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Everything posted by geert_2

  1. No experience with nylon. However, I regularly print carabiner hooks in PLA and PET, and use them daily, just to learn how the materials flex and behave on the long term. The PLA ones always crack in the same place. The PET ones are more flexible and survive. Unless I pull too hard, and then they fracture too, usually at random places (not necessarily in the corners). So, if you would already have PLA or PET, try these materials first, and see how the model flexes and where it breaks. It gives an idea of the stress concentrations and weak points. Then, nylon will just be stronger and easier to flex than PET, and unlikely to break. Would a real full-scale model also be in nylon? Or rather in composite, thus much harder and stiffer than nylon (in which case it might behave more like PLA or PET, althoug much stronger)? Anyway, it looks like a very interesting project, which might also be usefull for composite airplanes. A question: how much turbulence do the little ribs create? And doesn't that disturb the smooth airflow and spoil the efficiency of the wing? Or will these ribs be covered with an extra plate later on? Would this flexible shape be more efficient than the crude profile changes achieved by traditional flaps and ailerons in airplane wings? Left and center: PLA/PHA-blend (colorFabb). Right: PET (ICE). The PET is more flexible and survives repeated opening well. The PLA/PHA show the usual point of faillure.
  2. I don't have an UM3, and never ran out of filament while printing, so I can't comment on that. But if the printer has been "printing" dry, then it is possible that the last piece of molten filament has been sitting at hot temperature in the nozzle for a long time, and that it got burned, and may have clogged the nozzle. So I would first make sure that the nozzle is not clogged, and thoroughly clean it, before restarting any print.
  3. I agree on thinkergnome with that question: usually top and bottom should be about the same thickness as the walls, but it depends on the model and material. If too thin, it can't bridge and close the top gaps. So I would suggest you begin with 0.8mm, same as the walls. Concerning printing speed, start a test piece with 50mm/s, and adjust up and down in steps of 10mm/s on the fly (if your printer allows that), to see how it affects print quality. Idem for temperatures: start with a safe average recommended for your printer (may differ from brand to brand, model to model, and material to material), and gently adjust up and down in steps of 5°C while watching it. Idem for bed temp: too hot and the model will sag, or peel off. Too cold, and the model won't bond well and may suddenly pop off. Try to find the point in-between where bonding is optimal, without deformation.
  4. I think you would best contact the manufacturers directly, such as for T-glase (is that Eastman Kodak?). Most of us have tried printing transparent parts, but with very limited success. Due to the inevitable entrapped air, both in-between the extruded sausages as in the center of the sausages, it is very difficult to get a better clarity than "frosted glass" or shattered glass. This is good enough to show a watermark, and let some light shine through. Suitable for model trains, and lenses for rear lights of bikes. But far from usefull for long real light guides and optical datacables. Another problem are surface defects due to layer lines, which act like lenses and which deform the light path. All these defects combined will probably play a much greater role in the disturbance of the ligth than the pure material characteristics. For good transparency, you will have to mould and cast, I think. See these blocks (20mm x 10mm x 10mm), with a hollow watermark halfway inside, printed at different speeds (50mm/s and 10mm/s, top and bottom) and different layer heights (0.40; 0.30; 0.20; 0.10 and 0.06mm left to right). This material is waterclear PET (brand: ICE, from Trideus in Belgium), but yellowed due to printing too slow at the bottom, thus subjected to heat for too long. In the second pic, one of the blocks is polished, to remove the outer defects.
  5. I have no experience with nylon, but from the recommendations I read here before: did you keep the spool in a dry-box with lots of desiccant during printing? And with a teflon tube from that box to the printer? So that no normal moist air comes in contact with it? It is known that especially in a moist environment, in a few hours nylon can absorb so much water that is can not be injection moulded anymore. I guess the same would apply to 3D-printing? Of course, theoretically there could be other causes too, such as dust accumulated on the filament and pulled into the nozzle, or the spool tangling up after some time of printing, or filament burning in the nozzle and gradually clogging it, etc..., but I guess you checked for these.
