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Everything posted by geert_2

  1. With a standard nozzle the extruded "sausage" is 0.4mm wide. But then it gets squeezed onto the model and spreads a bit. So, it will be hard to print lines and corners smaller than 0.6mm to 0.8mm. Maybe it could be done with a 0.25mm nozzle? But I still don't think the gear will mesh properly and run smoothly. Anyway, for best accuracy print slow and cool (e.g. 185°C for PLA). Also, keep in mind that if you print the gear in PLA, and it has some friction or is mounted close to a motor, it will deform from 50°C on, which can be reached very soon in an enclosed housing. So you might need a h
  2. I believe gr5 is right: the first layer should *not* look like round sausages that are dropped onto the bed. But it should look like a very thin plate that is really squeezed *into* the bed. Very different. If not squeezed into the bed enough, the molten filament will stick to the nozzle, instead of to the bed. And that is what I see in your videos. Especially for tiny details, such as holes, short lines or dots, this is very important in my experience: that is the first place where bonding will fail.
  3. Also important: use a 3D-program of which you can find lots of good training-videos, and that has a relatively low learning curve, feels natural, and still a lot of possibilities. So you can show the kids a video, and let them repeat. For toddlers it won't be suitable, but for kids of about 10...12 years with some computer experience, DesignSpark Mechanical might also be a good choice. It is legaly free (requires only registration), is a feature limited version of SpaceClaim, and you find lots of good tutorials on Youtube, or elsewhere. Most of the functions use the same "push and pull" st
  4. I think in cars they call it "partial slip", most noticable when braking very hard. On dry surface, you get the best grip of the tires when they slip about 15% (according to an article in an automotive magazine I read years ago). At which point they already start making a grinding noise. A 100% slip is when the wheels are locked up while braking. And (almost) 0% slip is when the car is just rolling down the road, without adding power, without braking. So most ABS systems are designed to prevent locking up, but allow the partial slip that gives the highest friction and best braking performance.
  5. On my two UM2 (non-plus) I do atomic pulls more gently and with less risk of damage, as follows: - Put print head in a front corner. - Remove old filament, remove bowden tube, insert a piece of filament used as cleaner, heat nozzle to appropriate temp, - Gently push filament manually through nozzle, until it's a nice stream. - Dial nozzle temp to zero. - Gently push a bit more, but not too much. - Then do a small manual retraction of a few millimeters: this takes the pressure off the half molten filament, at the border between nozzle and teflon coupler, and makes it easier to pull out th
  6. On my UM2s the speed of printing increases, and the speed of extrusion changes accordingly (so you get the same filling of the model); but also the speed of traveling increases. It does not change temp. However, if you make brutal speed changes halfway a print, you will see that in the model: it gives different ringing effects around corners, and if the model is small, the difference in cooling time per layer is also visible. Further, if the speed increases brutally, filament has less time to melt in the nozzle, which will give a higher pressure and less extrusion. This is also visible in the
  7. Do not use windows cleaners, white spirit, cheap alcohols for cleaning. They tend to leave soap or oil residues on the glass, which destroy bonding. Only use isopropyl alcohol, which dissolves oils. Then wipe again with pure water. And don't touch with your fingers. The current marks look like fingerprints. If you live in a moist climate, moist air also reduces bonding. Then I would suggest you try a bonding method: try my "salt method" (PLA only), see: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ Or try dilluted white wood glue (1 part glue in 10 parts water), or hair sp
  8. I have very little personal experience with lathes, and that is 30 years ago, thus not relevant. But a now retired collegue of mine is a professional metal worker; used to work on big manual lathes all life. He also tried a small lathe for small models, but that didn't work: it was okay for wood and plastics, but had not enough power for metals. And the clamps for the tools would move if subjected to too much force from the milling. So he dropped that machine, and went back to the big stuff, even for all plastics. I don't know which brand and model, but it was a very small thing, 50cm long or
  9. If the filament is near the end of the spool, thus if it has a very narrow bending radius, try stretching it manually (if you haven't done that already). Wind it bit by bit in the opposite direction around a 7cm diameter skater wheel, or something similar. So it has a bending radius of about 50cm, almost equal to that of the bowden tube. This will greatly reduce friction in the bowden tube and in the nozzle. Further, if you remove the bowden tube and manually put a piece of filament in the nozzle, you can often feel if the coupler is getting worn out: this often causes a higher friction at so
  10. If hard filament like PLA is wound too strong on the spool, especially near the end, then this creates a huge amount of friction in the bowden tube, coupler and nozzle. Also, this narrow bending radius acts as a strong spring, that resists unwinding. The UM2 feeder motor has enough power, but seems to have difficulty translating this power into filament movement. I guess that the pits that the knurled wheel bites into the filament get stretched out (=sort of partial slipping). If they get stretched by 20%, then that would amount to 20% underextrusion. For PLA, try this: with the PLA spool in
  11. Are you really sure you would want Windows 10 to flash your printer's firmware (if I understood that well in the docs), and to have it provide all the drivers? This might not be as bad as let Windows 10 flash your airplane's computer and provide its own drivers, but still... This sounds like a nightmare to me, and a recipe for disaster. Especially with Windows' automatic updates that you can not disable anymore (even not the incompatible ones), so they are going to happen halfway a 40 hour print? And with its huge amounts of spying functions and back doors? That means that not only Microso
  12. Cool and inventive concept, and nice achievement, especially for a student job. It must have been a mathematical nightmare, with all those 3D-rotations. But I still don't see how this concept is going to work for an upside-down U-shape, a table, or similar bridges, where you would need a 90° upwards rotation. Or for small models, where the head would have problems reaching into the details, while the table is rotating.
