Skip to content

Instantly share code, notes, and snippets.

@eraserhd

eraserhd/z_axis_bracket.clj

Created July 15, 2026 19:34
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save eraserhd/19c2e87bc273eaef963e7a833bff1279 to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save eraserhd/19c2e87bc273eaef963e7a833bff1279 to your computer and use it in GitHub Desktop.
Download ZIP
Raw
z_axis_bracket.clj
#!/usr/bin/env bb
(def width 60);
(def extrusion-size 20);
(def extrusion-vertical-distance 75)
(def linear-rail-carriage-height 13)
(def linear-rail-carriage-width 27)
(def linear-rail-screw-distance 20)
(def linear-rail-screw-hole-diameter 3.5)
(def linear-rail-countersink-diameter (+ 6.5 0.5))
(def linear-rail-countersink-depth (+ 3.5 0.5))
(def leadscrew-height (- 75/2 39.47))
(def leadscrew-nut-diameter 10.5)
(def leadscrew-nut-flange-diameter 22)
(def leadscrew-nut-flange-thickness 4)
(def leadscrew-nut-length 10)
(def antibacklash-nut-width 11.2)
(def antibacklash-nut-depth 25)
;; 1mm (ruler=1mm) + 0.198in (gauge blocks=4.8mm) + 7.94/2 (half leadscrew=3.97mm) +))
;; 10mm (half extrusion) + 8mm (rail thickness) = 27.9992
(def leadscrew-distance-from-extrusion-centerline 28)
(def thickness 13)
(defn translate [geom [x y z]]
{:type :affine-transformation
:matrix [[1 0 0 x]
[0 1 0 y]
[0 0 1 z]
[0 0 0 1]]
:child geom})
;; OpenSCAD-specific rotation
(defn rotate [geom [x y z]]
(let [x (* x (/ Math/PI 180))
y (* y (/ Math/PI 180))
z (* z (/ Math/PI 180))
sx (Math/sin x)
cx (Math/cos x)
sy (Math/sin y)
cy (Math/cos y)
sz (Math/sin z)
cz (Math/cos z)]
{:type :affine-transformation
:matrix [[(* cy cz), (- (* cz sx sy) (* cx sz)), (+ (* cx cz sy) (* sx sz))]
[(* cy sz), (+ (* cx cz) (* sx sy sz)), (+ (* (- cz) sx) (* cx sy sz))]
[(- sy) , (* cy sx) , (* cx cy)]]
:child geom}))
(def z-axis-bracket
(let [plate (-> {:type :box
:size {:x width,
:y thickness,
:z (+ extrusion-vertical-distance linear-rail-screw-distance 10)}}
(translate [0 (/ thickness 2) 0]))
m3-shcs-counterbored {:type :union
:children [{:type :cylinder
:height (+ thickness 0.2)
:diameter linear-rail-screw-hole-diameter}
{:type :cylinder
:height (+ linear-rail-countersink-depth 0.1)
:diameter linear-rail-countersink-diameter}]}
chamfer 2
wall-thickness 2.5
carriage-offset (- (/ extrusion-vertical-distance 2)
(/ linear-rail-carriage-width 2)
0.5)
ls-offset-from-back (- leadscrew-distance-from-extrusion-centerline
(/ extrusion-size 2)
linear-rail-carriage-height)
back-boss (-> {:type :linear-extrude
:height width
:child {:type :polygon
:points [[carriage-offset 0]
[carriage-offset
(+ (/ antibacklash-nut-width 2)
wall-thickness
(- chamfer)
5)]
[(- carriage-offset chamfer)
(+ (/ antibacklash-nut-width 2)
wall-thickness
5)]
[(+ (- carriage-offset) chamfer)
(+ (/ antibacklash-nut-width 2)
wall-thickness
5)]
[(- carriage-offset)
(+ (/ antibacklash-nut-width 2)
wall-thickness
(- chamfer)
5)]
[(- carriage-offset) 0]]}}
(rotate [0 90 0])
(translate [(- (/ width 2))
(- thickness ls-offset-from-back)
0]))
linear-rail-screw-holes {:type :union
:children
(for [x [(- (/ linear-rail-screw-distance 2)) (+ (/ linear-rail-screw-distance 2))]
z [(- (/ extrusion-vertical-distance 2)) (+ (/ extrusion-vertical-distance 2))]
zz [(- (/ linear-rail-screw-distance 2)) (+ (/ linear-rail-screw-distance 2))]]
(-> m3-shcs-counterbored
(rotate [-90 0 0])
(translate [x -0.1 (+ z zz)])))}
antibacklash-nut-drills (let [offset (Math/sqrt (- (Math/pow (/ leadscrew-nut-flange-diameter 2) 2)
(Math/pow (/ antibacklash-nut-width 2) 2)))
depth (- width (* 2 leadscrew-nut-flange-thickness) (/ leadscrew-nut-length 2))]
{:type :union
:children
[(-> {:type :cylinder
:height depth
:diameter 14}
(translate [0 0 -0.1]))
{:type :hull
:children (for [p [(- offset) (+ offset)]]
(-> {:type :cylinder
:height antibacklash-nut-depth
:diameter 11.7}
(translate [p 0 -0.1])))}]})]
{:type :difference
:minuend {:type :union
:children [plate
back-boss]}
:subtrahend [linear-rail-screw-holes
(-> {:type :union
:children [(-> {:type :cylinder
:height (+ width 0.2)
:diameter (+ leadscrew-nut-diameter 0.5)}
(translate [0 0 -0.1]))
(-> {:type :cylinder
:height (+ leadscrew-nut-flange-thickness 0.1)
:diameter (+ leadscrew-nut-flange-diameter 0.5)}
(translate [0 0 (+ (- width leadscrew-nut-flange-thickness) 0.1)]))
antibacklash-nut-drills]}
(rotate [0 90 0])
(translate [(- (/ width 2))
(- thickness ls-offset-from-back)
leadscrew-height]))]}))
(defmulti openscad :type)
;; OpenSCAD cube is a box or rectangular cuboid, not necessarily a cube
(defmethod openscad :box
[{{:keys [x y z]} :size}]
(format "cube([%s, %s, %s], center=true);" x y z))
(defmethod openscad :cylinder
[{:keys [height diameter]}]
(format "cylinder(h=%s, d=%s);" height diameter))
(defn- format-vector-of-vectors [v]
(str "["
(str/join ", " (map (fn [row]
(str "["
(str/join ", " (map str row))
"]"))
v))
"]"))
(defmethod openscad :affine-transformation
[{:keys [matrix child]}]
(format "multmatrix(%s) %s" (format-vector-of-vectors matrix) (openscad child)))
(defmethod openscad :difference
[{:keys [minuend subtrahend]}]
(format "difference() {\n%s\n%s\n}\n"
(openscad minuend)
(str/join "\n" (map openscad subtrahend))))
(defmethod openscad :union
[{:keys [children]}]
(str "union() {\n"
(str/join "\n" (map openscad children))
"\n}\n"))
(defmethod openscad :polygon
[{:keys [points]}]
(format "polygon(points=%s);" (format-vector-of-vectors points)))
;; Research: is this OpenSCAD-specific?
(defmethod openscad :linear-extrude
[{:keys [height child]}]
(format "linear_extrude(%d) %s" height (openscad child)))
(defmethod openscad :hull
[{:keys [children]}]
(str "hull() {\n"
(str/join "\n" (map openscad children))
"\n}\n"))
(spit "z_axis_bracket.scad" (openscad z-axis-bracket))
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment