Glass bed woes at E3D???

Discussion in 'BigBox General Chat' started by mike01hu, May 13, 2016.

  1. mike01hu

    mike01hu Well-Known Member

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    Got my hybrid kit and checking through the parts dicovered a new addition to the kit . . . lumps of bed glass stuck to the base layers and a pig to remove! But, the Haribos were there . . . yipee!
     
  2. R Design

    R Design Well-Known Member

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    Yes, I've heard of that before.

    I also noticed that my Y-motor mount has Z bands every 5mm or so! ;-)
     
  3. TstarkEngineering

    TstarkEngineering Well-Known Member

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    they must be going through beds like crazy....
     
  4. orcinus

    orcinus Well-Known Member

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    Had quite a few shards of glass embedded in my parts too.
    That + the shoddy bearings (4/8) + one cracked acrylic piece + missing smooth rod end caps + bearing holes in the bed NOT enlarged (in other words - i got the pre-Z-fix bed acrylic, despite being #400 or so).

    I think they were in over their heads and in a huge hurry by the time the last kits were going out.
     
  5. Colin

    Colin Well-Known Member

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    I really don't like that the official answer is 'just order a replacement glass bed' like £20.00/$35.00 isn't that much. The glass bed is pulled down from e3d-online.com right now so they probably feel the same way, I have a few missing chunks I am printing around currently. Hopefully they have an alternative to offer soon. They said the glass beds were expensive for them to order so I doubt they have a very high markup, and they have spent a long time earning the reputation of dependable high quality parts.
     
  6. Sanjay

    Sanjay Administrator
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    @mike01hu That's odd and certainly not normal. What's probably happened here is that Edge got printed on a bed prepped with aggressive print bed adhesive that was intended to be for the material that we use to print the higher temp parts. I know we've been rearranging the print farm a lot.

    When we use UHU Stic with Edge we get zero chipping. If we use aggressive adhesives like Dimafix, 3DLac, Wolfbite etc we definitely get chipping. I have yet to find glass that can resist chipping with the combination of very adhesive plastics like Edge and very adhesive bed coatings. Toughened glass is an improvement, but by nature of how it is made it is impossible to get it acceptably flat for a BigBox sized bed. Plate glass is flat, but cracks on heating and cooling cycles. Borosilicate is best and what we're using, but it still wont stand up to adhesive plastic and strong adhesives.

    Rich Horne had an interesting solution for using the aggressive adhesives with sticky plastics which was to have a finishing GCODE that slowly lowers the temperature of the bed. So print at say 80C, finish the print, set bed to 70C, wait 5 minutes, set 60C, wait 5m and so on. Reportedly this works well.

    If someone finds glass that is flat, resistant to thermal shock, and won't chip when used with strong adhesive and sticky plastics I'm all ears. As it stands I can't really say that the glass is defective, because we're shipping the absolute best glass we could possibly find, and we went through legion suppliers and types.

    The solution as it stands is to use the right coating for the plastic being printed, since we've been using UHU we've had no chips whatsoever, and can print Edge, PLA, ABS, Nylon and pretty much everything else without issue. Also it's quite important to let the whole plate of both parts and the glass cool before removal.

    I'm curious to know from you guys what situations your glass chipped in? Which material and bed coating? Removing parts from a hot bed or cold?
     
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  7. mike01hu

    mike01hu Well-Known Member

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    Yes @Sanjay it's a minefield because of the huge range of filaments, temperatures and adhesives. I do advocate the cool down and do use it. I've had one small chip with Edge on PVA juice (250C/75C 200micron) before I implemented the process but have had no problems with CF20 to date, also on PVA juice, but the print areas are relatively small (150mm x 30mm) and single piece rather than multiple (cautious) although there is quite a long longitudinal stress. You can see the parts here.
     
  8. GrodanB

    GrodanB Well-Known Member

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    One thing that worries me was the fact that when we forgott a plastic lid in our hot glass top stove we got a large chip out when we removed it... no adhesives of any kind...

    But this means that with slow cooling and correct adhesives this will not happen on the BB.

    Good to hear.

    I saw something about using large anti scratch plastics but can they handle the heat?
     
