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    CNC Router Machine Basics

     
    PolyFab's CNC Router
     
    Finished example
         
       
    Finished example
     
         
    Click on images to enlarge
     

    The CNC router is one of the most versatile machines available for cutting plastic, wood, aluminum, brass and other soft materials. The basics of all CNC routers are the spindle or motor which turns a cutting bit at speeds of 18,000 rpm and higher, a mechanical system to move the spindle and/or the workpiece, and a CNC (computer numeric control) controller.

    Machine layout

    The most common arrangement for 3 axis CNC routers holds the workpiece fixed on a table and has a gantry which moves along the long axis (x axis).  The spindle moves from side to side (y axis) and vertically (z axis) on the gantry. All mid range and better machines built today feature simultaneous motion on all three axes.

    Spindles

    The lowest cost CNC routers use fixed speed spindles which are routers designed as hand tools placed in special mounts. Better quality CNC routers use spindles coupled with programmable inverters which allow the spindle speed to be controlled from the CNC controller.  This is important because the rotational speed should be slowed down when the travel speed is slowed down  and also depends on the type of router bit.

    Router bits

    Some of the manufacturers which provide a wide variety of standard bits are:

    Most of these manufacturers have representatives that resell their products.

    CNC Controllers

    The purpose of the CNC controller is to convert commands from the operator into electrical signals that control the electric motors that position the router bit.  Bottom end CNC routers use stepping motors which respond to the number of input pulses to move to the required position.  More accurate machines use servo motors which compare the actual position of the motor to the desired position and force the two to agree.  There is at minimum one servo motor per axis.
    The vast majority of CNC controllers receive instructions from the person programming the motion in the form of “g-code”.  This programming language first appeared in the 1950's and was designed at Massachusetts Institute of Technology. The g-code precisely defines the path of the router bit step by step.  There are many software programs that take the input of the part geometry from a part drawing package and create g-code for the part.  These software packages are so powerful and inexpensive that most shops use them.

    Factors affecting cutting speed

    In soft materials the most important factor affecting cutting speed is the stiffness and precision of the system moving the router bit.  If the results are not accurate enough, the normal reaction is to slow down and take a lighter cut.
    In harder materials the power required to drive the cutting bit becomes important.  The CNC routers with higher horsepower spindles, (above 5 HP) also have high powered and accurate servo motors to position of the router bit at high speed.

    PolyFab provides:

    3D routering for prototypes, special fittings and forms, vee bit carving of signs, 2D cutting of sheet stock in all plastics and wood products. We can accept your electronic file or work from your drawings or sketches.

    Router Services

    CNC router with a 5 ft x 10 ft cutting area and 12 inch vertical travel
    2D and 3D cutting in all plastics and woods

    • Milling
    • Panels
    • Doors
    • Fretwork and grills
    • Sign letters, stencils and 3D carving
    • Molds and forms
    • Patterns
    • Templates
    • Your files accepted

    For 2D cutting: *.dwg, *.dxf, *.eps, *.ai,
    For vee bit carving: *.eps, *.ai,
    For 3D machining: *.igs, *.3dm, *.stl