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geert_2

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Everything posted by geert_2

  1. In its simplest form, the "box" around the model would be a simple standard food box, as in the photo. Or two on top of each other, for a better insulation. Just put it over the print at the moment it finishes, adjust build plate temp manually to the desired level, let it sit there for a couple of hours, and then very slowly let it cool down. Maybe I forgot to stress this point in the previous posts: after annealing, let the prints cool down *very gradually and very slowly*, preferably over a period of a few hours. Don't remove the cover before it has totally cooled down to room temp. So th
  2. Here are a few pictures: one is from a very small transparant block (about 0.5cm), with a small metal ball from a bearing pushing on it: you see the stress distribution due to this load. The other photo is from a moulded part in Araldite two-component resin, containing a lot of bubbles due to the mixing. You see the stress concentrations around each bubble. And the last shows the moulded in stresses in a dental appliance, especially around the metal pins. The higher the stress concentration, the closer the coloured lines are sitting together. This is a bit like height-lines on a map (I
  3. I also have this on small parts, for example on fine text of a few mm height. It indeed seems to be caused by the head stopping for a fraction of a second while retracting, and then moving on. I can reduce it but not eliminate it by reducing temperature and printing slower, for PLA down to 180°C or 190°C, and 20mm/s, for small parts.
  4. The idea is not to reduce warping while printing, but to reduce internal stresses that would cause problems later on during the part's service life. A bit more about the background: when any parts are moulded in metal, glass or plastic (for example via injection moulding), they have huge amounts of internal stress moulded in due to the force of the flow that was used, and due to the always uneven cooling that follows. Edges and thin areas cool faster than the inner parts and big volumes. If you watch transparant parts of glass or plastic under polarised light, you will see al those nice colo
  5. In another post user Artiz mentions as a side note that he anneals his polycarbonate prints by moving the glass plate directly from the printer into an oven, and let it sit there at elevated temperature for a couple of hours, to relieve the stress due to uneven cooling caused by the printing process. This seems like a very good idea. The advantage of doing this on the glass plate, immediately after printing (thus without the glass cooling down) is that the models do not warp as long as they sticks well to the glass. I have done annealing in an oven too, but only after removing the parts. In
  6. If you *tune* the speed up to 150%, then you not only increase printing speed, but also traveling speed (which is usually much higher than printing speed). If traveling speed would for example have been set to 200mm/s, then that would become 300mm/s after tuning, which might be higher than the maximum the stepper motors can handle without skipping. Could that be the cause? When playing around with tuning speed up very high, just to see what would happen to my extrusion, I experienced something similar. I would suggest you try setting the printing speed at a desired high value in Cura (or wha
  7. Since about 10 days I wipe the nozzle with non-stick silicon oil prior to printing, and then again after each print. I use the sort of silicon oil that is also used for easier release of castings from a mould. Since then I have no more build-up of molten material under the nozzle. Maybe you could try that? First clean the nozzle's outside thoroughly: warm it up a bit (to 120°C or 150°C or so) and wipe it clean with a tissue. Then spray silicone oil on a small paper tissue (but do this far away from the printer, so that you get no oil on the build platform, which would destroy sticking). And w
  8. Do you make them on a vacuum thermoforming machine where the model and the plate to thermoform are both placed under a heater, and the hot molten plate is then pulled over the dental model, and sucked vacuum? (Such as the Erkodent thermoforming machines?) In that case, probably the heat is the main problem. PLA starts getting soft from around 50°C, and your thermoforming plate is heaten to maybe 120 or 150°C or so. So I would suggest that you try printing the teethmodel with 100% infill, just for testing, and that you put that model in the freezer prior to thermoforming. Do not yet insert
  9. I see that you print with 2mm filament? I guess by that you mean: "2.00mm", is that correct? could you check that again? Normally, the filament should be 2.85mm (which is sometimes referred to as "3mm filament"). So, if you use 2.00mm filament indeed, you will sure get underextrusion, since the printer expects a much thicker filament. The surface area of 2.85mm filament is about twice that of 2.00mm filament. So you need to accurately measure the filament diameter and set this correctly in the settings (but I don't know where to find that setting), or you need to adjust flow rate accordingly
  10. I never use the official method to change filament. It goes much easier in this way: - Remove the horseshoe clip on the head, and remove the bowden tube from the head, with the filament still in it. Since the Ultimaker2 does a large retract after each print, this goes easy. - Move the material 1 cm forward, and cut off that irregular molten end. This eliminates the risk of getting that irregular blob stuck in the feeder, or getting the thin string in the feeder. - Do an atomic pull to remove the remains of old material from the nozzle, and to clean it at the same time. Do more atomic pulls
  11. The software seems to be their own development. The basic idea is brilliant, definitely worth remembering. But at this moment the distortion seems to be too much concentrated in a few small areas. If the distortion was more equally distributed over a much larger area, this would greatly improve component life, I think.
  12. I used to say that 3D-printing was not accurate enough to create smooth dolls like barby dolls or so. But obviously I need to revise that statement. Then a question: instead of using a brush, have you ever tried using a spray bottle? The sort of bottle with a hand pump, and adjustable spray nozzle, which people also use to spray plants? If the spray could be adjusted fine enough in a fine mist, without big drops and pooling, then you wouldn't need to touch the model while spraying. So you have less risk of getting marks on the model. Or would that have other side-effects?
