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geert_2

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Everything posted by geert_2

  1. I kind of like the worn-out look of the first lady. Looks a bit like a corroded ancient statue that is in restoration, after being discovered in an old castle. Maybe you could keep it this way? Just fill and sand the splits, but no painting?
  2. That overhang is very impressive, indeed. And what is the effect of this setting on the "curling up" tendency of steep overhangs? Where the edges bend upwards instead of sagging, causing the nozzle to bang hard into them, and causing vibrations and ugglyness too? And in extreme cases knocking the model off the bed? See these tests.
  3. I was about to suggest this. 🙂 If they are totally separate, with a gap, and support is switched off, I see no reason at all why the base plate would be influenced by the X-character? Weird... 1. Have you tried printing them in one material, with only one nozzle? But with tiny gaps everywhere (even 0.01mm should do)? Just to see how it is sliced? 2. Have you tried putting both models into one STL-file? (Your models above are in separate files.) At 100% infill, on my single-nozzle UM2, the model below is sliced correctly in my older Cura. I quickl
  4. Also, when calculating the STL-triangles in MATLAB, make sure the coordinates of begin- and end-points of shared triangle-vectors are exactly the same, down to the last digit behind the decimal point. If these X-, Y- and Z-coordinates would be rounded off in your calculations, even to 20 digits behind the decimal point, it might create gaps in the STL-file, and then it would no longer be watertight. Let's say you have 3 triangles A, B, and C that share one corner. If this corner is (x, y, z): for triangle A=(10.00001, 20.00001, 30.00001), and for B=(10.00002, 20.00002, 30.00002), a
  5. As far as I know, STL-files have no dimension units (mm, inch, meters,...). But if I remember well from older posts, Cura *assumes* that the dimensions are in mm? Is that correct? If so, maybe you can set that in MATLAB to render or export the model to a size of maybe 20...50mm? And then definitely run it through an STL-analysis and repair, just to be sure.
  6. Yes, that is how I also understood it. That is what I meant by "moving the parts around on the glass": place the lowest model the furthest away from the home-position, and the highest the closest-by. And then hope that Cura is clever enough to print the furthest and lowest parts first, and then the nearby high parts. For low objects (<20mm) this seems to work in my older Cura version for my UM2-printers: at least it starts from the furthest away models. But this does not work for high models (100mm or so): then it prints them all at once. I have no idea about newer Cura versions and printer
  7. My old Cura version can display this model, although it appears extremely small, maybe 1mm^3. So I have to scale it up 20...50x to make it printable. However, this older Cura-version can not slice it: then it hangs up. Maybe there is something wrong with the STL-file? Maybe try saving it with different parameters? Or run it through an STL-analysis and repair program? But I have no experience with these, as I never needed them for myself.
  8. For dimensioning threads, I think you could reuse the guidelines for plastic injection moulding. These threads generally use shallower angles than typical metal threads (M20, etc...), wider teeth, rounded corners, to improve the molten plastic flow, increase strength, and reduce stress-concentrations in corners under load. Indeed very similar to what you have done. If you use a standard thread, you can screw existing caps on it (e.g. recovered from PET bottles). Search for "injection moulding guidlines pdf", or: "part design guidelines for injection moulding pdf", "lanx
  9. This is indeed what I would expect to work, at least if you have 100% infill. If less than 100% infill, say 20%, then I could imagine that the slicer would generate a heavier structure below the letters, to support them. I guess this will have to be answered by the developers, or people with a dual-nozzle machine and a better understanding of the slicing-internals.
  10. If the model is opaque, and the letters are raised, then maybe you could make the whole baseplate in one solid model/color? And only switch to the letters once you are above the baseplate? Thus without digging into the baseplate, rather like icing on top of a cake? If it has to be transparent, or if the letters are recessed into the baseplate, then of course this method would not work. (Note: I don't have dual-nozzle printers, so no experience, and just guessing.)
