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fix some issues with hirth and add skew option

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Adrian Mariano 2024-11-06 16:36:50 -05:00
parent e9b229bb50
commit 785bfb69de
1 changed files with 57 additions and 42 deletions
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joiners.scad
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@ -1247,54 +1247,72 @@ module rabbit_clip(type, length, width, snap, thickness, depth, compression=0.1
// to remove. The teeth valleys are chamfered by half the specified value to ensure that there is room for the parts
// to mate. The base is added based on the unchamfered dimensions of the joint, and the "teeth_bot" anchor is located
// based on the unchamfered dimensions.
// .
// By default the teeth are symmetric, which is ideal for registration and for situations where loading may occur in either
// direction. The skew parameter will skew the teeth by the specified amount, where a skew of ±1 gives a tooth with a vertical
// side either on the left or the right. Intermediate values will produce partially skewed teeth. Note that the skew
// applies after the tooth profile is computed with the specified tooth_angle, which means that the skewed tooth will
// have an altered tooth angle from the one specified.
// .
// The joint is constructed with a tooth peak aligned with the X+ axis.
// For two hirth joints to mate they must have the same tooth count, opposite cone angles, and the chamfer/rounding values
// must be equal. (One can be chamfered and one rounded, but with the same value.) The rotation required to mate the parts
// depends on the skew and whether the tooth count is odd or even. To apply this rotation automatically, set `rot=true`.
// Named Anchors:
// "teeth_bot" = center of the joint, aligned with the bottom of the (unchamfered) teeth, pointing DOWN.
// "mate" = center of the joint, pointing UP, but with the correct spin so that the part will mate with a compatible parent joint.
// "teeth_bot" = center of the joint, aligned with the bottom of the (unchamfered/unrounded) teeth, pointing DOWN.
// Arguments:
// n = number of teeth
// ir/id = inner radius or diameter
// or/od = outer radius or diameter
// tooth_angle = nominal tooth angle. Default: 60
// cone_angle = raise or lower the angle of the teeth in the radial direction. Default: 0
// skew = skew the tooth shape. Default: 0
// chamfer = chamfer teeth by this fraction at tips and half this fraction at valleys. Default: 0
// roudning = round the teeth by this fraction at the tips, and half this fraction at valleys. Default: 0
// rounding = round the teeth by this fraction at the tips, and half this fraction at valleys. Default: 0
// rot = if true rotate so the part will mate (via attachment) with another identical part. Default: false
// base = add base of this height to the bottom. Default: 1
// crop = crop to a cylindrical shape. Default: false
// anchor = Translate so anchor point is at origin (0,0,0). See [anchor](attachments.scad#subsection-anchor). Default: `CENTER`
// spin = Rotate this many degrees around the Z axis after anchor. See [spin](attachments.scad#subsection-spin). Default: `0`
// orient = Vector to rotate top towards, after spin. See [orient](attachments.scad#subsection-orient). Default: `UP`
// Example: Basic uncropped hirth spline
// Example(3D,NoScale): Basic uncropped hirth spline
// hirth(32,20,50);
// Example: Raise cone angle
// Example(3D,NoScale): Raise cone angle
// hirth(32,20,50,cone_angle=30);
// Example: Lower cone angle
// Example(3D,NoScale): Lower cone angle
// hirth(32,20,50,cone_angle=-30);
// Example: Adding a large base
// Example(3D,NoScale): Adding a large base
// hirth(20,20,50,base=20);
// Example: Only 8 teeth, with chamfering
// Example(3D,NoScale): Only 8 teeth, with chamfering
// hirth(8,20,50,tooth_angle=60,base=10,chamfer=.1);
// Example: Only 8 teeth, cropped
// Example(3D,NoScale): Only 8 teeth, cropped
// hirth(8,20,50,tooth_angle=60,base=10,chamfer=.1, crop=true);
// Example: Only 8 teeth, with rounding
// Example(3D,NoScale): Only 8 teeth, with rounding
// hirth(8,20,50,tooth_angle=60,base=10,rounding=.1);
// Example: Only 8 teeth, different tooth angle, cropping with $fn to crop cylinder aligned with teeth
// Example(3D,NoScale): Only 8 teeth, different tooth angle, cropping with $fn to crop cylinder aligned with teeth
// hirth(8,20,50,tooth_angle=90,base=10,rounding=.05,crop=true,$fn=48);
// Example: Two identical parts joined together (with 1 unit offset to reveal the joint line). With odd tooth count you can use the CENTER anchor for the child and the teeth line up correctly.