  6. I also had this once too. Got it out with fine tweezers. Otherwise, use a stick with chewing gum or sticky wax attached to it. Maybe it doesn't hurt the machine to leave it in there, but it does hurt your peace of mind. And then print a couple of these. See here, and scroll down a bit: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/
  7. I have no experience with soap models, but with moulding and casting in general with silicones, yes. First, I would suggest you start with a simpler model, a dolphin or shark, that can be made in a two-part mould. And then, as kmanstudios said, go to Youtube and search for: silicone mould making and casting This gives a wealth of information, with hundreds of very good tutorials, and product info. What I often do is: first print the model in PLA. Then in plasticine (a no-sulphur variant) I model a box closely around the part. And then I pour liquid silicone into the box. After curing, I remove the plasticine, and very carefully cut the silicone on appropriate places. These seam-lines are important: they should be in a place that does not deform the model, and they should allow you to remove the model from the silicone mould. Also, the seams should make it possible to assemble and align the mould correctly later on. Another option is to use paste-on silicone. Paste that onto the model and let cure. Then paste shell-material onto it: this is a paste that hardens into a very hard plastic, like polyester. Some people use gypsum too. Make the shell so that it can be removed, thus in multiple parts. Include alignment features in the shell, so it fits back together in the correct position later on. And provide channels in which you can pour the soap, and through which entrapped air can escape. There are lots and lots of things to consider and keep in mind. Making a good mould takes a lot of planning and studying, even for fairly simple models. Hence the importance of the Youtube tutorials: even if you spend a whole day studying them, you will soon win that time back.
  8. On my printers overhangs work better with thick layer heights: 0.3mm and 0.2mm are more beautiful than 0.1mm (haven't tried 0.06mm with huge overhangs). In 0.1mm layers, the edges of overhangs tend to curl up. Try to optimise the settings and design on *small test pieces* first, so you don't waste too much time and material. And indeed, a round underside might need a brim, or a custom flange designed in CAD, to make it stick. If it has to be a demo-model, I do understand your concerns about elegance: square tubing doesn't look as nice as round tubing. And especially a house-shape (=square with roof) might look ugly due to the unsymmetry. Maybe you could try a couple of small test pieces in different shapes next to each other? A round shape with brim, a house-shape (=square with roof), a true pentagon shape, triangular shape? Although personally I wouldn't use a triangular shape, due to the restricted volume and huge inner surface area, causing more friction to the flow. Then the students can see all the alternatives, and the benefits and disadvantages of each.
  9. Try a couple of these custom supports? They might work for your model. But don't expect miracles, it will allways be ugly. The ribs allow to make the gap smaller, without the support totally fusing with the model. If you provide enough methods for removing the support later (separate parts, holes for hooks and pliers, handles to wiggle things loose,...) you can also reduce the gaps. Making the support extend a bit (see bottom right in first pic) lets the model adhere better. The bridge in the last two pictures uses a separate support-bridge, so the supports don't go all the way down and don't destroy the text. It also has ribs for smaller vertical gaps. Maybe the same results can be achieved with standard supports in Cura nowadays. But I prefer to design my own custom supports, due to my often small or specialised models.
  10. I have no experience with soft 3D-printing materials. But soft plastics do not necessarily handle ink better. There are lots of soft plastics that do repell water, like PP and PE, so they wouldn't work at all. Have you tried treating the surface of PLA-stamps, to accept the ink better? Or try changing the ink, so it adheres better? If you could print in PLA, you would get the best details, I think. For example, try lightly sanding the stamp surface with fine gritt paper, so it is matte? And try adding a little bit of alcohol to the ink, so it spreads easier onto the stamp? The advantage of sanding (or similar treatment) of the print-surface only, would be that the symbol attracts the ink well, while the rest of the stamp repells it. This might give more accurately printed/stamped symbols on paper?
  11. Yes: they change surface tension: soap decreases surface tension (so the water spreads into a very thin layer), and salt increases surface tension (the water tends to pearl). That is how I came to the salt: I reasoned: if soap and oils reduce surface tension *and* bonding, then maybe I need something that increases surface tension, and hopefully bonding too? After googling, I found salt is one of the few things that increases surface tension. And it seems to work, at least for PLA, compared to printing on bare glass. But I am not sure this is the real cause, there could still be another explanation. Also, in manuals on glue, you find that the *glue* should have a very low surface tension to make it spreak easily, so it can easily wet and penetrate the parts to glue. And thus the part to glue needs to have a higher surface tension than the glue. I don't really know the chemics/physics behind it, apart from this simplification. If we would know more about the real mechanism, maybe we could find even better methods. And maybe this principle could also be helpfull for filament-development, to make it stick better to glass.
