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geert_2

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Posts posted by geert_2

  1. 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.

     

  2. 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

     

  3. 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/

     

     

  4. 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.   :-)

     

  5. 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
  6. 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

     

     

    • Like 1
  7. On 7/20/2021 at 9:28 AM, knutselsmurf said:


    just a warning, “dichloromethane” is carcinogenic !!

    I think Geert is working at a Chemical Laboratory like me, but to you all: don’t use it!

     

    Yes indeed, I have a lab, and a professional fume extraction cabinet for chemical and biochemical fumes. So I use it in this cabinet. In addition I use extra safety glasses (swimwear style googles that fully cover the eyes). And I don't touch the liquid, I use brushes or dipping instead, and chemically resistant gloves when there is risk of touching.

     

    However, I do think you can use it at home, but outdoors only, upwards of the wind, with good safety glasses of course, and gloves. No spectators, unless well educated on the subject and well protected. Definitely no babies, no toddlers, and no animals around.

     

    Indoor use can only if you have good fume-extraction. Some hobbyists do have an extraction cabinet, as they use it for soldering, welding, spray painting, sanding, etc... Or use a gas mask that covers the eyes too (like in horror films), with a *fresh and correct filter cartridge for this chemical*, analog to what you should do for spray painting. Make sure you don't breathe the fumes, and can't get spats in your eyes.

     

    I believe the health risks are similar to those of acetone, but less than chloroforme (at least, it requires no special permissions here, contrary to chloroforme). But don't believe me, everyone should study the risks and safety measures for himself.

     

    But that said, dichloromethane can really improve the quality of PET-prints (and PLA, and maybe ABS too), especially when making moulds for casting silicones. Then smoothing is really required, otherwise you can't get the casts out, as each layer-line acts as an undercut, firmly gripping onto the mould. Chemical smoothing is way easier and faster than endless sanding and polishing in areas that you can't reach. See the photos above.

     

    @ Sander: do you already have feedback from the engineering department on my questions above?

     

  8. If this is on the bottom of the print (=touching the glass), or a very thin print of only 1 or 2 layers, I would suspect grease or oil on the glass, so it does not stick and lifts off. But if this is on the top of a thicker print (hard to see on photo), it is something else: maybe too little infill, or a too thin top surface?

     

    For this sort of things, you could best watch closely while printing: often you can see what is happening, and why. For example, if there would be oil on the glass, you can see how the filament does not stick in certain areas and is dragged around. Or you can see material accumulating on the nozzle, and being deposited on the print, and all sorts of other irregularities.

     

  9. I do understand what you mean, but I don't know if there is a setting for that. What could also help is making the walls and top shell thicker.

     

    But if you are going to cast concrete anyway, what about using the model as a base for making a mould, and cast the whole model in concrete? So you have a fully concrete model without plastic?

     

    In a CAD-editor, subtract the model from a block, so you have the inverse hollow shape of the model. Cut that block into two parts (or more if required), so the cast can be released from it later on. Add alignment features so both halves snap in place. Then add clamping features, and add pouring and venting holes. Think these over carefully. Smooth the inside, spray mould-release spray, and you have a mould that you can use for multiple concrete casts. This combines the advantages of 3D-printing with casting, and you have the stone-like texture of cement in the casts. You could add marble or other powder to the cement mix for additional effects.

     

    On the internet you can find a lot of good tutorial videos on mould making and casting.

     

  10. If you have this only with a 0.25mm nozzle, but not with a 0.4mm nozzle, maybe you are printing too hot for it, and the heat still creeps up into the filament due to not enough filament flow? Or the filament begins to decompose?

     

    If you do a cold pull (atomic pull), the tip should look like the orange one at the very bottom here (minus the color-change, this was when changing colors, to clean the nozzle). If it looks like the white one, with a thick ring or blob where the teflon meets the metal part of the nozzle, then the teflon is definitely worn-out.

     

    Also, it could be that the bearings of the little fan are worn-out, so that it is still running, but way too slow to generate enough airflow? If it makes rough sounds like "rheu-rheu-rheu" then it is for sure worn-out. Or maybe there are hairs stuck in it, reducing speed and flow? Airflow goes with a power of RPM, not linearly, so a small reduction in RPM gives a huge reduction in airflow. When looking at your pictures, I still have the idea that the third fan's cooling is not sufficient, and heat is creeping up, melting the filament before it reaches the nozzle, as gr5 said.