// Example(3D,NoScale): Two identical parts joined together (with 1 unit offset to reveal the joint line). With odd tooth count and no skew the teeth line up correctly:
// hirth(27,20,50, tooth_angle=60,base=2,chamfer=.05)
// up(1) attach(CENTER,CENTER)
// hirth(27,20,50, tooth_angle=60,base=2,chamfer=.05);
// Example: Two conical parts joined together, with opposite cone angles for a correct joint. With an even tooth count you must use the "mate" anchor for correct alignment of the teeth.
// Example(3D,NoScale): Two conical parts joined together, with opposite cone angles for a correct joint. With an even tooth count one part needs to be rotated for the parts to align:
// hirth(26,20,50, tooth_angle=60,base=2,cone_angle=30,chamfer=.05)
// up(1) attach(CENTER,"mate")
// hirth(26,20,50, tooth_angle=60,base=2,cone_angle=-30, chamfer=.05);
// up(1) attach(CENTER,CENTER)
// hirth(26,20,50, tooth_angle=60,base=2,cone_angle=-30, chamfer=.05, rot=true);
// Example(3D,NoScale): Using skew to create teeth with vertical faces
// hirth(17,20,50,skew=-1, base=5, chamfer=0.05);
// Example(3D,NoScale): If you want to change how tall the teeth are you do that by chaging the tooth angle. Increasing the tooth angle makes the teeth shorter:
// hirth(17,20,50,tooth_angle=120,skew=0, base=5, rounding=0.05, crop=true);
module hirth(n, ir, or, id, od, tooth_angle=60, cone_angle=0, chamfer, rounding, base=1, crop=false, orient,anchor,spin)
module hirth(n, ir, or, id, od, tooth_angle=60, cone_angle=0, chamfer, rounding, base=1, crop=false,skew=0, rot=false, orient,anchor,spin)
{
ir = get_radius(r=ir,d=id);
or = get_radius(r=or,d=od);
dummy = assert(all_positive([ir]), "ir/id must be a positive value")
assert(all_positive([or]), "or/od must be a positive value")
assert(is_int(n) && n>1, "n must be an integer larger than 1")
assert(is_finite(skew) && abs(skew)<=1, "skew must be a number between -1 and 1")
assert(ir<or, "inside radius (ir/id) must be smaller than outside radius (or/od)")
assert(all_positive([tooth_angle]) && tooth_angle<360*(n-1)/2/n, str("tooth angle must be between 0 and ",360*(n-1)/2/n," for spline with ",n," teeth."))
assert(num_defined([chamfer,rounding]) <=1, "Cannot define both chamfer and rounding")
@ -1302,9 +1320,9 @@ module hirth(n, ir, or, id, od, tooth_angle=60, cone_angle=0, chamfer, rounding,
assert(is_undef(rounding) || all_nonnegative([rounding]) && rounding<1/2, "rounding must be a non-negative value smaller than 1/2")
assert(all_positive([base]), "base must be a positive value") ;
tooth_height = sin(180/n) / tan(tooth_angle/2); // Normalized tooth height
conic_ht = tan(cone_angle); // Normalized height change corresponding to the cone angle
ridge_angle = atan(tooth_height/2 + conic_ht);
valley_angle = atan(-tooth_height/2 + conic_ht);
cone_height = -tan(cone_angle); // Normalized height change corresponding to the cone angle
ridge_angle = atan(tooth_height/2 + cone_height);
valley_angle = atan(-tooth_height/2 + cone_height);
angle = 180/n; // Half the angle occupied by each tooth going around the circle
factor = crop ? 3 : 1; // Make it oversized when crop is true
