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#! /usr/bin/env python
# -*- coding: utf-8 -*-
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" "
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'''
Copyright ( C ) 2007 Aaron Spike ( aaron @ ekips . org )
Copyright ( C ) 2007 Tavmjong Bah ( tavmjong @ free . fr )
Copyright ( C ) http : / / cnc - club . ru / forum / viewtopic . php ? f = 33 & t = 434 & p = 2594 #p2500
Copyright ( C ) 2014 Jürgen Weigert ( juewei @fabmail.org )
This program is free software ; you can redistribute it and / or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation ; either version 2 of the License , or
( at your option ) any later version .
This program is distributed in the hope that it will be useful ,
but WITHOUT ANY WARRANTY ; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE . See the
GNU General Public License for more details .
You should have received a copy of the GNU General Public License
along with this program ; if not , write to the Free Software
Foundation , Inc . , 59 Temple Place , Suite 330 , Boston , MA 02111 - 1307 USA
2014 - 03 - 20 jw @suse.de 0.2 Option - - accuracy = 0 for automatic added .
2014 - 03 - 21 sent upstream : https : / / bugs . launchpad . net / inkscape / + bug / 1295641
2014 - 03 - 21 jw @suse.de 0.3 Fixed center of rotation for gears with odd number of teeth .
2014 - 04 - 04 juewei 0.7 Revamped calc_unit_factor ( ) .
2014 - 04 - 05 juewei 0.7 a Correctly positioned rack gear .
The geometry above the meshing line is wrong .
2014 - 04 - 06 juewei 0.7 b Undercut detection added . Reference :
http : / / nptel . ac . in / courses / IIT - MADRAS / Machine_Design_II / pdf / 2_2. pdf
Manually merged https : / / github . com / jnweiger / inkscape - gears - dev / pull / 15
2014 - 04 - 07 juewei 0.7 c Manually merged https : / / github . com / jnweiger / inkscape - gears - dev / pull / 17
2014 - 04 - 09 juewei 0.8 Fixed https : / / github . com / jnweiger / inkscape - gears - dev / issues / 19
Ring gears are ready for production now . Thanks neon22 for driving this .
Profile shift implemented ( Advanced Tab ) , fixing
https : / / github . com / jnweiger / inkscape - gears - dev / issues / 9
2015 - 05 - 29 juewei 0.9 ported to inkscape 0.91
AttributeError : ' module ' object inkex has no attribute ' uutounit
Fixed https : / / github . com / jnweiger / inkscape - gears - dev
'''
from os import devnull # for debugging
from math import pi , cos , sin , tan , radians , degrees , ceil , asin , acos , sqrt
two_pi = 2 * pi
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import argparse
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from boxes . vectors import kerf , vdiff , vlength
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__version__ = ' 0.9 '
def linspace ( a , b , n ) :
""" return list of linear interp of a to b in n steps
- if a and b are ints - you ' ll get an int result.
- n must be an integer
"""
return [ a + x * ( b - a ) / ( n - 1 ) for x in range ( 0 , n ) ]
def involute_intersect_angle ( Rb , R ) :
" "
Rb , R = float ( Rb ) , float ( R )
return ( sqrt ( R * * 2 - Rb * * 2 ) / ( Rb ) ) - ( acos ( Rb / R ) )
def point_on_circle ( radius , angle ) :
" return xy coord of the point at distance radius from origin at angle "
x = radius * cos ( angle )
y = radius * sin ( angle )
return ( x , y )
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### Undercut support functions
def undercut_min_teeth ( pitch_angle , k = 1.0 ) :
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"""
computes the minimum tooth count for a
spur gear so that no undercut with the given pitch_angle ( in deg )
and an addendum = k * metric_module , where 0 < k < 1
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Note :
The return value should be rounded upwards for perfect safety . E . g .
min_teeth = int ( math . ceil ( undercut_min_teeth ( 20.0 ) ) ) # 18, not 17
"""
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x = max ( sin ( radians ( pitch_angle ) ) , 0.01 )
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return 2 * k / ( x * x )
def undercut_max_k ( teeth , pitch_angle = 20.0 ) :
""" computes the maximum k value for a given teeth count and pitch_angle
so that no undercut occurs .
