Lifting Problem

[mike-truly 3]

I have a 1st layer, brim lifting problem I'm currently dealing with and it's got me puzzled.

 

As I watch the 1st layer of the problem print go down... I am getting good squish into the bed and the meld is great (adjacent lines meld into 1 surface).  But as layer 1 progresses... I can see lifting starting to occur (only in certain regions of the bed) after 1 or 2 line passes.

 

It's a PLA full bed print and the bed is level.  I am printing slow for the first layer (as I always do) etc.  I tried the bed temp at a standard 60C.  Then I tried bumping up the bed temp to 70C to get the nether regions of the bed hotter.

 

I have a 2015 vintage U2 (now upgraded to U2+)  with a plexiglass enclosure door and top cover.  I also have a thermometer present in the build area and a laser thermometer to read the bed temps.  (Basically the bed shows all the irregularities in temp as seen in other posts where the center of the bed is warmer and the outer regions are slightly cooler, etc.).

 

 

I normally print with a glue stick film on the glass and don't have a problem with adhesion (but the print size is usually NOT the full bed size).  On other prints, when I go to remove the print with my scraper, the print is adhered to the bed but pops off easily when barely hit with the scraper.

 

On this print... after using the glue film on the bed, the aborted print popped off about the same and had the same adhesion as normal.

 

Then I wiped off all the glue and was basically back to bare glass.  When I went to remove this aborted print with my scraper... it was SUPER hard to remove (much harder than my normal prints are to remove).  So the adhesion seems very good on the bare glass...  yet the print lifts in areas of the bed.

 

This image shows an aborted print (probably into the 2nd layer)... but the first lifting starts to occur shortly after the line is laid down in the 1st layer.

 

These areas of the bed do not show anything unique temp wise.  For example, if the bed is set to 70C... it's 71ish in the center and maybe 65-67ish on the outer edges.

 

Do I need to print on blue tape to get large prints to adhere?

 

Thanks for any ideas!

 

Mike

 

 

 

[gr5 2,173]

Well my first thought is that you got some oil on the glass and you should clean with soap and water and then dry and clean again with glass cleaner.  Then apply an invisibly thin layer of pva.

 

But after looking at the photo - the right rear corner is even worse and looks exactly as expected if you aren't squishing enough there.  So I would raise that.  And raise the right edge a bit:

front right screw CCW (raise glass) a half turn, front left screw CW (move down) 1/4 turn, rear screw 1/4 turn CCW (glass up).

 

It's possible that your glass isn't flat (typically the glass is thicker in the center).  It's also possible that your gantry isn't planar.  In other words it's possible to be quite level at the 3 leveling screws but low in the right edge and right rear corner.

[mike-truly 3]

Thanks for these tips!  I will give them a try and report back.

 

Thanks again.

 

Mike

 

[mike-truly 3]

I should note that it may be a bit before I can report back as the print is now currently working and I'm going to let it run for now.

 

 

As a test, I changed from a brim to a skirt and spun the glass plate around.

 

(I've been having concerns that my original glass plate may be warped/not flat as my U2 is older and the print 1st layer showed areas where the print was very thin (glass higher) which were to the left of center.  When I spun the glass around, then there were areas of thinness to the right of center).

 

Thanks again.

 

Mike

[yellowshark 153]

I am sure @gr5 is right. I had the same problem about a year ago and it took me some time and effort to resolve it. It was all about bed level and nozzle to bed distance and of course when you start getting desperate you start playing with other things like extruder temp too. For me my brim and walls were fine, it was the infill that was exhibiting the problem. I cannot recall what the solution was although I will have notes somewhere of the settings I was trying, I was trying lots of nozzle to bed distance variations and extruder temps - I figured that as the problem was not in the middle, for me it was not a levelling problem. But to this day I cannot say I really know what it was.

 

One other thing not to overlook, especially as your problem is at the perimeter, is that your bed heater may well be focussed on the bed centre and it will take time for the perimeters to reach the correct temp. On my printer when the middle of the bed reaches the target temp. the perimeters will be at least 10 degrees cooler and may take 10-15 mins to reach target temp. Of course for smaller models it is not an issue but for large surface areas like your print it could well present problems if you do not wait and check the perimeter temps.

 

If you are happy with your current method of adhesion then personally I would leave well alone rather than potentially adding to your problem. As @gr5 says just be careful and make sure your bed is really clean especially in the area that is giving you problems

[jfryer 0]

mike-truly,

 

I have the exact same issue with the back right print bed not adhering as well as the rest of the bed. 

 

gr5 and yellowshark make some interesting points that I will also try.

 

Here are a couple of the things I've been doing:

 

1. Pre-heat the bed 5-10 minutes before I start the print. Based on yellowshark's comment I will probably increase this to 15 minutes. 

2. Print a skirt. If the skirt prints OK, the rest of the print probably will too.

3. I watch the first layer and if I see trouble in the back right corner, I very slightly push up on the bed with my hand from underneath the print plate. I know this sounds crazy and dangerous, but it works for me.

