( spindle-encoder.ngc )
( by Lawrence Glaister VE7IT )
( Sept 15 2007 )
( lerman - thankyou for named variables and owords.... very cool )
( Cut from arborite stock with 0.049" endmill. )
( This encoder ring mounts on the lathe spindle drive pulley. )
( Ring encoder provides A,B,Z phases using 3 H21TLB slot sensors. )
( The H21TLB sensor use 5v and can directly drive parallel port pins. )
( The sensor apeture is 0.035", so I used double that for the slot length )
( to allow for some runout on mounting the ring. )
( The main constraint is that the main track opto has to be able to physically )
( read the inner track... reaching over the outer index track )
( To preview what it will look like, set _endmill_dia = 0.0 below. )
( With a high speed spindle you may be able to cut to depth in 1 pass. )
( This example only cuts to -0.020... this can be edited and the program )
( rerun to do 2 passes )

(======================================================================)
(============================= Subroutines ============================)
( cuts a circle at request diameter around x,y to requested depth )
o100 sub
  (Subroutine to do a circle)
  ( P1=X center P2=Y center P3-diameter P4=depth P5=feedrate )
  g0 z#<_safe_Z>
  g0 x[#1-[#3/2]] y#2
  g1 F[#5/2] z#4
  g2 F[#5] x[#1-[#3/2]] y#2 i[#3/2] j0
  g0 z#<_safe_Z>
o100 endsub

(======================================================================)
(=================== Define Constants/Variables =======================)
#<_endmill_dia> = 0.049  			  	  ( endmill diameter )

#<_safe_Z> = 0.100		                  ( safe Z height )
#<_Zcut> = -0.020		                  ( Z depth to cut encoder elements )
#<_feedrate> = 5.0			              ( cutting feedrate )

( define characteristics of encoder and index tracks )
#<_main_track_dia> = 7.250		          ( diameter of main signal track )
#<_index_track_dia> = [#<_main_track_dia> + 0.140] ( diameter of index track )
#<_inside_cutout> = 5.500                 ( diameter of interior cutout == inside of pulley)
#<_outside_cutout> = 7.525		          ( diameter of exterior cutout ~= enough space for tracks)
#<_encoder_cycles> = 90			  	  ( number of slots to cut 180 * 4 == 1/2 degreee resolution)
#<_slotlen> = 0.070                       ( finished slot length for 1 encoder element ~= sensor aperture + runout )

( define 3 params for the mounting arrangement )
#<_mount_circle> = 6.000				  ( mounting bolt circle diameter )
#<_mount_holes> = 6						  ( number of holes to mill for mounting bolts )
#<_mount_hdia> = 0.150					  ( sloppy #6 or a #8 bolt )

#<_PI> = 3.14159
#<_endmill_rad> = [#<_endmill_dia>/2.0]   ( endmill radius )
#<_encoder_theta>=[360.0/#<_encoder_cycles>]  ( angular step around circle  - degrees)

(======================================================================)
(========================= Start of Main Code =========================)


G20 G90
G64 P.002
G0 z#<_safe_Z>
G0 X0 Y0

m0(DEBUG,spindle_encoder.ngc: #<_encoder_cycles> cycle disk uses #<_endmill_dia> dia endmill, material top,center at 0,0,0 ... unpause[S] when ready)

( cut the main encoder slots )

( compute angular size of cutter at cutting extremes )
#<inner_dia> = [#<_main_track_dia> - #<_slotlen> +  #<_endmill_dia>]
#<outer_dia> = [#<_main_track_dia> + #<_slotlen> -  #<_endmill_dia>]
#<icutter_deg> = [#<_endmill_dia>*360.0/[#<inner_dia>*#<_PI>]]
#<ocutter_deg> = [#<_endmill_dia>*360.0/[#<outer_dia>*#<_PI>]]
#<slot_deg> = [#<_encoder_theta>/2.0 ]
#<slots> = #<_encoder_cycles>     ( counter for cutting this many slots )
#<angle> = 360                    ( starting angle to cut )

( rough check to see if cutter dia and disk resolution are feasible )
o5 if [#<icutter_deg> GT #<slot_deg>]
  (print,icutter_deg= #<icutter_deg>, slot_deg= #<slot_deg>)
  (DEBUG, Unable to cut encoder because #<_endmill_dia> cutter is too large for a #<_encoder_cycles> cycle #<_main_track_dia> dia disk)
  m2
o5 endif
( check to see if we can machine mounting holes )
o7 if [ #<_mount_hdia> LE #<_endmill_dia> ]
  (print,Unable to machine mounting holes as #<_endmill_dia> endmill is too big to cut #<_mount_hdia> dia holes )
  (DEBUG,Unable to machine mounting holes as #<_endmill_dia> endmill is too big to cut #<_mount_hdia> dia holes )
  m2
o7 endif

( main loop to cut encoder slots around disk )
o10 do
  #<centerx> = [#<_main_track_dia>/2.0 * cos[#<angle>]]	 ( x center of slot )
  #<centery> = [#<_main_track_dia>/2.0 * sin[#<angle>]]  ( y center of slot )
  g0 z#<_safe_Z>
  g0 x[#<centerx>] y[#<centery>]
  ( do a cut to the final depth at the cw inner corner of the slot )
  #<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<icutter_deg>/2.0]]
  #<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
  #<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]
  g1 x[#<myx>] y[#<myy>] z[#<_Zcut>] f[#<_feedrate>/2.0]  ( decend to cut depth )