  13. As Didier says. I also had this once when the 230V power cable came loose from the power supply. After that I made a clamp from steel wire, so that the power cable can never detach by itself. Never happened again. Also, on the Ultimaker2 (I don't know about the plus), the little power connector at the back of the printer needs to *click* into place. Otherwise it is not inserted deep enough. I would check these first.
  14. If you would ever have an issue with PLA not sticking well to the glass plate, try my "salt method" first: dissolve some table salt (NaCl) in water, and use that to wipe the glass plate. Let it dry into a thin mist of salt stuck to the glass. This gives an excellent bonding when hot (60°C), and no bonding at all when cold (20°C). Salt and water cost you nothing. - For Ultimaker and colorFabb PLA: excellent bonding, no corners lifting at all, no need to use brims or whatever. - For ICE-PLA: still good bonding, but not perfect: occasionally corners of difficult objects (big, 100% filled) do li
  15. Does it need to be 3D-printed? Another option might be to print a negative in 3D, thus a mould, carefully sand that so it has a perfect shape, and then use that to cast the models in any appropriate material? For example polyurethane? This comes in a lot of different qualities, from hard, to tough but still hard, to very flexible. If it needs to be stiffer, or reflective, you could add in filler particles, such as metal. If you need a lot of copies, this might be the fastest way? In Youtube, search for: mould making and casting, to get an idea.
  16. My printers were too busy to print a FilCatch thing. So I decided to model one out of steel wire (chromium steel, inox, very hard and with spring-effect; the same steel as used for dental retainers on kid's teeth). But apart from that it is the exact same concept as yours. I placed it on a height where the nozzle just touches it when moving across. When the buildplate rises, it also touches the steel wire, but due to the spring steel, it bends upwards and then bends down again without damage. This works well too, and it should live longer than a plastic one. So, thanks for that great idea. Thi
  17. Hello Sander, Did one side of the glass plate get a special surface treatment to get different specs? And if so, which one, and why exactly (in chemical/physical properties)? Having a better understanding could help in case of other adhesion problems too.
  18. I would suggest you handle all sensitive equipment yourself: cameras, computers, 3D-printers... Or let it do by reliable family or friend. Some transport companies will do a good job and be very careful. But I have also seen postmen unloading a train by just throwing the boxes out onto the concrete floor, which was a two meter drop. Even boxes labeled with the "fragile - glass" symbol. To survive that, you would need 0.5m of shock absorbing material around anything.
  19. My two UM2 printers were delivered with 4GB Sandisk SD cards. Obviously they work. I don't know if it are SD or SDHC (I can't pull them out now since the printers are busy).
  20. What I would certainly do, is have a small object printed in front of my eyes. Then it is obvious if it works well or not. Maybe also print a big low object (e.g. 200mm x 200mm x 0.5mm) that almost fills the build plate, then you see if all axes move fine. Carefully watch and listen. Also ask about the PTFE couplers in the nozzle (the white cylinders): have they been replaced recently? If not, they will be worn out and you will need to replace them.
  21. I am not sure if PLA is the best choice for this. There do exist special filaments for casting. I haven't used them, and don't remember the names, but I saw a thread a few months ago. Maybe you could find that? There were waxes and other materials. If you print in wax, attaching other wax parts should be less of a problem. PLA might leave black ashes when it is burned away beforehand. And if you pour hot metal directly onto it (without burning it away prior to casting), it might catch fire and explode in your face.
  22. Even if you would succeed in printing this in one shot, it is likely to break when removing the supports, due to the very thin items, and since they are printed in the "wrong" direction, not along the layers (like wood cut in the wrong direction, instead of along the direction of the fibers, is also very brittle). If you can edit the model, it might be worth trying to split it up in several parts: railings apart, stairs apart, etc... And then print each part flat on the bed, without supports, and glue them together. Like the model railroad houses we built as kids. This would cost you less ma
  23. That FilCatch is a nice idea: I use to do the same manually with a pincette, but this would automate the process. But for sharpening the filament tip, cutting it off in an angle of 45° to 60° (thus in a sharp point) with an electronics cutter seems way faster and easier. Then it can easily be inserted in the feeder too.
  24. Apart from all other solutions above, what about rotating that model 45°? Almost all skulls are way narrower than long (and I have seen quite a few in our dissection rooms). Then it might fit on the platform? But whatever orientation you print it in, any round object is always going to require a lot of support structures which need to be removed and which will leave marks. FDM-printers may not be the best option for printing skulls, balls, skelets, or similar things; and nor may lithography printers (laser in liquid bath). For this sort of model, in real size, I would rather recommend usin
  25. Just to make sure: it's not about layer thickness, but about layer surface. (I use Cura 14.09, where all layers have the same thickness, except the first one.) If I have a model which has - at a given point during printing - a surface area of 10cm2 on let's say layer nr. 86, and then that surface area suddenly changes to only 1cm2 on layer 87, then that big change in surface area will be visible on the side walls. It causes a "thick line" on the side. On models where this is an issue, I usually print multiple parts at the same time (so each layer gets enough cooling time to almost environmen
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