterjet cut time scales almost linearly with thickness. A part cut from 0.500" plate costs roughly half as much as the same part from 1" plate (in machine time). Material cost also scales with thickness. If your design allows 0.375" instead of 0.500", you'll see 20–25% cost reduction.
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