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geert_2

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  1. Using two-part moulds will for sure cause the silicone to leak, if it is a slow curing one (>10min). A very fast curing one (<5 minutes) might not leak too much. Unless you fill the seams. Silicone leaks through microscopic pores. A common method to seal the seams, is to use plasticine or wax. But it has to be a plasticine that is compatible with silicone, it should not contain any sulphur (plus a lot of other stuff) which inhibits curing. Do a compatibility test before with a little bit of silicone and the plasticine or wax. You can find good tutorials on Youtube. Search for: silicone mould making and casting. Concerning details: if you use good silicone, *everything* that is visible in the mould, will be visible and mirrored in the casting, just everything. Silicone reproduces up to microns. So: all layer lines, underextrusion gaps, blobs, strings, fingerprints in plasticine parts, nail marks, hairs, dust, any defects,..., all will be horribly visible. And you may have entrapped bubbles if you don't remove them by vacuum after mixing both parts of the silicone. Another way to reduce bubbles, is pouring the silicone in from very high in a very thin stream. And gently (!) blow on bubbles, or prick them with a needle. If you have a shaker while pouring in the silicone, that also reduces bubbles: maybe try an electric tooth brush, or your girl friend's pleasure toys. :-) Do a lot of small test prints, before doing a big one, just to get familiar with the materials.
  2. I haven't had NGEN warping and coming off the bed, but I haven't printed big items either: mine took maximum 3 hours and were low flat models. PET sometimes did warp if printing on bare glass, in the beginning when I used 100% cooling. Now when using no cooling, it does not warp anymore. But here too, my models are low and flat, and take maximum 3 hours. So, try to print without cooling if the model allows it (=no overhangs, no bridges), or try a good bonding method. I used gr5's bonding method a couple of times (=white wood glue 10% dilluted in water) on models that needed cooling, which gives excellent bonding. But that bonding is sometimes too strong and might chip the glass, depending on the model... The problem with no cooling for PET is that it tends not to pull nice strings when bridging, contrary to PLA. PLA gives really nice bridges. But PET-bridges tend to snap and fold back onto the nozzle into a blob: it is too rubbery. So the gap or bridge isn't closed. And that blob gets deposited onto the next wall when the nozzle arrives. The accumulation of blobs will finally close the gap, but it is ugly. At least, that is with the PET I have here... So it may take some trial and error to find the right balance. Before doing long prints, make a small test print that will undergo some load, for example a clamp. And try if that survives well in your car, under load. Or try it in a test-environment at the same temperature.
  3. Before ordering on any website, always check if they have an official address listed on their site (company, street + nr, city,...), phone and email, officially registrated business numbers, etc... And then look it up in an official phone directory, and on Google Maps. If you can see the company logo in the street view on Google Maps, it is probably okay. However, if the company is located on an abandoned garbage pile on Google Maps, better be cautious.
  4. I usually design custom supports, so that I can make sure that I can get in there with a knife, or get in with pliers and hooks to pull out the support. In custom support I can also increase or decrease clearances as desired. Some of my usual examples, in case you need ideas: Various support concepts. The ribs (0.5mm wide, 1mm aparat) on top allow tighter clearances. Orange and pink are supports: they have extensions so I can grab them with a plier, as the model is too tiny to get in with a knife. The brim is for added bonding, due to the large overhangs (they float above the yellow). A totally free hanging support: easy to remove, consumes very few material, and does not damage the underlying parts. The inverted staircase at the underside of the support reduces its tendency to curl up, compared to a triangle shape.
  5. geert_2

