[Solved] Pimple/Bumps on Top of Print  

RE: Pimple/Bumps on Top of Print

Looks like bed contamination bleeding through the bottom layer buildup.

RE: Pimple/Bumps on Top of Print

FYI: The bed is now officially scratched because I foolishly used too rough a sponge to last clean it...key learning. Nice that I did BOTH sides without first trying a small area...damn.

The filament is from Zyltech (cheap, I know).

I just tried a test print using eSun (same bed, in the same condition) and I am NOT seeing the blobs.

I'll run another test tomorrow with a different color of Zyltech and see if I can confirm its the filament.

I am not ruling out a dirty bed - I'll clean it and try again but I am suspecting the filament.

I also have a powder coated bed, I may try that as well...

-Dave

RE: Pimple/Bumps on Top of Print

Actually, the scratches from the sponge improve bed adhesion. Chris Warkocki even recommends scuffing the PEI sheet (evenly, mind you) for best results.

RE: Pimple/Bumps on Top of Print

Posted by: Vojtěch

Actually, the scratches from the sponge improve bed adhesion. Chris Warkocki even recommends scuffing the PEI sheet (evenly, mind you) for best results.

Yeah - I *meant* to do that! 🙂

So, after a good cleaning, I've reprinted this on both the steel sheet (seen above) and powder coated sheet with 2 different filaments from Zyltech and I continue to get those blobs on the top surface.

When I switch to eSun filament, the blobs do not appear.

Before I officially declare the Zyltech filament quality bad, any ideas why this is happening? Maybe I am printing at too high a temperature for the Zyltech filament?

I am printing at 210 for the nozzle and 65 for the bed. Maybe some other setting in Simplify3D?

I'd hate to come to an incorrect conclusion on filament quality if the real problem is a setting I control.

Thanks!

Dave

RE: Pimple/Bumps on Top of Print

I wonder - any chance the Zyltech filaments have been exposed to moisture?

Also, there are PLA's that need printing below 200°C, so trying a lower filament/bed temperature is certainly an interesting datapoint to obtain.

RE: Pimple/Bumps on Top of Print

David: Please do not fall for the "sanded PEI" is better crock. A clean PEI sheet out performs most anything else. I swear these guys are just trying to make themselves feel better for destroying their own sheets by getting others to do the same.

Soap, hot water, and paper towels are the go-to standard for cleaning the PEI.  Alcohol is good to remove the PLA residue that accumulates after several prints (you'll see a dull shadow of the part on the bed). And acetone can be used infrequently to remove PEI oxides that build over time from heat cycling. 

I have seen first layers of spools contaminated by the packer or the bag lining. Essentially, the person putting the spool in the bag used hand lotion and coated the outer filament layer with muck; that or a hydrophobic coating inside some anti-stat bags sloughs off onto the filament.

Bad filament can be caught by watching the filament extrude - the pile it makes should be 0.4mm -- any foaming or larger diameter is evidence of contamination. With sputtering and sizzling evidence of moisture absorption. Here's a sample of a bad section of filament - my finger prints when loading were enough. Note the fat sections.

And these image show bed contamination - the light spots where the plastic is lifting: all are new and older finger prints.

And this is after an alcohol wash: the oils are now thinned evenly distributed and preventing any real adhesion.

RE: Pimple/Bumps on Top of Print

Tim - your posts have brought me solidly over to the "keep the bed clean" argument and I've been pretty good about using the warm water/soap/SOFT sponge approach. Its been working quite well...until I started with the weird bumps on this particular model.

I also agree with you that alcohol seems to just smear things around - I was NOT getting a good clean bed when wiping it after every few prints with alcohol - maybe I wasn't using enough...no matter, the soap and water is easy enough and the sink is right next to the "shop floor". 🙂

I am really thinking this is a filament issue (freshly cleaned bed/different bed) has made no difference.

Filament has not be exposed to moisture (at least on my end)... I am now trying a test print with Zyltech filament on my other MK3 just to see if I can narrow this down to a printer-related issue...ugh, all this to save on the cost of filament! I am about ready to just go back to eSun and Hatchbox and call it a day...

-Dave

RE: Pimple/Bumps on Top of Print

The plot thickens...I suddenly noticed that the bumps actually line up with 2 different test prints (each with different Zyltech filament):

They are more pronounced on the bottom example - but look at how they basically appear in the same places between the two...