  11. Can't you move them around on the build plate, and in that way influence the printing order? In older Cura versions you could print multiple models apart, as long as they would not collide with the print head and rods. So you couldn't put very much parts on the bed. I haven't tried this in newer versions. But especially for very small parts, printing model per model separately, instead of all together, might not always be a good idea: then the model does not get enough cooling, since the hot nozzle is constantly on top of it, radiating heat, and adding hot f
  12. Thanks for the photos. It might be fillers in the black that decompose due to the acetone? Or due to UV-light, or age, moisture, or whatever else? Or the fillers that reduce layer bonding, and thus make it more prone to splitting? Also, I think manufacturer should mention in their specs for each filament: "Can be acetone-smoothed" or "Can be whatever-smoothed", and then the recommended product, time, method (brushing, wiping, dipping, vapour, whatever), and amount (thin, thick). I have just smoothed a handle (using your brush-on method), yellow PLA, and now
  13. I have colorFabb glowfill, and indeed, it does not glow for very long. It is very bright for a *very short* time, and then quickly fades. Usefull brightness as a sign is a few minutes, maybe 5 at best. And then it is still barely visible, but unreadable, in pitch black darkness for indeed maybe 20 min. Just a blurred pale green shade. Useless as emergency exit sign, or as night-light in a room. In the old days they had radio-active glow-in-the-dark paints, used on clocks. These did glow *very* bright all night, for +10 years. This was really fascinating, and very usefull. But these
  14. I believe the effect you see is overextrusion, due to the printer slowing down at the corners or ends, but the nozzle pressure is still up and takes some time to dissipate by leaking away. This gets more visible when printing lots of small segments. Printing slower and cooler helps, but does not eliminate the effect. But for me it is no problem. I haven't tried features like "coasting" (if I remember the name correctly, stopping to extrude just before a corner, so that pressure has time to drop). Maybe this might help? But if you overdo it, it might cause gaps at the st
  15. I have tried it this way: - cut off both filament ends at 90°, - heat a knife in a flame, - align both filament ends in a holder (see pic), and push them down with your fingers, - insert the hot knife in-between both ends, and push both ends onto the hot knife (don't push your fingers onto the hot knife), - let these ends melt a little bit, - remove knife, and push both ends together, so they melt into each other, - keep pushing them down, and let them cool and solidify, - using a Dremel tool or similar, cut off the flanges, otherwise it won't go through
  16. Hoi cloakfiend, Have you ever tried *post-curing* an acetoned model? Thus: print, sand, acetone, wipe, dry, as usual, but then let it sit at an elevated temperature for maybe a day, or two days? The temp has to be above glass-transition temp, maybe 60-70°C, but below melting the model of course (may depend on the model what it can withstand). This could reduce residual stresses, so it might be less likely to split later on. And then primer, paint or plate as usual. If it is going to split anyway, it might already split during this process. I am not sure it is going to w
  17. Another factor is cooling: in small models it doesn't get enough cooling time. So the whole thing stays soft and sags. On sharp corners, the strand is pulled inwards like a rubber band. See the tests I did a few months ago. This is PET. Nozzle = 0.4mm. Layer-thickness from left to right (mm): 0.4, 0.3, 0.2, 0.1, 0.06. Top row: 50mm/s, bottom row: 10mm/s. You see the same rounding and not-enough-cooling effects in the thickest layers (left), although less than in your tests.
  18. The screendumps below show why you should not use SketchUp. The vectors do not match up, they do not connect. So you do not get watertight solid models. SketchUp models are a mix of separate surfaces and half-solid parts. Especially if you then do boolean operations on these, it becomes a mess. Below this effect is shown in simple text, before it is extruded into 3D, but the same also happens in other SketchUp models. SketchUp was designed for visual representations only: of buildings, like in games, or for Google's original Earth and Maps views. Not for 3D-printing.
  19. Also try using mechanically interlocking features. Since this is highly recommended for injection moulding in overmoulding, according to the manuals, I think it also applies for 3D-printing. At least, it shouldn't hurt. Think of a dovetail system, or hooks, or chains that interlock. Think of these concepts, but then all melted and squeezed into one solid block. Have a look at how it is done in tooth brushes: most of them also have overmoulding with interlocking features.
  20. If you are courageous and have some electronics knowledge, and you want to rule-out the bed-heater influence, you could try to fix a LED-lamp onto the heating-connector. And then babysit the printer to see if the bed-heating LED and print-lines occur at the same moment? (Use a diode + LED + suitable current-limiting resistor, all insulated, not a bare LED alone). But here you risk making short circuits and burning out electronics, so you must know what you are doing. While babysitting a print, also watch if there are any feeding issues: bends in the filament cause increased resista
  21. If it is at *random* heights, or at a fixed height not related to model-features, I would think of a Z-axis issue, such as dirt (thoroughly clean the screw), or play in the nut or driver. But I am not familiar with diagnosing and solving that. If it is always at the exact same height as big changes in print-area, or changes in infill, or changes in wall-thickness, then I would think that there is still something there to improve (thicker walls?), even on bigger models. I have seen models where the infill-pattern shined through the walls, causing indents. A bit similar to the struct
  22. Do you mean that the 8mm rod on which the pulley is mounted, could be shifting (or be shifted) axially, due to too much axial play, or an incorrect plastic spacer? Or one of the pulleys being mounted a bit too far away from the printer-housing? That could also explain the phenomena.
  23. For PET, I get good layer adhesion by printing much slower and cooler, and *without fan*. But then the bridging and overhangs suffer (but most of my models need no bridging and no overhangs). The "printing cooler" is to prevent the filament from burning and decomposing in the nozzle, due to the much longer transit times. I don't know if this would also work for PVC? Anyway, watch out for chlorine gasses, if it would decompose. Should be easy to smell, like in a swimming pool where they overdid it.
  24. I don't have these printers, but on my older UM2, changes in print-area per layer can result in horizontal lines. Especially on smaller models. I think this is due to differences in cooling time per layer, but I am not sure. In your models, are the lines where the solid top and bottom layers begin or end, or where there are big changes in surface area to print? If so, printing with thicker walls, or 100% infill for small models, could help. Also: placing a dummy block next to the real model can help, especially if it is less or more in the inverse shape, or inverse print-area per l
  25. I also had this on one belt on one of my UM2: a squeeking sound which turned out to be caused by the belt rubbing against a flange of a pulley. I gently lubricated the edge of that belt with a little bit of silicone grease. But only the edge, and only a *tiny little bit*. Not on the teeth, otherwise it might skip teeth. And I used *silicone* grease: the thick white sort that is also used for microscopes and binoculars. This does not leak away and does not dry out. Don't use petrochemical oils or greases on rubber: this may damage it. This is not an official
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