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geert_2

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Everything posted by geert_2

  1. I think most silicones will get hard and brittle, when exposed to hotter temps (250°C) for a longer time. Maybe you could also try *pure* aluminum, which is very, very soft? You can almost scratch it with a finger nail, and it is too soft to tap threads and screw bolts in it. Maybe try doing a scratch test between such pure aluminum and a brass nozzle (or whatever nozzle material you use), and verify under a microscope if it wears out?
  2. Just thought about this: you can not use other people and patients as guinea pigs. But you can use your own body. So, if you really want to know what these materials do in an aggressieve environment like the mouth: print a bridge for yourself, and put that over a couple of your own teeth. Use a transparant colorless material, so you can see all the little voids inside. For best accuracy, print slow and cool, but that means less flow and thus bigger voids in the model. Keep it in your mouth for a couple of weeks, and then watch it change color as bacteria grow and eat into the model. PLA is likely to decompose due to the aggressive enzymes whose job is to break down food, and PLA being bio-degradable... Other materials will probably get brown soon and start to smell. Part of the game is: you are allowed to clean the outside of the model when you brush your teeth, but not the inside, since you wouldn't be able to do that on a real crown too. So, any accumulated dirt will stay there. This would be a nice little experiment, but I am not going to do it.
  3. I don't think it is a good idea to use FDM 3D-printed objects in the mouth for more than a couple of hours. They are not accurate enough, so they are likely to cause irritation. But above all: the layer lines and little holes in-between are going to cause bacteria-growth and infections. However, maybe you could use a 3D-print as model to cast a crown from? Then you can sand, polish and seal the model prior to making the mould, so the cast does no longer have any layer lines or imperfectoins? Then of course you could use plain PLA, or whatever you like most, and print slow and at low temp.
  4. You are... OP is taking advantage of the infill patterns generated by Cura, to make an interesting outer shell on his print... Ah, okay, now I see. Thanks. If the design software allows to create "patterns" (=terminology in SpaceClaim / DesignSpark Mechanical; I don't know the name in other packages), then another solution might be to create one hole, and repeat that a number of times in X- and Y-direction, with 0.5mm walls inbetween (for a 0.4mm nozzle). I used that to create a sieve, which has a similar pattern. This requires very little work. Then you might still have some blobs, but at least it is already a bit more beautiful since the nozzle is now traveling along the lines only.
  5. I don't really see the problem with the head traveling over the infill? This will be closed and become invisible anyway, so why would it matter? Or am I missing something?
  6. I have a spool of Ultimaker nylon, but I haven't printed with it yet. Out of curiosity I cut off 10cm of filament and put that in water for a couple of days. After some time it does get more flexible, and it gets a sort of waxy feel: feels more like low-density polyethylene (LDPE) now than like nylon. A lot of 3D-printing materials are chemically modified for easier printing, to have less warping and better bed adhesion. Maybe one of the modifiers changes properties in water? Maybe one of the UM chemists could shine a light on this? I guess other brands may show similar changes? Since this is just one strand of 2.85mm filament, not printed, I don't have any idea what this would do to the strength of a print, and to layer bonding. I am gonna dry it at 60°C and see if it changes again. Edit: it has been drying for two days now, and it seems to recover to its original stiffness. At least to my subjective feeling, since I haven't done any scientific strength tests.
  7. I would suggest: if possible, have a small PLA test print made *while attending it*. Watch and listen carefully. Then it will be obvious if everything is okay: bed and nozzle heaters and sensors, display, fans, feeder, stepper motors, all bearings still working, belts,... Even with the original feeder, you can get excellent results, on the condition that you manually unwind and stretch very hard filament (like PLA), so its bending radius is not so tight anymore, and it has less friction in the bowden tube and nozzle. This already allows you to start and get all the rest right (bonding to bed, slicing your designs, etc...)
  8. Try printing as cool as possible. Also, try putting a table fan in front of the printer, after it has printed the first two layers (do these without fan for good bed adhesion). I found these things help, although they do not totally solve the issue. But too much cooling might cause temp errors, if the bed- and nozzle heater can not keep up with the loss.
  9. Yes, but you can handle that with a bit of chemically inert silicone grease. The sort of thick white or yellowish silicone grease that is also used in binoculars, camera's and microscopes. And this thick grease does not leak and does not splatter around. But do not use petrochemical oils or greases, as they might chemically attack the rubber. Gently wipe the edge of the belt with it.
