Complete

grommet.scad

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+/* ================================================================
+   Cable Grommet for Sheet Metal  —  TPU Print
+   ================================================================
+   Protects cable insulation from sharp drilled-hole edges.
+   
+   The grommet body fits inside the drilled hole while the two
+   flanges seat flush against each face of the sheet metal,
+   creating a smooth, rounded channel for the cable.
+
+   INSTALLATION:
+     Squeeze / fold the grommet (TPU flexibility makes this easy)
+     and press it through the hole until both flanges snap flat
+     against the sheet metal on each side.
+
+   TIPS FOR TPU PRINTING:
+     - 3–4 perimeters / walls for durability
+     - 20–40% infill
+     - No supports needed (prints flat on bottom flange)
+     - Slow print speed recommended (≤ 30 mm/s) for clean bridges
+   ================================================================ */
+
+
+// ================================================================
+//  USER PARAMETERS — edit these to match your application
+// ================================================================
+
+// Diameter of the hole drilled in the sheet metal (mm)
+hole_diameter = 13;
+
+// Thickness of the sheet metal (mm)
+sheet_thickness = 1;
+
+// Thickness of the grommet body wall (mm)
+//   This directly sets how large the cable hole is:
+//     cable hole = hole_diameter - 2 x wall_thickness
+//   Decrease to widen the cable hole; increase to narrow it.
+wall_thickness = 2.0;
+
+// How far each flange lip extends beyond the hole edge (mm)
+//   Larger value = more grip on the sheet metal.
+flange_lips_overhang = 2.0;
+
+// Thickness of each flange lip (mm)
+flange_lips_thickness = 2.0;
+
+// Chamfer radius at each cable entry/exit (mm)
+//   This is the most important feature for insulation protection.
+//   The chamfer creates a smooth funnel so the cable never contacts
+//   a sharp edge even under vibration or flex.
+cable_chamfer = 0;
+
+
+// ================================================================
+//  RENDERING QUALITY
+// ================================================================
+$fn = 128;
+
+
+// ================================================================
+//  DERIVED VALUES  (do not edit below this line)
+// ================================================================
+_body_d    = hole_diameter;
+_flange_d  = hole_diameter + (2 * flange_lips_overhang);
+_cable_d   = _body_d - (2 * wall_thickness);
+_body_len  = sheet_thickness;
+_total_h   = (2 * flange_lips_thickness) + _body_len;
+
+// Sanity-check echoes (visible in OpenSCAD console)
+echo(str("=== Cable Grommet Summary ==="));
+echo(str("  Body outer diameter : ", _body_d,   " mm"));
+echo(str("  Flange diameter     : ", _flange_d, " mm"));
+echo(str("  Cable hole diameter : ", _cable_d,      " mm"));
+echo(str("  Wall thickness      : ", wall_thickness, " mm"));
+echo(str("  Total height        : ", _total_h,       " mm"));
+if (wall_thickness < 1.5) {
+    echo("  WARNING: Wall thickness is thin — consider increasing wall_thickness.");
+}
+if (_cable_d <= 0) {
+    echo("  ERROR: wall_thickness is too large — cable hole is zero or negative.");
+}
+if (cable_chamfer > flange_lips_thickness) {
+    echo("  WARNING: cable_chamfer is larger than flange_lips_thickness — chamfer will be clipped.");
+}
+
+
+// ================================================================
+//  MODULE
+// ================================================================
+module grommet() {
+    difference() {
+
+        // ── OUTER SHELL ──────────────────────────────────────────
+        union() {
+            // Bottom flange
+            // Wider at the sheet metal face, narrower at the outer (free) face.
+            cylinder(d1 = _flange_d - 1.5, d2 = _flange_d, h = flange_lips_thickness);
+
+            // Body — the section that lives inside the drilled hole
+            translate([0, 0, flange_lips_thickness])
+                cylinder(d = _body_d, h = _body_len);
+
+            // Top flange
+            // Wider at the sheet metal face, narrower at the outer (free) face.
+            translate([0, 0, flange_lips_thickness + _body_len])
+                cylinder(d1 = _flange_d, d2 = _flange_d - 1.5, h = flange_lips_thickness);
+        }
+
+        // ── CABLE BORE ────────────────────────────────────────────
+        // Straight through-hole for the cable
+        translate([0, 0, -0.01])
+            cylinder(d = _cable_d, h = _total_h + 0.02);
+
+        // ── BOTTOM ENTRY CHAMFER ──────────────────────────────────
+        // Smooth funnel on the side the cable enters from.
+        translate([0, 0, -0.01])
+            cylinder(
+                d1 = _cable_d + (2 * cable_chamfer),
+                d2 = _cable_d,
+                h  = cable_chamfer + 0.01
+            );
+
+        // ── TOP EXIT CHAMFER ──────────────────────────────────────
+        // Mirror chamfer on the other side — equally important when
+        // the cable flexes back toward the sheet metal.
+        translate([0, 0, _total_h - cable_chamfer + 0.01])
+            cylinder(
+                d1 = _cable_d,
+                d2 = _cable_d + (2 * cable_chamfer),
+                h  = cable_chamfer + 0.01
+            );
+    }
+}
+
+
+// ================================================================
+//  RENDER
+// ================================================================
+grommet();