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Posts posted by geert_2

  1. A print speed of 40mm/s seems quite fast to me, for such a big nozzle and layer? If I had to print it, I think I would rather go for 25...30mm/s.


    At least, that is my experience with PET: print as cool as possible, well below decomposition temperature, and then print slow and in thin layers to give it enough time to melt and bond well to the previous layers, and to cause not to much ringing-effects due to speed.


    These below were a couple of tests with PET.


    Top row speed: 50mm/s.

    Bottom row speed: 10mm/s

    Layer-height from left to right (mm): 0.4, 0.3, 0.2, 0.1, 0.06

    Temp: 215°C, except 0.06mm @ 10mm/s: 210°C; and 0.4 + 0.3mm @ 50mm/s: 225°C

    Nozzle: 0.4mm

    Material: transparent PET (brand: ICE)


    Printing slow and cool in thin layers gave by far the best results. But there was a bit decoloration (browning), so it was still close to decomposing temperature. I could have gone lower to 200°C for these thinnest slowest prints.

















  2. Edit:

    Quick summary: dichloromethane (=also known as methylene chloride), formula C H2 Cl2, can be used to smooth the surface of PLA and PET, in order to remove or reduce layer lines, and seal tiny openings in-between the printed sausages, or seal mild underextrusion. Dichloromethane can also be used to bond PLA and PET.


    Also see the Wikipedia info: https://en.wikipedia.org/wiki/Dichloromethane


    Below you find a lot of photos of the smoothing-effect on PLA and PET, and of the bonding.




    I just received a bottle of dichloromethane and did a couple of quick PLA-smoothing tests by brushing it on. Thus the cloakfiend-method (see his extensive tests and guidelines on the forum), but then using dichloromethane instead of acetone.


    Dichloromethane works better for smoothing PLA than acetone, and makes a shiny surface, "glossification". But it is not as good as acetone on ABS. It is somewhat halfway inbetween those. It does melt the surface a bit, rounds sharp edges a little bit, and closes tiny gaps. But it does not totally remove layer lines on crude models (haven't tried fine models yet). Overdoing it, by leaving thick drops on the surface, causes molten material to ooze out. It evaporates equally fast as acetone, thus very similar in that regard.


    I haven't tried vapour-smoothing yet. And obviously, I have no idea of the long-term effects yet.


    Photos will come later, when I have more time and more light. I just thought I would let you know that this could be an option too.


    Dichloromethane is easier to get than chloroforme, and does not require special permissions. But of course, being a strong solvent, it is poisonous as well, similar to acetone. And should only be used in well-ventilated rooms, such as a garage with open door, or outside. Or in a fume-extraction cabinet in a lab.


    • Like 1
  3. I have been printing PET or PETG (I don't know for sure which one) quite regularly on my UM2 (non-plus). Whether this is officially supported, I don't know, but it works.


    Don't print on bare glass, use some sort of glue instead. Otherwise the print may eat chips out of the glass upon removing.


    A disadvantage of PET is that it tends to leave burnt residu in the nozzle: a sort of glossy black varnish, which is more difficult to remove than the black powder residu from PLA. At least the sort of PET that I have (brand: ICE). For best results, I need to print slower than PLA, and on the cool side of the temp-range of this material. But that may differ from brand to brand.


    These are PET:





    Transparent PET is good for doing watermarks in the print, thus hollow letters sitting 0.5 to 1mm below the surface, as shown below, or in the ruler in the stems of the parts above. Note that this text is very small: caps-height is 3.5mm, leg-width is 0.5mm, nozzle-width is 0.4mm.



  4. You can make it a lot easier to remove/replace the bowden tube by printing a couple of these clips. They are much easier to handle than the standard pneumatic clips. Pull it out, push the white ring down, and pull out the tube. Replace in opposite way: push tube down while lifting the ring, then insert the clip.




    See here for the files (and then scroll down):



    • Like 1
  5. I don't know about current Cura-versions, but on older versions special characters could make files invisible to the printer.