  9. TstarkEngineering

    TstarkEngineering Well-Known Member

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    I've chipped glass beds before using petg and a uhu stick, that's why if I have to print petg I always use some sort of surface other than glass
     
  10. K3LAG

    K3LAG Active Member

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    I had mine chip on its own with UHU stick and ABS. I let the print finish while I was at work and got home to find that a nearly 1" diameter hunk of glass was torn out. It almost seemed like the part was adhered to the bed so well that when it shrunk as it cooled the glass let go rather than the glue. The part was mostly free from the bed at that point, but a corner diagonally across from the area where it chipped was still stuck. This was a part with a lot of surface area on the bed. Off the top of my head probably about 50 square inches in contact with the bed.
     
  11. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I had mine chip with abs and wolfbite nano. I used wolfbite a lot, probably 20-30 prints, and everything was fine, but then I noticed a small chunk out of the middle. I turned this bed into my PEI bed, and ordered a new glass one, maybe I will try to slowly cool it and go back to wolfbite to see how the new bed does.
     
  12. Henry feldman

    Henry feldman Well-Known Member

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    @Sanjay it's not abnormal at all. Lots of us early on reported glass chips in our BB parts (I had a few). I've had 2 chip since (using wolfbite) but I have yet to have a glue stick not fail as an adhesive on me so not sure what to do since glue stick doesn't seem to stick where I have any confidence that my part will adhere. That cool down seems pretty cool as an idea, might have to try it.
     
  13. Alex9779

    Alex9779 Moderator
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    Take care of the commands you use. "M109 Sxxx" to heat and wait but it does not wait on cooldowns only if the temp of the hotend is lower than the target.
    You have to use "M109 Rxxx" to wait also if the target temp is lower...
     
  14. orcinus

    orcinus Well-Known Member

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    Chipping is quite a normal occurrence, even without adhesive, when printing PET (e.g. T-glase).
    If i understood correctly, Edge is a PET copolymer.

    So - not really surprised at all.

    What helps it not chip is reducing the temperature of the heated bed.
    I ended up printing T-glase at 55-60ish degrees, but with polymer spray. This offers enough adhesion while printing, but releases gently as soon as it starts cooling down, with way less thermal shock than having the bed at 80-90.
     
  15. jet

    jet Well-Known Member

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    Is there a reason not to use local borosilicate glass the way we did on Mendles? I can get a good price from a local store and my wife does stained glass and I trust her to make all the cuts.
     
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  16. orcinus

    orcinus Well-Known Member

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    AFAIK, this is borosilicate glass.

    Borosilicate glass chips.
    Soda-lime glass cracks.
     
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  17. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    This is an interesting problem!

    I'm wondering if it's thermal shock on the glass or maybe the adhesion of the part is stronger than the glass?

    If the bottom of the part is at the heated bed temperature then the heat is removed, how quickly do they lose heat? Assuming the part is quite tall or the bed has moved away from the head, the fans are not going to be giving rapid cooling so the thermal shock may not be happening. We're only looking at <100 degrees for the bed and (I think) this is the type of glass used in labs where a Bunsen burner is applied direct to it from cold.

    If the part is locked onto the bed plus the different thermal expansions of the part and bed are sufficiently different and the part is big enough, the part may still cut a lump from the glass even through slow cooling.

    A couple of suggestions (guesses!):

    If the part is printed on a raft, make it not a solid surface, therefore the differential expansions work over smaller areas and may not be quite so damaging. Unfortunately, part of the point of a raft is to be a solid surface for better grip......

    If a thicker glass was used, the thermal gradient across it wouldn't be so large so expansions of the top and bottom surfaces may be less likely to cause issues.
    (This may make glass temperatures a little lower than we expect though).


    Just some food for thought,

    Have fun!

    Jason
     
  18. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I for one dont ever want to have to deal with rafts again lol. And I hear they are almost unusable with PETG, because its to itself so well. Thicker glass maybe.
     
  19. Alex9779

    Alex9779 Moderator
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    Me neither... I tried some raft prints but I hate it, I don't like the surface of the part, I rarely use the for parts with a tiny tiny footprint so. But they don't have a real bottom surface so it doesn't matter... I see no point using a raft on a flat part...
    Regarding warping I had good success with a skirt very close but not touching the part itself. When I started with my Ultimaker Cura was setup to make a 5 lines skirt around the part you had to cut off. I realized that when I change the distance of this skirt to about 0.5mm to 1mm away from the part it had the same warp preventing effect but you didn't have to cut it off...
     
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  20. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I'll keep that in mind lol I figured it need to be at 0.
     

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