156 lines
4.0 KiB
Markdown
156 lines
4.0 KiB
Markdown
# 🛠 Calibration & Tolerance Testing
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*PVC Friction-Fit Dial-In System*
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This folder contains OpenSCAD scripts and calibration STLs used to fine-tune the press-fit connection between the modular PVC frame and 3D-printed hubs.
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---
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## 🎯 The Challenge
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PVC pipe OD varies by brand + batch.
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3D printers introduce tolerance changes due to:
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- Shrinkage
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- Flow variance
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- Layer squish
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- Heat expansion
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To achieve the ideal **“firm twist, no hammer”** fit, we use **Ring Tests** to identify the correct clearance offset.
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---
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## 📋 Test Parameters
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| Setting | Value |
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|--------|-------|
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| Material | PLA+ (re-test per brand change) |
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| Printer | Elegoo Centauri Carbon (CoreXY) |
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| Wall Thickness | 3.0 mm |
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| Test Height | 10 mm |
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| Inner Surface | Chamfered 3 mm |
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---
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## 🔍 Notch System — Physical Versioning
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Each ring includes notches on the outer wall that define its offset.
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| Notches | 1″ Offset | ½″ Offset | Fit Description |
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|:------:|:---------:|:---------:|----------------|
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| 1 | +0.05 mm | +0.10 mm | Extreme press-fit (heat needed) |
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| 2 | +0.10 mm | +0.15 mm | Structural tight fit |
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| 3 | +0.15 mm | +0.20 mm | **Current Standard — Recommended** |
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| 4 | +0.20 mm | +0.25 mm | Smooth sliding fit |
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| 5 | +0.25 mm | +0.30 mm | Loose / removable |
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| 6 | +0.30 mm | +0.35 mm | Oversized — needs shim |
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> Current Winner (as of R1): **Notch 3** on **Charlotte Pipe** + **PLA+**
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---
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## 🚀 How to Run a New Calibration
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Run this when:
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- New filament
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- New PVC supplier
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- Temperature change in workspace
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**Process**
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1. Open `tolerance_test_array.scad`
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2. Select correct pipe size block (1″ or ½″)
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3. Render + export STL
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4. Print @ 0.20 mm layer height (no supports)
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5. Test each ring using **the actual pipe**
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6. Update `fit_offset` in hub OpenSCAD files
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➡ Files to update:
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- `hub_H1.scad`
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- `hub_H2.scad`
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- `hub_H3.scad`
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Record results in **CHANGELOG.md**
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---
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## ⚠️ Flow Rate First
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Before testing tolerances:
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- Calibrate **extrusion multiplier**
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- Ensure **bed leveling** is perfect
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- Dry filament if needed
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Bad flow = bad sockets.
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---
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## 🌡️ Environmental + Speed Troubleshooting
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| Issue | Symptom | Root Cause | Quick Fix |
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|------|---------|------------|-----------|
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| Thermal Expansion | Morning fit ≠ afternoon fit | Workspace heat | Test at real use temp |
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| Wall Bulge | Lumpy inner walls | Overspeed / PA not tuned | Reduce **inner wall speed** |
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| Elephant’s Foot | Jams only at bottom | First layer squish | Chamfer + reduce initial expansion |
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| Moisture | Rough interior / blobs | Wet filament | Dry filament fully |
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---
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## 🛠 Quick Field Repairs
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| Symptom | Fast Fix |
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|--------|----------|
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| Slightly too tight | Sand pipe end w/ 80-grit |
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| Slightly loose | 1 wrap electrical tape |
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| Won’t start at all | Scrape blobs inside socket |
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| Pops out | Warm PVC and flare slightly |
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---
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## 📌 Calibration Status Log
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| Round | Offset | Filament | Printer Profile | Environment | Notes |
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|------|--------|----------|----------------|-------------|------|
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| R1 | +0.15 mm (Notch 3) | PLA+ | 0.4mm / 0.20mm | 22°C Indoor | Current baseline |
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> Update each time PVC or filament changes.
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---
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## Folder Structure
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## 📌 Calibration Status Log
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| Round | Offset | Filament | Printer Profile | Environment | Notes |
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|------|--------|----------|----------------|-------------|------|
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| R1 | +0.15 mm (Notch 3) | PLA+ | 0.4mm / 0.20mm | 22°C Indoor | Current baseline |
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> Update each time PVC or filament changes.
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---
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## Folder Structure
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/calibration
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├── tolerance_test_array.scad
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├── ring_notch_tests/
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│ ├── 1in_ring_test_x6.stl
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│ └── 1-2in_ring_test_x6.stl
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├── results/
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│ ├── R1_report.md
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│ └── images/
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└── README.md (this file)
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---
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## Best Practices Summary
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- Tune flow **before** tolerances
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- Use real pipe sections for testing
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- Store PVC indoors for consistent sizing
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- Validate at expected booth temperature
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---
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If this README is updated, **increment version** in CHANGELOG.
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Version 1.0 — Initial Documentation
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---
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