  12. Changing feeder tension changes the depth of the indents, and thus the effective diameter of the feeder wheel. And it changes the partial slipping of the filament (=filament speed not exactly matching the wheel, due to the indents being stretched by the resistance in the feeding traject). So I can see that both variables (depth of indents, stretching of indents) have an influence. And they will change with material stiffness too. The wheel will bite deeper into a softer material, and it will stretch more. Additionally, speed and temperature are going to play a big role too, because they affect flow-rate, and mechanical accuracy (overshooting, ringing). So I guess there will allways be quite some trial and error for this sort of jobs, especially if you are going to print it in different colors and materials. Which usually is the first requirement of kids, of course. :-) On the Lego-website I once read that the development of "simple" bricks requires quite a lot of precision engineering, to get a good fit.
  13. Does the inside of the tube have to be round? If you would give it a sort of teardrop shape, overhangs on top would be less steep. Then it could be printed in one material without supports. Or maybe you could even try a square tube, with pointed roof, similar to the "home" icon 🏠 in your browser? The tube would look weird, for sure, but it might work? Try this on a very small part first.
  14. An electric fault could of course be the cause, or a ground-wire with high resistance. Let's say you have a ground-resistance of 25 ohms, and a fault current of 4A (=not enough to trip the fuse), then you would get a voltage of 100 Volts on the ground pin of the socket. However, if this would be the cause, then it should happen every time you touch the frame of the printer, and *as long as you keep touching it*. If it is only a short shock and then nothing, it is static charge which is discharged when touching a grounded frame. So I would guess it is the latter? Maybe due to a change in clothes (wool, some synthetics?), or different shoes? Or very dry and cold weather? Or some other equipment that charges up, which transfers its charge to you, and then you discharge it via the printer and ground? For example old monitors with CRT tube were known for this. Try attaching a voltmeter to the ground-pin. If it is static charge, it will be very hard to measure due to the input resistance of the meter being too low and the charge leaking away. However, if it is a fault, it should be very easy to measure (try both AC and DC).
  15. @SandervG: This is weird, because I had the exact opposite experience when printing on bare glass, before I started using the "salt method. When the water spread out into a very thin layer, bonding of PLA would be bad: filament would curl up, the corners would lift, or the whole model would even come off. And vice-versa: when the water would stay in nice round bubbles, bonding would be reasonable. Now, with the salt method, the water also stays in nice round drops. And bonding of PLA is very good, as long as the glass is warm. So my reasoning was that the substrate (=surface to print on, thus the glass) should have a very high surface tension, and the wetting agent (=here the molten filament) should have a low surface tension. So that the molten filament easily attaches to the glass and spreads onto it. This is the concept what glues are based on, if I understood it well? (Correct me if I see this wrong.) Anyway, salt increases surface tension and increases bonding of PLA. And soap and oils reduce surface tension and reduce bonding. But I am no chemist, so I would like to hear the viewpoint of a chemist experienced in glues and bonding, for a better understanding of the basic laws of nature on this.
  16. If you would like to use a more gentle atomic pull, you could try my method here (scroll down a bit): https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ It lets the nozzle cool down much further than usual, and uses gentle wiggling and turning instead of brutally pulling. This avoids the risk of displacing the teflon coupler or nozzle, or bending rods.
  17. Maybe you should try spraying bright red fluorescent paint in the same way? You would be astonished for far it goes and how wide it spreads. After a few applications, your whole printer and half of your table will have a fine red cast to it. Years ago I used a big cardboard box in which I sprayed silicone oils on moulds, and black conductive paints on electron microscopy samples. Even though there was a strong vacuum flow sucking out the spray from the back of the box, it still went everywhere in front and left and right of the cardboard box. I have seen the same in other spray cabines from collegues. Similar, on old HP inkjet printers, after a year the whole table on which they were sitting, had a black cast around the printer. Just from the ink dust caused by the little sprays. It goes much further than you think. So I would recommend spraying only in a box, with air extraction, and far away from the printer or other sensitive stuff.
