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geert_2

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Everything posted by geert_2

  1. 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... :-)
  2. 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.
  3. 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
  4. 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.
  5. 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
  6. 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.
  7. 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.
  8. 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?
  9. 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?
  10. 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
  11. 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).
  12. 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
  13. 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
  14. 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).
  15. Yes, but then it's a single use mould. Not the best option if you need a lot of casts. It sort of defeats the idea of moulding and casting. A good alternative to a fully 3D-printed mould, could be a silicone mould in a hard 3D-printed shell. It goes a bit like this: - Print the real model in PLA or whatever. - Design in CAD a shell that is sitting at some distance from this real model, maybe 5mm to 10mm (depending on the size of the model: bigger models need a bigger distance). This can be a very simple shell: two parts, with clamping flanges, alignment keys, stabl
  16. If I had to do this, I would probably do the mould-making in CAD: subtract the model from a solid block. And then cut the block to pieces along natural seam lines, so the cast can be demoulded. Next add flanges to clamp mould parts together, add alignment features ("keys"), add a stable baseplate so it does not fall over or slide away when pouring heavy plaster in it, add air venting holes if required, add pouring holes if required, add features to lift the whole mould, add features to insert a screw-driver in-between mould-parts to wiggle them apart later on so you can open the mould, etc...
  17. Not NGEN, but for other similar products (PET): I have to print them very slow, in very thin layers, and around the lower edge of their temp-range, in order to get them reasonably transparent. After printing, sand and polish to remove layer lines. It is the entrapped air in-between the sausages that causes the whiteness, due to reflections and diffractions. Like sugar crystals look white, although they are transparent. If sitting in the nozzle for too long, due to the slow printing speed and thin layers, PET starts to decompose and discolor brownish. So, lower temp to m
  18. A few tips (maybe you already know them, maybe not): If you would go the moulding and casting route, be sure to post-process your mould very well: remove all layer lines as much as possible by sanding, coating/painting, or chemical smoothing. Otherwise the cast may be very hard to remove, as each layer line acts as a tiny undercut. Don't ask how I know... :-) I do the smoothing with dichloromethane now. (See my separate post on: chemical smoothing PLA and PET with dichloromethane, should come up in search.) And I make my moulds in silicone from 3D-printed models, and i
  19. Normally, a well-tightened connection of a pipeline is absolutely gas- and watertight, even up to pressures of 200bar, as in my hydraulic machine. This is brass on brass, or brass on inox. However, the tiniest damage can cause it to leak. So I could imagine that one of both parts has an uneven mating surface from earlier contamination, or from careless machining, or from dropping or hitting something. Or one of the treads could be too short. Or, if the thread-cutting is done after machining the part to length, it will cause deformation and an uneven surface close to the cuts. That
  20. I would have some doubts about carbon-filled materials. The leads of pencils are carbon-filled too, and are *highly conductive*: short-circuit a battery with a pencil lead, and you get a really nice welding arc... Black anti-static mats get their properties from the carbon too. Make sure you measure conductivity on a small test print, and also the breakdown voltage. So the glass-filled looks like a better idea to me. Maybe PET should also do, at least for normal house-hold voltages? But I have no clue about its high-voltage properties. Also, have
  21. If I had to do that, I would consider printing a mould, and then cast some sort of rubber (PU? - which exists in various hardnesses) into it. Or print a real model, print a shell, pour silicone in-between model and shell, and thus make a silicone mould. And then pour rubber into that silicone, to prevent it from sticking. Then you have the advantages of both 3D-printing and casting.
  22. I would print a dummy "cooling tower" next to the real model. So the hot nozzle is moved away from the model, while it is busy printing the dummy, and the model has time to cool down and solidify. Where the bottom of the dummy is empty, since the real model is big enough, and the top of the dummy is 100% filled for the extra cooling time. My standard pictures on the subject: Printing with and without dummy: Concept: inverse shaped dummy, to keep printing time per layer constant: Part of a real model, with pink dummy. The dummy is only
  23. I occasionally print PET. In the beginning I tried printing on bare glass, which gave mixed results. Then I tried dilluted wood glue, which gave *very good* bonding. Way too good, because at one time, it chipped the glass. This already happened while cooling down, I heard it crack violently. When I removed the print, it came off without any force, but with the glass chip stuck to the print. Now I use my salt method: apply a few drops of salt water to the glass bed, and wipe that with a paper tissue until it dries into a very thin mist of salt. For PLA, and as long as the glass is h
  24. I don't see any underextrusion or broken lines any more. A couple of blobs and what appear to be "insect antennas" (at the right, but hard to identify in this picture), which is what you can expect with PET in my experience.
  25. If the rest of the part was still okay, thus not worn-out and not brittle or crumbling apart, and if it was my machine, I would probably consider modeling only the damaged areas. And then cut these off the original part, drill a couple of holes, and bolt the new 3D-printed parts on, using a M4 or M5 bolts and nuts. That is, if there would be enough room for that in the machine and in the part, of course. But this won't work if the original is crumbling and too brittle (it looks a bit like that?). It seems to be an ABS-blend, as I noticed the words ABS on the side.
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