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geert_2

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Everything posted by geert_2

  1. On my UM2, the tube is also worn-out, but it keeps clamping well. If the nozzle is not blocked, and there are no temperature problems (printing too cold, so it does not melt), the tubing is the correct diameter, and the filament is not too thick, or any other things that block feeding, then I keep thinking that you might not be inserting the tube well enough? It is not sufficient to just push-in the tube all the way down. At the same time, you also need to lift the white ring as high as possible by pulling hard: this lifting is what will cause the locking afterwards. Could you veri
  2. For the future, get your staff and students to use other software than SketchUp for 3D-printing, or you will keep running into problems and keep repairing errors. SketchUp was designed for visual models only, not for 3D-printing. It produces sort of "cardboard" models where the edges do not fit together and are not watertight, not solid. It is excellent if you want a quick idea on-screen for an architectural concept, as long as you are not going to print it. Students and educators can often get free or cheap educational versions of professional 3D-CAD software. Otherwis
  3. I wonder how this would reduce stress? Wouldn't most of the stress be caused by adding hot new layers to a colder base, causing an *upwards* pulling force due to shrinking? Further, I think this might cause more ugly corners: now the ringing effects are on only one side of a corner, and they are the same for each layer. When alternating, these effects would alternate too. This might cause the same combing effects as on interlaced videos?
  4. I just printed a filter for my vacuum pump, to prevent it from sucking up big particles when suddenly applying vacuum. The filter was printed on an UM2, thus in a single material, no supports. I printed the first model at 0.3mm layer height, 25mm/s. This was *not* airtight: when I put tap water on it, maybe 10 tiny jets spurted out of the shell, through tiny holes. The holes were where the layer-changes and take-offs and landings from traveling had occured. The second model was printed at 0.06mm layer height, and 50mm/s. This model is *absolutely watertight*. Yes it too
  5. I think the basic idea is excellent, and worth trying out. But maybe an optical sensor or mechanical switch might be more reliable? I would fear that a thermal switch could cause false alarms, e.g. when printing hot and slow without cooling fan, so there is no airflow. Then it might get too hot and trip. Or it might miss real leaks when printing fast, cool and with full cooling fan, if the air blows directly on the sensor, and it cools the outer shell of the leaking plastic too fast. Such a sensor should never give false alarms and abort a good print, nor miss real events: that will be the mos
  6. I never used sprays for 3D-print adhesion. But years ago I did use a lot of silicone anti-stick sprays for moulding and casting models. I had built a special cardboard box with fume extraction at the back, to take away the spray mist. And I only sprayed deep into that box. But even then the whole area outside of that cardboard box got slippery with silicone oil too, after some time. I have seen similar setups where people used spray paints, and there too the whole environment got colored. Even though they had fume extraction in their cardboard box, just like me!
  7. If it is a lab with normal ventilation, and you did not sit with your nose directly above the printer all day, and if you only printed PET or PLA, it probably will not have done any damage. Seems very unlikely to me. I don't know where you live, but here in Belgium the laws require that the air in a lab is renewed several times per hour (was it 6x or 10x? I don't remember). So you should get plenty of fresh air in the lab anyway. In a research lab, most other products you use will probably be more dangerous: solvents, biochemicals, composites,... Things woul
  8. Steep overhangs tend to curl up. Maybe that might cause this deformation? Watch closely while it is printing, then you can see if this is the cause indeed. If you can't get it to print well, another thing you could do is make an undeep thread, so the overhangs are not so steep. And then using a standard thread cutter, cut the final thread. When cutting threads in PLA, go very slow, and with lots of cooling. Otherwise everything will just melt. Don't ask how I know... :-)
  9. I have silica gel with a moisture indicator, which turns from dark blue when dry, into pink when moist. To the Ultimaker-developers: maybe you could try adding this moisture-sensitive pigment to the PVA? Then people can see at a glance if their PVA is still dry enough? I don't need it, since I only have single nozzle UM2-printers. But moist PVA seems to come up again and again here on the forums.
  10. I didn't make a real font-file, since I don't know how to do that. So to set text, you need to copy and pasted each character from the character set, letter by letter. Like in the old days of metal printing. This is good for a short copyright notice, but not very suitable for 3D-printed newspapers, obviously. The character set is in DesignSpark Mechanical's native format, RSDOC; and DesignSpark Mechanical is freeware (requires registration). If you would like to convert these characters to a real font, thus a TTF-file or similar, feel free to do so. Just kee
  11. When mounting the bowden tube, do you push it far enough in, all the way down? Thus: first lift the rentention ring with your finger nails. In my printer this is a white ring on top of the head, where the tube goes in. Then insert the bowden tube all the way down, while you keep the white ring lifted. And then insert the horseshoe clip? If the tube is not inserted deep enough, it may not grip well upon pulling. That could produce the phenomena you see. (But that does not mean there can't be other causes, such as a worn-out tube, or incorrect outer diameter.) For easier
  12. Extruding thin wires of consistent diameter is not easy: try manually extruding a sausage from your printer, by slowly turning the wheel. Through a 0.4mm nozzle, I can get sausages ranging from 0.05mm up to 1.0mm, by varying temperature and pressure alone. The extruded plastic contracts length-wise after coming out of the nozzle, while still molten, as the molecules tend to go back to their usual curled-up shape (instead of being too stretched-out). This makes the diameter very unpredictable, and requires a very constant temperature, pressure, speed, cooling; and constant monitorin
  13. Where did the old printers go? Were they sold, given away, or are they sitting somewhere in the basement, collecting dust? If given away and they still worked, I would suggest you just donate the filament too. If they are sitting in the basement, you could revive them in a separate room, and let students mess around with them for their hobby projects, and let the students take care of them, thus out of the official curriculum.
