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geert_2

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Everything posted by geert_2

  1. Hi John, I think this is a good idea. And if it works for you, obviously, it works. If you would like, feel free to use my old warping test, shown in the photos above. I would be curious about the results, to see where the limits are? This is a small test that prints quickly: total model size = 50mm x 50mm; height=5mm; top-width of each arm = 10mm, bottom-width = 2mm. So, a tiny bottom area to bond to the glass, but a huge top area to produce warping forces, combined with steep overhangs peeling the model off the glass. And overhangs curling up.
  2. I thought I would add a few safety recommendations, as not everyone may be familiar with handling chemicals. (I have worked in the chemical industry with highly explosive and agressive chemicals, although very long ago.) When using chemicals like dichloromethane (=ethylene-chloride), ethylene-oxide, acetone, xylene, ether, and similar solvents, use good precautions. - Always use safety glasses. Not just any safety glasses, but the kind that look like diving goggles. So the spats can not fly parabolically behind it and still get in your eyes, as with normal glasses. - Always u
  3. I did tests with PET. In short: print as slow as you can, in as thin layers as you can, and as cold as you can. Due to printing slow in thin layers, the material will sit in the nozzle for a long time and start to burn/decompose, so you might need to print even below the recommended temp range. See my tests here: - upper row printed at 50mm/s, bottom row at 10mm/s - layer thickness from left to right (mm): 0.40, 0.30, 0.20, 0.10, 0.06 - dimensions of the test blocks: 10mm x 20mm x 10mm - watermark text is sitting halfway in the model A couple of year
  4. Do you mean cleaning the outside cone, or the inside, or both? After each print I immediately wipe the outside with a thick tissue, while it is still hot, so it is clean immediately. If material is burnt onto it, and I can't wipe it off, I use a brass M3 screw thread to carefully file off the ashes. Use brass or copper, never steel, because steel would damage the sensitive cone. And always be very carefull and gentle. Also, regularly applying teflon and/or PTFE to the outside helps reducing build-up of goo on the outside. I clean the inside with atomic pulls
  5. I would also use brim, because steep overhangs also tend to cause huge warping forces, and in addition they tend to curl up. If you don't want a brim all around the model, design a custom one in CAD on the places where you need it. A custom brim gives you the option to make it thicker too, if needed, for example 2 or 3 layers. Try if your bonding method can hold an inverted prism down while printing. If yes, 99.9% of your other models will work too, because this is a hard test. This one is going to succeed well. This one might soon come off
  6. If you haven't done these already: Maybe take a gcode file that goes well at home, and try that on the printers at work? And take a file that goes wrong at work, and try that at home? Then you know whether it is in the gcode or not? Exchange spools of filament at home and at work, just for a testprint. Print both with the same gcode file. Then you know if it is in the filament? I was thinking about worn-out white teflon couplers, but from what you said, I think you already replaced them, so that can't be the problem anymore? Idem for worn-out feeder wheels,
  7. Because most of my models are small, or have fine details that I want to preserve. For example in the models above, the yellow bar has to slide smoothly in the red clamp, without too much tolerance. They are for medical use, hence the smoothing to remove layer lines and make desinfection easier. And I don't want to spend hours and hours of post-processing on filing and grinding. So, printing slower, and in thinner layers, removes most of the need of post-processing. Then I have less ringing, less thickening at corners (due to the head slowing down to take the corner), less stringing, less blob
  8. I usually print PET at: nozzle 215...225°C, bed 90°C, speed 25...30mm/s, layers 0.06...0.20mm thick, and no cooling if there are no overhangs and bridges. If bridges/overhangs, then a little bit of fan is needed, but that reduces layer bonding. And yes, expect more stringing and worse bridging than with PLA. These are PET: the left one is as-printed, the right one is smoothed with dichloromethane. The thumbscrew is a standard nylon M4, with 16mm head.
  9. A couple of years ago I did a lot of tests with small text: caps height 3.5mm, character width 2mm, leg width 0.5mm. Recessed text, thus engraved, always came out worst. This is because the nozzle can not get into tiny openings in characters like: N, M, K, H, G, B, 8, etc... So they get completely messed-up and the openings (engravings) get closed. You are better off making raised text. While it still looks a bit Flintstone-like, it is easier to read. If it has to be recessed somewhat to prevent it from being damaged easily, consider recessing a plate surrounding the text, but rais
  10. This can also be used for bonding PLA and PET. Or bonding can be an undesired side-effect if you are not careful enough. But I don't know if the bond will hold forever, how strong it is compared to the material itself, or if it is susceptible to shocks (like cyano-acrylates: they can be knocked apart) or to heat-decomposition. Here a few pics of the bonding. Also note that the smoothing removes layer lines, and seals underextrusion if not too bad, but due to the high-gloss and reflections, it might make the surface look rougher than the dull raw print before, in some ca
  11. Thanks for the feedback. I only see it now, must have overlooked it before. With that amount of shrinking, it could be good for artwork, toys like model railroad stuff, and other models that don't need exact dimensions. But less suitable for rulers or tight-fitting technical parts. If you would have real models that you can show, I would also appreciate that. In green state, after sintering, and then after further post-processing (tumbling, sanding,...). If possible, also in close-up? Would be good to see the differences in material structure.