"""
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x = max ( sin ( radians ( pitch_angle ) ) , 0.01 )
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return 0.5 * teeth * x * x
def undercut_min_angle ( teeth , k = 1.0 ) :
""" computes the minimum pitch angle, to that the given teeth count (and
profile shift ) cause no undercut .
"""
return degrees ( asin ( min ( 0.856 , sqrt ( 2.0 * k / teeth ) ) ) ) # max 59.9 deg
def have_undercut ( teeth , pitch_angle = 20.0 , k = 1.0 ) :
""" returns true if the specified number of teeth would
cause an undercut .
"""
return ( teeth < undercut_min_teeth ( pitch_angle , k ) )
## gather all basic gear calculations in one place
def gear_calculations ( num_teeth , circular_pitch , pressure_angle , clearance = 0 , ring_gear = False , profile_shift = 0. ) :
""" Put base calcs for spur/ring gears in one place.
- negative profile shifting helps against undercut .
"""
diametral_pitch = pi / circular_pitch
pitch_diameter = num_teeth / diametral_pitch
pitch_radius = pitch_diameter / 2.0
addendum = 1 / diametral_pitch
dedendum = addendum
dedendum * = 1 + profile_shift
addendum * = 1 - profile_shift
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if ring_gear :
addendum = addendum + clearance # our method
else :
dedendum = dedendum + clearance # our method
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base_radius = pitch_diameter * cos ( radians ( pressure_angle ) ) / 2.0
outer_radius = pitch_radius + addendum
root_radius = pitch_radius - dedendum
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# Tooth thickness: Tooth width along pitch circle.
tooth_thickness = ( pi * pitch_diameter ) / ( 2.0 * num_teeth )
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return ( pitch_radius , base_radius ,
addendum , dedendum , outer_radius , root_radius ,
tooth_thickness
)
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def generate_rack_points ( tooth_count , pitch , addendum , pressure_angle ,
base_height , tab_length , clearance = 0 , draw_guides = False ) :
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""" Return path (suitable for svg) of the Rack gear.
- rack gear uses straight sides
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- involute on a circle of infinite radius is a simple linear ramp
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- the meshing circle touches at y = 0 ,
- the highest elevation of the teeth is at y = + addendum
- the lowest elevation of the teeth is at y = - addendum - clearance
- the base_height extends downwards from the lowest elevation .
- we generate this middle tooth exactly centered on the y = 0 line .
( one extra tooth on the right hand side , if number of teeth is even )
"""
spacing = 0.5 * pitch # rolling one pitch distance on the spur gear pitch_diameter.
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# roughly center rack in drawing, exact position is so that it meshes
# nicely with the spur gear.
# -0.5*spacing has a gap in the center.
# +0.5*spacing has a tooth in the center.
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if tab_length < = 0.0 :
tab_length = 1E-8
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tas = tan ( radians ( pressure_angle ) ) * addendum
tasc = tan ( radians ( pressure_angle ) ) * ( addendum + clearance )
base_top = addendum + clearance
base_bot = addendum + clearance + base_height
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x_lhs = - pitch * 0.5 * tooth_count - tab_length
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# Start with base tab on LHS
points = [ ] # make list of points
points . append ( ( x_lhs , base_bot ) )
points . append ( ( x_lhs , base_top ) )
x = x_lhs + tab_length + tasc
# An involute on a circle of infinite radius is a simple linear ramp.
# We need to add curve at bottom and use clearance.
for i in range ( tooth_count ) :
# move along path, generating the next 'tooth'
# pitch line is at y=0. the left edge hits the pitch line at x
points . append ( ( x - tasc , base_top ) )
points . append ( ( x + tas , - addendum ) )
points . append ( ( x + spacing - tas , - addendum ) )
points . append ( ( x + spacing + tasc , base_top ) )
x + = pitch
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# add base on RHS
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x_rhs = x - tasc + tab_length
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points . append ( ( x_rhs , base_top ) )
points . append ( ( x_rhs , base_bot ) )