  10. Nylon absorbs a few percent of water, but then it should stay in a sort of equilibrium. And it definitely should not dissolve or decompose. A lot of clothing is nylon, and you can wash it without it falling apart. Also in industrial all-weather applications, you often find nylon blocks and rods being used for bearings. I have seen them here in automatic bridges from ships to the wall (dutch: "loopbrug"). Are you sure you have real nylon? I seem to vaguely remember that there do also exist some sorts of "biological nylon", based on plants instead of on mineral oil, which might indeed decompose? Maybe you need to google into that? Or maybe you use incompatible lubricants in the system? In model trains I have seen nylon gears swelling (just swelling so they would not rotate freely anymore, but no decomposing), but that was due to incompatible oils. Also, maybe you could ask your maintenance staff what they use in the industrial water? Usually this is just plain tap water and collected rain water that is stored in a big tank and recycled, with a desinfectant added (chlorine?) and or with UV-light treatment to kill bacteria? It shouldn't be corrosive, since then it would eat away all rubber seals too. Unless you would work in a recycling environment where they do clean sewer waste water by using plastic eating bacteria, and your watertank has been infected with these...
  11. These photos show what I mean (see my post above). This is a tiny cone: 20mm wide, 20mm high, printed in PLA. With default settings, deformation suddenly occurs when the layers don't get enough cooling anymore. When printing at a lower temp, and with a dummy tower next to it, this deformation occurs much later. But you still can't avoid it.
  12. This seems to be a very tiny model? If so, excess heat might also contribute to the deformation, I think. When I need to print very small models, and when there is a sudden change in surface area to print (from a big surface to a very small), I also see deformations. This seems to have to do with temperature: different cooling times between layers do show up as deformations. And not enough cooling time in very small details shows up as blobs and overextrusion, similar to the one you have here. I am guessing now, but if you print the base at high speed and high temp, and then the printer has to slow down considerably to print the tiny part (due to the minimum layer time setting), you may have too much pressure in the nozzle, and too much heat accumulated, before the system has time to adjust to the new lower speed and heat requirements? Could that be the technical cause? Anyway, I reduce this effect by printing a dummy block (e.g. a tower of 15mm x 15mm) next to tiny models, to give the printed layers enough time to cool down, before putting on the next layer. And I print as slow and as cool as possible. If you want to get really fancy, you could give the dummy tower the inverse shape of the real model: make a cube, put the original in it, subtract the original from the cube, so the dummy cube now has a hollow in the shape of the original. Then fill the bottom of the cube with a thin layer of 0.5mm, for good bed adhesion. So, now each layer area is the sum of the cube and original model, and it always has the exact same printing surface and cooling time (except for the bottom layer, but good adhesion is more important). This method may pay off for very small models. If there is a little bit of overextrusion, or junk accumulated on the nozzle's outside, or you are printing rather fast and hot, or if the material flow setting is higher than default, that worsens the situation in my experience. This does not exclude other possible causes, such as Z-problems, of course.
  13. Maybe you could try non-abrasive kitchen cleaning aids, like those used to remove burnt cooking rests in ovens? They work in a chemical way. Just make sure they do not get into the bearings, as they might be acidic or caustic, which could attack metals if staying on it too long; or they could contain solvents, which might attack the plastics around the bearings. If you want to polish, you could consider using a soft polish for plastic lenses? These should be far less abrasive than metal polishes. Anyway, try them on a small spot in the least used corner first (left back?) Or even better, try them on a separate piece, like a dirty coin. Edit: I just realised: in a car shop, you may find plastic lense polish. This is used to polish plastic head light covers to fully transparant again, when they have become dull due to the sun, or when they are scratched and sanded by sand and stones thrown up from the road.
  14. First do cold pulls or atomic pulls as the others said (search for the manuals on this site). Or if you want to do a more gentle pull, try my method. This method does not require brutal pulling, but works by cooling deeper, and by gently wiggling and rotating the filament prior to pulling. See: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ Then you should be able to see through the nozzle from above, or from below with a mirror: light must be shining through. Inspect the pulled-out pieces: are there bits of residu or foreign parts in it? I also sanded down a needle (one with a glass ball, so I have a good grip) to a diameter of 0.39mm. Normally they are 0.50mm here, which is of course too wide for my standard 0.4mm nozzles. Then after doing an atomic pull, I gently (!!!) poke through the nozzle from below. This also helps removing accumulated residu in the nozzle tip. But do this very very gently: steel needles are much harder than the brass of the nozzle, otherwise you would damage the nozzle.
  15. Could it be that the nozzle gets blocked, so the melt has no other way to go than upwards?
  16. I don't like the idea of information on one topic being fragmented over lots of sites: that makes it a pain to find anything back later on. So, info on Ultimaker stuff would best sit on the Ultimaker site, especially since they are very open to all sorts of discussions. (It would be different if discussing problems and solutions was not allowed, but this is not the case.) Further, I don't like "Faecesbook". First of all, you can not access the info without logging-in. And if you log in, you make yourself vulnerable to all sorts of data- and identity theft (since that is Faecesbook's business model). So, I will not join. This is my viewpoint, but of course, you are free to see things differently.
