Polycarbonate build plate…. No bed heat Success!!!
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My PEI bed, if left un-clamped, but oriented the way it is on the build plate, has a concave top, and a convex bottom – IE the edges of the PEI plate curl upwards. When clamped down, the plate is flat to about 50-100 microns. When printing, eg, a large hollow cylinder with a diameter that occupies a large part of the build plate, the print adheres fine entirely through the print. The edges of the circle are touching the build plate, as well as the middle of the circle. However, when the print is removed, there is a noticeable convex surface on the bottom of the print. If you now place the object (cylinder) on the bed, the center of the circle is touching the build plate, and the object would have a tendency to rock around. IE there is a "bulge" on the bottom of the print, approximately equal to the curvature of the print surface when unclamped. The warping does not occur during the print, seemingly the PEI "holds" the print down enough to resist this -- but when the part is removed, the condition presents itself.
It's easily fixed by heating up the bottom of the part, and pushing it flat against a surface plate. It's odd, and I'm wondering if the phenomenon I sometimes see is the same as was described here.
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Gotcha so basically the cupping of the plate then shows itself as warping when the part is removed. Well its hard to say at this point because the objects that I have printed do not show this effect albeit they were only up to 80mm but his parts were small as well.
I think its important to eliminate these other issues first. What is odd about his heightmap and print issues is if you look at the height map even when clamped down it shows the middle cupped upward and the edges downward but then the exact reverse effect after printed, I wonder if the bed is passing this along to the PC plate as well because his raw bed heaightmap is similar. I do not see this on my height maps (waiting on a piezzo to arrive for better accuracy) or prints but we will see with larger ones.
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Hi there,
Yesterday I edited the config.g to change acceleration and jerk for my extruder, as it was low compared with my previous settings in marlin. So far, it seems that it's not under extruding, at least, with the couple of parts I've printed in PLA.
However, I tried again with PETG… and failed again, I'm not sure if my PETG is just crap or there is something I'm not doing right... an image worth more than 100 words:
This is with my 3DCPI PETG @ 245 degrees with 0 at the bed, the skirt didn't stick to the bed, but the part sticked so well that I had tons of problems to remove it. Layer height was 0.1 and Z offset AFAIR 0'25 o 0'27. First layer seemed ok, but after a couple of layers you can see the result.
I have another PETG, from Prima Select, and it was even worse, I wasn't able to even stick the filament to the bed… the filament started to create little blobs in the nozzle, and I had to stop the print. I tried with several temperatures between the recommended range, and a bit low too, with no success... I'm looking forward to receive the rigid.ink PETG, if that fail too, I will start thinking on not using PETG anymore, it's only creating frustration and the results are not worth it.
I printed another part in PLA, with a BQ filament (I don't like this filament, so I'm using for non-important parts), the part is 105mm long, and came out pretty much OK, no elephant foot, gorgeous first layer (I really like the finish of the PC in the bottom layer) and I was able to remove it by bending just a bit the PC sheet, so quite happy about that, seems that the offset I'm using (0'11mm with the precisionPiezo) is the right one. I couldn't check the cuping/warping, as I looked it before coming to the office, I will check it tonight.
BTW, the effect you mention for the center of my bed I think is because my bed is too large (300x300), I have a little screw in the middle of the bed to push up a bit, seems that I will need to adjust it too, I may forgot about doing it.
Cheers
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Thats the effect I am seeing right now orkercho, i will let you know when I have a chance to troubleshoot (the filament)
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Okercho,
I just wanted to show you that I am able to reproduce what you are experiencing. But more testing needs to be done before i can draw a conclusion.
This was with a freshly sanded build plate. The part on the left was printed and easily removed just by sliding a scraper underneath. It did not show any signs of cupping. For that print I used a known working roll of PETG it was Taulman Guidl!ne I have also printed Taulman TechG (petg) and Rigidink Petg without issue.
The second one showed warping after flexing the plate… as you can see it was difficult to remove breaking the part in the process. This was with a roll of Taulman Bluprint which is a high temp petg printed at 290
I am not yet ready to blame a bad roll of filament as i need to do more testing (extrusion issues and horrid first few layers) i want to see if different settings will resolve those issues before coming to a conclusion but it is looking like a filament issue.
Its just going to take some time because i will need to keep resanding until i get it right. I will report back when i know more.
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So here are my findings and conclusion. Clear PETG has a tell tale that you do not see in your colored PETG. When clear PETG gets too hot it gets a lot of micro bubbles giving it an opaque white look instead of a translucent appearance.
