I’m using the Bambu Labs smooth PEI built plate with the Bambu charcoal PLA matte filament. using the default settings to print with.
I notice there is are light coloured marks on the bottom layer. As I want this bottom layer to look as good as possible I’m wondering what is causing these marks and if I can get rid of them? Is it just what happened with this filament?
Picture of the issue
Grey marks are stress in the plastic. A quick pass with a blow torch will get rid of them.
The extrusion lines you cant do anything about, but if you use the textured plate it will cover them up with the texture.
I notice that the outer wall appears to have less marking, the speed for the initial layer is 50mm/s and the initial layer infill is 105mm/s. If I change the infill speed to 50mm/s would this reduce the marks?
Thanks, I’ll give that a try. Do you know if there is any way to get rid of these marks during the printing by changing any settings? I’m not bothered about the extrusion lines, they are not very noticeable with the naked eye, and I might change the pattern to hide them even further.
I was using the textured plate, but I want a smooth finish as I am printing a bezel for a display (the parts in the image are just test prints of other parts I needed) and the textured finish doesn’t look very nice, it’s too textured and shiny for what I’m looking to achieve, so I’m experimenting with different build plates to see if I can get a better finish.
That’s just how 3D prints turn out, can’t do anything about them, I would suggest a large resin printer like the Elegoo Saturn series for your needs. Resin printers have no layer lines or extrusion lines, and have best aesthetic quality prints, just like what you need for that bezel. No matter what plate you use you still going to see some imperfection like those, those turned out great, they could have been worse.
For PLA prints, you can do much better than that. Especially with the Smooth PEI.
My workflow relies on dry and well calibrated filament (cheating: X1 autocalibration), applying a number of lines of PVA glue stick which I subsequently dissolve with a 1/4 of a moist/wet paper towel to leave a thin PVA film across the plate.
During printing, I keep my chamber at around 35°. This usually gives me a very, very smooth finish.
& 
PS: For cooler bottom surfaces, have a look at the effect plates. But beware, they need a few particular setting changes, can be temperamental until broken in and punish even minor errors.
Thanks I will give the bambu liquid adhesive a try (as I have some already) to see how that works.
I did consider getting the carbon fibre effect plate actually, but wanted to try a smooth finish first. Maybe I will try the pattern plate as well.
I didn’t have a blow torch to hand so used a lighter and it worked brilliantly to remove all of the stress marks. The filament lines are hardly noticeable and only show up in photos much more profoundly. So I’m happy with the results.
I like the liquid glue although it is a little bit too viscous. I managed to get some glue lines visible on the bottom surfaces. However, even though Bambu advises against it, I did get good results with a little bit of extra water. Glue stick is cheaper though.
Working with the smooth PEI is a good starting point to prepare for effect sheets. But they need to be really clean and require higher bed temps (and a higher first layer nozzle temp helps as well). Some also require a good, long initial heat soak.
&
You are just talking about the round black parts right? If yes you might want to pop them out of the silver/grey arms and take pics of just the round parts and zoom in some. That is if it is not a dual color print.
That lone mark on right hand black circle looks like a fleck of the silver material that was on build plate when it laid down the black on the build plate.
I tried the liquid glue and at first I thought it was a huge improvement, but in certain lights it’s possible to see glue lines on the surface. They are actually quite hard to see though, and only visible when the light is at one specific angle. I wonder if I can water it down, or smooth it off somehow once on the build plate.
The stress marks were all but gone though and filament lines are vastly reduced as well. If I can work out how to remove the glue lines it will be a great finish.
When you say you used a moist paper towel, are you wiping the glue with it, or just placing it on top?
My experience exactly.
I usually just place a few lines of glue on the plate, than take a small paper towel piece which I soak in water and then run it over the Smooth PEI. I continue doing so until the glue lines are no longer visible and (ideally) there are no obvious glue accumulations. Once I have that smooth film, I dump the remainder of the paper towel (containing excess glue: That is why I only use small towels) and put the plate on the heat bed.
&