  17. I like this direct drive concept with the motor separated from the drive gear and print head. This removes a lot of weight and inertia from the system. This should be the direction to go for the factory UM2++ or UM2+++, I think. Have you tried magnesium as the drive shaft? This would weight less, but I do not know if it is strong enough, and if it is safe enough (as magnesium can catch violent fire when hot)? Another question: what is the purpose of the long slider with coupler, connected to the print head? Wouldn't it be possible to connect the square shaft directly to the extruder gear (with only a small conversion piece to convert it from square to the round hole of the drive gear)? But without this long block? This would save a lot of weight, and complexity, I think? I guess you will have a good reason for doing it the way it is now; it is just that I don't see it.
  18. Yes indeed, you are right; I just tried it now. I had not tried this when writing my previous post, but since you said earlier that it only searched the forum, I had simply *assumed* it would not search the manuals. My bad. So everything is okay for me.
  19. Hi neotko, This week I first encountered this phenomenon you described, when printing in PLA at a bit higher temperature. Good prediction! So it seems to happen occasionally when the material is quite liquid due to higher temps, and when there is a long travel through air. Never had it with my PET up till now, since that stays more rubbery like chewing gum, and doesn't leak so much. So traveling through air definitely benefits from a fast move. While traveling over land for PET and PLA at low temp, seems to work better with slow traveling speeds, to avoid the "bits of morse code".
  20. Have you measured if the first layer really is 0.1mm thick? In the first photo it looks much thicker, almost 0.3 to 0.5mm. Which could mean that the nozzle is too far away from the glass. (But if you had set the first layer thickness to 0.3mm it could be okay, of course.) Also, did you clean the glass plate with soap, window cleaner, white spirit, thinners, methanol, or other cheap cleaning stuff that might leave a soap- or oil-residu, which could destroy bonding? I think it is best to clean only with isopropyl alcohol and pure warm water. Further, I would rather start from 210 or 215°C for the first layers, and then if desired tune temp down. This too gives a better adhesion of the first layer. But if it has worked a 1000 times for you at 200°C before, this shouldn't be the problem.
  21. I think it would be a good idea to have a test part printed on various machines, via a 3d-hub service, or via hobby clubs in your environment, and see which models deliver the quality you want. Instead of buying a cheap assembled model, you could also consider buying a do-it-yourself kit. This will generally give you a bigger and better printer for the same amount of money. But this only works if you have enough technical insight to assemble it yourself, of course. If you are not confident in assembling such a complex thing, it could become a nightmare.
  22. For me the search works fine now since it is Google-based. But I could imagine that searching through the manuals and help-section too would be useful, not only the forum. For example if someone wants to know how to replace a teflon coupler.
  23. At first I was also confused, since some parts in the original photo seemed okay, some seemed gaps and underextrusion, and some seemed blobs and overextrusion. But when seeing the new photos, and when seeing the original in Photoshop with only the blue color channel (blue is opposite of orange, and shows more contrast), then it is clear that there are lots of gaps. So I guess it is underextrusion. If one layer is underextruded, then of course the next layer will sink into the gaps left by the previous layer, causing an irregular surface. Could it be that printing PLA at 0.2mm layer height and 60mm/s is a bit too fast or too cold for this combination, so the filament has not enough time to melt? This maybe in combination with tightly wound filament near the end of the spool, or with a worn-out teflon coupler? What happens if you print it at 215°C or 220°C?
  24. For nylon and ABS this is a well known problem: in a few hours they may absorb enough moisture from the air to make printing or injection moulding impossible, or with very poor results. But I hadn't heard about this for PLA yet. Although it does degenerate over time (months, years) due to moisture absorption: this breaks down the polymer molecules. I store all my filament in big boxes with a disseccant with color indicator (blue = dry, pink = moist). I found in a car shop: to dry car interiors and to avoid condensation on the windows. So it has a high absorption capacity. There are also a few people who have made boxes with a spool holder, and with a small exit hole, with disseccant, so they can keep the filament dry even when printing. Maybe that would be a solution for you? Just find a suitable polyethylene food storage box, drill a few holes in it. Then design and print a spool holder and fix it in it.
  25. I once made a filament welding tool like this: Procedure to weld: cut off filament ends at 90°. Then put both filament ends in the groves, and hold them down firmly with your fingers. Heat a metal knife in a flame, put the hot knife in-between the filament ends and push them onto it, melting both ends. Remove knife, and slide your fingers towards each other so the molten ends bond. Then wait until cooled down, and with a Dremel tool remove the excess flanges. It worked well, feeds correctly, but still, I didn't like it, so I don't use it anymore...
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