3 files changed, +44 −10 1.1.0: Real teeth. detail = simple keeps a plain bar.

part.py +26 −5

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		@@ -1,16 +1,37 @@
1		-"""Open-ended GT2 (2GT) timing belt as a straight envelope for assemblies: a bar of the belt's overall height and width, length along X, centred on the
2		-origin, back of the belt up. Teeth are not modelled."""
	1	+"""Open-ended GT2 (2GT) timing belt, straight, 2 mm pitch: length along X, centred on the origin, back of the belt up, teeth down on the XY plane. detail = "full": the teeth along the
	2	+length; tooth width is a proportion for looks, not for design (only the height and pitch are published). A belt over 500 mm carries teeth along 250 mm at each end, the middle at full
	3	+height: more teeth build too slowly for a belt. detail = "simple": a plain bar of the belt's overall height."""
	4	+import math
	5	+
3	6	from steve import Model
4	7
5	8	width = 6 # mm Belt width
6	9	length = 300 # mm Belt length
	10	+detail = "full" # full: teeth; simple: a plain bar
7	11
8	12	# Handson Technology, GT2 belt data sheet: 2 mm pitch, belt height 1.38 mm, tooth height 0.75 mm.
9	13	HEIGHT = 1.38
	14	+TOOTH_HEIGHT = 0.75
	15	+PITCH = 2.0
	16	+TOOTH_WIDTH = 1.2 # a proportion for looks
	17	+TOOTHED_LENGTH = 500 # mm: the most of a belt that carries drawn teeth
10	18
11	19	model = Model()
12		-with model.sketch("belt_sketch", on="XY", name="Belt") as sk:
13		- sk.rect("outline", (-length / 2, -width / 2), (length / 2, width / 2))
14		-model.extrude("belt", "belt_sketch", distance=HEIGHT, name="Belt")
	20	+if detail == "simple":
	21	+ outline = [(-length / 2, 0), (length / 2, 0), (length / 2, HEIGHT), (-length / 2, HEIGHT)]
	22	+else:
	23	+ back = TOOTH_HEIGHT
	24	+ outline = [(-length / 2, back), (-length / 2, HEIGHT), (length / 2, HEIGHT), (length / 2, back)]
	25	+ count = int(length // PITCH)
	26	+ centres = [(i - (count - 1) / 2) * PITCH for i in range(count)]
	27	+ if length > TOOTHED_LENGTH: # teeth at both ends, so an end view shows them
	28	+ kept = int(TOOTHED_LENGTH / 2 // PITCH)
	29	+ centres = centres[:kept] + centres[-kept:]
	30	+ for x in reversed(centres):
	31	+ half = TOOTH_WIDTH / 2
	32	+ outline += [(x + half, back), (x + half * 0.6, 0.0), (x - half * 0.6, 0.0), (x - half, back)]
	33	+with model.sketch("belt_sketch", on="XZ", name="Belt section") as sk:
	34	+ sk.polyline("outline", outline, closed=True)
	35	+model.extrude("belt", "belt_sketch", distance=width, both=True, name="Belt")
15	36	result = model.result()
16	37

pypart.toml +17 −3

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		@@ -1,11 +1,11 @@
1	1	name = "steve/timing-belt"
2		-version = "1.0.0"
	2	+version = "1.1.0"
3	3	runtime = "steve"
4	4	license = "MIT"
5	5	summary = "GT2 (2GT) open timing belt as a straight envelope: width and length as parameters, with common lengths as presets."
6		-description = """Open-ended GT2 timing belt, 2 mm pitch, as a straight bar of the belt's overall height and width, for assemblies. Teeth are not modelled. \
7		-Length along X, centred on the origin. See the README; not affiliated with any belt brand."""
	6	+description = """Open-ended GT2 timing belt, 2 mm pitch, straight, with its teeth. A belt over 500 mm carries teeth along 250 mm at each end. detail = simple is a plain bar of the overall height for big assemblies. Length along X, centred on the origin. See the README; not affiliated with any belt brand."""
8	7	tags = ["belt", "timing-belt", "gt2", "2gt", "power-transmission"]
	8	+changes = "Real teeth. detail = simple keeps a plain bar."
9	9
10	10	[parameters.width]
11	11	type = "number"
		@@ -22,6 +22,13 @@
22	22	max = 5000
23	23	unit = "mm"
24	24	label = "Length"
	25	+
	26	+[parameters.detail]
	27	+type = "choice"
	28	+default = "full"
	29	+choices = ["full", "simple"]
	30	+label = "Detail"
	31	+description = "full: teeth. simple: a plain bar of the overall height, for big assemblies."
25	32
26	33	[[presets]]
27	34	id = "GT2-W6-L50"
		@@ -121,3 +128,10 @@
121	128	aliases = ["GT2 9mm belt 1000", "GT2 9mm belt"]
122	129	standard = "Handson GT2"
123	130
	131	+[[presets]]
	132	+id = "GT2-W6-L300-simple"
	133	+title = "GT2 belt, 6 mm wide, 300 mm, simple (no teeth)"
	134	+params = { width = 6, length = 300, detail = "simple" }
	135	+aliases = ["GT2 belt simple"]
	136	+standard = "Handson GT2"
	137	+

README.md +1 −2

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		@@ -1,7 +1,6 @@
1	1	# Timing belt (GT2)
2	2
3		-Open-ended GT2 (2GT) belt, 2 mm pitch, as a straight envelope. Length along X, centred on the origin, teeth side on the XY plane. The teeth
4		-aren't modelled.
	3	+Open-ended GT2 (2GT) belt, 2 mm pitch, straight. Length along X, centred on the origin, teeth down on the XY plane. Tooth pitch and height are published; the tooth's width and taper are proportions for looks, not for design. A belt over 500 mm carries teeth along 250 mm at each end, because more take too long to build. `detail = "simple"` is a plain bar.
5	4
6	5	## Source
7	6