Final Project - Design Concept

System Overview

The CNC router consists of the following subsystems:

  • Computer: CNC software, machine control software and USB interface.
  • Embedded controller board (on CNC)
  • Stepper motor drivers: x-axis, y-axis and z-axis driver boards
  • Stepper motors: x-motor, y-motor and z-motor.
  • X, Y and Z limit switches
  • DC power supply

    • The overall system block diagram is shown below.

    CNC Block Diagram

    Before I can begin building the CNC router, there are a number of factors that I need to consider:

    Step 1: Key Design Decisions

  • Identifying the right design: mobile bed vs gantry
  • Required cutting area
  • Space available
  • Materials used
  • Tolerances
  • Construction methods
  • Budget

    • Step 2: The Base and X-axis Frame

  • Full supported or partially supported frames
  • Solid or aluminium profile
  • Different frame designs

    • Step 3: The Y-axis Gantry Design

  • Different frame designs
  • Forces and moments on the gantry

    • Step 4: The Z-axis Assembly Design

  • Different designs for Z-axis assembly
  • Forces and moments on the Z-axis assembly
  • Linear bearing rails/rods
  • Plunge arm design

    • Step 5: The Linear Motion System

  • Design of linear motion system
  • Shaft & bushings vs rails & guide blocks vs rods & bushings

    • Step 6: Mechanical Drive Components

  • Choosing right drive components for the design
  • Lead vs ball screws, radial & thrust bearings
  • Belt & pulleys
  • Motor coupling & mounting
  • Availability & cost

    • Step 7: Choice of Motors

  • Stepper vs servo motors
  • Motor sizing, NEMA standards
  • Choosing the right motor for the design

    • Step 8: Cutting Table Design

  • Different cutting table designs
  • T-slot vs perforated vs cutaway beds
  • Vacuum table

    • Step 9: Spindle Options

  • Types of spindles: dedicated or dremel
  • Mounting & cooling options
  • Chip load, cutting force & feed rates

    • Step 10: The Electronics

  • Choosing electronics for the CNC
  • Control panel, wiring & fusing, buttons & switches
  • MPG's, jog wheels & power supplies

    • Step 11: The CNC Controller Options

  • Choosing controller board
  • Choosing motor driver boards
  • Sizing power supplies for CNC
  • Communicating with the host computer

    • Step 12: Selecting the Software

  • CNC related software overview
  • CAD & CAM software
  • NC controller software
  • gcode, json, stl or gerber support
  • Free vs commercial software

    • Phew! Loads of sweat & nervous chewing of fingernails... That's a lot of stuff that need to be considered when designing a CNC machine. I hope to make some headway over the next few weeks, so that I can begin working on some of the subsystems as we progress in the course.