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geert_2

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Everything posted by geert_2

  1. I have seen brown, grey and black debris, but no green yet. These were all from burnt material inside the nozzle. If you do an atomic pull (also named "cold pull"), is any dirt green too? It could be that some of the white additives decompose, or react with the decomposing PLA and turn green when too hot? What you could try is keep an end of filament in a flame until it melts and starts burning, and see what color that gets?
  2. PLA does get dull and brittle. Out of curiosity, I tried a filter in the waste water syphon of my lab. It took a year or so, and it still functioned, but you could clearly see the dullness and color change (more pale, white-ish). So there is some degradation going on. I haven't tried any other materials, but I would guess that PET or its derivatives are worth a try. They are used for lots of drink bottles anyway. If you select a water-clear filament, you can easier see what is going on inside the material (e.g. color changes).
  3. Just winding it up again might work, while gently guiding the filament by hand. If it is not tangled too much, it might just snap back onto the spool with a little help. At least it does so for my PLA. Otherwise remove the spool from the machine, walk it down your room, hall, garden and street until the filament is all straightened out, and from there wind it up again. Or cut off the unwound piece from the spool and use it up like it is.
  4. If the problem is only on small parts, the cause might be not enough cooling time for each layer, and slight overextrusion due to the print head having to slow down and change direction very often. A solution you could try: print slow and cool (e.g. for PLA: 180°C to 190°C, and 20mm/s). And print a dummy block or tower next to your models. So the printer has to spend some time on that dummy block, and the real models get enough time to cool down. You could also try to set the flow rate to 95%. In my experience this helps for small parts.
  5. What you could also do, is keep the spool of filament locked in a sealed bag with disseccant (if I spell that correctly). And only take it out to unwind and cut off the required amount of filament. Then immediately put the spool sealed away again. And only feed the cut off end into the printer. The disadvantage is that you need to calculate some spare in, and the piece of filament in the bowden tube is always lost. You you have a lot of waste pieces of filament. But this might cost you less than destroyed models, especially in a commercial environment. I am not a fan of wasting material, but in this way the total waste may be less than if you have too many failed models.
  6. In my experience, there are two main causes: 1) For good bed adhesion, the first layer needs to be squished hard agains the glass plate. This tends to spread that layer out a bit, thus widening it. Solution: calibrate the build plate for a higher gap between nozzle and first layer, so that the first layer isn't squished so hard. 2) The heated build plate makes the bottom layers melt and sag a little bit, since the optimal build plate temp is around the glass transition temp of the material (= the temp at which it begins to get weak). Solution: use a lower build plate temp. Both solutions give a far worse adhesion of the model to the build plate. So I usually prefer a little bit of elephant feet, rather than bad adhesion, especially for difficult to print models.
  7. In addition to the tips above from cloakfiend and GR5, if the models are small, you could also try printing them with 100% infill. For better bed adhesion, you could also try the "salt method": gently wipe the glass plate with a tissue moistened with salt water, prior to printing. In my experience this greatly improves bonding of PLA to the bare glass. (It does not work for ABS, and I don't know yet for other materials.) See the full PDF-manual on this salt method at:https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/
  8. Forgot to say: Another method that sometimes works, depending on the model is this: - at the bottom touching the glass plate: a solid layer of 0.5mm thick. - then a gap of 0.5mm - solid layer of 0.4mm - gap of 0.5mm - solid layer of 0.4mm - gap of 0.5mm - and so on... - solid layer of 0.4mm - ribs of 0.5mm wide, 90° rotated to the direction of the fill-in of the bottom layer of the model, as shown in the pic above. - gap of 0.2mm to 0.3mm - rest of the model above the support So the support structure consists of separate layers above each other, all "floating" in the air. Due to the sagging of the first layer, they will bond very weakly to the layer below, so they break off easily. So you get a very stable support that is not knocked over, but you can easily peel it off layer by layer afterwards. It all depends on the model, and it may require some prototyping.
  9. If you design the models yourself, then also design the support structures. Think about these points: - Design hooks, holes or other features into the support, so that you can pull them out with pliers, screw drivers, or other tools. - Allow enough room for these tools. - Allow enough room for a sharp knife or scalpel (surgical knife) to move in-between the supports and the model, so you can cut the supports loose from the model. - In difficult to access areas, extend the support to outside of the model for easier access. So you can easily grip it from the outside with a plier. - Between side walls and support, allow at least 0.5mm spacing, or better 1mm, so that supports don't stick to the walls. - Between a model layer and the supports, I usually allow 0.5mm spacing. - Between a support and bottom layer of overlaying object, I usually leave a gap of 0.2mm to 0.3mm. Thus that gives: last layer of model below support, then 0.5mm gap, then solid (!) layer of 0.5mm as the base of the support, then the support scaffold, then a solid layer of 0.5mm which is still part of the support, then ribs of 0.5mm wide and 0.5mm high, then a gap of 0.2mm to 0.3mm, then the first layer of the model above the support. - Make a test print with different sizes of gaps, and try which works best for your material, sizes and temperatures. Bigger models require bigger gaps between model and support. Higher accuracy and smaller models need smaller gaps. Have a look at this image to illustrate the gaps and ribs: Here too I can cut the supports loose with a scalpel, and pull them out with a plier. Edit: the ribs at the bottom of the support can help but are not really necessary in my experience. The ones above the support are. And they should be 90° rotated to the direction of the infill of the bottom layer of the part above the support.
