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geert_2

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Posts posted by geert_2

  1. Most of the time you need to clean tiny holes out anyway. So, consider filling each hole with a thin bottom layer of just one print-layer? Then the slicer only sees one rectangular plate from below. After printing, drill-out each hole manually with a suitable drill bit (which you probably have to do anyway, if they need to be accurate).

     

    Or otherwise remove any downward structures, below the bottom plate, print them separately, and glue them on afterwards?

     

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  2. As I understand it, the overhangs are not formed well, but sag into spaghetti instead? Is that correct? You need a support structure to print overhangs and big roofs, they can not print in plain air without sagging.

     

    So you need to enable support in the slicer. Or otherwise, design custom supports into your model in CAD. This is what I usually do, so I have more control over the support. This will prevent it from sagging. After printing, remove the supports, and clean up the model.

     

    Or you could redesign the model, so there are no more steep overhangs. (If its functionality allows redesigning.)

     

     

    A few of the custom support concepts I used during the years:

    support_ideas1.thumb.jpg.01b652b9b15851890834b65181100d91.jpg

     

    Table with custom supports:

    overhangtest11e.thumb.jpg.1f92bf0e3eb064e1d9edbdf9edd16b3c.jpg

     

    After printing. Notice how the supports did sag, but that doesn't matter, but the table itself is nice and straight:

    DSCN5727b.jpg.8aeeef6796d24bf7adbbdaa5eb24f52a.jpg

     

    After removing the supports and a little bit of cleaning, it looks like this. For reference: all panels are 1mm thick in this model:

    DSCN5751b.jpg.6fe2a62d2f784ac49dee578aca5c2479.jpg

     

     

  3. Consider moving away from SketchUp: this was never developed for 3D-printing, only for on-screen 3D-models. Try DesignSpark Mechanical instead: it is freeware too (requires registration), and has a very similar modeling-style with "push-pull" concept. I never had any STL-problems. There are lots of good tutorial and demo videos on DesignSpark Mechanical on Youtube. And it is very easy to learn, as easy as SketchUp. It takes time to learn, yes, but you will soon win that time back due to far less printing problems and model debugging. You will still have printing problems, but then mostly due to poor design decisions (trying things that can not print well, like too steep overhangs), but not due to poor design-software and its bugs.

     

  4. I have seen this too in my small letterings. Upon reaching the end of a text-leg, the printer stops for a brief moment, does a retraction, and only then moves to the next letter. It is that short stop that seems to cause this little blob. Printing very slow, cool and in thin layers reduces the effect, but I could not get totally rid of it. I never tried playing with other settings (acceleration etc.), so I don't know their effect, if any. But I can live with this sort of defects, I consider it production-method limitations, similar to parting lines, ejector pin marks, and injector nozzle marks in injection moulded parts.

     

    For a 0.4mm nozzle printer, designing letters with exactly 0.4mm wide legs did not work well in my tests. In curved segments the real line-width could vary between maybe 0.39mm and 0.41mm, due to the STL-triangles (=straight lines) instead of smooth curves. So, parts of the text tended to fall away, when smaller than 0.40mm. Now I usually design my text on a 0.5mm grid, or a 0.25mm grid but then use 2 blocks to get 0.5mm wide legs, and 0.35mm caps height.

     

    These characters are printed at normal speeds of 50mm/s and 0.1mm layer height, so quite visible blobs indeed:

    DSCN5751b.jpg.6fe2a62d2f784ac49dee578aca5c2479.jpg

     

    DSCN5645.thumb.JPG.8c0a292e655cd93fd53baded45b4a915.JPG

     

  5. I am not familiar with single wall stuff, so I can't comment on this issue.

     

    However, what I have been wondering about is why do people print wings *vertically*? Then the problem is that the wing has the least strength in the direction of the biggest load in flight, due to the layer lines. Any high G turn could rip off or fold-up the wings. Just like in an overloaded real plane (I recently saw a crash-analysis video of such an event).

     

    Why not print the wings horizontally? Why not cut the wing horizontally across the cord line to get a flat plate, and then print the top half and bottom half separately (with a bit of support), and then glue top and bottom half together? It would be a bit heavier, but much stronger I think? Wash-out of most wings (=designed-in twisting of the surface) is not that big that this method would be impossible.

     

    Anyway, when printing in PLA, never leave the plane in your car on a sunny day, even not a mild spring or autumn sun: it will definitely warp. Also, don't let it sit in the sun on a hot concrete runway.

