Surface defects on large prints with Prusa XL  

How thick is the part?  Please show us the underside of the print.

Cheerio,

RE: Surface defects on large prints with Prusa XL

I print in 3 walls with a layer height of 0.15 mm.
The height of the part is between 25 and 30 cm or more.
The first Layer is perfect.

Some warping by the look of it - hold a straightedge against the base to check.  If so the most likely cause is a cold draft - have you just turned on the AC?

Cheerio,

RE: Surface defects on large prints with Prusa XL

The printer is in an enclosure with the HEPA filter activated. The temperature fluctuates between 29 and 31 degrees inside during printing. There is indeed a slight warping on the corners despite the border around the part.

Maxence.

OK, that warping could be enough to cause the top layer rippling. 

As you are using an enclosure drafts become less suspect ... make certain the print sheet is absolutely clean, add a brim, and perhaps raise the bed temperature by 5° - 10°.

Cheerio,

RE: Surface defects on large prints with Prusa XL

Thank you for your answers, I will try to increase the temperature of the plate to 65 degrees instead of 60. However, I already add a 10mm edge, should I increase its size?

If you are already using brim make sure it's connected - zero the value in:

Print Settings > Advanced > Elephant foot compensation

 - and make certain the print sheet is absolutely clean.

Cheerio,

RE: Surface defects on large prints with Prusa XL

Thanks for all your answers, I'm reprinting a piece with the new settings. I'll post photos of the result and I pray that it doesn't warp 🙂

RE:

Well, I just got another part out with your advice, the result is a little better but there is still a slight warping and the surface quality is really ugly (see photos).
My plate is new and always well cleaned with isopropyl alcohol and its printing temperature is at 65 °.
If you have other advice I am a taker because I am a little lost with the settings.
Thanks in advance 🙂
Maxence.

It's hard to get enough contrast photographing white filament and I can't be sure; please check, are the remaining defects spaced more or less evenly over the upper surface?  Does this coincide with infill spacing?  Have we got rid of the wider areas of ripple?  If so an extra top layer or two should fix it.

Cheerio,

RE: Surface defects on large prints with Prusa XL

Thanks for your answers 🙂 Here's the result I got :

Surface :

Bottom :

Surface with a light through to see the filling :

There's still a very, very slight warp at the corners, and the surface is truly horrible 🙁
I just re-launched a part with two additional top layers. If you have any information that could resolve these issues, I'd love to hear it. I'll keep you posted 🙂

The ripple train starting from the corner is typical of warping and it's always worse with bigger prints. Even those apparently small corner lifts allow thermal contraction from the glass transition temperature (about 60°C) down to the enclosure temperature to shorten the upper surface so that the correct amount of filament no longer fits and starts to pucker and fold.

Is that grid infill?  You may find cubic better for stiffness and it may redistribute the stresses.  Gyroid is slightly less likely to warp but may reduce rigidity.

To improve the bed adhesion try adding Helper-discs (from your shapes gallery) to the corners - they are sometimes called (Mickey) Mouse ears if you need to look up their use.

IF possible, if the design permits it, break the long runs of extrusion to relieve the contraction stress.  A few narrow (0.2mm wide) grooves on otherwise flat surfaces and sides are usually enough, like this:  __/\__ - although functional they can often be disguised as aesthetic features.  They can be staggered to maintain strength if necessary.

Cheerio,

RE: Surface defects on large prints with Prusa XL

I had similar problems with PLA printing (see attachment).
Reducing the flow rate and increasing the fan speed to cool the print helped me.
It may not be the right solution, but it worked for me.
Note: each PLA material behaves differently. MK4S prints fine, XL has problems. From this, I concluded that the XL printer was not cooling sufficiently.