Stackup problem with small parts?
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I've got a small part, an eccentric. 0.375" thick.
I multiply each parameter by 25.4 to get into metric units. It consists of these layers: EccentricSheeveThick = 0.078125 EccentricSheeveThick = 0.078125 EccentricGrooveThick = 0.0625 BossLength = 0.15625 Which when stacked, should equal the total length (the eccentric thickness). EccentricThick = 0.375 total But in the SCAD file, the center cylinder (bore) is taller then the stack up of the 4 parts, seen on the rendered graphic. A DXF exported to and then scaled back to inches ( scale 1/25.4) shows each of the layers as being shorter then specified. Stackup? Or hopefully did I make an error? Thanks for looking. -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org |
Re: Stackup problem with small parts?
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Sharing the source code will help.
----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! |
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Sure,
Here's the source code for eccentric: /* * Horizontal Steam Engine eccentric * * eccentric * * 03/23/2018 alm */ scale = 25.4; // for imperial $fn = 100; EccentricSheaveDia = 0.625 * scale; EccentricSheeveThick = 0.078125 * scale; EccentricGrooveDia = 0.500 * scale; EccentricGrooveThick = 0.0625 * scale; EccentricOffset = 0.09375 * scale; EccentricBore = 0.28125 * scale; BossDia = 0.4375 * scale; BossLength = 0.15625 * scale; EccentricBossSetscrew = 0.089 * scale; EccentricSetScrewLen = 0.375 * scale; EccentricSetScrewOffset = (BossLength + EccentricSheeveThick) / 2.0 * scale; EccentricThick = 0.375 * scale; //projection(cut = true) // project X - Y plane for creating DXF // rotate([0, 90, 0]) // flip over if needed Eccentric(); // top level function // ======================================================== module Eccentric() { translate([0, 0, EccentricSheeveThick / 2.0]) // get 1st sheave bottom on XY plane to simplify calcs { difference() { union() { /* Sheeve */ translate([EccentricOffset, 0, 0]) linear_extrude(height = EccentricSheeveThick + 0.2, center = true) circle(d = EccentricSheaveDia, center = true); /* Groove */ translate([EccentricOffset, 0, EccentricSheeveThick]) linear_extrude(height = EccentricGrooveThick + 0.1, center = true) circle(d = EccentricGrooveDia, center = true); /* Sheeve */ translate([EccentricOffset, 0, EccentricSheeveThick + EccentricGrooveThick]) linear_extrude(height = EccentricSheeveThick + 0.1, center = true) circle(d = EccentricSheaveDia, center = true); /* boss */ translate([0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick ]) linear_extrude(height = BossLength, center = true) circle(d = BossDia, center = true); // /* Bore .. goes below as a diff */ // translate([0, 0, (EccentricThick / 2.0) - (EccentricSheeveThick / 2.0) -.1 ]) // linear_extrude(height = EccentricThick + .2, center = true) // circle(d = EccentricBore, center = true); } /* set screw goest here! */ translate([BossDia / 2.0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick + (BossLength / 2.0) ] ) rotate([0, 90, 0]) linear_extrude(height = EccentricSetScrewLen, center = true) circle(d = EccentricBossSetscrew, center = true); // /* Bore goes here! */ // translate([0, 0, (EccentricThick / 2.0) - (EccentricSheeveThick / 2.0) -.1 ]) // linear_extrude(height = EccentricThick - .1, center = true) // circle(d = EccentricBore, center = true); } } /* put in as solid to check */ /* Bore */ translate([0, 0, (EccentricThick / 2.0) -.1 ]) linear_extrude(height = EccentricThick + .2, center = true) circle(d = EccentricBore, center = true); } // ======================================================== THANKS! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org |
Re: Stackup problem with small parts?
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Administrator
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Is it the extra 0.2 from:
linear_extrude(height = EccentricThick + .2, center = true) ? ----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Admin - PM me if you need anything,
or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! |
Re: Stackup problem with small parts?
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Administrator
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No, sorry...
----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Admin - PM me if you need anything,
or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! |
Re: Stackup problem with small parts?
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Administrator
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It is all the center=true in the linear_extrude() in the union().
Change them to false, and remove the z translate at the top and it works. Use "%" at the front of each linear_extrude() to clearly see where each layer is ATM. ----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Admin - PM me if you need anything,
or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! |
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This post was updated on .
Thanks, I just tried it!