     

    Maybe the warping tendency could be reduced, and strength and impact-resistance increased, by injecting very lightweight but very sturdy PU-foam into the wings? Or maybe make the whole wing out of PU-foam? Print a mould in PLA, sand and polish that, and cast the foam wings in it (with plenty of release spray)? Just an idea, I don't know if it would work...?

     

  6. For tiny holes, design them bigger (1.5mm to 2mm) and then go through them with a *manual* drill.

     

    For text: you can't easily do tiny, clean cut-out letters: for example in the letter "M" or "W", the nozzle has to come into the letter to fill the white-space. But that infill can only have the width and roundness of the nozzle, even less, and thus tends to spread and destroy the vacuum of the character-legs. It is like printing inverse text (white on black background) with poor quality black ink on poor quality recycled paper: much of the text is lost due to the ink spreading into the white areas.

     

    Thus cut-out text looks worst of all. If possible, try raised text: then the nozzle just has to follow the lines of the text-legs. It still looks clumsy, but way better than recessed text. A solution in-between is to lower a rectangular area, and in that recessed rectangle, place your raised text. This is often done in injection moulding.

     

    I made test-text models a few years ago, for all sorts of texts: recessed, raised, hollowed-out (watermark), etc. Feel free to try them and play around with them. See here (and then scroll down a bit):

    https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

     

    Anyway, for best results printing fine details, print slow, cool, and in thin layers. For comparison, also print it fast, hot, and in thicker layers once, to see the difference. Printing it in a material that flow well like PLA also gives better results than more elastic materials when hot like PET.

     

    Raised text (all characters in these photos are 3.5mm caps height, text legs are 0.5mm width):

    image.thumb.png.78c8f2262d3b2d5beaf962fdad1883c7.png

     

    Hollow watermark, thus sitting totally inside the model (idem: 3.5mm caps, 0.5mm legs). Works only with transparent or well translucent materials obviously:

    microscope2.thumb.png.644b518f5f407e623cb8cfa46e8512c7.png

     

    Hollow watermark text, this time vertical, top one chemically smoothed, bottom one as-printed:

    pet17.thumb.png.011e4577338966d526332f59527c63a1.png

     

    Use this to go through tiny holes manually to clean them out. This method gives good feeling, enough torque, and does not melt the plastic:

    DSCN5622.thumb.JPG.bcd33809236414534d665e6ac120651f.JPG

     

  7. Vacuum cleaner tip: excellent idea. Now I need one too. Just never thought of it...

     

    Concerning the anatomical model above: I always thought the "thing you think it is", had a sort of *ring* around the inner tubing? But I don't see any ring here? So I am wondering if it really is that thing we think it is? Or is it something else instead, like inner-ear structures, or glands, maybe the one at the back of the brain?

     

    • Like 1
  8. Removing all the hydraulics and electrics, and just pulling the top open and closed by hand, like in the Mazda MX5 (Mazda "Miata" in the USA?), wouldn't that be an option? At least, our hands work reliable. If not, we shouldn't be driving at all.   :-)

     

    (PS: indeed, I know how such car-jobs go: I am just now searching and watching dozens of videos to see if and how I can make the headrests of my car removable or retractable easily, so I get better visibility sideways and to the rear. I know how to remove them permanently, but I want a easy foldable/retractable solution. I will have to do myself what car companies couldn't figure out in 50 years with their zillion dollar budget... But this one will probably require steel, not 3D-printed plastics, for safety...)

     

  9. Up till now I have only printed single-nozzle models, thus with support in the same material as the part, and with older Cura-versions. So I can't really say what is going on here, or what the best option is.

     

    If I had to print it for myself, and if the model and function would allow it, I would redesign it slightly, so it can be printed without supports. By adding 45° angles to the overhanging areas. And I would use a brim (or even custom designed brim) to keep it stable on the bed, to prevent it from being knocked over.

     

    If redesigning would not be possible due to its functionality, I might consider designing custom supports, maybe a mix of free-hanging supports with an interface-layer of PVA? But I don't know if this would work, I never tried it. See the concepts below.