I remembered this when extruding into air and seeing it come out clear at 5mm/s then i remembered i had lowered all of my jerk and accell settings to match a post that deckingman had made during his testing of pressure advance. I was already slicing at 75mm/s with no reductions in speed for any features accept first layer.
So i raised my accel and jerk settings a lot and increased first layer speed to 80% though 70% is probably better then reprinted with the Taulman Blueprint….
The print popped right off as i tapped it with a scraper.
On the left is the new print, on the right is the failed print from before.... as you can see as the print got to smaller features and slowed down the PETG started breaking down and becoming opaque.
I think it is safe to say you are seeing the same thing, your filament is spending too much time in the hotend or you need to lower your temps if speed is not a factor
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These findings also seem to make a good case for using clear filament to calibrate your printer because they give you a clue when settings are negatively impacting the filament through overheating.
Looks like I have some more tuning to do
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I've read about polycarbonate build plates before and the tenor was, the parts often stick too good. Maybe it's the sanding, that makes all the difference? Would it work with shotblasting too? I guess it depends on the stuff you shoot at it?
Where did you get the POM filament from? ( Why do they offer it, when it is "known" to be unprintable? )
I've made these 2040-sliders from PTFE, but POM would be much better I guess.Motedis sell POM Filament http://www.motedis.com/shop/3D-Filaments/3D-Filament-POM-175mm-05kg-Made-in-Europe::3540.html
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This surface works really well.
ABS printed on 80 C heatbed from https://www.thingiverse.com/thing:1504207
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Is that the PC Bed material?
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Just some of my experiences trying to find cheap and usable filaments, I have no affiliation whatsoever with the companies:
Hobbyking sells PA Nylon, POM and PETG filaments for very reasonable prices (little over 20$/20€ per a kilo roll).
I can't say anything about the POM or PA yet as I don't have a suitable print surface (nor an enclosed printer) but I really like their black and white PETG (solid colors).
It's not spooled so nicely, but the dimensional accuracy seems good and it prints very nicely and the parts are durable so it has replaced ABS for me almost completely. Hope they get more colors as well.I print it on ABS juice on glass with no sticking issues whatsoever (80-90 C bed / 255C hotend). AT this temp it flows really well and the parts come out durable and with very good layer adhesion. At 240C the parts tended to get harder and more brittle.
I have also used PETG from a Czech seller (on Ebay.de) called Filament PM. Very nicely spooled and packaged and the dimensions seem good. To me it seems a tiny bit harder to print than the Hobbyking variety as it seems a bit more viscous so has to be printed a bit slower but they do have more colors. I have not made any strength comparisons but both produce definitely usable parts easily. The layer adhesion is much better than with ABS and no warping to talk about and no smell!
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Hi there!
Long time since my last report here… I've great success with PLA using the PC surface, even with quite big parts. I'm still having little beding as mentioned before even if the part don't warp at all, but is barely noticeable and doesn't happen for all prints, so I'm really happy, so I tried the next step... ABS!
Yesterday I tried to print for the first time with ABS, and I started to test the distance to the bed. I'm using 0'13mm offset for PLA (no warp, stick perfect and no elephant foot), but in order to get the ABS I had to use baby steps and get it 0'2mm closer to the surface, which doesn't make any sense... Anyway, my first print was a failure, as one of the parts stick too much (I couldn't remove it, I will need to use a sharp today and probably resand a bit) and the other warped a lot after 5 layers, so I had to stop the print...
@Whitewolf, what do you recommend as offset for printing successfully ABS? I will continue making tests during the weekend…
BTW, I bought some PETG and ASA from rigid.ink, but I wasn't able to test it yet...
Regards!
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As POM seems to stick on PC, what about making the bed with a POM sheet? Do you think PLA/ABS can stick on it?
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FMA, pretty much nothing sticks to POM in my limited experience. Also POM is pricey and releases nasty gases when it is overheated.
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Ok. It was just a thought…
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Yeah it's good that we keep trying different options though. I have some PC now based on whitewolf's recommendations so hope to try it later this week
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Any suggestion where to get PC in the UK? All my searches turn up the clear stuff but no opaque white.
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Is opaque better?
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I think that it depends on the sensor you're using. If you use an optic one, you can have issues with the transparent one… for a capacitive or a piezoelectric, I don't think there is any difference, and in terms of adhesion, I cannot think in a reason why it should be different.
Regards
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Well, I guess opaque PC have some additional stuff, so they can change a little bit the behaviour…
BTW, clear PC is nice, because you can put leds all arround (if thick enough), which illuminates the printing part!
