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geert_2

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Everything posted by geert_2

  1. This is the maximum I ever got. From my tests: print as slow as possible, as cool as possible, and in as thin layers as possible. The best here is 0.06mm layers, 10mm/s speed, and around 200...210°C. This is transparent PET (brand no longer available). Top row 50mm/s, bottom row 10mm/s; layer-height from left to right (mm): 0.4; 0.3; 0.2; 0.1; 0.06. Blocks are (in mm): 20 x 10 x 10, with my hollow watermark sitting halfway. Do similar small tests to dial-in optimal settings for your system and material. Sanding, polishing, or chemically smoothing with dichloromethane ma
  2. Hoi Sander, I would be interested, but I have a few questions: - Can this PETG be smoothed with dichloromethane too? How well does that work? - How transparent can you get parts, with which optimised settings? - How is UV-resistance, when sitting outside in the sunlight? - Over time, does printing with this PETG accumulate dirt in the printer-nozzle? The brand of PET that I use now, does leave a sort of glossy varnish coating in the nozzle, which is hard to remove. Contrary to PLA that rather leaves powder-like ashes that easily come off. - When parts fract
  3. Do *not* use SketchUp: this might seem to work well in the editor, but it will be an endless nightmare, as soon as it comes to printing, because it always creates defective models. Big no-no. I use DesignSpark Mechanical: this is freeware, only requiring registration. Good for geometric shapes like machine parts. It is easy to learn, and there are lots of good tutorial videos on Youtube. Not suitable for organic shapes. Other people prefer other programs. Search on Youtube for 3D CAD software tutorials, and try a program of which the workflow appeals to you.
  4. Indeed, PLA changes crystal structure into more crystaline as it ages, becoming more brittle; this is reversible. Also, it degenerates due to water-absorption, this is not reversible. I also found that if a string of filament is stretched for a longer time, like in the bowden tube, micro-cracks tend to form. This also makes it brittle. Probably this is what you have? Also, some colors and brands are worse than others. So, I remove the roll after printing, and store it in a plastic box with bags of desiccant. These bags can be re-used by heating t
  5. Yes, you can glue PET parts with dichloromethane, on the condition that they are touching each other. Dichloromethane dissolves the outer layers and makes them bond. But since it is a very thin liquid, it has no "filler" properties, contrary to epoxy glues. So the parts have to mate almost perfectly. I mate them first, and then let dichloromethane drip and seep inbetween both surfaces, using a brush. Bonding strength is comparable to contact glues: not very strong, by far not like composites, but in most cases good enough. Smoothing/bonding also helps to seal tiny holes and makes it water-tigh
  6. Mine are both: Sandisk, SDHC, 4GB, speed class 4. Any speed-class should do, as they are all faster than the printer anyway. With most of my gcode-files being 2 to 5MB, it could contain about 1000 files.
  7. If I had to make such a thing, I would print a mould in PLA, or in a dedicated mould-making filament. And then cast a hard and pressure-resistant material in it, some sort of sand- or metal-filled epoxy or so? Be sure to use huge amounts of release-spray, or it will glue like hell to the mould. Or 3D-print an original model in PLA, make a silicone mould around it, and then a stiffer harness. And cast the epoxy in the silicone mould. Saturate the mould with silicon oil prior to casting, to extend its life. In this way, you can make the mould from multiple pieces, glued t
  8. 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 wi
  9. 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.
  10. 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-smo
  11. 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.
  12. 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 hollow
  13. 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 r
  14. 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.
  15. 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...
  16. 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, includi
  17. 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
  18. Maybe change the title, and add " - solved" to it? Should be possible, I think.
  19. 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
  20. 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.
  21. 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 m
  22. 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.
  23. 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.?
  24. 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 ha
  25. 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.
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