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Everything posted by geert_2

  1. If you print 4 or 5 "skirt" lines around the object, this also allows you to verify and if necessary fine-tune the distance between nozzle and print bed (at least on UM2 printers, I don't know if this still applies to UM3).
  2. No I haven't. I only use cyanoacrylate glue, which works very well. If I have to pull parts off again, I often tear the PLA apart, not the glue. I did try "rotational friction welding": put a piece of filament in a Dremel tool, and then at high speed rotate that along the seam line, so they are melted together. This gives a very strong bond, it's all molten plastic. But it is also terribly ugly, and requires huge amounts of post-processing. If I would be printing art and statues, I would try two-component glue and add fine sand as a filler, to pour into the model to give it additional streng
  3. I also have this sometimes: the auto-logout function kicking in after one hour or so. The best thing to do is write the message in Notepad++, and then copy and paste it into the browser. But of course, I usually do not follow my own advice... It would be good if we could set the default auto-logout time in our preferences. I would probably set it to 4 hours. And then I would lose the next reply at 4:05h.
  4. Up till your question, I hadn't even heard about PMMA as 3D-printing filament, even though I have used lots of two-component PMMA materials (powder + liquid) and PMMA-based light-curing materials. So I googled it: indeed it does exist, and some people like it, but some complain it is very brittle (which is what I would expect, similar to two-component PMMA), and it shrinks too much, like ABS. Is there a reason you need PMMA, and can not use PET, polycarbonate, some high-temp polyester, or even PLA (but only for moulds not subjected to temperatures above room temp)?
  5. Or split the model in such a way that the seam lines sit in a natural indentation or other dimensional change of the model. Or create an indentation or decoration to hide it. So it becomes a "feature" rather than a defect. This may of course not always be possible.
  6. Moisture might indeed prevent sticking. I had that too in the beginning when the weather was warm and wet. Also, some cleaning aids (window cleaners or some alcohols) do contain soap or oils that prevent sticking. So, I would recommend to clean the glass with pure warm tap water only. You could use isopropylalcohol first (this should remove oils without leaving traces), but then clean again with warm water only. For printing PLA, I always wipe the glass with a tissue moistened with salt water: gently wipe and keep wiping until it dries. This should leave an almost invisible mist of salt st
  7. In the standard UM2 firmware you can also manually heat the build plate, via "Maintenance > Advanced". However, if you keep the temp high after print completion, then how are you going to get the models off? They do stick like glued, and you can lift the whole printer by pulling up a tiny model. While after cooling down they come off all by themself, without requiring any force. It may take you more time to get the models off a heated bed, than to wait until it is cooled and simply pick them off. You could speed up cooling by putting a fan in front of the printer, after completion. And
  8. More and more engineers in the USA and UK are switching to the metric system. Once you are used to it, it is sooooo much simpler and more logical than imperial units with their weird multiplying and conversion factors, and where some "units" have totally different dimensions, depending on where you are (such as gallons, if I remember well). It is just a question of time before everyone uses the metric system. So you can better be among the first than among the last. You will not regret it.
  9. Maybe you could leave the holes the size they are: they will probably come out slightly smaller anyway. And then drill. Just try. I would recommend drilling by hand, not with a machine: manually gives you much more feeling. A machine generates too much heat and may melt PLA or other low-temp plastics. Don't ask me how I know. I have bought a separate drill clamp (I don't know the correct name in English) to mount my drill into, so I can get a good grip on it. Edit: added photo of drill clamp for manually drilling.
  10. I don't have an UM3, so this is only a guess: from the photo there appears to be a way too big gap between support structure and bottom of the model. So the first layers of the model do sag. Also it looks like the support structure is not dense enough: not enough contact points between support and model for good support. I can't comment on the cause: a problem in the design? Or a problem with underextrusion of the support material? Or wrong settings?
  11. If material is leaking out of the nozzle while jumping over gaps (thus causing strings), then indeed you could have underextrusion in the area after this. The software has no knowledge of these leaks, it doesn't supply extra material to compensate. If you print slow, you might try a lower temp, so the material is less liquid: 10°C less or so? PS: don't leave a PLA printed model in your car in sunny weather, or don't leave it sitting in the sun on a concrete runway: it will warp. I don't know what effect warped wings would have on flight characteristics, but I don't think it will do any good.
