80 lines
3.7 KiB
Markdown
80 lines
3.7 KiB
Markdown
🛠 Calibration & Tolerance Testing
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This subfolder contains the utility scripts and STL files used to calibrate the friction-fit tolerances between the 3D-printed connectors and the PVC piping.
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The Challenge
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PVC pipe outer diameters (OD) vary slightly by manufacturer, and 3D printers experience material shrinkage. To achieve a "hammer-tap" friction fit without using glue, we use Ring Tests to find the perfect offset.
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📋 Test Parameters
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Material: [Your Filament, e.g., PLA+]
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Printer: Elegoo Centauri Carbon (CoreXY)
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Wall Thickness: 3.0mm
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Test Height: 10mm
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🔍 Understanding the Notch System
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To avoid confusion after removing parts from the build plate, each ring is physically marked with "Notches" on the outer wall.
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Notches 1" Offset (mm) 1/2" Offset (mm) Fit Description
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1 +0.05 +0.10 Extreme Press-fit (Heat may be required)
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2 +0.10 +0.15 Tight Structural Fit
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3 +0.15 +0.20 Current Project Standard (Winner)
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4 +0.20 +0.25 Standard Sliding Fit
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5 +0.25 +0.30 Loose / Removable Fit
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6 +0.30 +0.35 Oversized / Needs Shim
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🚀 How to Run a New Calibration
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If you switch filament brands or buy PVC from a different hardware store:
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Open tolerance_test_array.scad.
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Render and export the STL for your specific pipe size (1" or 1/2").
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Print with 0.2mm layer height and no supports.
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Test each ring on a scrap piece of the actual pipe you intend to use.
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Update the off or off12 variables in the main hub.scad files with the new winning value.
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⚠️ Maintenance Note
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Because the Centauri Carbon is a high-speed machine, ensure your Flow Rate is calibrated before running these tests. If the flow rate is too high, it will "over-stuff" the walls and make the holes smaller than the CAD intends.
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🌡️ Troubleshooting & Environmental Factors
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3D prints and PVC pipes are both susceptible to thermal expansion and moisture. If your "Winner" (Notch 3) suddenly feels off, check the following:
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1. Thermal Expansion (The Garage Factor)
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The Issue: PVC and PLA/PETG expand when hot. A fit that is perfect in a cool morning might become "seized" in a hot afternoon garage.
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The Fix: If the booth is for outdoor or garage use, calibrate your rings at the average temperature of the workspace. If the fit is too tight to disassemble, use a hair dryer or heat gun (on low) to slightly soften the plastic.
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2. Wall Bulge (Speed & Acceleration)
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The Issue: On high-speed printers like the Centauri Carbon, the printer may "overshoot" corners or circles if the Jerk or Pressure Advance settings aren't dialed in. This causes the inner walls of the socket to bulge inward.
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The Fix: If the ring feels "lumpy" inside rather than smooth, reduce your Inner Wall Speed by 25% and re-test.
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3. Elephant's Foot (First Layer Squish)
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The Issue: If the pipe fits into the top of the hub but gets stuck at the very bottom, you have "Elephant's Foot." The first layer is squished too hard against the bed, narrowing the opening.
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The Fix: Use a deburring tool or a hobby knife to chamfer the inside bottom edge of the print. In the slicer, you can also adjust "Initial Layer Horizontal Expansion" to a negative value (e.g., -0.1mm).
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4. Moisture Absorption (Filament Swelling)
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The Issue: Wet filament (especially PETG or cheap PLA) bubbles and creates a rougher surface texture. This increased friction makes a +0.15mm offset feel like a +0.05mm offset.
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The Fix: Dry your filament. If the surface of your ring test looks "fuzzy" or has tiny zits, your tolerances will never be consistent.
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Quick Reference: "The Field Repair"
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Symptom Quick Fix
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Slightly too tight Sand the tip of the PVC pipe with 80-grit sandpaper.
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Slightly too loose Add one wrap of electrical tape around the end of the PVC pipe.
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Pipe won't go in at all Check for "zits" inside the print; scrape with a flathead screwdriver. |