     

    Concept of (almost) free-hanging supports:

    overhangtest11c2.thumb.jpg.a46d23123127b77f81082a2efa4daa80.jpg

     

    As printed (the middle part of the bridge got similar almost free-hanging supports, but they are not shown in the CAD-model above):

    DSCN5727b.jpg.8aeeef6796d24bf7adbbdaa5eb24f52a.jpg

     

    After cleaning-up: there is very little damage to the side-walls due to the thin connection-strands, and of course no damage at all to the design at the bottom. For reference: all walls are 1mm thick here:

    DSCN5751b.jpg.83314ceaef2ec8232c901f14cca77733.jpg

     

    Concept sketch of basic support structure in PLA, with a dove-tail interface in PVA, so the bottom areas of the real model on top are kept clean. This would give a very stable support base, easy to print in cheap PLA (in case the model is PLA). The dove-tail is to have the support-interface in PVA stick very well to the PLA base. But as said: I don't know if this would work in reality, never tried it yet, but it seems like it should work.   :-)

    support_sandwich.thumb.jpg.e42b127a279f4a760c444239c73a086c.jpg

     

    If you would consider these concepts, do tests on small dedicated test-models, so you don't waste too much time and material. Stay with the printer and watch closely how it prints.

     

  10. I do cold pulls regularly to clean the nozzle, but I never had really stuck filament. The worst I had was that it got partially stuck due to worn-out teflon couplers on UM2, causing a thickening of the filament in the coupler. Normally it should come free as soon as the plastic starts melting, thus ca. 60-70°C for PLA, and 90-100°C for PET. If it is still stuck at elevated temperatures, it seems the temperature once crept up into the filament, making it now stick somewhere way above the heating zone, in what should be the cold zone? This could indeed have been caused by a non-working fan. Not sure how to handle that safely, without doing further damage to the nozzle...

     

  11. I would say, try to minimise nozzle pressure and leaking by printing at the slowest possible speed, lowest temperature where you still get good flow, and thinnest layers. That should reduce the defects, or at least make them smaller, less visible and easier to remove. And then sanding and polishing...

     

    Could you show us a completed and post-processed ball? It looks like a nice design.

     

  12. In my UM2 the walls seem to be slightly rougher, but the corners seem to be a little bit cleaner, when printing at 45°, compared to the standard 0°. But hardly noticable, mainly on small features. I am not sure if that is due to the printer, or the slicer making different moves, or my imagination. Definitely not big enough to care about.

     

    I would say: just try it. Put them both on the same bed (so, same material, same external circumstances, same filament), but one 45° rotated, and watch carefully? Maybe add a few small details to three sides of each block (=on one side on each axis X, Y and Z).

     

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  13. It looks like the effect is mainly on heights where there is a sudden big difference in surface area? Is that correct?

     

    In the past I noticed that when the surface area per layer changes abruptly, this causes visible horizontal lines, a bit similar to yours. But mainly in *small models* (I don't do much big models). So in my case it is most likely due to changes in cooling time per layer, I guess.

     

    Do you have the same printing speeds for all (inner and outer walls and infill)? If not, a sudden change of speed may cause fluctuations in nozzle temp and pressure, and that may be visible in the print too.

     

    I am not saying that this is the cause, but it might be worth examining.

     

    Notice the change in appearance here, when the printing of the outer edge is completed, and only the central stem remains. Huge difference in printing area, and cooling time per layer.

     

    zeef_zoom1.thumb.jpg.396d23dadef6116bef79017ae5a906ea.jpg

     

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  14. As said above, the curling up appears to be due to insufficient cooling. On small areas, the hot nozzle stays on top of the part, so it can not cool and not solidify. So the nozzle is sort of "wading through hot mud", instead of printing on top of a solid area. Printing a dummy tower next to it, helps, but does not eliminate the problem.

     

    For overhangs, I found that printing in thicker layers makes them curl up less. Here too: it reduces the effect, but does not eliminate it. On overhangs, the freshly applied material is hanging partly in the air, and it has no or very little support from below. So it is subject to both sagging (gravity) and curling up (shrinking while cooling) at the same time.

     

    Try printing on the coolest edge of the temp-range. (At least, if that doesn't affect the rest of the print, else you need to prioritize.)

     

    DSCN5603b.thumb.jpg.83c20560cfab90d56590243bc6015f12.jpg

     

  15. If too moist, under a microscope you can see bubbles in the extruded plastic, due to water forming into steam (=gas), and during printing the plastic is solidifying before the water-vapour had time to condense and being absorbed by the plastic again. So, if the prints have a foamy effect, you could expect too much water-absorption in the filament.

     

    If you wouldn't have a microscope, sometimes a smartphone camera with close-up lens add-on could be enough for good photos. Or even a simple webcam with close-up lens.