    So indeed the above is very good advice: use only short filenames, only lower case letters a...z, numbers 0...9, and underscores or minus-signs. Nothing else. Definitely no spaces: they go broke in URLs and across some operating systems, and in batch-programs (batch copying or backups). No special characters, i.e. no: * / \ & | ? : + = " @ etcetera, as they are often interpreted as commands by operating systems, instead of as character. No foreign language characters.


    The reason for no uppercase characters is because Linux is case-sensitive: there can be two files "data.txt" and "DATA.TXT" in one directory, each with different content. However, if you copy both to a Windows system, one is lost, because Windows is not case-sensitive, and considers both the same. So it will or overwrite the first one you copied, or skip the second one. You may or may not get a warning message "file already exists", but if you have no clue about the cause, you won't understand it anyway.


    So, only: "a...z", "0...9", and "_" or "-". And short names indeed (UM2 can display max 20 characters, I don't know about other printers).


    Then the file is most compatible with all operating systems and devices.


    The diffence between "_" and "-" is mainly with search engines and line-breaks: an underscore is considered a normal non-breaking character, thus "john_johnson" is one word for search engines and word-editors. Whereas "john-johnson" is two words, and indexed and split over multiple lines accordingly.

    This doesn't mean that the filename is the cause of your current issues, maybe, maybe not, but it is definitely good practice.


  6. I haven't used ABS myself, but I read it can tend to clog the nozzle after some time, because its melting temp is close to its decomposing/burning temp? Have you cleaned the nozzle?


    Maybe printing a bit slower and cooler could help?


    If you suspect the bearings anyway (I don't know your printer), then try a small test-cube first, so you don't waste too much plastic and time on a complete big model. And see if it is present there too. If not, it's not the bearings probably.


  7. Tiny holes (e.g. <1mm) tend to get filled up because the molten filament is pulled inwards into the curve, like when you try to pull a rubber band into a circle.


    But most likely your model is defective, and has unwanted surfaces on top and bottom? So you might need to correct that in Blender, or run the STL through a repair-program. But I have no experience with this, so I can't give recommendations. When designing in DesignSpark Mechanical, I never had such problems, it always produced good STL files.

  8. If regular cleaning would fail, and you are going to drill out the nozzle anyway: maybe consider making your own drill from a 3mm copper or brass rod, or a brass M3 threaded rod? Brass is less hard than steel drills, and thus far less likely to damage the nozzle internally. Ideally, give the tip of your self-made drill the same shape as the internals of the nozzle-tip.


    So your custom drill should be softer than the nozzle-internals, but harder than the plastic you want to remove. (Maybe this would be a good tool to provide standardly with all printers?)


    I sometimes use a brass M3 rod to clean the side-walls of a nozzle, if there is too much dirt accumulated. It scrapes the sides like a soft file, sort of. But that probably won't work for you, since you need a sharp tip to cut through the PVA from the top, not the side. So you have to reshape the M3 rod on a grinding disk, and then cut big cutting-paths in it (I dont' know the correct name) with a thin nylon cutting disk on a Dremel, so it can bite into the PVA and remove the loose debris.


    Also, for cleaning the nozzle tip (=0.4mm on my UM2), I have modified a thin injection needle: I cut off the sharp tip and round the edges. Now I can insert this from the bottom into the hole, to remove partial blockings. But this alone won't help if the whole nozzle is blocked of course. Don't use a needle with sharp tip: this will damage the nozzle by biting into it.


    See the pics:


    Brass M3 thread, with rounded end to minimise risk of damaging nozzle internally.



    Gently scraping the side walls of the nozzle, to remove accumulated dirt. Always gently, never use brute force.



    Fine modified injection needle.




  9. In addition to what thinkergnome said: do *not* design it in SketchUp, as this creates exactly the problems you have now. And probably also not in Blender, as this also occasionally seems to cause problems, but less than SketchUp, and it is way more powerfull (also way more complex).


    Another program you could use is DesignSpark Mechanical (freeware, requires registration). I never had any such problems in many hundreds of designs.


