7.2 KiB
7.2 KiB
Bills Of Materials (BOM) Evaluation
This document outlines and evaluates the Bill of Materials (BOM), pricing structure, and mechanical design decisions for two scales of the DIY/Semi-Professional Portable CNC Router:
- The 1m x 1m Small-Scale Prototype
- The 4' x 8' (1.2m x 2.4m) Full-Sized Production Build
1. Small-Scale Prototype (1m x 1m Working Area)
Objective: Low-cost, fast 3D-printable assembly, standard stepper driver electronics, safety/proof-of-concept testing.
1.1 Mechanical Design Decisions
- Kinematics: 4-Belt suspended triangulation (simplifies initial testing).
- Core Carriage Sled: 3D-printed PLA with 3 anchor points per corner (dual mount holes for up to 8 belts).
- Belts: standard GT2 timing belts (6mm width, reinforced fiberglass) connected to 4 corner anchor pegs.
- Corner Anchors: 3D printed with manual clamp handles.
- Spindle: Dremel-style rotary tool (65mm body clamp adapter) or cheap 500W brushless DC spindle.
1.2 1m x 1m Prototype BOM & Cost Structure
| Category | Component | Description | Qty | Unit Cost ($) | Total Cost ($) | Source / Note |
|---|---|---|---|---|---|---|
| Electronics | ESP32 NodeMCU | 38-Pin development boards with WiFi/BLE | 1 | $6.00 | $6.00 | Amazon/AliExpress |
| Electronics | CNC Shield V3 | standard GRBL Arduino shield (adapted to ESP32 via jumper pins) | 1 | $10.00 | $10.00 | standard CNC breakout board |
| Electronics | TMC2209 Stepper Drivers | Silent step resolution, up to 2.8A peak | 4 | $7.00 | $28.00 | BigTreeTech |
| Power | 24V 10A DC Power Supply | Meanwell LRS-250-24 or similar | 1 | $28.00 | $28.00 | Meanwell |
| Motion | NEMA 17 Stepper Motors | 59 Ncm torque, 1.8 degree step, dual shaft for spools | 4 | $14.00 | $56.00 | StepperOnline |
| Motion | GT2 6mm Timing Belts | 6mm Width Fiberglass, 10m roll | 2 | $12.00 | $24.00 | Amazon/Gates clone |
| Motion | 3D Printed GT2 Spools | Designed to fit NEMA 17 shafts | 4 | $1.50 | $6.00 | Self-printed PLA (approx. cost) |
| Hardware | Skate Bearings (608RS) | For spool guide rollers | 8 | $1.00 | $8.00 | For friction reduction |
| Tooling | Bosch Colt / Makita Body Clone | 65mm body trim router (e.g. vonhaus, katsu) | 1 | $45.00 | $45.00 | Amazon clone router |
| Z-Axis | Mini Linear Slide Stage | Custom Z-axis lift with T8 lead screw & Nema 17 | 1 | $35.00 | $35.00 | Pre-assembled mini-slide |
| Mechanical | Screws, Nuts, Spacers | M4 and M8 bolts/washers assortment | 1 | $15.00 | $15.00 | Local Hardware |
| Total Estimated Cost (Prototype): | $261.00 | Budget-friendly POC build |
2. Full-Size Production Build (4' x 8' / 1.2m x 2.4m Working Area)
Objective: Semi-professional woodworking, high-torque geared DC servos, closed-loop feedback, maximum rigidity, and constraint-locked 8-belt kinematics (Gordix style).
2.1 Mechanical Design Decisions
- Kinematics: 8-Belt constraint-locked kinematics (twin lines running to four corner wall anchors) to lock yaw rotation and prevent sled tipping/slipping over large cutting spans.
- Core Carriage Sled: Heavy-duty, rigid CNC-milled 6mm aluminum baseplate (increases downforce, minimizes router vibration).
- Belts: High-tensile Dyneema/UHMWPE braided cords (1.5mm - 2mm, tested for 300+ kg breaking load). Timing belts are prone to stretching/flapping over 4-meter spans; braided cord behaves as zero-stretch steel cable but wraps cleanly around spools.
