Another case of lifting corners

[Mike Hunter]

Morning:

I've had my M2 for a bit over three months now and the printing has gone smoothly and except for my own dumb mistakes, exactly as programmed. Having said that I'm facing a slight dilemma with a few of my latest prints using black PLA. The corners of these prints lift off the table (see pics). I've checked the flatness and gap setting, which is fine, and tried other tips that have been posted here and on other forums, but the problem persists.

Example #1

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Example #2

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I printed my first (in house designed) vase using red PLA, which came out flat and with no bottom lifting (see pic). Sorry for the lack of sharpness in the photo. My camera phone is very finicky, as well as my occasional shaking (getting old sucks as we all know or will find out )

Red PLA Vase

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I've checked the thickness of the parts and found the max variation, when measured at 6 points around the profile to be .003, which tells me that the bed is flat and the gap setting OK. I've tried reducing the temps from 65 (bed) and 225 (extruder) to 60 (bed) and 210 (extruder). The problem still appeared in my latest print (see pic).

My Latest print

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I'm still searching forums for additional tips, but perhaps this problem has a simple solution which is eluding me.

THANKS for reading ...

Mike H.

[Tim]

Increasing bed temperature is more effective than lowering it, although PLA generally is not finicky about bed temperature, and much above 65C will be too much for PLA.

What are you putting on the glass for bed adhesion? That, I think, makes the most difference for PLA. Most people here on the forum use (in apparent order of preference, judging from posts) glue stick, hairspray, and painter's tape. I don't recall that I've ever had any PLA part peel up off of painter's tape, but sometimes I had difficulty peeling the painter's tape off the part. . .

Lightening up on the infill percentage can help, too. Even PLA undergoes some contraction as it cools, although it's much less than most other types of plastics. Even so, the larger the object, the more likely it will be to contract enough to pull off the bed; and the more overall material, the more likely it will be to pull up.

[Mike Hunter]

True be told, I don't use anything on the glass, I just clean it with Windex and scrape it between prints with a razor blade. With the exception of these last couple of prints, everything I've printed, from a cookie cutter to smaller light clips (printed 2 runs of 12 pieces each) stays stuck to the glass. I use white, red and the black PLA for the various prints to date, totaling about a dozen or so different design and tooling objects.I've read the posts explaining the various adhesives that members use, but I've not had a reason to try them yet.
I'm printing Rev B of the Z axis Return Spring I posted earlier and I've removed the raft I programmed on Rev A as the residue from the raft is a pain to clean off. But I also changed the Filament to red PLA as it (the red PLA) seems to print more trouble free.
The black PLA is the sample roll sent with the machine. The white and red are "sainsmart" brand bought from Amazon.
Perhaps I'll need to use an adhesive for certain prints. Is it a common practice to alter the type of adhesive used or should I stay with one regardless of whether it's needed or not?

Mike H.

[Mike Hunter]

I had just hit the "submit" button for the last reply when I looked over at the current print and saw this ...

Should have left the "raft"

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I guess I'll repost the program with a raft as the small width of each leg, around 3mm, doesn't seem to be enough to ensure sticking.

Mike H.

[Tim]

It seems to be a common experience that the plain glass works just fine for maybe up to a dozen prints and then prints just stop adhering to it so well. Maybe it's not possible to keep the glass as squeaky clean as it comes out of the manufacturing process, or maybe there's some residue from the manufacturing process that's the best unknown adhesion surface. Regardless, your experience is a common one. Expect to need some sort of prep work on the glass.

I tend to favor hairspray myself (unscented, in a pump-spray, not aerosol, bottle), because one coating can be good for a number of prints (like 5 or 6), and it washes off easily in hot tap water. But I haven't tried the glue stick, and that gets good reviews, too. Both are trivially easy to apply.

[Tim]

Rafts are good for small parts or parts with only small areas contacting the glass surface. Not so good for holding down the corners of large prints. Sure, it will hold down the corners, all right, but it also tends to just fuse to the print, and you'll be spending a lot of time cutting the raft off (at that point, it's basically like a brim). If you increase the spacing between the raft and the print, you risk having it not stick to the raft, which is just as bad as not sticking to the glass. Possibly there is a perfect value for spacing that will cause the print to adhere properly to the raft without either bonding to it permanently or lifting up, but I haven't found it.

[insta]

Tim,

In my experience once the PLA is stuck (60-70C) it stays stuck until that magical "too cool" temp (40C?) and then the part just pops off at once. Too warm (65C+) during the print allows the PLA to soften.


Mike,

If you're not wanting to adulterate your print bed with hairspray or gluestick (having used both I prefer hairspray), you can try washing it with hot soapy water (until it's absolutely crystal clear!), and then wiping it down several times with mineral water while the bed is hot. The idea behind that is the hard water residue will give the PLA something to stick to.

Use hairspray or gluestick...

[Mike Hunter]

THANKS for all the input everyone. I'll try each (suggestion) out and determine which is best for my situation. I guess I got caught up in the "new printing" experience. It's still a blast and I hope will remain that (way) for a long time

Mike H.

[Capt. John]

What infill percentage are you using?
Best PLA filament I've used is from MakerGear.

Not overly impressed with Sainsmart stuff. Their colors are bright on the roll
then, when printed ...the filament color darkens quite a bit.

Not sure if there's much help I can offer other than start using a bed prep glue stick, or hair spray and
slow the first layer to speed 60% and kick up the first layer extrusion setting to 140%-160%.

There's a lot of forces to overcome as all filament tends to contract a little as it cools.

[Capt. John]

Thought long and hard about this. Seen many reoccurring themes/topics here about liking
or not liking certain bonding agents. Liking has zero to do with 3D printing.
I use what works. 60C bed temp in PLA with rsilvers profiles are a problem solver.
You will notice in the rsilver's profiles, infill percentage is relatively low.

Be happy for the 3 corners that did stick with no bonding agent. New clean glass PLA will stick
for a while, but that duration is limited. Found this out when prints came loose and ended
up with a pile of strings and goo.

My task is to print 400 diver rings in ABS and make a product that retro fits an
existing product with tight tolerances. Had to upsize in S3D for ABS over my first factory
files that were PET+ files. Then, have to grind off any minor interior imperfections to get a quality fit.
I learned not all plastic filaments shrink at the same rate. Even in the same name of ABS certain
brands shrink/contract more then others. Evidenced more strongly in glow, or the operator
that made the master batch.

Without a bonding agent, my ring project would be dead in the water.
Also, I've come to accept a .001 deviation in a flat base is an acceptable part.

Shrink is a part of making things out of heated plastic.
My injection molding company over-sizes my tools/molds some where's in the neighborhood
of 2% to allow for polycarb shrink to make specs. So, no matter what type of plastic filament
you're using shrink is always going to be there.

The 150 plus ABS glow tabs in the below pic had to be upsized in S3D 1.0700 over standard ABS for
the same fitment requirement:

TABS.jpg

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Dust on my 40mm fan needs to be cleaned. My machine runs around 12-15 hours each day and
moves a lot of air. Just like desktop computers, every now and then, compressed air is needed
to clean them out. See now, the outline single layer is not needed too.