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geert_2

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Everything posted by geert_2

  1. It could be the glass: glass is never totally flat, it has bumps and pits. If you look through a car window, especially on older cars, and in curved areas of the window, you will see the lens-deformations caused by this unflatness. But it could also be the rods not being totally straight. If they would only be 0.025mm curved, almost nothing, that would show up as a 0.05mm difference in layer height, in a sort of sine-wave. Thus a full layer in fine settings. If both rods have it, you could get a pattern like yours. Maybe you can check if the repeating frequency is one full turn of
  2. Your first layer should probably look more like these:
  3. I just think about it: if you want to make moulds, it is a good idea to have a look at manuals of injection moulding too. These manuals explain very well how plastic behaves when casted. And which guidelines to follow in mould-design. Although intended for injection moulding, a lot of principles apply to any kind of moulding. Search for: injection moulding manual bayer basf. And maybe other companies: most manufacturers of plastic pellets do have such manuals, available for free, because they want customers to be satisfied with their plastics.
  4. A couple more smoothed compared to original 3D-prints. These are in translucent PET too. In real life the difference is even bigger, but it is hard to get on photo. The thumbscrew is standard nylon, M4 thread, 16mm wheel. Layer-heigth was 0.06mm.
  5. I don't think you can easily cast in HDPE or PET, that normally requires injection moulding. Most casting products are two-component epoxies, polyurethanes, polymethylmetacrylates (=PMMA, as in plexiglass and dental models), silicones, and similar. So they are often quite thin liquids, and then chemically cure into hard plastic or silicone. PMMA should be food-safe when fully cured, otherwise they couldn't use it for dental applications in the mouth. I don't know about fully cured PU. Most platinum-cured silicones are also food-safe, like in commercial baking moulds. The basic proc
  6. Maybe you could put them in a well controlled oven, at the glass-transition temperature, and put a heavy weight on them, so they get flat again? Let it sit for several hours, and then very gradually let it cool. Or heat-up the bed of your printer, and let it sit there for overnight, with a weight on top? And then very slowly cool down. They might get straight again? Your models are thin, so I don't think they would warp too much if you use the glue stick, 3Dlac, hairspray or something similar for bonding? Worth trying. If it fails, then at least you know. Otherwise, you have an add
  7. Also, shells are 100% filled, and the shell in the curved part is longer than in the straight, which could give a bit difference. But so much...? I think you would best print them at the same time, on the same bed, and 100% filled. So there are no differences in infill-pattern, and no differences in shell vs. infill, and no differences in speed, temp, extrusion-rate (or underextrusion), etc... Maybe scale it down to 50%, for a quick test, so you don't waste too much material?
  8. Yes, to me too your part looks big enough not to worry about layer-time. Except if you would have tiny features protruding from the top. I wrote that reply because you asked it. But it is more for very small items. Very often I have models with a tiny top surface of ca. 10mm x 10mm with very fine details (as in the blue thing above). And then it becomes a necessity. And even then I often give the dummy a very crude shape: just hollow below the top area, and filled as soon as the tiny features are reached. Just to get the nozzle away, let that cool, and keep the flow going steadily.
  9. Yes, but don't do the whole model yet. Do a small test part: let's say only one bulb, attached to a short stem. And that with different gap-variations. See which gap works best. Then you will lose the least amount of time and material.
  10. User MakersMuse on Youtube has designed a testpart with various tolerances, specially for this purpose. After printing, you can see which parts still move, and which not. Then you know what tolerances you need to apply in your own designs. Also, printing circumstances have a huge influence: printing hotter, will melt them more together. Thick layers will reduce accuracy, as well as printing fast. So, printing slow, cool and in thin layers should give best results. Theoretically...
  11. Dichloromethane works for PET as well, and it is even more agressive: in one generous brush-on application, it removed all layer lines in my tests. See the photos. The outer layer stays soft for quite a while. Sometimes it gets a bit milky, but that goes away with time, and/or can be wiped off the day after. Pro: much smoother surface, no layer lines anymore. And internal features such as watermarks in transparent/translucent PET become better visible. Contra: the tiny bubbles... And the fact that I have no idea about long-term effects: deformations, changes
  12. Not sure, but I think a gap of 0.5mm might be a little bit too big? Maybe make a small test piece with gaps of 0.1, 0.2, 0.3, 0.4, and 0.5mm. Print that and compare what works best for you? It will also depend on the material, cooling, printing speed, printing temp: obviously, hotter will melt things more together. It will also depend on the width of your support: wider will be more difficult to remove. I usually take "one nozzle-width" for such supports (thus 0.4 to 0.5mm wide for a 0.4mm nozzle): that is still easy to cut off. And gaps between 0.2 and 0.4mm, depending on the model. My fixed
  13. I think you will need to provide images of the models, of the cross sections, and of the layer-views while slicing, and project files and parameters. Otherwise it would just be wild guessing.