    If you have to redesign from scratch anyway, see if you can replace the thread with a plain hole, and a bolt and nut, or similar standard hardware. That would make printing easier, and cause less post-processing afterwards. (I don't know what has to go in there, so hard to say what the options are.)


  10. I already said it in another post, but I don't remember which one, so I can't immediately find it...


    Some time ago I printed a filter for use in a vacuum pump, to prevent ingestion of pieces. I tested watertightness by putting tap water under pressure (8-9 bar) on it.


    If I remember well, it had a single outer shell, thus one pass of the nozzle. Printed at 0.3mm layer height it was not watertight: lots of small jets squirted out. But at 0.06 mm, printed slow and cool, it was absolutely watertight.


    If required, chemical smoothing such as acetone smoothing on ABS will also greatly reduce layer-defects and improve watertightness.


    The filter-effect was created by printing the bottom with 70% infill, or something like that (I don't remember the exact value, I tried a couple different ones), so it was a little bit porous. But the side-walls had to be watertight. After printing, both halves were glued together by adding glue around the mating edges.





  11. First check if that random movement is not in the layer preview in Cura. Most likely not, but there could be model problems or software bugs too. If okay, indeed clean the SC-card slot as Torgeir says: human hairs (I had that once), dust and filament hairs can get into it, causing poor contacts. If you have compressed air, blow it out. Or try a new SD-card. Try to write a long video to the old card, until full, and see if that plays well. Or run a disk check program on it.


    Something else I just come to think about: nylon can absorb too much moisture from the air in a few hours, degrading print quality. So when printing nylon, do it in a very dry climate, or put the nylon spool in a dryer box, even while printing, and route filament from there to the printer.

  12. I have heard about spontaneous unwinding of spools, especially near the end where they are tightly wound-up. Stiff filament acts as a quite strong spring, trying to wind up again. But if there is some sideways twist or rotation force present in the filament, it may jump off sideways.


    Indeed, anti-unwinding clamps are a good idea.

  13. In winter it might work, in summer I doubt it. And not if in direct sunlight behind a window. Standard PLA will for sure deform in a car left in the sun, even in mild spring or autumn weather. (Don't ask how I know this... :-) So if tough PLA is similar, then that will happen too.


    Also think about where the lamps will be: on a ceiling is hotter than on the floor, and above a radiator could be quite hot too.


    Do a few tests, and try them in the worst places, and then add enough margin.


  14. Exactly: print as slow, cool, and thin layers as possible. And, depending on the model, print multiple items at once, so the hot nozzle is moved away and the parts have time too cool down and solidify. Otherwise they stay molten.


    For more complex models, I also print a dummy tower (with inverted shape) next to the real model, for this cooling, and to make the printing time equal for each layer. Big changes in printing area do produce horizontal lines, due to differences in cooling time.


    See these:


    Left: printed without dummy tower, right: with dummy tower. This reduces the effect, but does not eliminate it.



    Dummy tower with inverted shape, for increasing and equalizing printing-time per layer. Concept model.



    Idem, real model.





  15. On my UM2 (=non-plus) the clicking noise is when the feeder tries to feed more material than the nozzle can eject. This is a sort of protection against overloading, I don't know the official name.


    Not sure if that is still the same on an UM2+?


    So, could it be that you are printing too fast, too cold, or in too thick layers? Or a bit of all, so that the nozzle can't melt it in time?


    Try a small testpiece and print a bit slower, hotter, thinner layers (whatever you think might be the cause)?


    But apart from the poor layer bonding, it seems the gear teeth come out quite well?

    • Like 1
  16. The normal procedure is to print slow, in thin layers, rather cool (because of the thin layers and slow speed), and set all temperatures equal. But it looks like you already did that, so... Maybe check if it is visible in layer-view in Cura, but not in the model in CAD? To see whether it is a printer-issue or a software issue or model issue?


  17. When printing a filter in PLA, I used only one wall of 0.5mm, and very thin layers and slow speed, to get it water-tight. It is mostly the thin layers (0.06mm) and slow speed that does it. When printing at 0.3mm layer-heigth, I got lots of tiny waterjets squirting out, like from a very thin injection needle. But I would recommend multiple nozzle-diameter lines, at least two.