     

    This is the quality you can achieve with a simple webcam, with a small, old magnifying lens in front of it. This is a standard 5mm LED. Should be good enough to see any bubbles in a print too.testfoto01.thumb.png.44e26ab526df030668bc1023d195cb7e.png

     

  16. The salt-concentration does not really matter. I just pour some salt in a bottle, and stir it. After wiping, it should just leave a *very thin mist* on the glass. Definitely no thick, crusty layers, that reduces bonding again. Thinner is better. I am not sure why it works, chemically or physically, but for me it works, so...

     

    The photo with the gray above is about right (although contrast is enhanced in Photoshop, in reality it looks less), but in the photo with the red print, there is too much salt.

     

    But before applying the salt water, make sure the glass is clean: clean all grease with alcohol or so. There should be no grease, no oil, no dirty fingerprints on the glass. And no soap either, because that too destroys bonding. After cleaning with isopropyl alcohol, wash with luke-warm pure tap water only. No soap, no window-washer, nothing but water. Then apply the salt water: you could moisten a tissue, or using a pipette drop a few drops on the glass, and wipe afterwards (I usually do it that way). Then immediately start the print.

     

    I haven't used anything else in 6 years, I think. And I haven't taken the glass out of the printers in maybe 2 years.

     

    During your first prints, stay with the printer and see if and how it works for you. Try small but critical models, like the inverted pyramids, to see how far you can go.

     

    Bed temp needs to be between 55°C and 60°C.

     

    Bonding may also depend on the brand of PLA, I mainly use colorFabb and Ultimaker now, and they work well.

     

  17. I use my "salt method" for PLA: wipe the glass with a tissue moistened with salt water, immediately prior to printing. This should leave a thin, almost invisible mist of salt on the glass. For PLA this greatly increases bonding while the bed is hot (compared to printing on bare glass), but there is no bonding at all when cold, so the prints come off by themself. I don't need to take the glass out of the printer anymore. Just re-wipe for the next print, and go.

     

    For PET, it slightly reduces bonding, so the glass does not chip.

     

    I haven't tried tough PLA yet.

     

    For ABS, this method does not work, so I expect that it also won't work for other materials.

     

    I do not recommend it for very narrow, high models like lantern poles: these tend to get knocked over. Then use some glue instead. But it works very well for my typical long and flat models, think of rulers and similar.

     

    For the full (but old) manual on the salt method, see here:

    https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

     

    saltmethod3.jpg.b36952a07208ed06aea2e5142716121c.jpg

     

    This inverted prism is the maximum you can do with the salt method. This is a hard test, due to the tiny contact area and big overhangs that exert a lot of warping forces, and that curl up and cause the nozzle to bang hard into them.

    DSCN5814.thumb.JPG.579cd13d93beed9cc55ec4cb5ab6c366.JPG

     

  18. There do exist several clamps and guiding systems to prevent that. Some are mounted on the printers, some on the spoolholders, and some slide on the edges of the spools.

     

    Long ago I made a slider for my colorFabb spools, after I also had this problem. In fact, I had two problems: originally, some filaments were wound way too stiff on the spool, so it required way too much force to unwind it, it acted like a strong spring resisting unwinding. I had to manually unwind and straighten some filament first. But then it tended to fall off the spool sideways. This slider only worked on spools with a smooth edge that allowed sliding, obviously. So it did not work on older Ultimaker spools, as they had spokes blocking the sliding. I haven't tried it on newer spools.

     

    I would suggest you have a look on Thingiverse and similar sites (I don't know which search terms). Or you can borrow my concept (see picture below), or any other, and adapt it to your requirements. Make sure it slides very smoothly, otherwise if it would get stuck, it would cause failed prints by itself.

     

    I also use this clamp to store spools, and prevent the filament from unwinding or getting tangled up under itself while in storage. In storage I use it with these thumbscrews, and the filament should go through the little hole, to be clamped. For sliding around the edge while printing, obviously no screws should be used, and the filament should not go through the hole. So this is a multi-use thing. Feel free to adapt it to your spools, and test thoroughly: stay with the printer during the first couple of testruns.

    DSCN5645.thumb.JPG.8c0a292e655cd93fd53baded45b4a915.JPG

     

    The design is on this page (scroll down a bit):

    https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

     

     

  19. As long as you don't have dedicated doors and covers, you could start with a simple sheet of plastic as front door: for example the sheets used to protect A4-documents.

