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fix for extreme profile shifts

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Adrian Mariano 2023-08-05 16:10:53 -04:00
parent 6a20c8c34a
commit a24593041c
1 changed files with 13 additions and 8 deletions
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21
gears.scad
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@ -211,7 +211,7 @@ function _inherit_gear_thickness(thickness) =
// be automatically incorporated. (Consider the situation where one gear mates with multiple other gears.) With modest // be automatically incorporated. (Consider the situation where one gear mates with multiple other gears.) With modest
// profile shifts, you can probably ignore this adjustment, but with more extreme profile shifts, it may be important. // profile shifts, you can probably ignore this adjustment, but with more extreme profile shifts, it may be important.
// You can compute the shortening parameter using {{gear_shorten()}}. Note that the actual shortening distance is obtained // You can compute the shortening parameter using {{gear_shorten()}}. Note that the actual shortening distance is obtained
// by scaling the shortening fator by the gear's module. // by scaling the shortening factor by the gear's module.
// Figure(2D,Big,NoAxes,VPT=[55.8861,-4.31463,8.09832],VPR=[0,0,0],VPD=325.228): With large profile shifts the teeth need to be shortened or they don't have clearance in the valleys of the teeth in the meshing gear. // Figure(2D,Big,NoAxes,VPT=[55.8861,-4.31463,8.09832],VPR=[0,0,0],VPD=325.228): With large profile shifts the teeth need to be shortened or they don't have clearance in the valleys of the teeth in the meshing gear.
// teeth1=25; // teeth1=25;
// teeth2=19; // teeth2=19;
@ -1692,7 +1692,7 @@ function rack2d(
tthick = trans_pitch/PI * (PI/2 + 2*profile_shift * tan(PA)) - backlash, tthick = trans_pitch/PI * (PI/2 + 2*profile_shift * tan(PA)) - backlash,
l = teeth * trans_pitch, l = teeth * trans_pitch,
ax = ang_adj_to_opp(trans_pa, adendum), ax = ang_adj_to_opp(trans_pa, adendum),
dx = ang_adj_to_opp(trans_pa, dedendum), dx = dedendum*tan(trans_pa),
poff = tthick/2 - backlash, poff = tthick/2 - backlash,
tooth = [ tooth = [
[-trans_pitch/2, -dedendum], [-trans_pitch/2, -dedendum],
@ -2365,7 +2365,7 @@ function worm_gear(
assert(is_finite(gear_spin)) assert(is_finite(gear_spin))
let( let(
helical = asin(worm_starts * circ_pitch / PI / worm_diam), helical = asin(worm_starts * circ_pitch / PI / worm_diam),
pr = pitch_radius(circ_pitch, teeth, helical), pr = pitch_radius(circ_pitch, teeth,helical),
hob_rad = worm_diam / 2 + crowning, hob_rad = worm_diam / 2 + crowning,
thickness = worm_gear_thickness(circ_pitch=circ_pitch, teeth=teeth, worm_diam=worm_diam, worm_arc=worm_arc, crowning=crowning, clearance=clearance), thickness = worm_gear_thickness(circ_pitch=circ_pitch, teeth=teeth, worm_diam=worm_diam, worm_arc=worm_arc, crowning=crowning, clearance=clearance),
tooth_profile = _gear_tooth_profile( tooth_profile = _gear_tooth_profile(
@ -2662,9 +2662,11 @@ function _gear_tooth_profile(
? [last(line1), isect_pt, line2[0]] ? [last(line1), isect_pt, line2[0]]
: [line2[0], isect_pt, line1[0]], : [line2[0], isect_pt, line1[0]],
rounded_tooth_half = deduplicate([ rounded_tooth_half = deduplicate([
if (!internal) each arc(n=8, r=round_r, corner=rcorner), if (!internal && round_r>0) each arc(n=8, r=round_r, corner=rcorner),
if (!internal && round_r<=0) isect_pt,
each tooth_half_raw, each tooth_half_raw,
if (internal) each arc(n=8, r=round_r, corner=rcorner), if (internal && round_r>0) each arc(n=8, r=round_r, corner=rcorner),
if (internal && round_r<=0) isect,
]), ]),
// Strip "jaggies" if found. // Strip "jaggies" if found.
@ -3163,7 +3165,10 @@ function worm_gear_thickness(circ_pitch, teeth, worm_diam, worm_arc=60, crowning
// distance between the rack's pitch line and the gear's center. If you set internal1 or internal2 to true then the // distance between the rack's pitch line and the gear's center. If you set internal1 or internal2 to true then the
// specified gear is a ring gear; the returned distance is still the distance between the centers of the gears. Note that // specified gear is a ring gear; the returned distance is still the distance between the centers of the gears. Note that
// for a regular gear and ring gear to be compatible the ring gear must have more teeth and at least as much profile shift // for a regular gear and ring gear to be compatible the ring gear must have more teeth and at least as much profile shift
// as the regular gear. // as the regular gear.
// .
// The backlash parameter computes the distance offset that produces a total backlash of `2*backlash` in the
// two gear mesh system. This is equivalent to giving the same backlash argument to both gears.
// Arguments: // Arguments:
// teeth1 = Total number of teeth in the first gear. If given 0, we assume this is a rack or worm. // teeth1 = Total number of teeth in the first gear. If given 0, we assume this is a rack or worm.
// teeth2 = Total number of teeth in the second gear. If given 0, we assume this is a rack or worm. // teeth2 = Total number of teeth in the second gear. If given 0, we assume this is a rack or worm.
@ -3177,7 +3182,7 @@ function worm_gear_thickness(circ_pitch, teeth, worm_diam, worm_arc=60, crowning
// internal1 = first gear is an internal (ring) gear. Default: false // internal1 = first gear is an internal (ring) gear. Default: false
// internal2 = second gear is an internal (ring) gear. Default: false // internal2 = second gear is an internal (ring) gear. Default: false
// pressure_angle = The pressure angle of the gear. // pressure_angle = The pressure angle of the gear.
// backlash = Add extra space to produce the specified backlash // backlash = Add extra space to produce a total of 2*backlash between the two gears.
// Example(2D,NoAxes): Spur gears (with automatic profile shifting on both) // Example(2D,NoAxes): Spur gears (with automatic profile shifting on both)
// circ_pitch=5; teeth1=7; teeth2=24; // circ_pitch=5; teeth1=7; teeth2=24;
// d = gear_dist(circ_pitch=circ_pitch, teeth1, teeth2); // d = gear_dist(circ_pitch=circ_pitch, teeth1, teeth2);
@ -3248,7 +3253,7 @@ function gear_dist(
pa_eff = _working_pressure_angle(teeth1,profile_shift1,teeth2,profile_shift2,pressure_angle,helical), pa_eff = _working_pressure_angle(teeth1,profile_shift1,teeth2,profile_shift2,pressure_angle,helical),
pa_transv = atan(tan(pressure_angle)/cos(helical)) pa_transv = atan(tan(pressure_angle)/cos(helical))
) )
mod*(teeth1+teeth2)*cos(pa_transv)/cos(pa_eff)/cos(helical)/2 + backlash*cos(helical)/2/tan(pressure_angle); mod*(teeth1+teeth2)*cos(pa_transv)/cos(pa_eff)/cos(helical)/2 + backlash*cos(helical)/tan(pressure_angle);
function _invol(a) = tan(a) - a*PI/180; function _invol(a) = tan(a) - a*PI/180;