Now I am thinking this might be something I can adjust in Simplify3D - maybe changing the fill from 5% or the number of top layers to print? I dunno...looking for advice on slicer settings I think.

Ugh - the prints still look perfect with eSun (or Hatchbox) and changing the temperature had NO impact - still getting the bumps with ZylTech.

Thanks (as always) for your replies to this thread!

Dave

RE: Pimple/Bumps on Top of Print

I do not have X-ray vision to see into your parts or how thick they are, but are the blisters aligned with infill?

RE: Pimple/Bumps on Top of Print

Ugh...things are a bit out of control over here. 🙂

A couple quick answers and a new observation:

1. Part is rather thin (about 5 mm).

2. Not sure if the infill lines up with the bumps, I'd have to look.

Ready for this? The new observation:

Using ZylTech filament on my second printer does NOT print the bumps - the print is perfect.

So now I am going to look closer at the first printer. What the heck?! I am not even sure what to check? Maybe another first layer calibration?

RE: Pimple/Bumps on Top of Print

If this is affecting the top layer, and the part is 5mm thick and there is infill inbetween, it's unlikely the first layer is causing that. Unless the part is moving around while printing. If there is infill, then you're looking basically at bridging/cooling performance. There may be residue baked on the nozzle from the outside, dragging the plastic with it. The effective temperatures may be different between the printers. The fans may be cooling the bridges differently ...

RE: Pimple/Bumps on Top of Print

David -

Can you post your STL ?? ... The pattern of dots repeating over and over seems suspicious. Either the model has warts or there is something on the bed in those locations.

Also, seeing a photo of the bottom of the part and the bed area where you are printing might help.

RE: Pimple/Bumps on Top of Print

I moved the part on the bed via the gcode file and am printing it again (but I honestly doubt this will change things). I'll post the photo when its done.

Attached is the STL for this part.

RE: Pimple/Bumps on Top of Print

No attachment ... 

Ignore the rest of this post, I am playing to see how to attach an STL to this new forum, myself.

gcode not accepted as drag & drop
stl not accepted as drag & drop

ZIP is accepted as drag & drop
STL.zip 

ps: and the Attach file: Choose File button ignored the gcode I had selected.

STL & gcode.zip

RE: Pimple/Bumps on Top of Print

So - place the STL in a ZIP folder, then drag and drop the zip into the text window; just like inserting an image.

RE: Pimple/Bumps on Top of Print

Some updates (and I think we can close this as solved):

1. You are right! The STL did not actually get attached...

2. Moving the model to a different spot on the (clean) bed actually made it look better, but not perfect. Why? Dunno...

3. Changing the slicer setting to force print 15 top layers and 15 bottom layers (essentially 100% fill) has made the problems COMPLETELY go away.

So, I am taking away the fact that it seems the model's top surface was simply too thin and was unable to fully cover up the infill artifacts. Why the original model printed with less blobs by moving it to another spot on the bed, I have no answer - maybe inconsistent bed heat?

Dunno - but I can now print this model on either printer, with any filament, and get perfect result.

RE: Pimple/Bumps on Top of Print

No mystery why moving the model on the bed affects the print: e.g., changing a model 90 degrees changes the airflow, less curl on an axis that might benefit; similar magic happens because the extruder fan shroud is closer to the power supply. 

RE: Pimple/Bumps on Top of Print

Posted by: david.p87

Some updates (and I think we can close this as solved):

[...]

3. Changing the slicer setting to force print 15 top layers and 15 bottom layers (essentially 100% fill) has made the problems COMPLETELY go away.

So, I am taking away the fact that it seems the model's top surface was simply too thin and was unable to fully cover up the infill artifacts. Why the original model printed with less blobs by moving it to another spot on the bed, I have no answer - maybe inconsistent bed heat?

Looks like typical "pillowing" due to lack of support, excessive heat, speed or simply not enough layers. I've encountered it with larger prints with more solid infill as speeds pick up. As you note, increasing top layers will often eliminate the problem. Slowing down solid infill speeds may help with quality overall.

RE: Pimple/Bumps on Top of Print

Yep - pillowing is/was the answer. Thanks all!