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Merge pull request #1227 from BelfrySCAD/revarbat_dev

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Improvements to _gear_tooth_profile()
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Revar Desmera 2023-07-31 03:11:00 -07:00 committed by GitHub
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1 changed files with 47 additions and 23 deletions
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gears.scad
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@ -2273,6 +2273,8 @@ function _gear_tooth_profile(
steps = 16,
circ_pitch = circular_pitch(pitch=pitch, circ_pitch=circ_pitch, diam_pitch=diam_pitch, mod=mod),
mod = module_value(circ_pitch=circ_pitch),
clear = default(clearance, 0.25 * mod),
// Calculate the important circle radii
arad = outer_radius(circ_pitch, teeth, helical=helical, profile_shift=profile_shift, internal=internal),
@ -2281,18 +2283,11 @@ function _gear_tooth_profile(
rrad = _root_radius(circ_pitch, teeth, clearance, helical=helical, profile_shift=profile_shift, internal=internal),
srad = max(rrad,brad),
clear = default(clearance, circ_pitch/PI * 0.25),
tthick = circ_pitch/PI / cos(helical) * (PI/2 + 2*profile_shift * tan(pressure_angle)) - backlash,
tang = tthick / prad / 2 * 180 / PI,
// Generate a lookup table for the involute curve angles, by radius
involute_lup = [
if (rrad < brad)
each xy_to_polar(arc(n=4, r=min(brad-rrad,clear), corner=[
polar_to_xy(rrad,90+180/teeth),
polar_to_xy(rrad,90),
polar_to_xy(brad,90),
])),
for (i=[0:5:arad/PI/brad*360])
let(
xy = _involute(brad,i),
@ -2335,10 +2330,7 @@ function _gear_tooth_profile(
undercut_lup = [for (i=idx(undercut)) if (i>=uc_min) undercut[i]],
// The u values to use when generating the tooth.
us = [
for (i=[0.0:0.02:0.2-EPSILON]) i,
for (i=[0:1:steps-1]) 0.2 + i/(steps-1)*0.8,
],
us = [for (i=[0:1:steps*2]) i/steps/2],
// Find top of undercut.
undercut_max = max([
@ -2354,15 +2346,41 @@ function _gear_tooth_profile(
// Generate the left half of the tooth.
tooth_half_raw = deduplicate([
for (u = us) let(
r = lerp(rrad, ma_rad, u),
a1 = lookup(r, involute_lup) + soff,
a2 = lookup(r, undercut_lup),
a = internal || r < undercut_lup[0].x? a1 : min(a1,a2)
) if(a<90+180/teeth) polar_to_xy(r, a),
for (i=[0:1:cap_steps-1]) let(
a = ma_ang + soff - i * (cap_step-1)
) polar_to_xy(ma_rad, a),
for (u = us)
let(
r = lerp(rrad, ma_rad, u),
a1 = lookup(r, involute_lup) + soff,
a2 = lookup(r, undercut_lup),
a = internal || r < undercut_lup[0].x? a1 : min(a1,a2)
)
if ( internal || r > (rrad+clear) )
if (!internal || r < (ma_rad-clear) )
if (a < 90+180/teeth)
polar_to_xy(r, a),
if (!internal)
for (i=[0:1:cap_steps-1]) let(
a = ma_ang + soff - i * (cap_step-1)
) polar_to_xy(ma_rad, a),
]),
// Round out the clearance valley
rcircum = 2 * PI * (internal? ma_rad : rrad),
rpart = (180/teeth-tang)/360,
round_r = min(clear, rcircum*rpart),
line1 = internal
? select(tooth_half_raw,-2,-1)
: select(tooth_half_raw,0,1),
line2 = internal
? [[0,ma_rad],[-1,ma_rad]]
: zrot(180/teeth, p=[[0,rrad],[1,rrad]]),
isect_pt = line_intersection(line1,line2),
rcorner = internal
? [last(line1), isect_pt, line2[0]]
: [line2[0], isect_pt, line1[0]],
rounded_tooth_half = deduplicate([
if (!internal) each arc(n=8, r=round_r, corner=rcorner),
each tooth_half_raw,
if (internal) each arc(n=8, r=round_r, corner=rcorner),
]),
// Strip "jaggies" if found.
@ -2381,14 +2399,20 @@ function _gear_tooth_profile(
mti = !angs? 0 : min_index(angs),
out = concat([path[i]], strip_left(path, i + mti + 1))
) out,
tooth_half = !undercut_max? tooth_half_raw :
strip_left(tooth_half_raw, 0),
tooth_half = !undercut_max? rounded_tooth_half :
strip_left(rounded_tooth_half, 0),
// Mirror the tooth to complete it.
tooth = deduplicate([
full_tooth = deduplicate([
each tooth_half,
each reverse(xflip(tooth_half)),
]),
// Reduce number of vertices.
tooth = path_merge_collinear(
resample_path(full_tooth, n=ceil(2*steps), closed=false)
),
out = center? fwd(prad, p=tooth) : tooth
) out;