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geert_2

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Everything posted by geert_2

  1. Another option would be to just print everything, and then compare them to the design on the computer-screen and puzzle... :-) I would not do this for the main buildings for clients, but if it is for the surrounding decorative buildings ("filler buildings"), which often don't matter too much, this could be done.
  2. I once tried melting PLA together with this tool. It worked fairly straight forward: cut both filament ends in a 90° angle, put them in the guides, and keep them in place with two fingers. Heat a knife in a bunsen burner, and insert it in-between both ends. A soldering iron should also work. Slide the ends towards the knife or soldering iron, let them melt, remove knife/iron, and push molten ends together. Keep a while until cool. This goes easier than describing it. But then I had to cut off the inevitable flanges and smoothen these out with a cutter knife or Dremel-like tool. It worked well,
  3. More than 50°C is too much for PLA, it will warp. It is best to stay below 45°C. While ethylene oxide may sterilise well, I am not sure if it is a good idea to use it. It is extremely explosive and requires very little ignition energy. It can explode in concentrations between 3% and 100%, contrary to most other gasses which only explode between 5% and 15% or so. The smallest spark is enough, e.g. from dropping a steel screwdriver. Almost all production plants in the world have suffered severe explosions. The plant I have worked in, also exploded a year after I left in 1986, and tha
  4. Yes, I was going to say it looked too big indeed... :-) But in my model, the connection strands are not plates, but just sort of tiny "hairs": they are 0.5mm wide (=a bit more than nozzle-width), 0.2mm high (=2 layers of 0.1mm), and 1mm long (=the distance of the gap). Before you print the whole box, try the concept on a small test piece first, to find the best dimensions for your materials and printer. The concept is clearer in this pic, where only the outer supports are shown. For reference: the upside-down stairs and the table plates are all 1mm. For smal
  5. Wow, if all that white is salt, then indeed you used way more than I usually do. I prefer a thin layer that is almost invisible: after applying the salt, usually my glass looks a bit "dusty" like a drinking glass that has been unused for a couple of years. For me, the first pic below (orange testmodel) has already too much salt; while the last one (with label "the salt method") has the optimal amount. Hardly visible when looking down vertically on it, and a bit misty when looking horizontally at it. But of course, it is best if you try different methods and choose what
  6. Most silicones I have seen can withstand 200°C, and up to 260°C for a very short while. But molten nylon is likely to be too viscous at this temperature: more like thick sirup instead of water. You would have to inject it at very high pressures and speeds (which would deform or damage the silicone). It will also be very difficult to get entrapped air out. And indeed, it will cool quickly upon touching the mould walls, making it difficult to fill the mould. You would need liquids that chemically cure, like ahoeben said. But then still make sure they are not too exotherm, as this may
  7. If you design custom support structures, maybe you could add sort of dovetail things in it? (I hope this is the correct English word.) Like they used to do in old woodworking. See this: the bottom red symbolises the custom support, the middle white is the PVA, and the top red is the real model.
  8. geert_2

    Brains!