     

    DSCN5237.thumb.JPG.8f29c03aad2ce9dd0d9490ed2ece9d98.JPG

     

    DSCN5238.thumb.JPG.c0b3c52c2588d4c4a95ec6ac24bd3e99.JPG

     

  11. Plastic folders crumbling apart after sitting in the daylight for a couple of years. And this was even behind sun-shielding green glass, which should catch most of the UV-light.

     

    These folders are usually made of PE or PP, but I have seen similar problems with other plastics. Last month I had a dustbin falling apart. A couple of years ago I have seen this in "weatherproof" garden chairs...

     

    That is why I would not trust plastics too much for load-bearing outdoor use, unless they are specifically tested and approved for it. 3D-printing materials are relatively new, and we don't have a lot of experience with long-term durability in this regard.

     

    plastic_folders_crumbling.thumb.jpg.599e36e56df41c193851806d30733021.jpg

     

  12. A 0.20mm line as designed in CAD might vary between 0.19mm and 0.21mm after exporting to STL, because the STL-file consists of straight line-segments, instead of smooth curves. The 0.19mm areas are likely to cause problems.

     

    Idem for lines of 0.40mm in CAD, for printing on a 0.40mm nozzle. I prefer to optimise the design in CAD, rather than rely on doing tricks in the slicer. So I design the lines a bit thicker in CAD: usually 0.5mm for my 0.4mm nozzles: this prints well, and aligns well on a 0.5mm grid while drawing.

     

    Maybe try 0.25mm lines for your 0.20mm nozzle? But I think a 0.2mm thick part is going to be way too fragile. If it was for myself, I would make it thicker. And I would then print it slow and in thin layers, to get good layer-bonding.

     

  13. If you have a single-nozzle printer,  and you can do CAD, then consider designing your own supports in CAD. Test various concepts and dimensions on a small testmodel, before doing large models.

     

    Standard supports are good for standard situations. But special cases might be better off with custom designs.

     

    A few examples:

     

    Pink and orange supports with custom brim to prevent them from getting knocked over. These are stable and solid supports, so I can grab them with a plier and wiggle them out. This model is way too small to get in there with a knife.

    ostrcp_key_v20_zoom.thumb.jpg.c85991865979ff09557a37d9ca6ad20f.jpg

     

    Concepts of supports, to minimise damage to the model. These require good testing: if the gap is too big, the model will fall off. If too small, the model will glue to the support, and separation will be difficult.

    anemometer1b.thumb.jpg.c006a1ccc8e1465c2c9a18fe6d91bf0f.jpg

     

    Free hanging supports, not going down all the way to the bottom, and thus not damaging the lower parts.

    supporttest12b.thumb.png.504e11c4d360abd18960d889c271f2a4.png

     

    Front view of these free hanging supports: they stay in place by the stringing of the material. This makes them very easy to remove (way easier than standard supports). The ribs on top are 0.5mm wide and high; the inverted stairs at the bottom are 1mm wide and high. This model could be printed without supports, but I want more accuracy, since another part has to slide accurately through the opening. The tabs on the side of the supports do almost no damage to the side walls of the model.

    supporttest12c.thumb.png.a4bbb089d43486b97df974e68e645196.png

     

     

    Printing tiny vertical models often causes this effect: the filament can not solidify due to the hot nozzle continuously sitting on top of it. So it deforms. Layer-adhesion and stress-concentrations could also be a factor. So you might want to design supports in such a way that they move the nozzle away for some time, and allow the model to cool (or print multiple models at once).

    DSCN5605b.thumb.jpg.2a696904daa58d988117c2f266bd4594.jpg

     

  14. In my experience the "insect antennas" are caused by the nozzle leaking while traveling through air. Upon reaching the next wall, that drop is deposited on the side of the wall. The next layer, the drop is deposited on the already existing drop, and so on, creating the "insect antenna" effect. Watch closely, then you see it happening. In PLA this is rare, but in more rubbery materials when molten, like PET, it is common.