  10. That Onshape change, is that only for new customers? I already had an account and I see no changes in behaviour? Private documents still seem to be private, and I can still make 9 private documents. Yes, nine private documents, not ten like before. I don't know why, but Onshape somehow claims that I have one document when I have none, so I can only add 9. Anyway, I rarely use Onshape, since I can not find my way in the user-interface: functions like opening and saving files are splattered all over the page at random, there is no consistency. At least, I can not find the logic in it.
  11. The only thing for which Sketch-Up has some limited use in design for 3D-printing, is when your 3D-editing package does not support some features and Sketch-Up does. For example text in DesignSpark Mechanical is not officially supported (although it can be done by adding and editing dimensions, and then projecting these onto a model). In such a case you could set the text in Sketch-Up (only the vectors, no 3D), and import that in DesingSpark Mechanical. But a lot of characters will need manual fixing, since sometimes the vectors do not touch each other, leaving a gap, and then you can not extrude that shape. So you manually need to connect and close those gaps. Otherwise Sketch-Up is useless. It is only good for visual modelling on-screen.
  12. Hello Cloakfiend: a way to release complex shapes from a silicon mould might be to use a thinner mould. Like they do when casting human bodies. A thin layer of silicone can be removed like a blanket. But then you need to design and 3D-print a tight fitting hard shell too, that can be opened, and with register marks, so you can fit it together exactly. Otherwise the silicon mould does not keep its shape. This also saves you a lot of money on silicone, because you need far less. Google for Youtube videos on mould making and casting. Another thing that helps, is to spray the model with silicon mould-release spray before casting the mould. Then it does not stick so much. But complex shapes with such deep and long undercuts like that logo will always be very difficult to remove. A very flexible silicone with high resistance to shearing may help (they come in different hardnesses), but they are dimensionally less stable, so then you definitely need a hard shell around the silicone. You could also 3D-print some "cores" (sort of long pilars or pins) that fit into the eyes and holes of your model. In such a way that after pouring and curing the silicone, you can first pull out these cores. Then the silicone comes loose, and is easier to remove. (If I find time, I will make a drawing to illustrate this.) Be sure to vacuum the silicone after mixing, pour it in the mould in a thin stream from some height, and tap or shake the model afterwards. All this helps to prevent and remove bubbles.
  13. As Nicolinux says: even within one brand and product range, some filaments have totally different stringing characteristics. For example in PLA/PHA from colorFabb: the "olympic gold" and "natural" colors do string more than standard white I had. Probably due to the amount and sort of fillers used? Ultimaker's "Pearl" (nice color by the way) also strings a lot. But they do stick very well to the build plate. ICE PLA strings far less, also prints nice, but does not stick so good to the build plate. Also, the sticky and "stringy" materials are more difficult to grind: the molecular structure appears to be more fibruous (I don't know if that is a good English word?), thus containing longer fibres. While the PLA from ICE grinds into a fine powder. I can imagine that the longer fibres in the molten material increase stringing.
  14. You could also have a look at shops for custom car parts, spoilers, wheels, accessories,... They usually have a lot of special metalic paints for plastics, and they should know how to get it to stick to plastic (how to grind, how to chemically activate the surface, apply primer, and so on).
  15. I don't know anything about Blender either, but is there no way to set physical dimensions? Or, if it would be a sort of "freehand sculpture", without any reference to dimensions, maybe he could create a little cube next to it, and give that cube exact physical dimensions? Since people can design planes exactly to scale in Blender, something like this should be possible.
  16. What I would try in such a case: - Thorougly clean the outside of the nozzle prior to starting the print, and then wipe it with silicone oil or ptfe oil, to reduce the build-up of molten filament during printing: this gives less "hairs" and less strings. Make very sure to not spoil any ptfe oil on the glass plate, or you will have no bonding at all. - Gently wipe the glass plate with *salt water* to improve bonding and prevent warping (it seems you have some corners lifting?). This works for PLA only, as far as I know. - Print speed: 20 to 25mm/s. - Nozzle temp: 190°C (start the first layer at 210°C for a good bonding, then gradually lower to 190°C and see if that still works). Do not go lower than 180°C. - Bed temp: 60°C. - While printing, watch the output and check that you have no over-extrusion (this causes material build-up around the nozzle, and causes hairs and strings). Some PLA brands and colors do string more than others. So, if you would have more available, try them.
  17. Even if you don't need it for real work anymore, why not keep the UM2, and use it to experiment with all sorts of things? Try different filaments, different bonding methods, try upgrades, whatever. Or use it as a demo printer for friends, collegues, kids,... to make toys or so?