  14. If I had to print this model, I would consider one of two options: 1. Split the model in half, top and bottom, print both halves separately, and glue or bolt them together. In case of bolting, provide holes for inserting bolts and nuts. I often use standard nylon M4 for most of my designs that need to be assembled and disassembled. 2. Design a custom support and brim in CAD, so it fully supports your model where you want. If well done, it should print better, give less deformations. But it will cost time and may take a bit of trial and error. If you leave a tiny gap bet
  15. In my experience not. (But other people may see things differently of course.) Because then the nozzle is sitting there and just waiting. The flow is stopped, the filament spends time in the nozzle, heating up more, thus getting hotter than before and more liquid. It may ooze, and it will surely have different flow characteristics than before, which will show up as horizontal lines. Also, the heat accumulated in the filament, still has to "evaporate" after printing. Thus if it gets hotter due to waiting, then that extra heat also needs to get out of the print. The only advantage is
  16. I would rather go for multiple smaller batches, than one big batch. Even though that costs extra warming-up and cooling-down time. But if something goes wrong and you have to abort the print, then you only lose a couple of hours and one model, not days of work and lots of people's work. This works best for my models which usually take 2-3 hours to print. But this is my personal view, and not necessarily suitable for everyone. And I only do all printing myself, no others touch it. MakersMuse on Youtube has been doing 3D-printer repair service in the past. His experience was that stu
  17. TPU 95A has a shore hardness of 95, I think. So that is quite stiff, much like hot glue after cooling down. If you print it in a thin layer of 0.1-0.2mm it will be flexible, but not in thick parts. You could try playing with less infill, but I have no experience with this, so no recommendations. If you need really soft materials, you could consider printing a mould, and then casting silicone in it. This exists in various hardnesses. There have been several posts about casting silicones, maybe you can search them?
  18. What about printing a mould, and then carefully sanding and polishing that mould, and casting your model in a food safe plastic? Then you still have the freedom of designing and 3D-printing, but you don't have the tiny holes in the final models. Use a low-exotherm, slow curing product, so the prints do not melt. And depending on the product, use a good mould release spray or coating so it does not permanently get glued into the mould.
  19. The formulas have been explained somewhere on this forum, but I don't know which keywords to search for (I don't remember in which context or topic it was). Maybe you can find it back? At the nozzle-end it started with line-width x line-height x speed, if I remember well, but the rest for the feeder etc., I forgot.
  20. It looks like you have severe underextrusion, something stopping or blocking the flow. There could be a zillion of reasons, blocked nozzle, nozzle too cold, filament too thick or getting stuck, kinks in the filament,... On this forum, try searching for causes of underextrusion. User gr5 has made a good and extensive diagnostics list that he posted several times. That should help you going.
  21. Do you have any timing recommendations, to start from? Is it in the range of seconds, minutes, quarter hours, hours,...? My prints are usually 100% filled, and not too big (see dimensions below). Edit: and any idea about long-term side-effects? Strength, brittleness, dimensional stability,...? I have an old magnetic stirrer: if that still works, it could help distribute vapours evenly, so they do not accumulate on top or on the bottom of the jar, if their weight would be different from air.
  22. I don't know your materials, but in my experience PET tends to ooze out and string more than PLA: molten PET is more rubbery than PLA, which is more like yoghurt. I see different types of blobs in my PET-prints: - Those that ooze out while traveling through air, and are then deposited onto the next wall, often forming "insect antennas". Printing slower helps, because then less pressure builds up in the nozzle, and thus less molten material leaks out. - Material that accumulates on the outside of the nozzle, and then sags and gets dropped on the print, often in big lightbr
  23. Still a couple more pics. All photos were taken with a Logitech C525 webcam, with a close-up lens in front of it. For some applications, smoothing may be nice, but for others (such as fine text) the untreated prints may look better and crisper. I don't know how the glossy surface of the smoothed areas would affect bonding of paint or plating later on. Untreated text and smoothed text next to each other. The smoothed looks terribly out of focus due to the rounded edges. Untreated Smoothed, but a bit overdone: notice the tea
  24. A couple more pics: Untreated Smoothed, but overdone: see the dull area near the top When overdoing, the holes shine through the bottom, indicating that dichloromethane penetrates quite deep into the plastic and keeps melting/dissolving it. These indents take some time to form. Untreated text: this text is ca. 7mm high Smoothed: it looks out of focus, but it isn't (the dust is sharp) Untreated, close-up Smoothed, close-up: notice the bubbles oozing out of the edge of the hole
  25. Here are a few photos of before and after smoothing with dichloromethane. Filament under test is only colorFabb PLA/PHA for now, because I have lots of old waste parts available for testing. Nozzle-size is always 0.4mm. Layer-heigts may vary between 0.1mm and 0.3mm (I don't remember for most parts, too old). Most parts are quite small, often ca. 10mm wide. All tests were done by brushing-on. I haven't tried vapour-smoothing yet. Smoothing still continues a bit after the dichloromethane has evaporated, while the PLA is drying. So you need to stop a bit early. Similar to
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