    Belt Clip

    Maybe you could redesign it so that it somehow latches after attaching, with a sort of snap-fit lock? So it would become a closed circle. That would largely prevent deformations. Almost all plastics will deform under continuous unbalanced load, and especially PLA and light-cured resins.
  6. Usually I also start with a clearance of 0.2mm, and then adjust as trial and error indicates. However this is on a 0.4mm nozzle. As Smithy says, small holes tend to get closed down a bit, and small rods tend to get too big (slightly overextruding). Also layer height has a big influence, as well as the amount of blogs, strings, ringing and other defects. Probably you will need to post-process tiny holes anyway. I always go through them with a drill (see pic): manually, not electrically, because that melts the plastic. The tiny purple things probably won't print correctly at all, so you would be better off using standard nylon screws or pins, or whatever you need.
  7. Yes, sometimes designing the supports takes time. But if that makes the difference between a succesfull or a failed print, or between almost no post-processing or a post-processing nightmare, I think it is worth the effort. I like designing more than post-processing... :-) Concerning the exact dimensions and gaps I would say: design a test piece in which you incorporate several variations, and try which works best for you. For me, the ribs on top work best if ca. 0.5mm wide, with horizontal gaps between 0.5mm and 1mm. Vertical gaps of 0.2...0.4mm usually work well for me. Smaller gaps give better accuracy, but make removal more difficult and vice-versa. This is all for single nozzle printers like my UM2; I have no experience with dual nozzle (I guess then you could make the gaps far smaller?). It also depends on materials, models, printing temperature (cooler is better), layer height, speed. So you need to find a balance that works for your models and materials. Takes some trial and error. Below a new one from yesterday which also works well. Here the supports are totally free hanging, with very small gaps. It works due to the stringing and the sagging first layers of the support just sticking to the side walls. This support causes very little damage to the rest of the model and consumes only a very small amount of material. Edit: to reduce overhangs curling up: thicker layers tend to curl up less than thin layers: a 0.2mm layer is *much better* than a 0.1mm. Also printing slow and with lots of cooling helps. Instead of an inverted triangle, an inverted staircase also curls up less (as in the support shown above). All these things help, but do not eliminate the problem.
  8. Even if you find a material, it is not going to pop up automatically, if printed flat. On the contrary: even if you would pull it up manually, it will tend to snap back into the flat shape as when printed, because that is how the molecules were solidified. You would have to print it in the upright position, and then manually push it down to make it pop up again from itself (if the material is flexible enough to survive this). You could do this by designing a custom support structure that does not consume too much support material.
  9. Maybe like in the old days? Put a paper logbook next to the printer, and for each print, write down username, date, begin and end time, estimated print time (from printer display), meters of used filament, type of filament, etc. And a separate column for total times. This method has worked well for hundreds of years, and is likely to be more stable than electronic means. The data would have to come from the printers anyway, not from Cura. Often a sliced model is printed numerous times. And some others are not printed at all, when changing our mind or improving the model. Cura doesn't know this.
  10. For special models and difficult to reach areas, you could model the supports in CAD in the design itself. Then you have full control and you can adjust it to your needs. See these examples for my single nozzle UM2 printers (I have no experience with dual nozzle): A few different support concepts I have used: some with extensions, so I can grab the support with pliers; some with holes to insert pins to pull the support out, some with layers that peel off easily, some with several tiny blocks instead of one big block so I can wiggle each tiny part loose, some with overhangs to improve the first real layer of the bridge, etc... These pink and orange supports extend from the model, so I can grab them with pliers, because the model is too small to get in there with a knife. Also they have a custom brim (footplate) for better sticking to the glass due to their huge overhangs: I do not want them to be knocked off when the overhangs curl up and the nozzle bangs into them. The ribs on top reduce the contact area and make removal easier, and they reduce sagging (the blue tray has to slide in the yellow part). These supports hang to the side-walls, so they don't reach all the way down. This is usefull if you want to reduce the amount of support material, or if you don't want the lower surfaces to be damaged by supports. The concept is based on an idea from another user (was that "smartavionics"?). The bottom layers of the center support bridge will sag a lot, but that does not matter, as they are discarded anyway. The inverted staircase shape reduces curling-up of the overhanging edges of the supports.
  11. I would suggest you look up some tutorials and demos on Youtube of the most popular free CAD programs. And then see if the workflow appeals to you. For my designs where I have to make frequent adjustments to technical models, DesignSpark Mechanical is good. But it is only suitable for geometric forms, not for organic form. And it is very easy to learn. Not in the list above: if you want to make organic forms, and you don't mind a steep learning curve, then Blender (also free) might be an option.
  12. I think this should be a standard for new printers, at least for single nozzle printers. But it might be complex with dual nozzles. Maybe only the coupling halfway close to the head should not be there, it adds complexity.
  13. I don't know if it is technically possible. But mechanically, the print head is so bulky that the nozzle can not come close to any object anyway, without hitting it. So I think it would be best to print the models separate, and then "collage" it together with the rest of the collage?
  14. Yes, I know the experience with PLa demo-models left in the car... Now I use PET and NGEN for parts for my car: dash cam filter mount, clamps,... Up till now these have survived unwarped. These materials are still easy to print.
  15. Thanks for the tip. I once tried to grind down a skaterwheel to make it smaller. But after a full day of grinding on an agressive water-cooled disk, I still had gotten only 1mm off. That was when I realised that skater wheels are supposed to be *very* wear resistant... :-) Something else I just think about: any 3D-printed suction cup is likely to be *not* watertight. So it might not work at all. The indents caused by the layer- and printing lines will allow air to seep in and destroy the vacuum. Even in glass lab vacuum equipment, the tiniest scratch will quickly destroy the vacuum. So, even if you make a 3D-printed mould for casting, that mould would require post-processing to remove or fill the indents. Even a very smooth bottom like this won't hold vacuum at all. Unless you have a strong vacuum pump that keeps running all the time.
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