 

I've experimented with different adhesives, but find printing directly to the glass to be the best. I clean and polish the glass and the prints stick very well, but pop off easily after it has cooled. 

[gr5 2,173]

I suspect the main problem for the 3 people here who have seen it is the glass.  The glass that Ultimaker sells is tempered and tempered glass tends to be thicker in the middle.

 

I don't know why they use tempered glass.  I think regular glass might be better.  It could be a very carefully thought out reasoning with lots of testing -- or it could be just that "tempered" sounds better.  I mean as an engineer I would definitely not have considered tempered - instead I would have considered pyrex which has a much lower expansion coefficient.  But tempered and non-tempered regular glass have the same expansion coefficient and need to be allowed to expand and shrink (hence the clips that hold it in which allow it to expand slightly.  People on the forums have gone this route without problems.  Again - I think it was a mistake to go to tempered glass but maybe there's something I don't know.

 

Anyway there are 2 types of glass that are probably superior to tempered glass for 3d printing.  One is regular glass - the most common type - found at any glass store - and glass stores are found in almost every town in the world - at least any town that has lots of houses in it with glass windows.  So anywhere you see glass windows in your area there should be a local glass shop that can sell you cut glass to fit your bed and they can even grind the edges so it's not sharp.  All very cheaply.

 

The other type of glass is called "neoceram".  Or ceramic glass.  It is used for high temperature settings - mainly fireplace glass.  I know some ultimaker owners who bought neoceram glass and were extremely happy with it.  It is usually much flatter than tempered glass but not always - some people who bought neoceram said it was flatter than .01mm edge to edge and others got pieces that were 0.5mm of thickness variations.  So who knows.  I've been thinking I should sell UM replacement glass but don't have the motivation right now to experiment.

[mike-truly 3]

Thanks to all for the ideas!  I will be experimenting with the various suggestions.

 

(One of the frustrating things with 3D printing for me (and I'm guessing everyone) is that you want to get work done...  (printing).  Yet you end up spending a lot of time trying to get the print/printer to work.  For example, I can print for days getting good prints (say mid-size prints) and then I need to print full size prints and now the bed level is no longer good and you have to go down a bunch of rabbit holes to get the problem solved.  Along the way, maybe you learn that the standard glass is not flat enough, etc.  I want my printer to print to the full build volume consistently & reliably.  All part of the process I guess, but I want to get to a stable pipeline so I can get work done).

 

I have read the threads about the glass beds and will probably have to invest in some new glass or neoceram to get to a flatter surface and eliminate the bed flatness issue completely.  Since my U2 is older and I've read that Ultimaker improved the specs on the glass, I'm wondering if getting the newer Ultimaker glass would make a difference for me.

 

Anyway, my theory (working in the litigation world) on why the tempered glass is used is this...  safety/liability.  Tempered glass is used so you don't die or injure yourself.  Tempered glass is designed to break into a million small pieces when it breaks (you might get some small cuts from it).  Regular glass breaks into sabre-like shards that can cut your wrist, jugular or femoral arteries in a heartbeat.  That's why automobile glass is tempered.  Also why by building code, household doorway glass is tempered (window glass, here in my state, does not have to be tempered by code as you are less likely to accidentally walk through a window opening compared to a doorway opening).  So if you do get regular glass, handle carefully!

 

Thanks again.

 

Mike

 

[gr5 2,173]

2 hours ago, mike-truly said:

I have read the threads about the glass beds and will probably have to invest in some new glass or neoceram to get to a flatter surface and eliminate the bed flatness issue completely.  Since my U2 is older and I've read that Ultimaker improved the specs on the glass, I'm wondering if getting the newer Ultimaker glass would make a difference for me.

I think the glass got worse, not better.  At least for me personally the glass on my UM2 and UM2 extended (which are a year older) is much flatter than the glass on my UM3.  In fact, early on, I was testing it on a table and noticed it really did not take much force to level (bend) the glass (a few ounces).  So I fixed the problem by bending up the rear two corners of my print bed.  I really pulled HARD on that aluminum bed to get it to bend up.  Only later did I realize I risked breaking the trace on my heated bed and destroying it (oops! )

 

[LePaul 321]

You could also try a sheet of PEI from PrintedSolid, they laser cut theirs to fit around the glass clamps.  

[mike-truly 3]

Thanks again for the ideas!

 

Currently, the answer for this print has been changing from a brim to a skirt (crazy as it sounds).  (My theory is that the wider brim was absorbing more heat or something and delaminating from the bed surface whereas the thin skirt cooled quicker or something but the thin skirt stayed stuck).  The print is progressing really well aside from the de-adhesion/fallover of a mystery support.  It is past the stage where this support could cause problems so I'm hoping it makes it to the end.

 

 

Interesting to know the later glass might be problematic.  I will have to play with the leveling when this print is done.

 

Interesting also to know about the PEI sheets... although it mentions on that page that the sheets shouldn't be necessary for PLA.  I suppose I could also try blue tape, but I like the flat finish of the glass surface for parts that mate together.

 

Thanks again.

 

Mike

 

Edited January 7, 2018 by mike-truly