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geert_2

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Everything posted by geert_2

  1. 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.
  2. 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
  3. 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.
  4. 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.?
  5. 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
  6. 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.
  7. 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...
  8. 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?
  9. 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.
  10. 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 a
  11. 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... :-)
  12. 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.
  13. Forgot to say: due to the dissolving-effect of the solvent, the outer layer of the parts gets soft for a while. So that will leave fingerprints, and it may warp the whole part if it is thin. Also, if you print with little infill, it may evaporate the solvent inwards into the hollows, where it keeps working. I found that a mould I printed with 25% infill and of which I smoothed the inside (=where the cast comes), began to warp slightly after one month. I think that might be a result of the dichloromethane-solvent, because it never happened in similar unsmoothed parts in the same conditions (=ro
  14. It might also be a good idea to search on internet for demo-videos. Then you get an idea of how smooth the extruded sausage is, and if it fits your application. Most models that I saw gave a quite irregular extrusion, or maybe seemed irregular due to our hands moving irregularly? It would work very well for creating trees in miniature railroad landscapes, but not for smooth geometric objects.
  15. At least for prototyping, I would begin with classic materials like PET or even PLA. But do some smoothing on their surface to reduce layer lines, so dirt and bateria have less grip. These do withstand desinfecting alcohol. For smoothing, have a look at the thread I did some time ago, with lots of pictures of the result. Search for: PLA and PET smoothing with dichloromethane. Chloroforme should also work, but I haven't tried that (too much hassle, requires special permissions here). Be aware that after smoothing, the parts will breath-out that chemical for several hours
  16. I just read this now. An option might be to print it in nylon, but a bit too small, and then using a vice press it on the brass element with brute force? So it will seal well and won't fall off? Nylon may be able to handle this brute force.
  17. Wouldn't you be better off using a lasercutter or waterjet cutter as base to start from? These are designed to go very slow, so they should have all the basic hardware ready. And they can run 2D DXF-files generated by most CAD-programs, I think.
  18. There are people on the forum here who use PLA or dedicated mould-making materials to print a model, and then encapsulate that in sand (or whatever special mould-material), then burn the plastic model out, and cast metal into the cavity. I have seen videos of it, but I don't know the exact methods and materials. There are jewelmakers who do this with silver and gold, and also general hobbyists who do it with aluminum. Maybe you can find tutorials on Youtube?
  19. Out of curiosity: have you tried, if you use different transparent colors, let's say blue and red, does it then get the subtractive mix color purple?
  20. Catia, isn't that from the Dassault company? If yes, I think it might use the same engine as DesignSpark Mechanical (but then at full power, not feature-limited like the freeware DSM)? I rarely have this sort of problems in DesignSpark Mechanical. But what occasionally happens is that things do not want to merge (or round, chamfer, cut, extend, whatever,...) if the edges do *exactly* fall together. If they overlap 0.01mm or so, this is not a problem. It is the "just touching" that is the problem. I have also seen this in other software, and in computer games as well: then you get f
  21. Also, printing in thinner layers normally gives a smoother surface. But twice as thin takes twice the time to print... These blocks are in PET, printed at 0.10mm and 0.06mm. The green model on the top right is in PET too. It's hard to see here, but the surface is quite smooth, letting a hollow watermark text shine through. Note that this model is small, see the ruler in mm and cm below. The red object shows 50% underextrusion (was part of an underextrusion test).
  22. An STL-file describes a 3D-model in triangular surfaces. But a 3D-printer can not print triangles, it can only print single extruded lines. So the model has to be cut into thin slices first, and these slices then have to be cut into toolpaths, trajects that the nozzle can follow while extruding. This cutting into slices and toolpaths is done with a slicer-program like Cura. It outputs a gcode toolpath file ("somefilename.gcode"). This gcode-file is the file you need to put on the SD-card to print. So you need Cura. You usually have 3 file formats of each design: - the model in
  23. Yes, just do tests on tiny items, so you know from which point on the dummies become necessary. This takes only a few minutes due to their small size, but it can later save a big model. After some time you know and you can add the dummies from the beginning in the design. Below is a real application: the dummy is the green cube at the top right. Its bottom is hollow, its top is filled from the height onwards where the large flat areas in the blue object ends, and only the tiny high yellow part remains. Without dummy cube, the top of the yellow part would seriously deform. For refer
  24. I am going to do some wild guessing: could this be a result of high pressure in the nozzle, after printing infill at high speed and temp, and then suddenly slowing down to the outer layer. Thus the built-up pressure and temperature has to leak away, sort of? Or a result of a move through the air, where it temporary stops extruding, with the same effect? Or both together? If the first, then setting all speeds and temps equal should minimise this effect. If the second, printing slower and cooler should minimise it (but printing cooler of course might reduce layer bonding).
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