  13. What happens if you print the infill at a different density, or 100% filled? (Or just a small test part of it, to not waste too much material.) In my experience, any sudden changes in layer area to print give clearly visible markings on the outside, especially on small models, due to changes in cooling time for that layer. So, if the infill pattern changes halfway, I guess that could cause this effect too. Further, a change in pattern could also give a change in support, and thus be visible too.
  14. I don't have PVA, but I store all my filaments in a big closed box, and put a big bag of silica gel in it. These can be found in car shops, used to dry car interiors to avoid condensation on the windows. I use silica gel bags with a blue indicator that turns pink when the silica gel is saturated and needs to be heated in the microwave to regenerate. Then there is no need to heat the filament or storage box for drying. You could also use a smaller food box (the size of one spool), drill a hole in it for filament exit, fix a spool holder in it, put silica gel in it, place that behind your print
  15. What does it do when you print a square plate of let's say 30mm x 30mm x 1mm, 100% infill? Without brim. Does the infill come out well, or also weird? And in your photo, is that overextrusion (too much material), or is it the material curling up due to poor bonding to the glass, and thus giving a different reflection? This is hard to see in the photo, but it should be clear if you remove the print and inspect its bottom.
  16. I think for the little fans, you should rather calculate 1000 to 2000h to be on the safe side. As in the old Pentium and Pentium II computers, their bearings might wear out fast, depending on the production batch. I have one UM2 fan (the tiny nozzle-cooling fan) that started to make noise after about 1000h. Which means its bearing is getting worn out. So I injected that bearing with oil (*), and now it is running smooth again, but this won't last forever of course. (*) I did this by puncturing the silver seal with an injection needle and injecting a drop of oil through that hole. If you pun
  17. You could remove the bowden tube at the back end, and then try to feed the material by hand. Heat up the nozzle and see if you can easily push it through. Or remove the bowden tube at the nozzle end, and feed it manually there. At least this will give you an indication if there are any mechanical blockings. Could it be that the filament is too thick (>3mm), or that it is squished into an oval or thin plate too much due to incorrect spring pressure in the feeder. If the spring pressure is too high for the material, one diameter might become let's say 3.5mm, and the other only 2.4mm, or so,
  18. Maybe you could also try a commercial service like Shapeways or Materialise? They have a variety of materials, technologies and machines. Or find a 3D print hub service in your neighborhoud? Go have a look first to see if the quality meets your expectations, as this may vary, based on the equipment, experience, and materials the owner has.
  19. Yes you are right. Try that first. When writing my remark, I had mould-making two-component silicones in mind, with an upper temp a bit above 200°C. Mine changed from very soft and a green color, into brittle and whitish. But I hadn't thought of these high temp moisture curing silicones for engine systems.
  20. Yes, I think this is a good idea: any details smaller than about 0.4mm in X- and Y-direction, will be hidden by the 0.4mm nozzle lines anyway (if you use a 0.4mm nozzle). And if you print in layers of 0.1mm, any vertical details smaller than 0.1mm will also be lost anyway. So you could as well reduce the details to these resolutions. If you plan to sand and paint the model for a smoother surface, you could reduce everything to 0.5mm resolution, I guess. The rest will be sanded off anyway. If you can cut the original model in small pieces, you could try this on a small part first, so you do
  21. Have you tried printing this with the build-plate temp 5°C or 10°C lower? Or have you measured that build-plate temp? If you could get the temp just below where the PLA starts to get flexible, but still has enough bonding, it might work. For a stable bottom layer, I think it needs to be at least 0.5mm to 1mm thick. If you only make it 0.2mm or so, it will not have enough rigidity to keep the walls upright, I think.
  22. 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?
  23. 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 lik
  24. 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.
  25. 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,
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