- Spindle: Commercial Makita RT0701C wood trim router (1.25 HP, variable speed 10,000-30,000 RPM, 65mm clamp body).
- Drive System: Closed-loop DC geared motors with magnetic/optical encoders. Steppers lose steps when overloaded or if wood chips jam the path; closed-loop gear servos will fault/pause safely or apply corrective torque.
2.2 4'x8' Production BOM & Cost Structure
| Category | Component | Description | Qty | Unit Cost ($) | Total Cost ($) | Source / Note |
|---|---|---|---|---|---|---|
| Controller | Custom ESP32-S3 Maslow 4 board | Custom PCB with ESP32-S3, closed-loop connectors, H-Bridges | 1 | $95.00 | $95.00 | Maslow-style customized board |
| Drive Motors | Etonm ET-WGM58AE | Custom 24V DC geared motor + Planetary Gearbox + High-res encoder | 4 | $45.00 | $180.00 | Spec motor or planetary equivalent |
| Power | 24V 15A DC Power Supply | Meanwell LRS-350-24 | 1 | $38.00 | $38.00 | Meanwell |
| Drive Lines | 2.0mm Dyneema Cord | 100-meter spool (breaking strength 450 kg), zero-stretch | 1 | $35.00 | $35.00 | Marine/Climbing supply |
| Sled Body | Milled Aluminum Sled Plate | 6mm clear anodized aluminum base baseplate | 1 | $75.00 | $75.00 | LaserCut/SendCutSend custom sheet |
| Motion | Custom Machined Spools | Aluminum or high-temp PETG reinforced spools with line guides | 4 | $8.00 | $32.00 | Custom lathe-bored or heavy PETG |
| Spindle | Makita RT0701C Router | Wood Router, 1.25 HP, 120V AC, very reliable | 1 | $110.00 | $110.00 | Makita |
| Z-Axis | Linear Rails + SFU1204 Ball Screw | Dual linear rails (12mm) + active ball-screw lift stage | 1 | $65.00 | $65.00 | AliExpress custom stage |
| Z-Axis Motor | NEMA 17 Stepper + TMC2209 | Handles active vertical wood carving | 1 | $25.00 | $25.00 | Standard stepper |
| Anchoring | CV-Joint Corner Brackets | 3D-molded steel swivel joints for frame corner anchors | 4 | $12.00 | $32.00 | Custom swivels |
| Dust Collection | Dust Boot + Hose | 3D printed active vacuum nozzle wrapping Makita body | 1 | $20.00 | $20.00 | Custom |
| Hardware Assortment | Assorted Locknuts, T-nuts, M4/M8 | Stainless steel fastners assortment | 1 | $30.00 | $32.00 | Assorted stash |
| Total Estimated Cost (Production Sled): | $737.00 | High reliability semi-prof build |
3. Detailed Software & CAM Decisions
To keep our DIY portable design isolated from closed ecosystems, the entire pipeline is structured on open software.
[ CAD Styling: Fusion360 / Onshape / Inkscape ]
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[ CAM Toolpaths: Kiri:Moto / Estlcam / OpenBuilds CAM ]
| (Generates standard G-code .nc)
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[ Web Control GUI: Web Interface hosted on ESP32-S3 Server ]
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[ Motion Controller: FluidNC Custom Kinematics on EPS32 ]
- CAD Modeling: Standard 3D CAD modeling (Onshape or Fusion 360). Flat vector exports from Inkscape/Illustrator for 2D profiles.
- CAM Software: Kiri:Moto (Free, open-source browser-based CAM) or Estlcam (cheap, highly detailed woodworking toolpaths). These generate standard Cartesian G-code (
.ncor.gcode). - Firmware Interpretation: FluidNC captures Cartesian coordinates. The custom kinematics engine translates
(X, Y, Z)Cartesian points into respective belt lengths for the 4 or 8 motor spools. - Active Calibration Loop: Using the Maslow 4 code structure, the router automatically calibrates. By spooling all belts completely in to their hard limits, the machine records the "absolute zero spool tension", then pulls itself to the workspace center to calculate the exact distances to the physical corner frame anchors. No manual measuring tape is required.