@ -1316,25 +1334,25 @@ module hirth(n, ir, or, id, od, tooth_angle=60, cone_angle=0, chamfer, rounding,
pts = [
[-angle*(1-chamfer/2), valley_angle+vchamf/2],
[-angle*chamfer, ridge_angle-vchamf]
]
],
full = deduplicate(concat(pts, reverse(xflip(pts))))
)
concat(pts, reverse(xflip(pts)))
back(valley_angle, skew(sxy=skew*angle/(ridge_angle-valley_angle),fwd(valley_angle,full)))
: let(
vround=rounding*(ridge_angle-valley_angle),
profpts = [
[ -angle, valley_angle+vround/2],
[ -angle*(1-rounding/2), valley_angle+vround/2],
[ -angle*rounding, ridge_angle-vround],
[ 0, ridge_angle-vround]
],
// Using computed values for the joints lead to round-off error issues
joints = [(profpts[1]-profpts[0]).x, (profpts[3]-profpts[2]).x],
segs = max(16,segs(or*rounding)),
rpts = round_corners(profpts, joint=joints,closed=false,$fn=segs)
full = concat(profpts, reverse(xflip(profpts))),
skewed = back(valley_angle, skew(sxy=skew*angle/(ridge_angle-valley_angle),fwd(valley_angle,full))),
// Using computed values for the joints lead to round-off error issues
joints = [(skewed[1]-skewed[0]).x, (skewed[3]-skewed[2]).x/2, (skewed[3]-skewed[2]).x/2,(skewed[5]-skewed[4]).x ],
roundpts = round_corners(skewed, joint=joints, closed=false,$fn=segs)
)
concat(rpts, reverse(xflip(select(rpts,1,-2))));
roundpts;
// project spherical coordinate point onto cylinder of radius r
cyl_proj = function (r,theta_phi)
@ -1342,33 +1360,30 @@ module hirth(n, ir, or, id, od, tooth_angle=60, cone_angle=0, chamfer, rounding,
let(xyz = spherical_to_xyz(1,pt[0], 90-pt[1]))
r * xyz / norm(point2d(xyz))];
bottom = min([tan(valley_angle)*ir,tan(valley_angle)*or])-base;
safebottom = min([tan(valley_angle)*ir/factor,tan(valley_angle)*or*factor])-base-(crop?1:0);
topinner = [for(ang=lerpn(0,360,n,endpoint=false))
each zrot(ang,cyl_proj(ir/factor,profile))];
topouter = [for(ang=lerpn(0,360,n,endpoint=false))
each zrot(ang,cyl_proj(factor*or,profile))];
bottom = min([tan(valley_angle)*ir,tan(valley_angle)*or])-base-cone_height*ir;
safebottom = min([tan(valley_angle)*ir/factor,tan(valley_angle)*or*factor])-base-(crop?1:0)-cone_height*ir;
ang_ofs = !rot ? -skew*angle
: n%2==0 ? -(angle-skew*angle) - skew*angle
: -angle*(2-skew)-skew*angle;
topinner = down(cone_height*ir,[for(ang=lerpn(0,360,n,endpoint=false))
each zrot(ang+ang_ofs,cyl_proj(ir/factor,profile))]);
topouter = down(cone_height*ir,[for(ang=lerpn(0,360,n,endpoint=false))
each zrot(ang+ang_ofs,cyl_proj(factor*or,profile))]);
botinner = [for(val=topinner) [val.x,val.y,safebottom]];
botouter = [for(val=topouter) [val.x,val.y,safebottom]];
vert = [topouter, topinner, botinner, botouter];
anchors = [
named_anchor("teeth_bot", [0,0,bottom], DOWN),
named_anchor("mate", [0,0,0], UP, spin=n%2==0 ? 180/n : 0)
named_anchor("teeth_bot", [0,0,bottom], DOWN)
];
attachable(anchor=anchor,spin=spin,orient=orient, r=or, h=-2*bottom,anchors=anchors){
intersection(){
vnf_polyhedron(vnf_vertex_array(vert, reverse=true, col_wrap=true, row_wrap=true),convexity=min(10,n));
if (crop)
zmove(bottom)tube(or=or,ir=ir,height=4*or,anchor=BOT);
zmove(bottom)tube(or=or,ir=ir,height=4*or,anchor=BOT,$fa=1,$fs=1);
}
children();
}
}
// vim: expandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap