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geert_2

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Everything posted by geert_2

  1. I haven't printed with PP yet, so no recommendations on that. Although generally (for PLA and PET anyway), printing slow, in thin layers, and at the cool edge of the temp-range, tends to lessen strings. But when manually sanding or filing PP (fridge boxes or so), this also gives lots of fibers: it is hard to get the surface smooth. This is the strength of PP, it is why live hinges are working so well. So I think this could be caused by the fibrous nature of the PP material itself. What might works is cutting them with a very sharp scalpel (surgical knife), or melting with a hot air gun?
  2. Maybe one of the hex screws getting lose, and that gear slipping over its rod? Or else there is too much friction in that direction, so the stepper motor skips steps? With the machine off, move the head around by hand: it should go smoothly in all directions, without requiring brute force.
  3. You can use dichloromethane, for both PLA and PET, and probably for ABS too. For PLA, this works much better than acetone, because acetone only works on the additives in the PLA, not on the pure PLA itself. Chloroforme should work too, but in most countries this requires special permissions from the authorities. Some time ago, I did a whole thread on this, with lots of photos of the results. Search for "PLA and PET smoothing with dichloromethane" (or something similar, I don't remember the exact wording). Just one photo here, a PET model smoothed and not-smoothed:
  4. As Smithy says: SketchUp is going to be an endless nightmare. In the time you need to correct its defective models, you can learn another editor that does work. SketchUp was never designed for 3D-printing, it was ment for visual models only, like in architectural sketches, computer games and virtual reality. I use DesignSpark Mechanical, freeware from RS (electronics supplier), requiring only registration. But there are other good programs too. Look on Youtube for tutorials, and try one that appeals to you.
  5. The only predictable gcode-manipulation method I know is design it in 3D in CAD. And then play around with printer-settings, so it doesn't get closed when printing the bottom layer. Instead of raised or recessed surface text: another option would be a watermark. In transparent or translucent materials the watermark can sit totally inside the model, shining through. Often gives a nice cool "watermark" effect indeed. Design the logo or logo-text outside of the model, separately, and once finished move (a copy of) it into the model. Then subtract, so you end up with hollows, voids, in your model. When using DesignSpark Mechanical as 3D-editor, subtracting isn't even necessary. Upon exporting to STL, it does so automatically. So you can just move the logo into the model. This makes subsequent editing much easier, since you can just hide the enveloping model, manipulate the logo, and make the outer model visible again. I usually make the watermark sit 0.5mm below the surface, preferably facing the bottom of the print. But other directions can work too if the watermark is big enough. Print slow, cool and in thin layers for best shining through. See the examples:
  6. Also, a big hot bed causes a lot of upwards airflow, cooling the sides of the model differently. And the nozzle-coolers also cool very unevenly, where they happen to be. If prints are removed from the bed too early, before being cold, I could imagine that they would also be more prone to warping. It seems that molecular structure of PLA also keeps changing for some time after printing, becoming more and more crystalline. It becomes more brittle, but I don't know if this changes stresses and dimensions? I always let parts cool in the printer on the bed slowly, before attempting to remove them. I never remove the bed from the printer, I just pick up the parts as soon as the bed is at room temperature. You can make stresses visible in transparent plastics and glues. I did that long ago in cast epoxies. But I have never tried it in 3D-prints; and I don't think it is easily possible due to the "sausages" and layers. The setup for making stresses visible: light-source - polarising filter - transparent object under test - polarising filter - camera. Rotate the second filter for best effects. Block of plexiglass with a tiny steel ball, under high load: Stresses around air bubbles in a cast epoxy (fully transparant and colorless parts, the blue is from the polarising filters): Stresses in dental applyances, especially around the steel wires: The colored stress lines are like height-lines on a map: when closer together, the gradient is steeper, thus higher stresses. Once you can see the stresses, you can guestimate if they are a factor - or could be - in deformations, cracks or other failures.
  7. Also keep in mind that most filaments contain additives: colors (inks or pigments), plasticizers, maybe UV-stabilisers, maybe thermal stabilisers, blends, etc. For biomedical applications, these might also be of importance.
  8. If you see this tangling beginning while it is still printing, a temporary solution is sometimes to manually unwind and loosen up some filament, very carefully, without interrupting the printing. Then roll it up again and make sure it is still free, so you can continue printing for a few more hours. Repeat untill your print is completed, and then you can really handle it as described above. I have had to do that too, I think we all have...
  9. Personally, I am not convinced that cutting millions of trees to make cardboard, in order to replace plastic, is an environmentally friendly solution. You can not recycle paper and cardboard endlessly. After 2 or 3 times, the fibers become too short, and the cardboard or paper crumbles apart. As we already see in paper bags for fruits and bread in our shops today. Then new trees have to be cut to make new usable paper. So, each second or third paper bag you use, is made from a freshly cut tree, destroying forests. Long ago the whole earth (land) was covered in green forest, including all current deserts, and even Greenland. But over the ages, all that green, carbon and life got burried underground in the form of black coal, brown coal, turf, etc. In the sea, dead life forms decomposed into an oily gel and sunk. Those gels decomposed further into gas and thinner oils due to the heat in the earth. As tectonic plates moved and got buried, some oil and gas got stuck under land now. All this buried carbon can no longer take part in life, and thus life is bit by bit extinguishing on the earth's surface, as life-carbon gets buried underwater or underground. Plants and trees die when the CO2 level in the air drops below 0.02%. We are now at 0.03%, barely above this level, and lots of plants are already in bad condition and dying. For optimal growth, plants need at least 0.12% of CO2 in the air, but preferably around 0.3%, thus 10x more than now. Then all plants would grow 6x to 7x faster than now by themself, without us having to do anything. All deserts would become green again automatically. Sea levels would drop, because lots of water would then be contained in the wood and leaves of trees, and in the ground around their roots. And temperature would first drop and then stabilise: we all know that in a forest the temperature is cooler and more stable than in a bare desert like the Sahara. In mountainous areas, trees would grow up to much higher areas than now. There would be lots and lots more food and more habitat for all animal and human life. This is all proven in scientific experiments. So, to save life on earth, we should dig up all buried carbon, thus all coal, oil and gas, and burn them, so that this carbon can take part in life again. But we should burn it in a *clean* way, with good particle filters and catalysts, so the only combustion products are life gasses water vapour (H2O) and CO2. In formula: - For plants: CO2 + H2O + E (sun energy) ---> C-H-O-chains (green, wood, sugars) + O2 - For animals and humans: C-H-O-chains (food) + O2 ---> CO2 + H2O + E (energy) CO2 and H2O are life-gasses, the source of all life on earth. This is what nature makes plants from, with energy from the sun. So, we humans live on sun energy, brought to us via plants, since we can not directly convert sunlight into meat bodies and into movement. Plant life, and human and animal life, are each half of the life cycle. Both formulas above are half of the life cycle, both equally necessary. They complement each other. Plastic is a very good product: it is made from oil and gas, and is formed into very clean and very usable products. After their usefull life, plastics can be burned cleanly (at least some of them, such as PLA, PE and PP, some burn less clean), and the resulting heat can be used to melt and form new products. If done well, there is no real waste. The "waste" gasses CO2 and H2O are not waste, but plant food. To make all deserts green again, we should produce more plastics, and burn more plastic, oil, coal and gass. More, not less. So, we in the 3D-printing community, are doing not too bad in saving life on earth. And of course, to save the earth, we should go driving in muscle cars with big fuel guzzling V8 engines, like in the '60s. Camaros, Corvettes, Firebirds, and Mustangs with 400HP. But now with good filters and catalysts on the exhaust. This is no joke, this is absolutely proven in true science. :-) For some basic understanding, search the old documentaries: "The greening of planet Earth", and: "The greening of planet Earth continues". But there are lots of other valuable documentaries. Just stick to the proven science. What I say above is no secret, it is all very basic biology and biochemistry science, taught in high-school, between 15 and 18 years of age.
  10. They were cooled, required to get them off the glass, and then put in my electronic lab oven and warmed-up again. Actually it is an incubator with range up to 99°C, very well controlled, but I only use it for this sort of 3D-printing stuff now. Maybe there is a difference if you would put a box on top of the part, directly in the printer immediately after completion, so it would not go through that extra cycle? I don't know, never thought of it. The photo with the fridge box above was just a quick one-time experiment. And yes, I also had lots of PLA-parts warping in the car, even in a mild spring or autumn sun, here in "rainland" Belgium. We are not yet talking about summer or equatorial deserts. :-) Even forgetting them in the trunk for a few hours can destroy them. And I had them warping in both directions too, first upwards and then after a few days downwards, as in the photos. Very weird. Now I print parts for the car in PET or NGEN: I haven't had issues since then. Annealing PLA parts with less critical dimensions (since the annealing itself changes dimensions) for later use in the car, did not work: they kept deforming and failing anyway in the car: hooks and clamps would lose their tension and bend. So, my suggestion is to go for a higher temp material from the beginning, and not waste time annealing.
  11. Maybe change the title, and add " - solved" to it? Should be possible, I think.
  12. Maybe 15% infill isn't enough? For moulds, I use 25%, and to me that already feels like the minimum. After printing, my moulds are totally flat, but they are much smaller, about 10cm long. Did you post-process the thing? I found that chemical smoothing with dichloromethane tends to make moulds warp slightly too. Especially since I only smooth the inside (=casting side), not the outside of the shell, so it is uneven. Probably the chemicals go deep into the material, and into the hollows of the infill, and keep working there. Acetone smoothing tends to make them crack after some time. Also, I would be carefull with annealing: it might destroy your parts, or change their dimensions too much to be acceptable. I found that ruler-like parts shrink severely in length, but expand in height. A bit similar to a thin piece of plastic that you overheat above a fire or with a hot gun. Also, my test parts tended to warp severely. Some first warp upwards, and after a while change direction and start warping downwards. If your parts do stick well to the glass, maybe try a slightly lower bed temp? Stay below glass transition temp, instead of at it or above it? And indeed, I would also recommend very slow cooling, as described above. That should never hurt. I did the tests in a controlled lab-oven, but you could also cover the model in the printer with a simple box, so it gets a smooth even temperature. Fridge box for slow cooling or annealing on the printer: Warped and shrunk severely after annealing test (PLA, up to 70°C or so, don't exactly remember): Annealing tests: some parts warp upwards, some up first, then downwards later on:
  13. When making a mould, include holes in the seam-line for a compressed-air pistol, so you can blow air between both mould halves. Also provide slots to insert a screw driver to pry both parts apart. This will greatly help you in demolding. Otherwise it could be a nightmare: silicone casts tend to suck vacuum very strongly, like a suction cup. You see both features here. This is a mould in PLA, for casting soft silicones. The round conic openings for the air pistol do not go into the silicone cast itself. They stop short of it, and are only to blow air in-between both mould halves. In this mould I have no pouring openings and no venting openings. I pour the silicone in one half of the mould, and then close it, and the superfluous silicone is pushed-out via the seams. It is too thick and cures too fast for pouring into tiny openings. I can't show the inside, but it also contains alignment features, and it makes sure no air is entrapped. Clamping is done with clamps on the outside, but depending on the size and design, you might need to design dedicated clamping areas and flanges as well. Round holes for inserting a compressed-air pistol, and rectangular slots for inserting a screw driver. First blow air, to separate the silicone from the mould, then pry both parts open with the screw driver. This works very well.
  14. For CAD, also consider DesignSpark Mechanical: this is freeware too, and only requires registration. It is easy to learn, and there are lots of tutorials on Youtube. This is for technical models and geometric shapes, but not suitable for organic shapes. For export to STL, set it to "fine": I never had any problems with that. Do *not* use SketchUp: this is going to be a nightmare, as it produces defective STL-files which are very hard to repair. Probably a slicer will be provided with your printer, or they will direct you to one on the internet. You could also consider multiple slicers: a simple one or old one for beginners, with just the basic features. And a more advanced one for more experienced users. Multiple software packages will give the users multiple viewpoints on the same subject. So they will get a better understanding of the concept, and are less likely to get mentally stuck in a specific application or user-interface. But users will need to invest a few weeks to get the basics anyway, and a few months to get to a more comfortable level. They have to be willing to invest that time and effort. It's not like baking cupcakes which you can learn in an afternoon. You may need to select your students on that too.
  15. On a single-nozzle printer, another option might be to cut out the drawing from the base, all the way down to the bottom. So you have two separte models: the base, and the drawing. Print both in separate jobs. And assemble and glue both together. You will need to add quite a bit of tolerances, test, and post-process each part, to get the thin parts into the base. And it won't look very smooth probably. But it should be doable.
  16. This method is new to me, but it could obviously have great potential. How well does NGEN bond to the PLA, and how well is it removable? And the other way round, PLA to NGEN? Does this also work for PET, CPE, etc.?
  17. Most bottles for chemical products are made from PE, both HDPE and LDPE, or PP, so these have a reasonable chemical resistance. For use on the ground, maybe this could be an option, if they meet your strength-requirements? However, for use in airplanes, I doubt if they meet the temperature range? Especially PP might become very brittle when well below freezing temperatures. Also, they degrade quite fast in strong UV-light, so not very suitable for outside applications, especially not at 30000ft. Impact-resistance of PP is lower than PE, this could also be a factor. I have no experience with printing them, so I don't know about layer-bonding, warping, settings, etc. Maybe another option might be to design and 3D-print a mould, and then cast a suitable material in it? Maybe PU-rubber, or hard PU (whatever you need)? Probably not silicone rubber: silicone is water-tight because it repels it. And it is chemically quite resistant. But it is for sure *not* oil-tight, and not solvent-tight. I found out after a full cup of liquid parafine leaked through it overnight... After cooling down, the whole silicone cup was impregnated with parafine too, opaque white instead of transparent yellowish. That is why it is a good idea to thoroughly impregnate silicone moulds with silicon oil, prior to casting solvent-like composites: this saturates the mould with silicon oil, and reduces the amount of solvents that can seep in and destroy that mould by curing in the silicone itself. I often make PLA moulds for casting silicone models. Or silicone moulds, around a PLA- or plasticine model, to cast PMMA epoxies. If you would go the moulding way, make sure to follow classic design and moulding rules: no undercuts, drafts, pouring openings, venting openings, etc... Print the mould very fine, and then smooth it by sanding or chemical smoothing (dichloromethane). If well done, you can make multiple casts from one mould.
  18. As gr5 said, design the supports in CAD. I almost always do this too, to have full control. I design features into them so that I can get in with scalpels, hooks, pliers, etc...., to easily remove the supports. Often, I also let them begin from the model, so they don't go all the way down, and don't damage underlying areas. Thus "free hanging supports", sort of. Here a few of my classic examples and ideas. Do test the concepts on a *small test model* that has your typical problem areas, before doing it on a large model that takes days to print. These free hanging supports are easy to remove and create very little damage to the side walls, and none to the lower areas: Idea for a spring: Here the supports (red and orange) have extra custom brim, to prevent them from being knocked over, due to their overhangs. More free hanging supports below. These are small models, the supports in total being ca. 5mm wide.
  19. I haven't printed with TPU yet, so no personal experience about its characteristics. Maybe set more retraction, or make sure you did not accidentally switch retraction off in the slicer? If "nothing else makes a difference", then disabled retraction might be the reason? Just guessing...
  20. A question: if you don't mind the seam, then why not just print two walls in normal non-vase mode? I don't see the point of a vase mode that creates seams?
  21. Annealing does not just shrink the model by 5%: it shrinks it in X- and Y-size, but it gets thicker in Z-size, and it severely warps due to the relaxation of built-in stresses. Better use filament that can handle the required temperatures from the beginning. And even then, the result is only a poor less than 10°C better temp-resistance for PLA: still not usable in a car, it will still deform in a mild spring sun. I tried annealing in different ways: by putting a fridge box on top of the model, and keep the build-plate hot (60...70°C for PLA). And in my well-controlled lab-oven. An untreated, and a "too well" treated model (a bit too high temp): this one got much shorter, but much thicker. And it obviously warped severely... Some filaments warp in both directions: first upwards, then after a day in the opposite direction downwards. Very weird, I have no explanation for this, and very unpredictable. Thus unusable for accurate parts.
  22. The cause is filament leaking from the nozzle while traveling through the air, due to the pressure in the nozzle not immediately dropping to zero. Especially with flexible, compressible filament. This leaking causes a sort of "insect antennas": the drop on the nozzle is deposited on the edge of the next wall the nozzle encounters. And then on the next layer, it is deposited on the previous drop, and so on, creating these antennas. However, you have a peculiar form of it. Rubbery materials (when molten) like PET also have this tendency. Maybe print still slower, cooler and in thinner layers? So there is very little pressure build-up in the nozzle and bowden tube? And the filament leaks less due to being cooler? Printers with bowden tube are more prone to this obviously than direct drive printers, due to their long feeding traject under pressure. A close-up of these "insect antennas": For comparison: ruler next to the item with antennas is in mm and cm.
  23. Something I just thought about: depending on the job, and if you would only need 2 color bands, maybe it might also be possible to do the coloring trick after printing? Then you can adjust the height of the color bands by dipping it deeper into the water? I think with pre-colored spools the outcome is always going to be a bit unpredictable, and variations in surface area are going to cause variations in color band height. @kmanstudios: I have no experience with food colors myself, but a friend uses them a lot for cupcakes. But they are not left long enough to fade... :-) What about textile colors? They can easily be found in supermarkets here, and should be reasonably stable I think. They work well for cotton and bamboo, but I don't know if they work for synthetic stuff like nylon? I don't even know if they are pigment particles or inks?
  24. I was going to say this, but you were first. :-) These models came out very well. On Youtube I have also seen videos on which colors/pigments to use, and the whole coloring procedure. If I remember well, some people used food-colors.
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