# We don't close the path here. Caller does it.
# points.append((x_lhs, base_bot))
# Draw line representing the pitch circle of infinite diameter
guide_path = None
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p = [ ]
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if draw_guides :
p . append ( ( x_lhs + 0.5 * tab_length , 0 ) )
p . append ( ( x_rhs - 0.5 * tab_length , 0 ) )
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return ( points , p )
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def generate_spur_points ( teeth , base_radius , pitch_radius , outer_radius , root_radius , accuracy_involute , accuracy_circular ) :
""" given a set of core gear params
- generate the svg path for the gear
"""
half_thick_angle = two_pi / ( 4.0 * teeth ) #?? = pi / (2.0 * teeth)
pitch_to_base_angle = involute_intersect_angle ( base_radius , pitch_radius )
pitch_to_outer_angle = involute_intersect_angle ( base_radius , outer_radius ) - pitch_to_base_angle
start_involute_radius = max ( base_radius , root_radius )
radii = linspace ( start_involute_radius , outer_radius , accuracy_involute )
angles = [ involute_intersect_angle ( base_radius , r ) for r in radii ]
centers = [ ( x * two_pi / float ( teeth ) ) for x in range ( teeth ) ]
points = [ ]
for c in centers :
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# Angles
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pitch1 = c - half_thick_angle
base1 = pitch1 - pitch_to_base_angle
offsetangles1 = [ base1 + x for x in angles ]
points1 = [ point_on_circle ( radii [ i ] , offsetangles1 [ i ] ) for i in range ( 0 , len ( radii ) ) ]
pitch2 = c + half_thick_angle
base2 = pitch2 + pitch_to_base_angle
offsetangles2 = [ base2 - x for x in angles ]
points2 = [ point_on_circle ( radii [ i ] , offsetangles2 [ i ] ) for i in range ( 0 , len ( radii ) ) ]
points_on_outer_radius = [ point_on_circle ( outer_radius , x ) for x in linspace ( offsetangles1 [ - 1 ] , offsetangles2 [ - 1 ] , accuracy_circular ) ]
if root_radius > base_radius :
pitch_to_root_angle = pitch_to_base_angle - involute_intersect_angle ( base_radius , root_radius )
root1 = pitch1 - pitch_to_root_angle
root2 = pitch2 + pitch_to_root_angle
points_on_root = [ point_on_circle ( root_radius , x ) for x in linspace ( root2 , root1 + ( two_pi / float ( teeth ) ) , accuracy_circular ) ]
p_tmp = points1 + points_on_outer_radius [ 1 : - 1 ] + points2 [ : : - 1 ] + points_on_root [ 1 : - 1 ] # [::-1] reverses list; [1:-1] removes first and last element
else :
points_on_root = [ point_on_circle ( root_radius , x ) for x in linspace ( base2 , base1 + ( two_pi / float ( teeth ) ) , accuracy_circular ) ]
p_tmp = points1 + points_on_outer_radius [ 1 : - 1 ] + points2 [ : : - 1 ] + points_on_root # [::-1] reverses list
points . extend ( p_tmp )
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return ( points )
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def inkbool ( val ) :
return val not in ( " False " , False , " 0 " , 0 , " None " , None )
class OptionParser ( argparse . ArgumentParser ) :
types = {
" int " : int ,
" float " : float ,
" string " : str ,
" inkbool " : inkbool ,
}
def add_option ( self , short , long_ , * * kw ) :
kw [ " type " ] = self . types [ kw [ " type " ] ]
names = [ ]
if short :
names . append ( " - " + short . replace ( " - " , " _ " ) [ 1 : ] )
if long_ :
names . append ( " -- " + long_ . replace ( " - " , " _ " ) [ 2 : ] )
self . add_argument ( * names , * * kw )
class Gears ( ) :
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def __init__ ( self , boxes , * * kw ) :
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# an alternate way to get debug info:
# could use inkex.debug(string) instead...
try :
self . tty = open ( " /dev/tty " , ' w ' )
except :
self . tty = open ( devnull , ' w ' ) # '/dev/null' for POSIX, 'nul' for Windows.
