"Extra material" piled up on first layer

So I figured I'd put a photo out there for others to see, and get feedback and help such that others might recognize a problem with their prints and how to troubleshoot it.

This is a print done with PLA at .2 layer height, with a first layer speed of 30%, with a first layer height at 80%:


The skirt looks good, and the initial holes in the part are well formed with their outlines. Adhesion to the bed is good, and the 2nd and 3rd layer eventually fill over and everything is OK... but the first layer just looks ugly! Sometimes the print head can even snag part of the built up extra material and tear part of it off the bed.

So, how do you fix that?

If I lower the Z axis I can clog the tip.
If I up the speed or filament temp I don't get good adhesion and the whole first layer can break off when it gets snagged.
If I I reduce the amount of first layer height I get down into the realms of 35-40% and it prints OK, but peels off the part when I remove it from the bed... or I don't get enough material to lay down a sufficient layer to get a good skirt even.

Certainly others see this, but I'm not seeing it really being discussed. {shrug}

 

What I've done to "fix" it is just keep ratcheting down the first layer height to lower and lower and lower percentages. At 40% I'm -=WELL=- under the recommendation from Jeff for a 80-100% layer height for the first layer, but it's clean and adheres. I'm not of the opinion that "the first layer is just ugly" and that if it is, somethings not right. It should print correctly from the get go, and if not, you have something else to adjust/fix/configure/tweak.

Maybe it's my filament. Maybe it's the humidity. Maybe it's this or that or whatnot. I dunno. When I first started I was laying down with .3 layers at 130%. Now, that's just making a total mess of things and doesn't even come close to getting the second layer to have a chance of going down as there's SO MUCH extra materiel that if the first layer goes down without being a complete mess, the second layer tears it to shreds.

I wish I could figure out why my settings have needed to change so dramatically. Maybe it's that as I learn more about the printer, my expectations are changing for what it should be able to do. When I got Mr Jaws to print that first time I was just giddy it printed anything at all. Now, I have expectations for reliable parts I can put into use in the shop for jigs and CNC axis and something that looks great... so maybe my first layers WERE ugly in those early days, and I just don't remember that now. My memory ain't exactly great I admit... there's a REASON I take as many notes as I do so I know WTF I did later!

 

That looks waaay to transparent for a first layer.. Your nearly smashing your head into the glass.. Back it off a slight twist. As what was shown you want the color to still exist, and you don't want it transparent.

 

My first layer is ~0.1mm +-0.05mm. I'm printing with a layer height at .25mm presnetly and getting my best results. I'm guessing that's just the color my blue filament is. Up to about 4 solid layers at .2mm it is almost totally transparent. {shrug} Three solid layers at .3mm is still completely transparent with a slight tint.

I'm setting the Z axis height with a 0.005" (0.127mm) feeler gauge... I don't have any metric only feelers and that's the smallest feeler in this set. The more I fought with it the more using a business card or piece of paper was driving me crazy so I finally broke down and went to the toolbox and grabbed some actual gauges... the other method is just too imprecise for me to use and I'm more comfortable with feeler gauges what with being a machinist. I then use the Z offset to get my last bit of adjustment from there, usually with a -0.05mm offset to start, and adjust it from there as needed +- up to .2mm depending of my layer height of .1, .2, or .3. I'm not totally happy with it... but for now it's working. I have also been adjusting my first layer height setting. It seems if I get that value TOO low, my hotend clogs... but before then that first layer looks GREAT... So I up my first layer height to just the point where it doesn't clog and that first layers extra material is as minimal as I can make it.

I suspect I could monkey around with the temperature some to try and get it more dialed in. My filament seems to like anywhere from 187 to 195c for extrusion. If I'm doing multiple parts, and am combating stringing, I drop it as low as 187, but otherwise I'm usually in the 190-195 range for just one part and burn off the strings once the print is done with a lighter.

 

So I think I got PART of the problem sorted. I ended up decreasing my Extruder Width - First Layer in the advanced tab of the Print Settings tab for Slic3r. I'm still getting some buildup on extra layers, but not NEARLY as much. I'm still saying that the first layer shouldn't look any different than the subsequent ones and that the "First layer is always a mess" or "First layer is always different" isn't correct thinking.

I'm still having to reduce the % amount for First Layer Height but I'm no longer getting down to those 30-40% levels which were just crazy and kept ending up with a clogged hotend with. I'm also able to ramp my first layer speed WAY up to 40-50% too. I have to watch my filament temp a LOT more. I'm noticing differences in just 1-2c making a BIG difference in strings and quality for those first 1-4 layers. I think part of that is my filament. I ended up using up my first spool yesterday, and this next spool is WAY different for how it's printing!!! The temps are way different (like 15c different!) and it's not adhering quite as well... it's from the same supplier, purchased at the same time, and is the same type... Blue PLA. Dunno why it's acting SO differently. Maybe there was a small hole in the bag so it's humidity level is different. I dunno. I don't know how PLA which has been exposed to too much acts to diagnose if that's it or not, but other than differences in how it was made, I can't think of anything else that would be causing it to act so differently than the prior spool. That's got nothing really to do with the "extra material" issue however.

