Bubble of bottom layer

[jsdonnelly]

While printing I noticed the attached:

photo.JPG (108.67 KiB) Viewed 13645 times

Layers added above smoothed it out. Not sure yet what the bottom will look like?

[ednisley]

Looks like poor adhesion to the glass: that entire bottom layer is un-stuck, except for the perimeter. Once the nozzle creates a wave by pushing the loose layer around, it just won't stop.

Higher layers will more-or-less fill in the low spots and everything will work out OK, unless the bottom layer comes completely unstuck, in which case you get a bird's nest.

Are you printing on bare glass? Using hair spray or glue stick? With which plastic?

So many ways to have a thing go wrong... [grin]

[jsdonnelly]

Thanks for the quick reply:
ABS, Extruder Temp 240, Bed 100
Kapton tape...

Which do you have the most luck with: Kapton, hair spray, gluestick ,

I had a few small bubbles in the kapton tape . Could this begin the wave

[jsdonnelly]

I found a description for bed treatments:
http://wiki.solidoodle.com/bed-treatments/

Lessons learned:
Reduce bubbles
Wipe Kapton down with acetone
sandpaper Kapton

I tried elmers glue stick (did not work very well. probably did not put enough on)
Pain to remove the glue from the glass

[Tim]

Try hairspray. It washes off easily in hot tap water. Plus it's trivial to put down, although you will want to take the glass off so you aren't spraying down the rest of the machine. Of the adhesion methods, glue stick is the easiest, followed by hairspray. Kapton tape is way down the list. . . total pain. Good adhesive surface, just not worth the trouble.

I have had bottom-layer bubbles form just because I put my finger down on the surface. It may not be your issue, but it is very easy to get a little oil onto the surface and end up with a spot of poor adhesion. Sometimes these imperfections correct themselves after a few layers, and sometimes they keep affecting layers all the way up.

[ednisley]

take the glass off so you aren't spraying down the rest of the machine

Or use a pump spray bottle: no overspray, no muss, no fuss. Spritz the middle of the plate, wipe it around with a cotton cloth, done! That's better for my hotrod M2, because the glass is bonded to the heater and firmly attached to the Y carriage.

Kapton tape is way down the list

Aye! I used Kapton tape atop an aluminum plate with the Thing-O-Matic and got great results, but the platform was about 100x120 mm and reasonably easy to cover. I pricked the top of each bubble with a pin, pressed the air out, cleaned the platform with acetone before each print, and that was Good Enough.

a few small bubbles in the kapton tape

Given the tight tolerances, any adhesion imperfection will cause trouble: fanatic attention to detail will be your friend...

[jsdonnelly]

This is interesting. The bubble waves occurred after a few layers we already printed.. This time in the other direction. This is the layer currently printing over a smooth one.

photo1.JPG (76.26 KiB) Viewed 13587 times

[jsc]

Perhaps you're over-extruding. One way to know if that is the problem is to use the dynamic extrusion control on your host (Simplify3D, Repetier, whatever you're using) and wait until you're getting some waves. Then turn down the extrusion by 20% and see if it stops. Then bring it back up slowly until the layer looks solid but without waves. Multiply your current extrusion setting by the multiplier you just dialed in and replace it with the new number.

[jsdonnelly]

I have noticed some extruder calibration techniques. Does this apply or it depends situation.

I have only noticed this with larger flat surfaces.

[jsc]

There are a number of techniques (measure single wall object, etc.) I'm sure they all work to some extent. Since you're going to be adding in a fudge factor anyway (extrusion multiplier), I take the expedient step of adjusting it by eye, but if you want to be more scientific about it, feel free.

I have had similar waves appear when printing in ABS, and the culprit was over extrusion. Adjusting the multiplier down cleared it right up. I didn't chime in earlier because Ed's theory seemed believable to me, but if you're getting it AFTER a flat layer, then it's probably not adhesion problems. Although it is strange to see that it's only happening in one orientation and not the other....

Hm, now that I review your first image, though, I notice that the bubble lines go against the grain. That's not what I've encountered. Maybe get a short video of the bottom layer going down?