# print >>self.tty, "gears-dev " + __version__
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self . boxes = boxes
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self . OptionParser = OptionParser ( )
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self . OptionParser . add_option ( " -t " , " --teeth " ,
action = " store " , type = " int " ,
dest = " teeth " , default = 24 ,
help = " Number of teeth " )
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self . OptionParser . add_option ( " -s " , " --system " ,
action = " store " , type = " string " ,
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dest = " system " , default = ' MM ' ,
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help = " Select system: ' CP ' (Cyclic Pitch (default)), ' DP ' (Diametral Pitch), ' MM ' (Metric Module) " )
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self . OptionParser . add_option ( " -d " , " --dimension " ,
action = " store " , type = " float " ,
dest = " dimension " , default = 1.0 ,
help = " Tooth size, depending on system (which defaults to CP) " )
self . OptionParser . add_option ( " -a " , " --angle " ,
action = " store " , type = " float " ,
dest = " angle " , default = 20.0 ,
help = " Pressure Angle (common values: 14.5, 20, 25 degrees) " )
self . OptionParser . add_option ( " -p " , " --profile-shift " ,
action = " store " , type = " float " ,
dest = " profile_shift " , default = 20.0 ,
help = " Profile shift [in percent of the module]. Negative values help against undercut " )
self . OptionParser . add_option ( " -u " , " --units " ,
action = " store " , type = " string " ,
dest = " units " , default = ' mm ' ,
help = " Units this dialog is using " )
self . OptionParser . add_option ( " -A " , " --accuracy " ,
action = " store " , type = " int " ,
dest = " accuracy " , default = 0 ,
help = " Accuracy of involute: automatic: 5..20 (default), best: 20(default), medium 10, low: 5; good acuracy is important with a low tooth count " )
# Clearance: Radial distance between top of tooth on one gear to bottom of gap on another.
self . OptionParser . add_option ( " " , " --clearance " ,
action = " store " , type = " float " ,
dest = " clearance " , default = 0.0 ,
help = " Clearance between bottom of gap of this gear and top of tooth of another " )
self . OptionParser . add_option ( " " , " --annotation " ,
action = " store " , type = " inkbool " ,
dest = " annotation " , default = False ,
help = " Draw annotation text " )
self . OptionParser . add_option ( " -i " , " --internal-ring " ,
action = " store " , type = " inkbool " ,
dest = " internal_ring " , default = False ,
help = " Ring (or Internal) gear style (default: normal spur gear) " )
self . OptionParser . add_option ( " " , " --mount-hole " ,
action = " store " , type = " float " ,
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dest = " mount_hole " , default = 0. ,
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help = " Mount hole diameter " )
self . OptionParser . add_option ( " " , " --mount-diameter " ,
action = " store " , type = " float " ,
dest = " mount_diameter " , default = 15 ,
help = " Mount support diameter " )
self . OptionParser . add_option ( " " , " --spoke-count " ,
action = " store " , type = " int " ,
dest = " spoke_count " , default = 3 ,
help = " Spokes count " )
self . OptionParser . add_option ( " " , " --spoke-width " ,
action = " store " , type = " float " ,
dest = " spoke_width " , default = 5 ,
help = " Spoke width " )
self . OptionParser . add_option ( " " , " --holes-rounding " ,
action = " store " , type = " float " ,
dest = " holes_rounding " , default = 5 ,
help = " Holes rounding " )
self . OptionParser . add_option ( " " , " --active-tab " ,
action = " store " , type = " string " ,
dest = " active_tab " , default = ' ' ,
help = " Active tab. Not used now. " )
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self . OptionParser . add_option ( " -x " , " --centercross " ,
action = " store " , type = " inkbool " ,
dest = " centercross " , default = False ,
help = " Draw cross in center " )
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self . OptionParser . add_option ( " -c " , " --pitchcircle " ,
action = " store " , type = " inkbool " ,
dest = " pitchcircle " , default = False ,
help = " Draw pitch circle (for mating) " )
self . OptionParser . add_option ( " -r " , " --draw-rack " ,
action = " store " , type = " inkbool " ,
dest = " drawrack " , default = False ,
help = " Draw rack gear instead of spur gear " )
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self . OptionParser . add_option ( " " , " --rack-teeth-length " ,
action = " store " , type = " int " ,
dest = " teeth_length " , default = 12 ,
help = " Length (in teeth) of rack " )
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self . OptionParser . add_option ( " " , " --rack-base-height " ,