     

    You can easily worsen the effect by switching off retraction, or by printing faster (=more pressure in the nozzle, thus more leaking). Reducing it can be done by printing slower, in thinner layers, cooler, and with all speeds the same (walls and infill). But I can not totally avoid it, unfortunately.

     

    The strings often come from material accumulating on the outside of the nozzle, and then slowly sagging onto the print. Sometimes this is deposited on the print and creates big blobs, often brownish color, and sometimes it just causes strings when moving from one to another part. Here too: it is rare in PLA, but common in PET, and printing slow, cool and in thin layers reduces it, but does not eliminate it.

     

    I haven't tried experimenting with retraction settings, so I don't know if that could help.

     

    So my solution is post-processing: cutting them off, and then light sanding and polishing, or chemical smoothing.

     

  15. This looks like a bit underextrusion. There is a video on this forum about possible causes and solutions for underextrusion, I think from user gr5. See if you can find that (I don't know its exact name, nor link to it).

     

    Further, if you could post more details such as material and settings, and a project-file of your settings, some people on this forum might be able to analyse it and give more advise.

     

  16. I have been printing with older spools of PLA without problems. But I do store them in a sealed box with dessiccant. It is true that old PLA gets harder, stiffer and more brittle, so it may be more difficult to find and to unwind from the spool.

     

    But don't throw the old spools away yet: first try drying them in an oven at 45°C for several hours, but well below its glass transition temp where it gets soft. Store in sealed boxes with dessicant.

     

    And use a bonding method for improved sticking to the glass: I use my "salt method": wiping the bed with a tissue moistened with salt water prior to starting a print, greatly improves bonding of PLA. Other people use the glue stick (a thin layer, and wipe with a wet tissue afterwards to spread it), dilluted white wood glue (ca 10% in water), hairspray (spray it outside the printer, never in), 3D-LAC, and similar. Try various methods and find one that suits you best.

     

    You can still find my old manual on the salt method here:

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

     

  17. I just took a look at the portable ladder in my lab: it is both riveted and welded. This makes it feel rock solid. If only riveted, each connection could still pivot a bit, causing a wobbly feeling. If only welded, the welds could be superficially glued instead of really melted together. I can't weld myself, but I heard from a professional welder that welding aluminum is difficult due to the very high temperatures required to melt the oxide layer. If not high enough, the connection may slightly stick, but is not welded and will separate under load.

     

    If yours will be mounted to a wall, pivoting will not be a problem. But if portable, make sure you provide multiple connections per step.

     

  18. Technically, it will probably work well if you design the parts thick and massive enough, if load is distributed well (=no stress points, correct orientation of layers), and if you print them correctly (temp, fill, flow), and regularly test for degradation and replace them.

     

    But personally, I would not really trust it. I wouldn't trust any plastic parts for such purposes. I have seen too many plastic things crumbling apart or breaking after a couple of years: dustbins, bottles, gardening tools, plastic toys, food boxes, garden tables and chairs, car bumpers, all sorts of composite casts,... And these were injection moulded parts, or cast parts, so they even didn't have the 3D-printing problems like layer-adhesion, stress-inducing entrapped air, uneven cooling stresses, etc.

     

    The biggest risk will probably UV-light degradation, plus to a lesser degree ozone, chlorine (if in contact with tap water or swimming pools), hydrolysis, drying-out (evaporation of plasticizers), fatigue,...

     

    I am not sure, but I do believe that here in Belgium weight-carrying plastic connections on ladders and stairs are even forbidden. At least, they are forbidden in our university: all connections have to be welded or rivetted.

     

    Without photos or drawings it is difficult to give advice, but what about using rivets? Or nuts and self-locking bolts? Maybe with use of copper-grease to prevent corrosion?

     

    • Thanks 1
  19. Also, check in the gcode if the "long straight lines" are long lines indeed, and not chopped-up in lots of tiny segments.

     

    And watch the printing through a magnifying lens, or through cheap glasses with high diopter (these work as magnifying glasses too) from the supermarket. Then you can see if the blobs gradually accumulate on the nozzle and are then deposited, or if they suddenly erupt.