So, I'm getting a little closer to figuring out how to tackle this great whale of mine... but for now, I appear to at least be headed in the right direction... I think...

 

I've sorta gone back to my "baseline" settings from last week and am having a BIT more luck with starting my Z axis higher up and ramping up the first layer to compensate. I'm still having some buildup, but not -=QUITE=- as much. My bed is PERFECTLY cleaned between each print. Remember, I'm printing with PLA and using the heated bed to get adhesion. It works a peach. Plus, when the print is done and the bed cools, the differential expansion pops the part off. Just lifts clean without any force required at all. Sure it takes an extra 5-6 minutes (sometimes a bit more depending on how large the part is) but I'll trade the time for now for the perfect adhesion. After each print is removed, I scrape the bed with a putty knife with a very crisp edge, raise Z to 25-30, remove anything from the hotend which might be attached to it, fire up the hotend and bed again to bring it back up to temp, and go back to object placement for the next print and slice. Once everything has been at temp for a few minutes and expanded, I go ahead and start the print, making sure to again check the hotend and remove any ooze.

I'm going to try reducing my first layer height a bit more... currently still using my old 130% first layer height and 200% for first layer width. I'll try dropping it down to 115% and 160% for each correspondingly and see what that does for me.

 

The default is 200%, on the advanced tab. I am running a slightly older version of repetier it seems so maybe it's changed. I'll give 0 a try tho, and see what it does. I've got the bed levelers printed... just printing off a spare set now as a just in case so if I break one while putting everything back together I don't have to abort...

You gotta pic somewhere of the assembly or do I just need to pull the four corner nuts and swap out the white spacers that are on there already with the new ones?

 

Belay that request... found it by searching the forum for the thingiverse ID.

http://forums.robo3dprinter.com/index.php?threads/bed-leveling-ideas.822/page-2

 

It's on and adjusted...I ended up drilling out the center of the bottom piece to accept the existing nut on the rail and just slip over it. I'm going to replace with longer bolts as the existing ones even with doing that give me JUST enough threads to get the nut on the top while still using the washer. I debated taking them off, but decided that wasn't a good idea. I think I need to reprint the dial indicator holder as well. Actually, if you could modify it somewhat to accept a bolt to lock the DTI in place that would help a lot. Currently I have to hold the DTI to keep it from shifting, which can throw my reading off by a few thou. In the meanwhile I'll just try and use a rubberband or three to hold it in place and resist movement...

Anyway, I've got an issue with my bed tho too. I can get the four corners inside the heated area to within 0.002" of one another, but the middle of the bed it's a good 0.012" higher. As a result, the corners are printing reasonably well (still have a little adjusting to do) and the skirt along the full outside perimeter looks great... but the middle... fscking mess! That's if it even sticks at all. I tried dropping five 20mm test cubes in the four corners and the center. The corners, that first layer goes down well enough (the front right is GORGEOUS) but the middle... well, of the four attempts I've made so far, two failed to stick at all, one delaminated during the infill, and the fourth just turned into a blob on the hotend.

I'm gonna go watch the TV with the wife and throw in the towel for the night. I'll try some more tomorrow afternoon.

 

Note the skirt on that photo is crap, was right after my first attempt and before I got it adjusted closer, but it's still producing the same results for the center... nothing.

 

Longer bolts. If your corners are close but the center is raised, then your corners are too low, hence, the nuts are pushing them down.

 

Wookie did you solve the warped bed?

 

I got it sorted mostly. The tension on the Y belt was able to be reduced back a bit and that reduced the amount of the bow. As it stands, my 4 corners are within 0.003" of one another. The center and right side of the print bed are spot on to the corners on that side of the bed. The "problem child" area is the area directly above the Y belt. That is still bowed UP from the timing belt tension and is pulled 0.007" up. It comes up pretty sharply at the center of the bed, so it's probably only the middle 25% of the bed above that section that's high. The rest of the bed is still within 0.004" everywhere else at worst on that side. End result is that as long as I don't START my print directly over that hump, it's fine. I can bridge over it and basically the first few layers might have a little problem there... especially if I'm doing a 150 micron or smaller print. At higher resolutions it seems to just smoosh around the raised section enough that while it's not GREAT print quality right there, as long as there's enough other area of the print not directly over the hump then it'll stay adhered to the bed and print fine. An example would be when I had to print a large fan for my TIG welder radiator.

The "hump" is most pronounced right at the "CAUTION" wording on the bed... so by putting the print on the surface being aware of the problem area, I can print no problem with it there...

 

Why is there so much stringing?

 

I don't know if I'd call that "so much" but maybe my expectations are not high enough. {shrug} The stringing could have been vastly reduced if I'd opted to not cross perimeters in slicing, but then print time would have gone up. I just hit it with a lighter and all the strings vaporized.