action = " store " , type = " float " ,
dest = " base_height " , default = 8 ,
help = " Height of base of rack " )
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self . OptionParser . add_option ( " " , " --rack-base-tab " ,
action = " store " , type = " float " ,
dest = " base_tab " , default = 14 ,
help = " Length of tabs on ends of rack " )
self . OptionParser . add_option ( " " , " --undercut-alert " ,
action = " store " , type = " inkbool " ,
dest = " undercut_alert " , default = False ,
help = " Let the user confirm a warning dialog if undercut occurs. This dialog also shows helpful hints against undercut " )
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def drawPoints ( self , lines , kerfdir = 1 , close = True ) :
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if not lines :
return
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if kerfdir != 0 :
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lines = kerf ( lines , self . boxes . burn * kerfdir , closed = close )
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self . boxes . ctx . save ( )
self . boxes . ctx . move_to ( * lines [ 0 ] )
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for x , y in lines [ 1 : ] :
self . boxes . ctx . line_to ( x , y )
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if close :
self . boxes . ctx . line_to ( * lines [ 0 ] )
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self . boxes . ctx . restore ( )
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def calc_circular_pitch ( self ) :
""" We use math based on circular pitch.
"""
dimension = self . options . dimension
if self . options . system == ' CP ' : # circular pitch
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circular_pitch = dimension * 25.4
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elif self . options . system == ' DP ' : # diametral pitch
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circular_pitch = pi * 25.4 / dimension
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elif self . options . system == ' MM ' : # module (metric)
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circular_pitch = dimension
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else :
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raise ValueError ( " unknown system ' %s ' , try CP, DP, MM " % self . options . system )
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# circular_pitch defines the size in mm
return circular_pitch
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def generate_spokes ( self , root_radius , spoke_width , spokes , mount_radius , mount_hole ,
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unit_factor , unit_label ) :
""" given a set of constraints
- generate the svg path for the gear spokes
- lies between mount_radius ( inner hole ) and root_radius ( bottom of the teeth )
- spoke width also defines the spacing at the root_radius
- mount_radius is adjusted so that spokes fit if there is room
- if no room ( collision ) then spokes not drawn
"""
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if not spokes :
return [ ]
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# Spokes
collision = False # assume we draw spokes
messages = [ ] # messages to send back about changes.
spoke_holes = [ ]
r_outer = root_radius - spoke_width
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try :
spoke_count = spokes
spokes = [ i * 2 * pi / spokes for i in range ( spoke_count ) ]
except TypeError :
spoke_count = len ( spokes )
spokes = [ radians ( a ) for a in spokes ]
spokes . append ( spokes [ 0 ] + two_pi )
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# checks for collision with spokes
# check for mount hole collision with inner spokes
if mount_radius < = mount_hole / 2 :
adj_factor = ( r_outer - mount_hole / 2 ) / 5
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if adj_factor < 0.1 :
# not enough reasonable room
c ollision = True
else :
mount_radius = mount_hole / 2 + adj_factor # small fix
messages . append ( " Mount support too small. Auto increased to %2.2f %s . " % ( mount_radius / unit_factor * 2 , unit_label ) )
# then check to see if cross-over on spoke width
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for i in range ( spoke_count ) :
angle = spokes [ i ] - spokes [ i - 1 ]
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if spoke_width > = angle * mount_radius :
adj_factor = 1.2 # wrong value. its probably one of the points distances calculated below
mount_radius + = adj_factor
messages . append ( " Too many spokes. Increased Mount support by %2.3f %s " % ( adj_factor / unit_factor , unit_label ) )
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# check for collision with outer rim
if r_outer < = mount_radius :
# not enough room to draw spokes so cancel
collision = True
if collision : # don't draw spokes if no room.
