CNC Circuit Mill/V2 Design Rationale
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Frame Objectives
The function of the frame is to move a part of the frame in 3 dimensions (relative to its base).
For performance, a good frame has:
For design, fabrication, assembly, and usage, a good frame also has:
- Uniform Dimensions and Other Parameter Values
- Maximum Simplicity (without sacrificing performance)
- Ease of fabrication, assembly, disassembly, and usage
- Modularity
- Durability
- Scalability
- Safe Operation
For the CNC Circuit Mill, a good frame also has:
- Workpiece mounting platform
- Large working volume of moving part relative to the mounting platform.
Major Frame Type
- Selected - Mobile gantry design (XYZ all linked) allows tremendous scaling potential.
- Mobile bed (X alone, YZ linked) requires a greater non-axis frame to support both X and YZ; scales ineffectively.
Frame Material
- Selected - 6061 Aluminum Alloy for rigidity, ease of machinability, and accessibility
Axis Drive
- Selected - Stepper motors provide high resolution in a simple open-loop system
- AC or DC motors with encoders necessitate complex closed-loop control systems
Rotary-to-Linear
- Selected - Leadscrew and Nut for high velocity ratio and lifetime operation
- Belts stretch and have low velocity ratio
Axis Supports
- Selected - Precision Shafts for ease of manufacturing and direct mounting
- Precision V-Rails
- Precision Extrusions
Spindle Drive
- Selected - Outrunner Brushless DC Motor has maintenance-free operation, over 90% efficiency, commutator-free long lifetime, precision speed control possible, quiet operation, more torque than inrunners
- Brushed DC Motors require regular maintenance, short lifetimes, noisy operation
http://www.youtube.com/watch?v=fPLdHeRQp_w