  12. For me, the salt method works very well for long, low, and 100% filled models like rulers, that take 1 to 3 hours to print. Thus for my typical models. I use it all the time, and almost never use any other method. It gives excellent bonding for PLA (may not work for any other materials), when the glass is 60°C. But no bonding at all below 25°C, so models come off by themself after cooling down. No need to remove the glass from the printer. I just drop a few drops of salt water on the glass, wipe it, and ready to go. That easy of use is the most attractive for me. However, narrow bu
  13. I read on the datasheets that Aquasys dissolves at 70°C-80°C: does that mean that this is the minimum temperature to make it dissolve, or is that just the optimal for the fastest results? How does it perform in cold or hand-warm water, thus below 45°C, for PLA? It would be good if you could some feedback on your experiences.
  14. If it are rods, then it should be the *outer rotating rods*, those with the belts. Because it is their wobbly rotation that causes the pattern (I think). Try measuring and calculating if the circumference of the pulley wheel and belt matches the distance between the spots? Visually guestimating, it could. Or you could make it more easy: using a marker, mark a spot on the pulley and on the belt, rotate the pulley, and each time it comes along the belt, then mark the belt as well on that same matching spot. After a few rotations, your belt should have marks with the exact same distan
  15. Hope you can read a bit of English. I can read German, but not write it. I use a standard thin injection needle, of which I cut the sharp tip off (that would damage the brass nozzle), and rounded the edges with sanding paper. It was a little bit too wide, 0.41mm, and did not go into the nozzle opening. So I had to grind the sides also until they were 0.39mm ... 0.40mm. And then very gently poke from the bottom upwards into the nozzle, and gently push and scrape. Do not use side-forces, so you do not deform the nozzle-opening. However, I never had a total blocking, only
  16. I don't know Fusion 360, nor your design and requirements, so it's hard to give good advice. But in general, if you have special support requirements, you can always design them in the CAD-model itself. Then you have full control. I often do this because my models are tiny, and the supports are hard to reach: there is no room to get in with a knife or plier. See the example below: these are self-hanging supports, and easy to remove. The slot where they are hanging in, is only 5mm wide. If printed in PET, I need the supports, otherwise it wouldn't bridge. If printed in P
  17. To repair: trying to bend the rods the other way round, doesn't seem like a good idea to me: chances are that it gets far worse. So I wouldn't do that. I would say: now that you know the most probable cause: if you can work around this by using a slightly thicker first layer, then try to live with it? To rule out the glass for sure as a cause, what you could try is: mark and measure the exact centers of the "dots" you see, from the edge of the glass. Then rotate the glass 180°, and do the test again. If the cause is the glass, then the pattern should have rotated also.
  18. Glad you are back. I already wondered what happened. Yes, I understand the frustration of losing abilities. But the good thing is that concerning art, you are still way above average. Most people would not be able to produce that at all, no matter how much time they got. Like I would never be able to compose a song, no matter how long I got.
  19. I don't know your filament, nor your printer and print-bed, so it is very hard to give advice on what bonding methods and preparations you could use. But the chemicals you are using, are toxic and cause cancer, especially xylene. Some of my previous collegues got cancer after using xylene carelessly for years, against all our safety-advice. So use them carefully in well ventilated rooms, and don't touch them. Preferably look for non-toxic stuff, or less toxic. I have glass beds, and most of the time I never clean them: I just wipe them with salt water, and go. For my PL
  20. Off-topic, how to get pictures right: There appear to be some bugs in the image-insertion module in the forum. Inserting and moving pictures around by dragging and dropping, does not seem to work well. To get pictures right, I need to do this: - Ffirst drag and drop them from Windows Explorer into the grey area at the bottom. Not in the message you are writing, but just below that window. Then they will be uploaded, but not yet included in the message. -Now position your cursor on the right place in your text, where you want the picture to appear. Preferably t
  21. 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
  22. Your first layer should probably look more like these:
  23. 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.
  24. 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.
  25. 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
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