Selective Laser Melting (SLM / LPBF) creates complex internal channels for non-pressure-retaining fluid-control parts.
Integrated geometry and precision
- Conformal variable-section channels, curved passages, cooling channels and multistage labyrinth trim can be built as integrated parts.
- Reference dimensional accuracy: ±0.02 mm. General process range: 20–80 μm layers and 20–250 μm laser spot, selected for the machine and feature.
- Internal finish after polishing: Ra ≤1.6 μm; the proposal gives Ra 0.4 μm as an abrasive-flow polishing reference. This is a finished-surface value.
Six-stage manufacturing workflow
- Flow design / scanning: CFD analysis, curved-channel optimisation and pressure-reduction allocation.
- 3D modelling: parametric channels and STL / STP model output.
- SLM build: TC4, Inconel 625 / 718 or AlSi10Mg; the example production workflow uses 20–40 μm layers.
- Post-processing: hot isostatic pressing (HIP), heat treatment and abrasive-flow polishing to the specified finish.
- Inspection: metallography, tensile tests, PT / UT and coordinate measurement according to the inspection plan.
- Assembly and delivery: sealing-face finishing, final assembly and functional tests. Qualifying urgent parts target 15 working days.
Pressure reduction, particle transport and cleaning
- Gradual section changes distribute pressure reduction across stages. The proposal reports pressure-loss reductions of 20–35% for optimised designs.
- Sinusoidal or smoothly curved centre lines are evaluated to manage secondary flow and cavitation risk.
- Sloped floors and spiral serrations guide catalyst particles, rust and welding debris toward the outlet.
| Feature | Reference geometry | Conventional process boundary | SLM design approach |
|---|---|---|---|
| Rounded internal corners | R ≥0.5 mm; ≥1.0 mm at turns | Open surfaces are accessible to CNC / EDM; enclosed deep channels restrict tool access. | Integrated rounded passages without internal joints |
| Self-cleaning floor | ≥3° | Five-axis machining can form an open sloped groove; enclosed paths are more constrained. | A continuous slope guides particles toward the outlet |
| Minimum passage | ≥2.5 mm | Straight drilling can achieve smaller bores; a small diameter alone is not an SLM advantage. | Variable-section geometry; the proposal also describes 1.2 mm channels, subject to build and powder-removal review |
| Spiral serrations | 45° ±5° | Straight / axial teeth can be machined; spatially curved internal combinations are constrained. | Spiral features combined with variable sections support particle transport |
Conventional investment casting, CNC and EDM remain suitable for accessible straight-hole staged cages. The proposal cites an 18-month black-water valve example. The SLM opportunity is the combined enclosed variable-section, sloped-floor and spiral geometry.
Reference values from the technical proposal. Results depend on the material, component, processing condition and operating duty; the drawing and agreed acceptance plan govern each order.
For non-pressure-retaining wear parts: valve trim, seats and sealing surfaces. Pressure-retaining components require project-specific qualification before acceptance.
Application examples
- Slurry valve trim for an iron-ore concentrator — The presentation reports continuous operation of at least 12 months and a cost reduction exceeding 50%.
- Feedwater recirculation valve seat at a thermal power plant — The presentation reports 16 months of continuous operation and no maintenance during the reported run, replacing the previous repeated-maintenance pattern.
- Inconel 625 choke cage for an oilfield injection well — The presentation reports 16 months of continuous operation, a threefold service-life improvement and annual total-cost savings of CNY 1.14 million.