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Old 27th August 2019, 06:22 AM   #141
bmc0 is offline bmc0  United States
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Hi Marcel,


I noticed that your program does not appear to match curvature between the OS section and the termination. The error is pretty small in most cases, but becomes obvious if Depth.ConicSectionPart is set to a low value (<0.3 or so).
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Old 27th August 2019, 07:44 AM   #142
mabat is offline mabat  Czech Republic
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Hi,

Yes, I realized this just after I released the tool... It's still tangent but curvatures at the joint may be (and will be) different. It's because I forgot to take the OS curvature into account - I just assumed it low enough, which is not allways true - especially near the throat, as you say. I will correct this. The solution is simple - to find the corresponding curvature on the clothoid and make the join at that point (now it's allways the origin of the spiral).

Thanks. At least someone is looking closely
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Last edited by mabat; 27th August 2019 at 07:49 AM.
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Old 27th August 2019, 08:17 AM   #143
bmc0 is offline bmc0  United States
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Glad to help. I noticed the issue after adding clothoid termination to my own waveguide generator script since I had made the same assumption that you did. I use a simple iterative algorithm to match the curvature, but I wouldn't be surprised if there's a better way (my math skills are a bit lacking compared to some others here ).
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Old 27th August 2019, 08:20 AM   #144
mabat is offline mabat  Czech Republic
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BTW, if an OS waveguide is terminated by just a circular arc (a simple radius), there will be a big step change in curvature ("2nd derivative") at this joint. It can be made much smoother with the spiral but as you can see, care must still be taken...
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Last edited by mabat; 27th August 2019 at 08:31 AM.
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Old 27th August 2019, 12:57 PM   #145
mabat is offline mabat  Czech Republic
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Ha ha, it won't be so easy after all - what must match is a curvature, tangency and a size at the same time. I guess some iterative algorithm will be necessary...
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Old 27th August 2019, 08:52 PM   #146
mabat is offline mabat  Czech Republic
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What we are talking about here - at the joint (the vertical line) curvatures don't really match. While the spiral begins with zero curvature the OS curvature is not yet near zero. It's quite difficult to notice but it's there.
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File Type: png curv_mismatch.png (10.3 KB, 487 views)
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Old 27th August 2019, 09:40 PM   #147
Patrick Bateman is offline Patrick Bateman  United States
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Here's a 3D printed waveguide built using your software: Metlako: A Small, Affordable Two-Way Unity Waveguide

This is the 2nd I've done. I need to dig up pictures and measurements of the first.
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Old 28th August 2019, 05:54 AM   #148
mabat is offline mabat  Czech Republic
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Cool! Aren't you afraid of the sharp edges on the bigger one? I would guess it could wreak havoc on the frequency response (OK, the slits will do it anyway ).
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Old 28th August 2019, 09:34 AM   #149
jzagaja is offline jzagaja  Poland
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Great feature would be split model at printer table size then able to generate different throat size section and angle for particular driver.
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Old 29th August 2019, 12:39 PM   #150
danibosn is offline danibosn  Croatia
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does the ath4 generate STL file which can be opened by STL viewers.
If not what is "Out.Write_STL = yes"
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