  18. I also have noticed that PET and NGEN (which seems to be similar to PET, from colorFabb) are not stronger than PLA. Although for snap-fit lockings, carabiner hooks, and similar things that need some flexibility, PET is much better than PLA, because PLA will crack over time. Also, PET can withstand the heat of the sun, and can be used in a car. PLA can not: it deforms even in mild sunny spring or autumn weather. But for pure strength where flexibility and temperature resistance are not required, PLA can often withstand more than PET. In my PET-models the fracture lines go diagonal through the material, and follow the stress concentrations. They do *not* follow the layer lines. So it has to do with material strength itself, not with layer bonding. However, if in your model the cracks would follow layer lines (=delaminate), there is a bonding problem. This could be due to printing too fast, or using too much cooling fan. So the next layer does not heat up the previous layer well enough, and it does not fuse together. Try turning off the fan, or reduce it to the absolute minimum required for your model. Also, try printing a bit slower: 25...30mm/s. At 20mm/s I can succesfully print PET at 2015°C (recommended range 215...250°C, brand = ICE, from company Trideus in Belgium).
  19. I think your cardboard box is a really great idea: it is very compact, and "part of the printer", sort of. But being of cardboard, it will absorb moisture by itself. It might be better to make it out of transparent plastic (and then you can see what is going on). And add little pieces of teflon tubing from the exit of the box to the feeder-entry. To close the seams between box and printer, maybe you could add soft foam like on window and door seals? I think it is worth developing this further. As Smithy says above, you should add *lots* of silica gel. I use 500 gram packs sold in car shops to de-humidify car interiors. These have a blue indicator turning to pink when saturated. Also, regularly regenerate the silica gel: once saturated it not only loses its function, but makes things worse. Also put dry silica gel in the box/oven while drying the filament. This silica gel bags are clean, easy, and can be regenerated on the central heating, or in a micro-wave.
  20. Maybe you could in CAD model a couple of little dots on the floor, separate from the real model? Then these dots will sit on the glass. All the rest will be at the desired height above it. The idea would be a bit similar to the cross-hairs in printing, to align the different ink colors cyan, magenta, yellow and black.
  21. I like the concept of the longer tubes. But I have a question: don't the red clamps pinch off the tube after some time? And how is unwinding resistance in this setup, compared to the standard spool holder?
  22. Hope you can read a bit of English. This problem is also present in the UM2, but less. It is most visible when using 100% infill and short infill strokes, when the head has to switch direction every few millimeters. This causes visible overextrusion in this area only. As Smithy says, print slow, cool, and with equal speeds (except travel speeds, which may be a lot faster). So that you get a flow that is as smooth and constant as possible, and without excessive pressure-buildup in the nozzle.
  23. Most likely causes, I think: (partially) clogged nozzle, deformed teflon coupler, or little fan not working? After cleaning the nozzle with atomic pulls, make sure you can look through it from above. If you want to use a more gentle atomic pull, instead of brutally pulling, try my method here: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ Check if the result of the atomic pulls is deformed near the seam of nozzle and teflon? If so, the teflon coupler is worn out. Check if the material is thickened or molten even before entering into the nozzle: if so, the little fan is not working (it tends to accumulate strings and hairs), and heat travels up too high into the filament. Manually heat up the nozzle and feed some material into the nozzle, and feel how much resistance you get, and where.
  24. I think yes and no. People who hope that a 3D-pen will be a cheap but good 3D-printer, are going to be hugely disappointed. (Sometimes it was marketed as such.) However I can see a niche market for it. For example if you want to create custom trees for HO-model train landscapes, then it gives you the freedom and organic irregularities you want. Realistic trees are very hard to model in CAD and print with a normal 3D-printer. Similar for some specialised decorations or juwelry. I am not sure how it would work for adding hairs, eyebrowns, moustaches etc. to 3D-printed models? But I think it could work. The question will be to find a reliable pen that works with an open filament system and with lots of different materials. One that is handy and pleasant to use. Handiness and versatility will be key points.
  25. I saw one in action a couple of years ago, but I don't remember the brand. It was something with "doodler" in the name, but the rest..? Not sure if it still exists. Anyway, I was not impressed with its performance: the art they produced with it, was primitive and clumsy at best. However, later on Youtube I saw others who got better results. So maybe you could do a search on Youtube? Both for getting an impression of pen performance, and of the techniques they use?
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