Seem to be learning this 3d printing stuff kind of the hard way.
Quote from: WobblyHand on November 16, 2022, 08:43:40 PMSeem to be learning this 3d printing stuff kind of the hard way.You seem to be doing rather well for someone who started printing only recently.
If you find that holes are printing consistently snug, CURA has a setting for tweaking just hole diameters. It also has a setting for scaling just the first layer to help with elephant's foot.
Bruce,Those measurements do not indicate any great problem begging for attention. A tweak to setting that reduced OD by further 0.1 and increased ID by 0.1 mm might suddenly take away a lot of thread friction.Anyway, I created more test prints and posted the STL files here: https://www.gatewaytoairguns.org/GTA/index.php?topic=204046.msg156387571#msg156387571
Bob and Bruce,Thanks for suggesting printer tuning, Bob. I was trying to figure out how to do this tactfully, without undermining the satisfaction and enthusiasm that Bruce has gained from his early level of success.Bob,The shape of the Maxim toroidal spirals is intended to drive smooth, "organized turbulence". I think that some level of roughness on the surface will actually improve flow, the way a rough shark skin improved bulk flow by creating many small Eddies, that work like a bed of ball bearings to "lubricate" the bulk flow. Think dimples on a golf ball.If the internal concave curves sag to the point of becoming straight, that should not cause any trouble with the bulk flow of air. If the sag turns the flat or concave surfaces into a more than slightly convex shape, then the flow may separate from the plastic surface and bounce when meeting the next curve. That oscillation may produce a vibration in the plastic with an audible component, although the initial speed of the air buzzing around the spiral should produce mostly ultrasound.Next time I design a thread for 3D printing I will use a 2 mm pitch so one can shave more off, without compromising useful thread overlap. Apart from the 1/2 20 thread, the custom thread holding the segments together has a 1.5 mm pitch.
"How flat" is also dependent on layer height, and where the layer lines meet the top of the arc. Thicker layers may have a greater chance of altering the top of the intended curve. I've never experimented to see what the slicer gives priority to, holes or solids...hmmm...
Below is a new take on screw stackable baffles. This time I modeled conical threads with a 2 mm pitch, rather than using separate conical alignment features. The thread is completely custom, with the thread having a 50 degree included cone angle.The body OD is a nominal 1.5", rather than 2" of the earlier version. Yes, I then added the gripping features and reinforced the thin ends of the conical thread supports. This LDC is intended for .22 caliber (8 mm bore in CAD), with as many or few "middle" baffles as you want to use.These baffles use conical air strippers only. No toroidal spirals here. Note print direction, with small end of cone pointing up to avoid the need for supports.The three part STL files can be downloaded for 7 days from wetransfer:https://we.tl/t-FDBktsMmtN
No idea how strong 3D printed conical threads are. The point of using them is that it should eliminate fighting with threads that are too tight or too loose; because they start loose, then take up all the radial slack as you tighten them.If these threads are too weak, then I wasted over 10 hours of design time; as this a design borrowed nothing from previous ones...