Build plate shadows  

RE: Build plate shadows

Posted by: @mikebuto

All,

I'm seeing 'shadows' of certain objects that I've made multiple copies of on my textured build plate. Normal gentle washing with Dawn does not remove them.  What's the best way to completely clean my plate?

Thanks,

Mike

Yes, you will see 'ghost' images of previous prints on the sheets, and that's pretty much normal.

There's been at least one post here that told of one case where it was severe enough that it showed up on the bottom of a subsequent print, but I have not seen that on any of my prints yet.  I'm even starting to see this on the textured sheet, after doing a run of single items.  Obvious solution to that is to not print small items always in the absolute center of the sheet.

As to what is the best way to clean the sheet, at risk of starting yet another Sheet Cleaning War,  TFM, written by Prusa says, and I quote "The best option is ​ Isopropyl alcohol ​ available in drugstores which is the best for ABS, PLA, and others."  I figure that Prusa would not intentionally print misinformation in their manuals, so that is what I do.  Some here insist, and even quite defensively, that dish soap is better.  Prusa does mention that as an option, along with denatured alcohol.

Personally, I think that how you clean the plate is not as important as the fact that you do clean it thoroughly and get rid of fingerprints and the like.

I have not been able to remove these 'ghosts', but they do fade over time, or rather, they are overwritten by ghosts of newer prints, and the resulting noise tends to cancel.  😉  That square you see in the photo below has long vanished, replace by newer ghosts.

RE: Build plate shadows

People who use glues to improve adhesion see the most ghosts as the glue build up over time. Alcohol as a solvent may remove some baked on glue. Acetone would be the next choice, but isn't recommended for the powder coating. Though, if you are ruining prints, not much to lose. Scrub with acetone, then wash with soap and hot water, then bake dry at 80c on the print bed for 10 minutes or longer.

With the smooth PEI sheet, ghosting is more common the hotter you print, the adhesive under the PEI deforms. Also, PEI oxidizes: this generally is only a visual artifact like a stain, one that reduces tack and lowers adhesion, but generally doesn't leave an imprint.  

For example, I've been using the same single side of my original smooth PEI sheet for well over two years - and it is only got dents in the PEI where I had to reef on TPU and PETG parts with pliers (before I learned the freezer trick for those times I didn't apply enough Windex).