  12. The bed temp should be around the glass transition temp of the material: that is the temperature where it begins to soften and get flexible (which is very long before it is melting). For most PLA this Tg is around 55°C, if I remember well. If you print PLA on bare glass, after wiping the glass with a tissue moistened with salt water, then the effects are as follows on my system: - no heated bed: model does not stick at all, extruded sausages curl up and come off immediately, - bed temp way too cold: printing starts fine, but model pops off suddenly during print, - bed temp a bit too co
  13. This is a late reply, but may still be useful. I am pretty sure it are micro-cracks indeed. When you manually bend a piece of translucent or transparant PLA, or when you straighten a bent piece (like a tight-wound piece near the end of a spool), then you clearly see white micro-cracks growing. Some colors show these cracks better than others. If you stop bending the filament and release it, the cracks stop growing. But if you keep it under stress, I guess they will keep growing until the material breaks or almost breaks. Near the end of spools, I always unwind a few meters of PLA, manually
  14. This is a normal effect on all similar 3D-printers. The filament is still molten or somewhat flexible when laid down. When the nozzle is printing a corner, as in tight circles around holes, it pulls the molten filament to the inside of the curve. In small holes this is even more visible: a 3mm hole may come out as a 1.5mm hole. It also depends on printing speed and temp. Solutions could be: change the dimensions in the design, or go through the hole with a drill.
  15. To prevent curling up, have you tried wiping the nozzle with a tissue moistened with silicon oil? And/or with PTFE oil? This reduces build-up of molten filament on the nozzle, but it also reduces the tendency to curl up when priming the nozzle. So it might help during the print too? If temp conductivity of a steel nozzle is much worse, maybe you could try increasing the temp by 10°C, and see what happens? If the filament is too cold when exiting the nozzle, it also won't stick well. Further: did anything change on the glass plate? Different glue, different preparation or cleaning, differ
  16. I think printing little test plates of 10cm x 2cm x 1mm would do. This doesn't waste too much material. Design them with a hole so you can hang them on a line, like a decoration. Even better: print two copies of each, and keep one stored inside in a dark space, to compare. Then every month you could compare the plates visually, and flex them to feel if they got brittle and if they snap under pressure. In some materials UV-damage may be visible, but in some it is not, and the item just falls apart when you flex it.
  17. I don't have any experience with replacing the heater and sensor on these printers. But I did build a couple of electronics machines in the past. So my comments below are educated guesses, but not necessarily correct or complete. Probably the heater got red hot because you disconnected the sensor from it. So the feedback-loop was broken, and the system kept on heating and heating, because it did not sense any change in temp. I don't know how long these heaters can withstand this without burning out? If - after assembling everything again - the temp overshoots a lot, with identical components
  18. To improve UV-resistance, maybe you could use black or highly opaque materials? This prevents the sunlight and UV-rays from penetrating deeply into the material. That was a reason they originally started to make car tires black by adding carbon in the old days. Originally they had the light brown natural rubber color. Of course, manufacturers use synthetic rubber now, and they add lots of other things into the mix (e.g. silicon), so I don't know if they do still add carbon. Disadvantage of black is of course that it accumulates more heat. So it definitely won't work with PLA. I guess you
  19. Concerning PLA smoothing, if you haven't done so, I would recommend that you read the thread about PLA smoothing created by user cloakfiend. This has lots of good info and photos (so you can verify the results). He is the specialist on PLA-smoothing. This thread contains about all that is known about this subject. It should be this: https://ultimaker.com/en/community/10412-acetone-finishing-on-pla
  20. You can import SketchUp files (skp-files or something, not STL or OBJ) directly into the freeware 3D-editor DesignSpark Mechanical ("DSM"). If you do that with fonts created in SketchUp (with the characters as vectors only, or as surfaces, not yet 3D-models) and then you try to make 3D-models out of them in DSM, you will see that in a lot of characters the vectors-ends do not match: there are tiny gaps. It are not closed shapes. In DesignSpark Mechanical this can be repaired manually by zooming in on the offending characters and vector-ends, and manually adding small vectors to close the gap
  21. As far as I understood, the basic reason is that ABS requires a very hot temperature to melt and fuse well. The new layers tend to cool down too fast, thus without proper fusing to the previous layers. You need to keep the temperature of the old layers way up too: close the front of the printer, switch off cooling fans, high bed temp, and don't print too fast. In combination with the huge shrinkage of ABS, this causes the splitting, or the coming loose from the build platform. ABS is good for injection moulding, but not so good for 3D-printing. If PLA would not be suitable for your model, yo
  22. I store all filaments in huge sealed boxes with a big (!) bag of disseccant, so they are dried and then stay dry. I use the sort of disseccant that is sold in car shops to dry car interiors and prevent condensation on the windows. They have a blue indicator that turns pink when the bag needs to be reheated in a microwave or other oven. For nylon, you should also put the spool in a sealed box with disseccant *while printing*: otherwise it may absorb too much moisture in only a few hours. This may require some bricolage: you need to make a spool holder, a small exit hole, and a holder for the d
  23. Another option would be to take a ruler and measure it. And then draw the thing in whatever CAD program you want.
  24. I have printed 10mm x 10mm x 10mm test cubes in that way: just set the wall thickness to more than 5mm indeed (in my case), and it spirals layer per layer. Then it prints only walls without infill, until the whole object is filled with wall. If your object would be larger than 10mm diameter, adjust wall thickness accordingly. However, the center of the spiral does not come out well: the nozzle stays too long in that little area, develops too much heat, and it has to slow down too much to go around the tight corners. This results in ugly blobs and overextrusion in the center of the spiral. Th
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