  14. It looks very similar to the Polyalchemy Elixir filaments, which were the first in this class as far as I know. It seems a lot of companies have jumped on that bandwagon of shiny silky filaments recently. Haven't tried them yet, but I might in the future, I like the metalic aspect. In your experience, how is surface quality? Does the shinyness hide defects, or does it rather make them more pronounced? And how are warping, layer bonding, and temperature, compared to standard PLA?
  15. Would it be an option to hollow-out the model in CAD, instead of in Cura? Let's say we have a solid cube. Then, in DesignSpark Mechanical you can delete one face, and set a wall thickness for the remaining walls (so it is printable). This turns the object from a solid cube into a hollow cup. I don't know if your software has such an option? Also, make sure you have enough contact-area to ensure a good bonding to the glass. This may depend on the bonding method. For my "salt method", a single wall is good for low flat objects, but it is likely to come off for
  16. In PLA-based filament it is known that microcracks can grow if the filament is bent or stretched (thus kept under a load) for a longer period of time. So, don't let material sit still in the feeding-traject after the print is finished, but unload the spool immediately. Some materials also get brittle due to changes in crystal structure, becoming more crystaline (often reversible), and due to moisture absorption and damage (not reversible as far as I know). Both happen in PLA. Keeping it dry obviously helps against hydrolysis. But I am not sure what the best solution is
  17. I was referring to the squishing of the filament indeed. I have two older UM2 printers with manual bed-adjustment, and I adjust it closer, so it is squished more. I prefer a nice glossy bottom, even if that causes a little bit of "elephant feet" sometimes. Not only does that stick better, but it makes watermark text in transparent materials (=inside the model, close to the bottom) easier to read. In Cura, I usually set the first layer to 0.2mm. This too helps in giving a flatter bottom than 0.3mm, and gives better bonding. I have no experience with UM3 or newer, so I ca
  18. If that is the underside, I would level the bed closer to the nozzle. It is hard to see from this angle, but I think it is not flat enough to my taste. :-) I prefer the bottoms of my prints to look more like this, or like the above photos.
  19. Belts are replaceble, and the procedure should be somewhere on the Ultimaker-site. If you are a bit handy, you can do it yourself. Your local dealer should be able to provide the belts. Or you can have him/her do it. While you are at it, I would take the time to have a look at the feeder too: is that clean and in good condition? Also clean the metal rods near the belts, and lubricate them with a thin oil that does not dry out. And also clean the nozzle with cold pulls or "atomic pulls". See the official method on the Ultimaker-site, or use my gentle method h
  20. Just randomly printing Lego pieces doesn't seem like a good idea to me, since: (1) they won't fit, as a 3D-printer doesn't have the required accuracy (microns), and so the pieces would be useless; and (2) you will soon run into copyright claims and huge damage claims, as these are protected models. What you could do however, is go to a local school, and say that you have unused printing capacity. And then let the kids design things themself, so they learn how to do it and they get enthousiastic, and then print those models. Also learn them the possibilities and limitati
  21. Most materials should be reasonably airtight if printed *slow*, in *thin layers*, and with good flowrate. So you get good layerbonding, and absolutely no underextrusion (important). A little bit of overextrusion could also help, but might create blobs. Do not use separate support materials (PVA) that dissolve: if they made strings in a print, these will dissolve and become holes. But all models will have tiny "canals" and pores where bacteria can grip and grow. It's just that the water or air won't blow through. For shell thickness, I would use at least 2 lines (=0.8mm
  22. If you look at the bottom, did it lift from the glass? Thus making a dent in the bottom? If yes, it could be caused by dirty, greasy spots on the glass? Clean with isopropyl alcohol, and then a few times with pure hand-warm tap water only. (No soaps.) A thinner bottom layer gives better bonding for me: 0.2mm is much better than 0.3mm. I guess because the material is squeezed more into the glass, and it has less room to escape sideways? Then use a bonding-method for better adhesion. Some people use the glue-stick, some use dilluted wood glue, hairspray, 3D-LA
  23. I haven't printed with nylon yet, so I can't comment on material-specific things. But if you are not happy with the default supports, you could design custom supports in CAD, and switch off support in Cura. In this way you can provide features to make removal easier: holes and gaps where you can insert knifes, hooks, pliers; or tree-like structures to save material and provide additional gaps for access; sideways support for higher models to prevent wobbling; extended supports with extra brim for or tiny features; free-hanging supports to not damage the plate below it; etc...
  24. And no soap: that prevents bonding as well. Clean with whatever means you need, then with isopropyl alcohol, and then a couple of times with pure hand-warm tap water only. Rub and wipe dry with paper tissue, without touching the glass with your hands. Also kinks in the filament which prevent the filament from passing through the feeder, or the filament stuck under other windings on the spool which prevent it from unwinding, can cause underextrusion. I had the last one recently. So, never let the loose end go, never let it hang around, and never let it get un
  25. The best is: make a few test models that have all typical features of your models. And then print them with various settings, to see the difference. Make them small enough so they don't waste endless amounts of time and material, but not too small, so the models still gets enough cooling (=without the hot nozzle sitting constant on top of the same place). Further: print slower and cooler than standard. This will give better corners. How slow and how cool depends on the model and material, and layer-thickness, so you have to try. For PLA, try something like 25...30mm/s and 200°C, an
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