CNC Circuit Mill/V2 Design Rationale

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.

Minor Frame Type

• Selected - Blocks on plate (Non-axis frame is a plate; X axis begins with 4 blocks on this plate)

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

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

http://www.rcgroups.com/forums/showthread.php?t=1118773

http://www.tcrconline.com/documents/electric%20flight.pdf

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

Block Dimensions

• 2 dimensions constant for uniformity advantages (40mm, 75mm)

Sleeve Bearing Mount Dimensions

• Mount circle diameter constant for uniformity advantages (32mm)

Leadscrew Nut Mount Dimensions

• Mount circle diameter constant for uniformity advantages (19.05)