messages . append ( " Not enough room for Spokes. Decrease Spoke width. " )
else : # draw spokes
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for i in range ( spoke_count ) :
self . boxes . ctx . save ( )
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start_a , end_a = spokes [ i ] , spokes [ i + 1 ]
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# inner circle around mount
asin_factor = spoke_width / mount_radius / 2
# check if need to clamp radius
asin_factor = max ( - 1.0 , min ( 1.0 , asin_factor ) ) # no longer needed - resized above
a = asin ( asin_factor )
# is inner circle too small
asin_factor = spoke_width / r_outer / 2
# check if need to clamp radius
asin_factor = max ( - 1.0 , min ( 1.0 , asin_factor ) ) # no longer needed - resized above
a2 = asin ( asin_factor )
l = vlength ( vdiff ( point_on_circle ( mount_radius , start_a + a ) ,
point_on_circle ( r_outer , start_a + a2 ) ) )
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self . boxes . moveTo ( * point_on_circle ( mount_radius , start_a + a ) , degrees = degrees ( start_a ) )
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self . boxes . polyline (
l ,
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+ 90 + degrees ( a2 ) , 0 ,
( degrees ( end_a - start_a - 2 * a2 ) , r_outer ) , 0 ,
+ 90 + degrees ( a2 ) ,
l , 90 - degrees ( a ) , 0 ,
( - degrees ( end_a - start_a - 2 * a ) , mount_radius ) ,
0 , 90 + degrees ( a2 ) , 0
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)
self . boxes . ctx . restore ( )
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return messages
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def sizes ( self , * * kw ) :
self . options = self . OptionParser . parse_args ( [ " -- %s = %s " % ( name , value ) for name , value in kw . items ( ) ] )
# Pitch (circular pitch): Length of the arc from one tooth to the next)
# Pitch diameter: Diameter of pitch circle.
pitch = self . calc_circular_pitch ( )
if self . options . drawrack :
base_height = self . options . base_height * unit_factor
tab_width = self . options . base_tab * unit_factor
tooth_count = self . options . teeth_length
width = tooth_count * pitch + 2 * tab_width
height = base_height + 2 * addendum
return 0 , width , height
teeth = self . options . teeth
# Angle of tangent to tooth at circular pitch wrt radial line.
angle = self . options . angle
# Clearance: Radial distance between top of tooth on one gear to
# bottom of gap on another.
clearance = self . options . clearance # * unit_factor
# Replace section below with this call to get the combined gear_calculations() above
( pitch_radius , base_radius , addendum , dedendum ,
outer_radius , root_radius , tooth ) = gear_calculations ( teeth , pitch , angle , clearance , self . options . internal_ring , self . options . profile_shift * 0.01 )
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if self . options . internal_ring :
outer_radius + = self . options . spoke_width
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return pitch_radius , 2 * outer_radius , 2 * outer_radius
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def gearCarrier ( self , r , spoke_width , positions , mount_radius , mount_hole , circle = True , callback = None , move = None ) :
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width = 2 * r + spoke_width
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if self . boxes . move ( width , width , move , before = True ) :
return
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try :
positions = [ i * 360 / positions for i in range ( positions ) ]
except TypeError :
pass
self . boxes . ctx . save ( )
self . boxes . moveTo ( width / 2.0 , width / 2.0 )
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if callback :
self . boxes . cc ( callback , None )
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self . generate_spokes ( r + 0.5 * spoke_width , spoke_width , positions , mount_radius , mount_hole , 1 , " " )
self . boxes . hole ( 0 , 0 , mount_hole )
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for angle in positions :
self . boxes . ctx . save ( )
self . boxes . moveTo ( 0 , 0 , angle )
self . boxes . hole ( r , 0 , mount_hole )
self . boxes . ctx . restore ( )
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self . boxes . moveTo ( r + 0.5 * spoke_width + self . boxes . burn , 0 , 90 )
self . boxes . corner ( 360 , r + 0.5 * spoke_width )
self . boxes . ctx . restore ( )
self . boxes . move ( width , width , move )
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def __call__ ( self , teeth_only = False , move = " " , callback = None , * * kw ) :
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""" Calculate Gear factors from inputs.
