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Am just wondering if any conclusions can be drawn from this:

Photo of poor adhesion

Three corners are solid, but not the one in the centre of the plate.

The bed was levelled before printing (and checked afterwards also). Even though the photo may appear to show a slant or lower corner (where the print is coming off), there is not. The bed is level, relative to the extruder, at room temperature.

The temperature of the bed is about 70 °C. I get inconsistent readings (with laser thermometer) but to the finger it feels about the same everywhere.

It's a glass bed, presumably with some coating. Is it degraded? Local temperature variation? Any ideas anyone?

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  • $\begingroup$ Try dropping the Z-stop by roughly half a layer height. "Squashing" the first layer helps maintain adhesion. $\endgroup$ Jul 11 '19 at 15:18
  • $\begingroup$ @TomasBy Please don't go testing temperatures over about 50 °C with your finger: it will damage your finger. Do you have a small spirit level that you can use to check the x-axis beam is level? If so, and the beam is not level, put something like folded card under the printer's feet to make it level. Then do the bed-levelling procedure. $\endgroup$ Jul 11 '19 at 19:33
  • $\begingroup$ @TomasBy Is the bed level in both directions, after bed levelling, according to the spirit level? If you print the object on the opposite corner of the bed, does the object's corner at the centre lift or the corner at the corner of the bed? (I realise it's going to be tedious if it takes two hours.) $\endgroup$ Jul 11 '19 at 20:53
  • $\begingroup$ I'm not absolutely sure the Y axis is horizontal, but nearly so at least. I believe I have checked it at some point. Have not tried to print in any of the other three corners of the bed except front right. I believe the surface in the centre of the bed is dysfunctional. $\endgroup$
    – Tomas By
    Jul 11 '19 at 21:05
  • $\begingroup$ So, the outline stuck but the print lifted? $\endgroup$
    – user77232
    Jul 12 '19 at 14:36
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From here: https://io3dprint.com/review-anycubic-i3-mega-ultrabase/

Ultrabase Bed The Anycubic i3 Mega Ultrabase is the latest version in the Anycubic i3 family. As hinted in the name, the main upgrade from the previous version is the Ultrabase bed. This is a textured coating on the Borosilicate glass bed that means you don’t need to apply any glue or tape to the bed to make your prints stick to it.

Ultrabase is similar to the popular BuildTak beds except unlike BuildTak it doesn’t wear off and the most significant benefit is that parts are exceptionally easy to remove once the bed has cooled.

The Ultrabase surface has a Moh’s hardness of over 7. This means you can safely use metal scrapers and blades to clean it without risk of it scratching!

Perhaps it was just not cleaned sufficiently from a prior print.

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  • $\begingroup$ I'm not sure the one I have is "mega", but I clean it with isopropanol between prints. $\endgroup$
    – Tomas By
    Jul 11 '19 at 12:43
  • $\begingroup$ Maybe scuff it up a little bit then. The PEX material on my plate was scuffed up with steel wool initially. Now I use a brass sponge, (grabbed one from a 5-pack on amazon with a holder to use with my soldering iron) to maintain the surface after a print, helps get rid of any rims, etc. that a print job might put down as an initial outline around a print. Then alchohol wipe again before starting the next one. $\endgroup$
    – CrossRoads
    Jul 11 '19 at 12:56
  • $\begingroup$ That sounds promising, but won't it damage the coating? $\endgroup$
    – Tomas By
    Jul 11 '19 at 13:25
  • $\begingroup$ You're not polishing it smooth, just lightly scuffing it up the first time. After that, it doesn't take much to get any plastic remaining from a print to clean it off. $\endgroup$
    – CrossRoads
    Jul 11 '19 at 13:48
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I cleaned the bed with acetone and it seems to have helped, so presumably it was just a build-up of something.

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  • $\begingroup$ Buildup, and a little hot. Try to lower the temperature a little $\endgroup$
    – Trish
    Jul 14 '19 at 14:34
  • $\begingroup$ I have tried many different temperatures. But you are probably right, I don't think the higher bed temperature makes much difference. $\endgroup$
    – Tomas By
    Jul 14 '19 at 14:51
  • $\begingroup$ Take your 70 as a start point and lower by 5 degrees in some test prints - if you get equally good sticking with lower temperature, it also save you energy. $\endgroup$
    – Trish
    Jul 14 '19 at 14:54
  • $\begingroup$ Yes, sure, it's just tedious that it's all so random. $\endgroup$
    – Tomas By
    Jul 14 '19 at 15:12

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