    But the parts are very likely to warp in the sun, if outdoors. And the material might gradually degrade due to moisture and UV-light, like most plastics.


    So I would also encapsulate the electronics in silicone (if it doesn't require regular recalibration or maintenance). You see this also on encapsulated transformers, or on the bottom of tooth brushes (the charger). Companies like RS-components and Farnell do sell silicones for potting electronics.


    These pictures show the concept. The bottom was printed with 70% infill or so, to make it porous and act like a filter, to prevent ingestion of parts into a vacuum pump. Yes, I could have bought a filter, but I wanted to try printing one...



  18. For PET, I need to heat the glass bed up to 80...90°C, for best bonding. And turn fan off or very low if you do not have too big overhangs. (You can't turn it off with big overhangs, otherwise they don't print well: the string snaps and curls up into a ball, instead of making a bridge. At least with the PET that I have.)


    I also had PET tearing a part out of the glass once, when I was using glue. So now I don't use glue anymore, but I wipe the glass with a tissue moistened with salt water prior to printing. For PLA, this greatly increases bonding, but for PET it seems to slightly reduce it, so no damage anymore.


    But my parts are mostly long and flat, not very much height.


    Never printed with ABS, except for a quick try, so no suggestions here.


    If you would print in PLA, be sure not to leave it in your car in the sun, even not in spring or autumn. It won't warp during printing, but it will warp in a car in the sun. Don't ask how I know.   :-)


  19. Your idea of using breakaway as raft made me think of this: what about using breakaway to clamp parts down? Like in the picture below. If the design allows it and if it has a sort of flanges at the bottom, or other features that you can grab, maybe you could hold it down like this? I have never tried it, so I have no idea whether it would work or not. But at least, if the breakaway adheres well enough to the glass, it would prevent the nylon model from coming off and sliding around. So it should prevent spaghetti? Theoreticallly and hopefully...


    Maybe worth trying on a small testpart? Stay with the printer to see what happens.


    Picture of the concept: clamping blue nylon part down with orange and red breakaway parts. Of course it should go around the corners too, to clamp it in all directions, but I haven't drawn that here, otherwise it would hide the concept.



  20. In my experience, there are a lot of things that influence accuracy: temperature, speed, flowrate, material, even color (some colors melt better than others, not sure why, maybe due to fillers?), etc. Further there are things like layer-lines (curved edges), blobs, ringing, thickening of corners due to nozzle slowing down,... All these have an effect.


    The only way to know, is test. Make your typical features in real size in a small test model, and try that. For me, I usually take 0.1 to 0.5mm extra, depending on how tight a fit I want, and whether it are inner openings or outer sides.


    Be aware that PLA will deform even under moderate warmth. You can not leave it in your car, even not in mild sunny weather in spring or autumn (internal stress relaxation). And it will deform quite fast under continuous load (creep deformation). Don't ask how I know.  :-)  This might not be suitable for every technical application.


    If the application allows it, I usually go for plenty of tolerance. Otherwise I calculate some post-processing in from the beginning: some filing, sanding, cutting,...


  21. I think CPE is very similar to PET? Anyway, PET feels totally different from waxy and floppy materials like PP and PE. It can flex a little bit, but definitely not like PP or PE, only rather like ABS. If overloaded it will very suddenly break without warning, almost like plexiglass.


    I have no experience with printing PP and PE, but I guess also a 3D-printed PP-model would probably feel different from an injection moulded one, due to the layer lines and poorer layer bonding?


    If I had to do it, I would probably go for what prints the best, the most accurate. And then post-process and smooth that, so that the shape is as close as possible to what you want. Even if it was in PLA. And then let the client imagine how that would feel and work in PP or PE. If he is used to these materials, he will be able to guestimate that, I think. Or at least I woud do that as a first intermediate step, to further discuss things and refine the concept?



    PLA carabiner hooks start to crack after some time of use (left, cream). PET carabiner hooks don't crack (right, green), but if overloaded break suddenly (fracture surface below). They don't ply like PP or PE.




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