Jerry
124 lines
4.4 KiB
Markdown
124 lines
4.4 KiB
Markdown
# 8 — Centrifugal pump impeller
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> **Prompt**
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>
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> Design a centrifugal pump impeller: a 90 mm diameter back-plate with a central 12 mm bore and a raised hub, and seven backward-curved blades that sweep from the hub out to the rim, each blade curving smoothly along its path.
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Fully parametric OpenSCAD built from the prompt above — adjustable dimensions and colours, exported as `.SCAD` and rendered to the orbiting preview with [`render.sh`](render.sh).
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<p align="center"><img src="08-centrifugal-impeller.gif" alt="Centrifugal pump impeller — orbiting render" width="380"></p>
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**Parametric controls:** 10 dimensions · 1 colour
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**What it demonstrates**
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- Seven **backward-curved blades** swept along curved paths (BOSL2) in a clean radial array
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- Raised central hub with a 12 mm bore on a circular back-plate
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- Smooth turbomachinery surfaces, fused manifold to the plate
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**Editable parameters**
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| Parameter | Default | Range / options | Description |
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| --- | --- | --- | --- |
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| `impeller_diameter` | `90` | `[50:1:150]` | Outer diameter of the impeller back-plate |
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| `bore_diameter` | `12` | `[4:0.5:30]` | Diameter of the central bore hole |
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| `backplate_thickness` | `3` | `[1:0.5:10]` | Thickness of the main back-plate |
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| `hub_diameter` | `26` | `[15:1:50]` | Outer diameter of the raised central hub |
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| `hub_height` | `20` | `[10:1:60]` | Total height of the hub from the bottom of the back-plate |
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| `blade_count` | `7` | `[3:1:15]` | Number of backward-curved blades |
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| `blade_height` | `12` | `[2:1:40]` | Height of the blades above the back-plate |
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| `blade_thickness` | `3` | `[1:0.5:8]` | Thickness of each blade |
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| `sweep_angle` | `75` | `[10:1:180]` | The angle (in degrees) that the blades sweep backwards |
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| `part_color` | `"#B0C4DE"` | `LightSteelBlue` | |
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| `steps` | `48` | `Curve resolution` | |
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<details>
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<summary>OpenSCAD source — <code>08-centrifugal-impeller.scad</code></summary>
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```scad
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include <BOSL2/std.scad>
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/* [Main Dimensions] */
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// Outer diameter of the impeller back-plate
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impeller_diameter = 90; // [50:1:150]
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// Diameter of the central bore hole
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bore_diameter = 12; // [4:0.5:30]
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// Thickness of the main back-plate
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backplate_thickness = 3; // [1:0.5:10]
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/* [Hub Dimensions] */
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// Outer diameter of the raised central hub
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hub_diameter = 26; // [15:1:50]
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// Total height of the hub from the bottom of the back-plate
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hub_height = 20; // [10:1:60]
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/* [Blade Parameters] */
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// Number of backward-curved blades
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blade_count = 7; // [3:1:15]
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// Height of the blades above the back-plate
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blade_height = 12; // [2:1:40]
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// Thickness of each blade
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blade_thickness = 3; // [1:0.5:8]
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// The angle (in degrees) that the blades sweep backwards
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sweep_angle = 75; // [10:1:180]
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/* [Appearance] */
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part_color = "#B0C4DE"; // LightSteelBlue
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$fn = 64;
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module centrifugal_impeller() {
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difference() {
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union() {
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// Back-plate
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cyl(d=impeller_diameter, l=backplate_thickness, chamfer1=1, anchor=BOTTOM);
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// Raised Hub
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cyl(d=hub_diameter, l=hub_height, chamfer2=1.5, anchor=BOTTOM);
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// Blades (logarithmic spiral for constant incidence angle)
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// Inner radius overlaps the hub slightly to ensure a solid union
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blade_inner_r = (hub_diameter / 2) - 0.5;
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// Outer radius stops slightly short of the rim so the round endcaps don't overhang
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blade_outer_r = (impeller_diameter / 2) - (blade_thickness / 2);
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steps = 48; // Curve resolution
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// Calculate the 2D path of the sweeping blade
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pts = [
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for(i = [0 : steps])
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let(
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t = i / steps,
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r = blade_inner_r * pow(blade_outer_r / blade_inner_r, t),
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a = -sweep_angle * t
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)
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[r * cos(a), r * sin(a)]
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];
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// Distribute and extrude the 7 blades
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for(i = [0 : blade_count - 1]) {
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zrot(i * 360 / blade_count)
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up(backplate_thickness)
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linear_extrude(height = blade_height)
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stroke(pts, width=blade_thickness, endcaps="round");
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}
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}
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// Central Bore (subtracted at the end to ensure a clean hole through hub and blades)
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down(1)
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cyl(d=bore_diameter, l=hub_height + 2, anchor=BOTTOM);
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}
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}
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color(part_color)
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centrifugal_impeller();
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```
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</details>
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