  #<myangle> = [#<angle> + [#<slot_deg>/2.0] - [#<icutter_deg>/2.0]]
  #<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
  #<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]
  #<myr> = SQRT[#<myx>*#<myx> + #<myy>*#<myy>]
  g3 x[#<myx>] y[#<myy>]  r[#<myr>] f[#<_feedrate>] ( cut inside edge of slot )

  #<myangle> = [#<angle> + [#<slot_deg>/2.0] - [#<ocutter_deg>/2.0]]
  #<myx> = [#<outer_dia>/2.0 * cos[#<myangle>]]
  #<myy> = [#<outer_dia>/2.0 * sin[#<myangle>]]
  g1 x[#<myx>] y[#<myy>]                  ( cut ccw edge of slot )

  #<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<ocutter_deg>/2.0]]
  #<myx> = [#<outer_dia>/2.0 * cos[#<myangle>]]
  #<myy> = [#<outer_dia>/2.0 * sin[#<myangle>]]
  #<myr> = SQRT[#<myx>*#<myx> + #<myy>*#<myy>]
  g2 x[#<myx>] y[#<myy>] r[#<myr>]                ( cut outer edge of slot )

  #<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<icutter_deg>/2.0]]
  #<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
  #<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]
  g1 x[#<myx>] y[#<myy>]                  ( cut back to inner cw point of slot )

  g0 z#<_safe_Z>
  #<slots> = [#<slots> -1]
  #<angle> = [#<angle> - #<_encoder_theta>]
o10 while [#<slots> GT 0]

( cutout index hole)

( compute angular size of cutter at cutting extremes )
#<inner_dia> = [#<_index_track_dia> - #<_slotlen> +  #<_endmill_dia>]
#<outer_dia> = [#<_index_track_dia> + #<_slotlen> -  #<_endmill_dia>]
#<icutter_deg> = [#<_endmill_dia>*360.0/[#<inner_dia>*#<_PI>]]
#<ocutter_deg> = [#<_endmill_dia>*360.0/[#<outer_dia>*#<_PI>]]
#<slot_deg> = [#<_encoder_theta>/2.0 ]
#<angle> = 360                    ( starting angle to cut )

#<centerx> = [#<_index_track_dia>/2.0 * cos[#<angle>]]	 ( x center of slot )
#<centery> = [#<_index_track_dia>/2.0 * sin[#<angle>]]  ( y center of slot )
g0 z#<_safe_Z>
g0 x[#<centerx>] y[#<centery>] 
( do a cut to the final depth at the cw inner corner of the slot )
#<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<icutter_deg>/2.0]]
#<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
#<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]
g1 x[#<myx>] y[#<myy>] z[#<_Zcut>] f[#<_feedrate>/2.0]  ( decend to cut depth )

#<myangle> = [#<angle> + [#<slot_deg>/2.0] - [#<icutter_deg>/2.0]]
#<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
#<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]  
#<myr> = SQRT[#<myx>*#<myx> + #<myy>*#<myy>]
g3 x[#<myx>] y[#<myy>]  r[#<myr>] f[#<_feedrate>] ( cut inside edge of slot )

#<myangle> = [#<angle> + [#<slot_deg>/2.0] - [#<ocutter_deg>/2.0]]
#<myx> = [#<outer_dia>/2.0 * cos[#<myangle>]]
#<myy> = [#<outer_dia>/2.0 * sin[#<myangle>]]
g1 x[#<myx>] y[#<myy>]                  ( cut ccw edge of slot )

#<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<ocutter_deg>/2.0]]
#<myx> = [#<outer_dia>/2.0 * cos[#<myangle>]]
#<myy> = [#<outer_dia>/2.0 * sin[#<myangle>]]
#<myr> = SQRT[#<myx>*#<myx> + #<myy>*#<myy>]
g2 x[#<myx>] y[#<myy>] r[#<myr>]              ( cut outer edge of slot )

#<myangle> = [#<angle> - [#<slot_deg>/2.0] + [#<icutter_deg>/2.0]]
#<myx> = [#<inner_dia>/2.0 * cos[#<myangle>]]
#<myy> = [#<inner_dia>/2.0 * sin[#<myangle>]]
g1 x[#<myx>] y[#<myy>]                   ( cut back to inner cw point of slot )

g0 z#<_safe_Z>


( mill some mounting bolt holes )

#<holes> = #<_mount_holes>
#<myangle> = 0
o20 do
    #<myx> = [#<_mount_circle>/2.0 * cos[#<myangle>]]
    #<myy> = [#<_mount_circle>/2.0 * sin[#<myangle>]]
              ( X )      ( Y )             ( Diameter )           ( Depth )    ( Feed )
    o100 call [#<myx>] [#<myy>] [#<_mount_hdia>-#<_endmill_dia>] [#<_Zcut>] [#<_feedrate>] ( one mounting hole )
    #<myangle> = [#<myangle> + [ 360.0/#<_mount_holes>] ]
    #<holes> = [#<holes> -1]
o20 while [ #<holes> GT 0 ]

( cutout encoder ring )
          ( X ) ( Y )             ( Diameter )             ( Depth )    ( Feed )
o100 call [0.0] [0.0] [#<_inside_cutout>-#<_endmill_dia>] [#<_Zcut>] [#<_feedrate>]      ( interior cutout )
o100 call [0.0] [0.0] [#<_outside_cutout>+#<_endmill_dia>] [#<_Zcut>] [#<_feedrate>]      ( exterior cutout )



M2