- Make list of radii , angles , and centers for each tooth and
iterate through them
- Turn on other visual features e . g . cross , rack , annotations , etc
"""
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self . options = self . OptionParser . parse_args ( [ " -- %s = %s " % ( name , value ) for name , value in kw . items ( ) ] )
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warnings = [ ] # list of extra messages to be shown in annotations
# calculate unit factor for units defined in dialog.
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unit_factor = 1
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# User defined options
teeth = self . options . teeth
# Angle of tangent to tooth at circular pitch wrt radial line.
angle = self . options . angle
# Clearance: Radial distance between top of tooth on one gear to
# bottom of gap on another.
clearance = self . options . clearance * unit_factor
mount_hole = self . options . mount_hole * unit_factor
# for spokes
mount_radius = self . options . mount_diameter * 0.5 * unit_factor
spoke_count = self . options . spoke_count
spoke_width = self . options . spoke_width * unit_factor
holes_rounding = self . options . holes_rounding * unit_factor # unused
# visible guide lines
centercross = self . options . centercross # draw center or not (boolean)
pitchcircle = self . options . pitchcircle # draw pitch circle or not (boolean)
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# Accuracy of teeth curves
accuracy_involute = 20 # Number of points of the involute curve
accuracy_circular = 9 # Number of points on circular parts
if self . options . accuracy is not None :
if self . options . accuracy == 0 :
# automatic
if teeth < 10 : accuracy_involute = 20
elif teeth < 30 : accuracy_involute = 12
else : accuracy_involute = 6
else :
accuracy_involute = self . options . accuracy
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accuracy_circular = max ( 3 , int ( accuracy_involute / 2 ) - 1 ) # never less than three
# print >>self.tty, "accuracy_circular=%s accuracy_involute=%s" % (accuracy_circular, accuracy_involute)
# Pitch (circular pitch): Length of the arc from one tooth to the next)
# Pitch diameter: Diameter of pitch circle.
pitch = self . calc_circular_pitch ( )
# Replace section below with this call to get the combined gear_calculations() above
( pitch_radius , base_radius , addendum , dedendum ,
outer_radius , root_radius , tooth ) = gear_calculations ( teeth , pitch , angle , clearance , self . options . internal_ring , self . options . profile_shift * 0.01 )
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b = self . boxes . burn
# Add Rack (instead)
if self . options . drawrack :
base_height = self . options . base_height * unit_factor
tab_width = self . options . base_tab * unit_factor
tooth_count = self . options . teeth_length
( points , guide_points ) = generate_rack_points ( tooth_count , pitch , addendum , angle ,
base_height , tab_width , clearance , pitchcircle )
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width = tooth_count * pitch + 2 * tab_width
height = base_height + 2 * addendum
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if self . boxes . move ( width , height , move , before = True ) :
return
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self . boxes . cc ( callback , None )
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self . boxes . moveTo ( width / 2.0 , base_height + addendum , - 180 )
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if base_height < 0 :
points = points [ 1 : - 1 ]
self . drawPoints ( points , close = base_height > = 0 )
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self . drawPoints ( guide_points , kerfdir = 0 )
self . boxes . move ( width , height , move )
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return
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# Move only
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width = height = 2 * outer_radius
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if self . options . internal_ring :
width = height = width + 2 * self . options . spoke_width
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if not teeth_only and self . boxes . move ( width , height , move , before = True ) :
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return
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# Detect Undercut of teeth
## undercut = int(ceil(undercut_min_teeth( angle )))
## needs_undercut = teeth < undercut #? no longer needed ?
if have_undercut ( teeth , angle , 1.0 ) :
min_teeth = int ( ceil ( undercut_min_teeth ( angle , 1.0 ) ) )
min_angle = undercut_min_angle ( teeth , 1.0 ) + .1
max_k = undercut_max_k ( teeth , angle )
msg = " Undercut Warning: This gear ( %d teeth) will not work well. \n Try tooth count of %d or more, \n or a pressure angle of %.1f [deg] or more, \n or try a profile shift of %d %% . \n Or other decent combinations. " % ( teeth , min_teeth , min_angle , int ( 100. * max_k ) - 100. )