     

    I was wondering: how comes you have such cold temperatures in *summer*, and then even in Africa? But then I realised your summers and winters are the inverse of ours.   :-)

     

  20. Yes, I do fully understand the concerns about waste; I am pro recycling too. But the recycling process itself should not cost more energy and resources, and produce more waste, than making new things. Otherwise it would be a lose-lose situation: you would get inferior products at a higher environmental cost.

     

    A 100% recycled cardboard item had to be made fresh in one of the cycles before, before it can be recycled. That first-make is what costs lots of trees. Further, both fresh and recycled cardboard and paper consume huge amounts of energy and fresh water: the paper/cardboard has to be cut, mixed with water into pulp, heated, stirred, treated chemically, pressed into sheets, and then dried. The water of the pulp is highly polluted afterwards, and thus needs purifying, which also costs energy. I don't know the total balance, but I would not be surprised if the total environmental cost of cardboard is far worse than that of plastic. So, production of paper/cardboard might cost more oil for heating and purifying, than the production of plastic. According to Wikipedia, it takes 200 tons of hot water to produce 1 ton of paper. If the water is recycled 10x before being wasted, it still costs 20 tons of fresh water for 1 ton of paper. And the waste-water pollutes rivers... The advantage of cardboard is that if thrown in a river, it rots away soon because it consists of wood-fibers, contrary to plastic.

     

    A similar difficult question is which plastic to use? Plant-based plastic such as PLA, or oil-based such as ethylene, propylene, styrene, ABS,...? The plant-based seems more environmentally friendly at first glance. But it requires food-products. So, first, forest has to be cut to make room for crop, and then that crop is used for making plastic instead of for making food for people and animals...

     

    Another similar question is that of glass versus plastic: glass bottles can be recycled, yes, while plastic ones can't. But it takes at least 100x more energy to produce glass than it takes to make plastic. So, even if the glass bottle can be recycled 5 to 7 times (max), it still costs 15-20x more energy than a plastic one. Also, the empty glass needs to be transported and washed, which also requires lots of energy.

     

    We need to consider the whole cycle, including the hidden energy- and environmental costs in the factories. Which are often difficult to estimate.

     

    But there is hope: in the past weeks Stephan from CNC-kitchen (Youtube) has been experimenting with shredding old plastics, and extruding fresh filament from it. He seems to have good results with it. That would be a first step. For home use the cost is way too high, but for research departments and schools having a lot of printers, it might be a solution, and it is very educational too.

     

    And maybe in the future we can go to a feeder that works directly with pellets, instead of filament. So you would only need one big 50kg-bag of pellets, and then add your own colors and additives. That would be a hybrid between injection moulding and 3D-printing. It will take 5 to 10 years, but I could see things moving in that direction.

     

    • Like 1
  21. In the beginning I used the glue stick (without wiping it afterwards, I didn't know that trick back then). But this gave an ugly bottom layer indeed, and non-optimal bonding. I also tried printing on bare glass without any glue: in dry weather this would work reasonably, but in wet weather it would lift off and cause defects like yours. Also, greasy glass would cause this effect. Cleaning with soap and window-cleaner can also produce this, since soap reduces bonding: you can't glue anything to soap.

     

    So, now I thoroughly degrease the glass first, and then wash it with pure luke-warm tap water only (no soap, no window-cleaner, nothing). And then I wipe it with a tissue moistened with salt water: this also improves bonding of PLA to the glass bed when hot, but the print comes off by itself after cooling down. For in case you want to print on bare glass, without glue, like me. If you would prefer using glue, dissolve it and spread it out evenly with a wet tissue, until it is an almost invisible thin layer.

     

    As others said above, also check the nozzle-distance from the glass. If too big, there is not enough contact and the print is likely to lift off. If too close, the nozzle may scrubb the print off the glass, also lifting it off.

     

    The bottoms of my prints usually look like this:

     

    Bottom layer, and reflection in the bottom layer (could not get both in-focus at the same time):

    underside_mirror.thumb.jpg.d9e8c12251778b0a33338a0eac202c6f.jpg

     

    PLA print, nozzle is 0.4mm, the round hole is ca. 4mm diameter:

    DSCN4938.thumb.JPG.90124a14e04953b171581afa5e8f9e9a.JPG

     

    PET-print, thin layers, ruler in the background is in mm and cm:

    DSCN6083.thumb.JPG.6fa2f0776aca10a340718c2065decdbf.JPG

     

     

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