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mevander

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Posts posted by mevander

  1. I've used UV-glues from Norton Adhesives in several different projects here at the university. It works pretty well and they have glues that are both heat and UV-curable which is great for parts that only partly are UV-transparent. You can find them here: http://www.techoptics.com/adhesives/optical-adhesives

    I can also recommend getting a hand-held UV-lamp like the dentists use. It's very convenient when gluing small stuff. In Sweden you can find it here: http://www.brotech.se/fusion-curing-light-blue/2960-0

     

  2. That looks very nice. We've had problems with voids/defects in the nylon if we go over 230C. I'm guessing it's due to water in the nylon but we've tried to dry it in a 50C over so many times but it still doesn't get better. We also store it in an airtight box with desiccant beads with color indicators. Do you have any good recipe for drying it?

     

  3. I also checked the gcodes with http://gcode.ws/ showing interesting stuff.

     

    Ooh, that was an interesting site. I can't claim to understand gcode very well but if I slice a cube and leave all settings except change the layer height from 0.1 mm to 0.2 mm, the site goes from showing me a solid rectangle to a rectangle with separated lines. Should it look like that?

     

  4. Thanks Bas, that was very interesting. I think that one difference is that what we see here is at fairly low flow rates. My test box was printed at 4 mm^3/s and we've seen it at much lower flowrates too. If we go really slow, 0.05-0.1 mm layers at 20 mm/s we get very nice prints but that is also the only settings we can use more or less.

     

  5. Ok, here's some new input from me. I did a test today with a test cube that always produces gaps. I printed it at 220 C and marked the filament at the beginning and the end of the print. I then did the same thing but let the filament go out into the air (without bowden tube or anything). I also took pictures of the filament pattern on the two runs.

    The amount of filament that was pushed through the hotend when printing the cube was 44.4 mm while the amount for the free filament was 51.3 mm! Cura says that it is supposed to be 51 mm. In other words, there seems to be a fairly large amount of slipping during the print.

    Here is the picture of the pattern on the "free" filament:

    gallery_36523_1334_42452.jpeg

    and here is the pattern of the filament that went through the bowden tube and hotend:

    gallery_36523_1334_125237.jpeg

    I unfortunately reversed the filament to get it out of the machine so there are two sets of pattern. There is still a pretty big difference in the patterns though and you can see that the "diamonds" are skewed.

    So, the question is how to solve this. More pressure on the filament? A better knurl pattern?

     

  6. Thansk for the more detailed underextrusion explanation. I've tested the temperature and that is not the problem in my case. I've also tested measuring the temperature inside the hotend (without filament in there of course) and was a bit surprised to see it being 20C higher than what the machine thermocouple measured. I'm still measuring at a different place than the machine so I'm not too surprised that it didn't match but rather by the large difference in temperature .

    I've previously seen that when pushing the filament towards the feeder rather forcefully, separating lines can merge again and as soon as you release the filament they separate back again. I've always assumed that I would not be able to push more material this way (as the motor while being powered should prevent this right?) but rather that I helped the motor overcome some of the torque needed to work against the friction in the bowden tube. This would be an indication of #2 then I guess?

     

  7. Just wanted to let you know that we're currently playing around with measuring the actual diameters of the hotends (the two we have were 0.412 and 0.46) and slicing the files with different nozzle diameters. So far it hasn't resulted in very much, we're still getting separating lines already at the 4th or 5th layer. I should probably also mention that we've now swapped machine to another one and it unfortunately ended up having the same problems ...

     

  8. No, you're absolutely right. I think that the point here was that rather than ordering expensive implants to test them you could do design and some tests with the simpler systems and then order a "real" printed implant when you had something you wanted to look more closely at.

    I think I read somewhere that Taulman was working on a certified medical grade nylon that would be very interesting. It would be one step closer to something I would trust more at least :)

     

  9. People have been discussing about testing both microfluidic chips or components of them that handle cells as well as some parts of a culture chamber where cells are expected to proliferate and be happy. I also had a colleague who work with implanting bone replacements in small animals who was a bit curious if it would be possible to model, print, test mechanically and implant designs.

     

  10. Hi.

    As I'm working with biomedical engineering, I've been getting some questions from colleagues regarding biocompatible materials for the ultimaker. I've understod that PLA actually is fairly biocompatible but it is also not as strong as we would like. Can anyone recommend other materials that would be ok for contact with living cells?

    Cheers

    Mikael

     

  11. Maybe that can explain some of my weird results I've been getting lately. However, normally when printing the sensor updates the temperature every second or so and it seems to be more or less correct temperature at least (I've checked with a probe). For some reason my printer seems to be a drama queen ...

     

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