I re-built and exported a DXF to my CAD program, and in the boss dia and overall length, I'm spot-on. A little off on the small thicknesses, 'tho, and they stack up OK as far as I can see. The errors are probably down in the 'noise' of the actual 3D printing, I'm guessing. Simpler without the 'true's in the various linear_extrudes anyway. So why the errors? I'd have thought it would have worked anyway. Is this unique? I've been using the 'center' quite a bit in my other engine parts. (I've yet to print, waiting on a 3D printer) and in most cases, 'center' simplifies things. I should check a few parts with a DXF... What is the internal precision for OpenSCAD? doubles or long doubles? What's a reasonable limit to the resolution I should expect? Thanks again! <http://forum.openscad.org/file/t2193/EngineAssembly2.png> -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list Discuss@lists.openscad.org http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org |
Re: Stackup problem with small parts?
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Administrator
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KM6VV wrote
> So why > the errors? As you were adding a smidgeon to their height, the center=true dropped their starting Z position by smidgeon/2, you were not taking that into account when you placed the next object. Try this to see (the "%" operator is your friend): module Eccentric() { translate([0, 0, 0]) // EccentricSheeveThick / 2.0]) // get 1st sheave bottom on XY plane to simplify calcs { difference() { union() { /* Sheeve */ translate([EccentricOffset, 0, 0]) linear_extrude(height = EccentricSheeveThick + 0.2, center = true) circle(d = EccentricSheaveDia, center = true); /* Groove */ translate([EccentricOffset, 0, EccentricSheeveThick]) linear_extrude(height = EccentricGrooveThick + 0.1, center = true) circle(d = EccentricGrooveDia, center = true); /* Sheeve */ %translate([EccentricOffset, 0, EccentricSheeveThick + EccentricGrooveThick]) linear_extrude(height = EccentricSheeveThick + 0.1, center = true) circle(d = EccentricSheaveDia, center = true); /* boss */ translate([0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick ]) linear_extrude(height = BossLength, center = true) circle(d = BossDia, center = true); } /* set screw goest here! */ translate([BossDia / 2.0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick + (BossLength / 2.0) ] ) rotate([0, 90, 0]) linear_extrude(height = EccentricSetScrewLen, center = true) circle(d = EccentricBossSetscrew, center = true); } } /* put in as solid to check */ /* Bore */ translate([0, 0, (EccentricThick / 2.0) ]) linear_extrude(height = EccentricThick, center = true) circle(d = EccentricBore, center = true); } > What is the internal precision for OpenSCAD? doubles or long doubles? > What's a reasonable limit to the resolution I should expect? See the wiki <https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/General#Values_and_Data_Types> . Generally resolution, in itself, is not an issue. There is a current known problem with tiny numbers, e.g. if your whole space is < ~10 and using fine details (e.g. 0.02), if you see strange things in such cases, multiply all you numbers by, say, 1000, then scale the final result down by 1000. ----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Admin - PM me if you need anything,
or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! |
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I see it: /* boss */ translate([0, 0, (EccentricSheeveThick * 2.5) + I had 2.0, so I was a half a sheeve (sheave) off. I did take out the 'true's in the linear_extrudes, and it looks better (simpler!): module Eccentric() { difference() { union() { /* Sheeve */ translate([EccentricOffset, 0, 0]) linear_extrude(height = EccentricSheeveThick + 0.2, center = false) circle(d = EccentricSheaveDia, center = true); /* Groove */ translate([EccentricOffset, 0, EccentricSheeveThick]) linear_extrude(height = EccentricGrooveThick + 0.1, center = false) circle(d = EccentricGrooveDia, center = true); /* Sheeve */ translate([EccentricOffset, 0, EccentricSheeveThick + EccentricGrooveThick]) linear_extrude(height = EccentricSheeveThick + 0.1, center = false) circle(d = EccentricSheaveDia, center = true); /* boss */ translate([0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick ]) linear_extrude(height = BossLength, center = false) circle(d = BossDia, center = true); } /* Bore goes here! */ translate([0, 0, -.1 ]) linear_extrude(height = EccentricThick + .2, center = false) circle(d = EccentricBore, center = true); /* set screw goes here! */ translate([BossDia / 2.0, 0, (EccentricSheeveThick * 2.0) + EccentricGrooveThick + (BossLength / 2.0) ] ) rotate([0, 90, 0]) linear_extrude(height = EccentricSetScrewLen, center = true) circle(d = EccentricBossSetscrew, center = true); } } Thanks for the link, I'll study it. I had kicked up my 'scale' to 254, but didn't notice a difference. I'll keep it in mind. I have a small 'slide valve' to model. I really enjoy modeling parts with OpenSCAD! A terrific tool, especially for a 'C' programmer with a little graphics! Thanks! <http://forum.openscad.org/file/t2193/Eccentric.png> -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org |
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