# alas annotation cannot handle the degree symbol. Also it ignore newlines.
# so split and make a list
warnings . extend ( msg . split ( " \n " ) )
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# All base calcs done. Start building gear
points = generate_spur_points ( teeth , base_radius , pitch_radius , outer_radius , root_radius , accuracy_involute , accuracy_circular )
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if not teeth_only :
self . boxes . moveTo ( width / 2 , height / 2 )
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self . boxes . cc ( callback , None , 0 , 0 )
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self . drawPoints ( points )
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# Spokes
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if not teeth_only and not self . options . internal_ring : # only draw internals if spur gear
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msg = self . generate_spokes ( root_radius , spoke_width , spoke_count , mount_radius , mount_hole ,
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unit_factor , self . options . units )
warnings . extend ( msg )
# Draw mount hole
# A : rx,ry x-axis-rotation, large-arch-flag, sweepflag x,y
r = mount_hole / 2
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self . boxes . hole ( 0 , 0 , r )
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elif not teeth_only :
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# its a ring gear
# which only has an outer ring where width = spoke width
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r = outer_radius + spoke_width + self . boxes . burn
self . boxes . ctx . save ( )
self . boxes . moveTo ( r , 0 )
self . boxes . ctx . arc ( - r , 0 , r , 0 , 2 * pi )
self . boxes . ctx . restore ( )
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# Add center
if centercross :
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cs = pitch / 3.0 # centercross length
self . boxes . ctx . save ( )
self . boxes . ctx . move_to ( - cs , 0 )
self . boxes . ctx . line_to ( + cs , 0 )
self . boxes . ctx . move_to ( 0 , - cs )
self . boxes . ctx . line_to ( 0 , + cs )
self . boxes . ctx . restore ( )
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# Add pitch circle (for mating)
if pitchcircle :
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self . boxes . hole ( 0 , 0 , pitch_radius )
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# Add Annotations (above)
if self . options . annotation :
outer_dia = outer_radius * 2
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if self . options . internal_ring :
outer_dia + = 2 * spoke_width
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notes = [ ]
notes . extend ( warnings )
#notes.append('Document (%s) scale conversion = %2.4f' % (self.document.getroot().find(inkex.addNS('namedview', 'sodipodi')).get(inkex.addNS('document-units', 'inkscape')), unit_factor))
notes . extend ( [ ' Teeth: %d CP: %2.4f ( %s ) ' % ( teeth , pitch / unit_factor , self . options . units ) ,
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' DP: %2.3f Module: %2.4f (mm) ' % ( 25.4 * pi / pitch , pitch ) ,
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' Pressure Angle: %2.2f degrees ' % ( angle ) ,
' Pitch diameter: %2.3f %s ' % ( pitch_radius * 2 / unit_factor , self . options . units ) ,
' Outer diameter: %2.3f %s ' % ( outer_dia / unit_factor , self . options . units ) ,
' Base diameter: %2.3f %s ' % ( base_radius * 2 / unit_factor , self . options . units ) #,
#'Addendum: %2.4f %s' % (addendum / unit_factor, self.options.units),
#'Dedendum: %2.4f %s' % (dedendum / unit_factor, self.options.units)
] )
# text height relative to gear size.
# ranges from 10 to 22 over outer radius size 60 to 360
text_height = max ( 10 , min ( 10 + ( outer_dia - 60 ) / 24 , 22 ) )
# position above
y = - outer_radius - ( len ( notes ) + 1 ) * text_height * 1.2
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for note in notes :
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self . boxes . text ( note , - outer_radius , y )
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y + = text_height * 1.2
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if not teeth_only :
self . boxes . move ( width , height , move )
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if __name__ == ' __main__ ' :
e = Gears ( )
e . affect ( )
# Notes