  18. For relatively simple technical parts based on geometric shapes, and where you often need to adjust dimensions, DesignSpark Mechanical (freeware) might be a good choice. Easy to learn, lots of good training videos, and you can also use SpaceClaim videos, since DSM is a limited subset of this. For complex organic shapes, I think Blender (also freeware) might be a good choice, but it has a *huge* learning curve. You might also have a look into Form-Z from Autodessys: not free, but they have quite a lot of functions for organic shapes. I once tried an old demo a couple of years ago (was 1 month free), and they had quite good support back then. Have a look at their demo videos and webinars. FreeCad is also useful if you know exactly what you want, without need to change it afterwards, because it is not flexible, and later updates usually break the model. So, not optimal for me. I also tried Onshape, but it was quite slow over the network here. From a technical viewpoint, it is absolutely wonderful that they get it done at all via a browser and the net. But it should run locally, and save files locally, I think. If you can live with an online package, it is quite powerful. Before deciding, first have a look at several demo-videos and webinars of each potential package, and see what appeals to your way of thinking and working. This may take several days, but you will win these back very quickly if you find the right software for you.
  19. I had a couple of typical 3D-models printed on an expensive Objet printer, which works similar to inkjet printer technology: a set of jets spraying liquid plastic, and an ultra violet lamp follows and cures it. Resolution is a bit better than on my UM2, especially for text on the top layer. But it is not exceptionally. And text on the sides is not readable at all. You still can't compare it to injection moulding quality. After each use, the printer requires at least 30 min of cleaning, otherwise the jets may block (1000 euro per jet x 8 jets). Resin costed about 1500 euro per liter. Support material costed about 700 or 800 euro per liter, if I remember well? Cleaning the support material off the prints, requires a high pressure water jet, and a special cabinet with protection. And of course water supply and drain. The mechanical strength is very, very poor: way lower than PLA or ABS: it deforms very fast under pressure, the so-called creep. And it snaps with a very brittle fracture when lightly overloaded. Also, white prints get yellow very soon. UM-users like cloakfiend can get almost equal results with an UM2, as those you could get on that Objet. So I guess with an UM3, with real support material, there will even be less differences. We also considered a Form1, but after noticing the small dimensions, the huge resin cost, and the very limited life of the glass plates, we dropped that idea. I don't know how other resin printers do (dedicated juwelry printers may be different), but for most purposes, I think FDM printers are more practical, way cheaper and give stronger results. Althoug with a bit less surface detail. And they are much cleaner to handle, with far less health risks. If you would ever consider buying a liquid resin printer, be very sure to visit someone who has one, and see how it works, have a demo model printed, see how the cleanup is done, ask what all the requirements are (such as separate water cabinets with high pressure jets, which are often not told during sales talks!!!), and test how strong the prints are. Depending on your needs, you might be very pleased, but you might also be hugely disappointed.
  20. Can't Blender or FreeCad open and repair them? They are both freeware, so that might be worth a try?
  21. The steel wire version of the FilCatch won't melt or break. I have been using this now for a couple of weeks, and it works well. So this was a very simple but great idea.
  22. I tried this today, but it did not work well. What I feared did happen indeed: molten filament creeps up between the nozzle and silicone cover, and it breaks the silicone at the top (where the nozzle meets the aluminum fan mounts) and pours out there in a big blob. This is probably due to the silicone cover being flush with the nozzle, so it sort of pushes a bit on the surface while printing. When there is a little bit of overextrusion, as on the first layer or on short strokes with frequent stops, the melt choses the way of the least resistance, which seems to be in-between the nozzle and silicone cover... It looked beautiful but didn't work, so I took it apart again. (I Forgot to take photos.) And I will stick to wiping the nozzle with silicone oil prior to printing.
  23. Hmm, the first annealing test in the Ultimaker was not totally convincing. In the photo above, the flat object is freshly printed, the warped one is annealed. Both are the same PLA. While it was sitting in the "oven" (=under a cover on the ultimaker bed), I couldn't resist playing with the temperature, and I increased it to 80°C, so it came loose from the build plate and reverted to a more relaxed state. I should have left it at 55°C, I guess... Anyway, this shows how high the built-in stresses can be, even in "low shrink" PLA. And what you might get when you leave such a model in your car in summer. So, when annealing, you really need to clamp the object very well, or it really needs to be stuck very well to the build plate. Otherwise you get what you see above.
  24. I have similar font weirdnesses as Daid describes, although not identical. It looks a bit like the font is drunk. Also the fonts in the title bar (Explore Products Stories etc...) look pixelated. OS: Windows 7 SP1 Browser: Pale Moon (most recent version). Pale Moon is a split off of Firefox which still uses the old-style layout with menu bars and status bars.
  25. Yes indeed, I hadn't thought of that. If the spray can totally consists of polypropylene or polyethylene, it will survive. But if it contains ABS parts, you would indeed have a real problem when spraying acetone...
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