    How did you convert the MRI-data to something slicable (STL/OBJ)?
  9. You need to make sure you have no undercuts, and that all side walls have draft (=wider opening at the top). Otherwise the models get stuck. If in doubt, make the walls out of multiple parts, and provide strong flanges with holes to screw them together. Provide big openings for pouring in the liquid, and openings for venting air. Make sure no air can get trapped. Weight could also be a problem in big models: make the walls thick enough, and provide extra supports where required (like the beams on the sides of castles and cathedrals). And heat dev
  10. A bit off-topic: before printing 230 copies, have you tested if these 3D-models are fully functional and can withstand the desired loads, plus any brutal abuse (dropping, slamming into things)? If they want 230 pieces, it probably is for a functional test, not just for a visual demo...
  11. I modeled this test table in CAD in DesignSpark Mechanical (freeware, requires registration). Dimensions in this test model: - for reference: most plates are 1mm thick, text caps height is 3.5mm, text legs are 0.5mm wide - horizontal gap between supports and model: 1mm - tiny connection strands to keep support attached: 0.5mm wide (for nozzle of 0.4mm) x 0.2mm high (=2 layers of 0.1mm). These can easily be cut off, and cleaned. - inverse staircase in supports: steps of 1mm. This staircase reduces the overhangs curling up, but does not eliminate it. But in my tes
  12. Did you write "alignment-marks" on the pulleys with a marker? To see which one, if any, is slipping? Also check if your print head moves smoothly. If it would get stuck (e.g. no lubrication, dry bearings, or oil that got too sticky), it could cause the stepper motor to skip steps. I don't know if this could also happen if the steppers simply get too hot? Printing too fast could also cause skipped steps.
  13. Like tinkergnome said: also inspect the rods, bearings, rubber bands, nozzle, bowden tube, and rotating knob for wear, and the housing for scratches. My UM2s have 1000...1500 hours, and they still print fine. But you can see some wear on these parts. Depending on the material and temp printed, expect that the teflon coupler might also be worn (but this is hard to see, you would need to do a cold pull and inspect the outcome for deformations).
  14. Yes, I have also had a glass chip while cooling: I heard the normal little ticking sound of the model coming off gradually, and then suddenly I heard much louder snapping sounds... Forcing the model off while the plate is still hot, also seems a no-no to me. That would rather increase the risk, I think. Try a thicker layer of not too strong glue, that can absorb the expansion/shrinking. Personally, I use my "salt method" here too: wipe the glass with a tissue moistened with salt water, prior to every print. Let dry into a thin mist of salt stuck to the glass
  15. Yes, but this might be ugly, since the printer outlines every character. And for letters like E, N, H, etc, the problem is the same: here it may not be able to fill the openings. Some time ago I made character test sets with extruded text, recessed text, positive watermark text (=characters are solid, surrounded by voids, all below the surface of the model), negative watermark text (=characters are voids). Recessed text came out worst. For opaque materials usually I prefer raised text of 0.2mm high, leg width 0.5mm, caps height 3.5mm. For transparent materials I use wat
  16. Up till now, all parts printed in transparent PET (brand: ICE, from Trideus in Belgium) and in NGEN (colorFabb) have survived well in my car, even in the hot summer of 2018. These can be printed quite easily, although NGEN is more difficult to glue with my cyanoacrylate glues. And indeed, parts in PLA warp, even in mild spring or autumn weather.
  17. For best quality of the text, I would print it on its back, thus the text facing up. But I would design custom supports, so that I would use far less material, and waste less time. Similar to this test with support bridges shown below, after an idea of user smartavionics if I remember well. I don't know if this feature is already integrated in newer versions of Cura? (I am using an older one.) If yes, try that first: it will probably give a much better undersurface. I have UM2 (non-plus) single nozzle printers, so I can print in one material only (this is PLA).
  18. If you suspect "not enough flow" is one of the causes, maybe you could try a (bigger) priming tower, or print a dummy block in PVA next to the real print, to keep more flow going through that print head? So it is always well purged? Try the idea on a small piece first, before doing a large job.
  19. I don't have a dual nozzle printer, so just guessing: When using dedicated support materials like breakaway or PVA, shouldn't the gap between support and model be zero? So that they are squeezed well together for a good bonding? Maybe you could try this on a couple of small test pieces?
  20. What about PET? This prints reasonably easy, although I don't know about compatibility with support material? Anyway, wasted PET bottles seem to survive very well in the ocean, without much degradation.
  21. For PLA, try wiping the glass with salt water and paper. For me this gives very good bonding when the glass is hot (ca. 60°C), but no bonding at all when cooled down to room temp. Also, make sure the first layer is squeezed well into the glass: the bottom surface should be flat and shiny, like this. This PLA-surface reflects almost like a mirror (the bottom pic shows the cover and fan blades of a fan behind the model, the top pic shows the model itself. It is the same model, but I couldn't get both in-focus at the same time).
  22. Wasn't there an option in Cura in which you could shift a second model into the first one, to modify the infill? So, if you would make a second model sitting on the glass, and change that to zero wall width, and x % infill? Then shouldn't that give an infill-only bottom plate? (I don't have the latest Cura version, so I don't know this, but I vaguely seem to remember reading about it: was that you kmanstudios who used that technique in your gyroid-filled statues? Or was it gr5?) Second option: maybe in CAD you could use the shell only of your model? Thus turn it into a surface
  23. In DesignSpark Mechanical this can easily be done in CAD in the model itself: - Make a backup and work on that (never on the original). - Select and delete all internal geometry you don't need. - Select and delete all screws etc. that you don't need. This may leave gaps. - Select and delete the gaps. - Select and pull any remaining walls that are too thin, into a thicker wall. Other method: - If the model would contain too much internal geometry to delete one by one, you can select only the outer surface and copy that surface only. That will remove all
  24. You will definitely need to chemically "activate" the surface before glueing, and use a glue designed for plastics and nylon. Otherwise bonding may not withstand high loads and repeated flexing. Maybe you could also look into mechanical bondings, in addition to glue? For example dovetails (I hope that is the correct word in English), recessed screws, recessed rivets flush with the surface, sewing (like in the old days of book-binding), or so? Another option that just comes to my mind: polyurethanes are usually easier to glue than nylon, and some of them are also flexibl
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