     

    Maybe wet filament might also cause this, due to steam generation? Although I am not sure, usually it gives little craters and bubbles, like foam. So I don't think this is going to be the (main) cause.

     

    But it still looks overextruded to me, it looks like the nozzle has been wading through the melt.

     

    Some time ago I did a couple of over- and under-extrusion tests.

     

    This is 100% extrusion, seems quite okay:

    extrusion_100pct2.thumb.png.01adb69154c978415b3f3b42f0267907.png

     

    Again 100% extrusion:

    extrusion_100pct.thumb.png.ff43c0e342347a78e2902e72ce17359e.png

     

    Way overextruded: 150%:

    overextrusion_150pct3.thumb.png.424d051378a7a21af52029e29451cbc4.png

     

    Same overextrusion, seen from another viewpoint, 150%:

    overextrusion_150pct.thumb.png.c61778173be97ca083fbbac0ab3b5acf.png

     

    Way underextruded: 50%:

    underextrusion_50pct.thumb.png.a98c4c9891552d4b1aa2875f35776686.png

     

    This brim was printed at 100% extrusion, but it is slightly overextruded due to my nozzle being a bit too close to the bed (on purpose):

    brim_slightly_overextruded.thumb.png.3b035853bb889cdbe6528180bcce0b28.png

     

    It is hard to see for sure on your photo, but your image looks closer to my 150% overextruded tests here. So that would mean that: or you have overextrusion, or your nozzle is way too close (resulting in effective overextrusion too for the first layer), or the temp is too high (melt too liquid), or wrong settings for the filament, or worn-out nozzle, or something along that line, I think. If it was my printer, I would go searching in that direction a bit further.

     

  20. There might be lots of reasons for blobs: overextrusion (for whatever reason); the nozzle being too close to the bed (also resulting in a sort of overextrusion-effect); a too fine STL-file with way too much polygons which slows down the printer; material accumulating on the outside of the nozzle, and then being dropped onto the print; and probably other reasons that I don't think of at this moment.

     

    I would suggest that you watch very closely while printing, maybe use a magnifying glass: most of the time you will see what happens, or you can narrow down the causes.

     

  21. Warping-tendency on the bed *while printing* seems to be lower with thinner layers: their bottom is flatter and has a bigger contact-area to the bed than thicker layers, so a better adhesion and less warping. Also, a very thin layer can excert less forces while cooling than a thick layer. A 0.3mm layer suddenly cooling down and shrinking will be able to pull much harder than a 0.06mm layer, I think.

     

    But for warping afterwards, for example the completed part sitting in the sun or in weather, I have no idea. Prints with thicker layers have more entrapped air (=are less transparent) than prints with thin layers. But I don't know if and how that would affect internal stresses and warping afterwards? Interesting thought though.

  22. The leaks come from when the nozzle jumps to another layer, or another part on the same layer. Just that transition-spot tends to have tiny holes. Printing faster and in thicker layers, worsens the effect, as the beginning and ending of the "sausages" are rounded. Put two sausages next to each other on a table, and you will see the same effect on a big scale.

  23. Layer-thickness also plays a role: generally I found that on my UM2 a first layer of 0.1mm is too thin and gets uneven. A first layer of 0.3mm is too thick and has less contact area and is not so flat at the bottom. A first layer of 0.2mm works best: this gives a nice flat and glossy bottom. The top of that layer tends to overextrude a bit due to it being printed at lower speed and without fan, thus with a lower viscosity and higher flow (less resistance in the nozzle). And I have calibrated my nozzle a bit too close to the bed. But as said above, that first layer is followed by others, so these effects are smoothed out after a couple more layers.

     

    The bottom of the bottom-layer is more important than its top, in my opinion.

     

    This is what the bottom usually looks like (above = camera-focus on model, below = camera-focus on reflection in the bottom layer; I couldn't get both in-focus at the same time):

    underside_mirror.thumb.jpg.d9e8c12251778b0a33338a0eac202c6f.jpg

     

    Another one:

    DSCN4938.thumb.JPG.90124a14e04953b171581afa5e8f9e9a.JPG

     

    Small item printed very slow:

    DSCN6083.thumb.JPG.6fa2f0776aca10a340718c2065decdbf.JPG

     

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