Second layer issues
Hello,
My parts require fine details I am using MMU2 for multicolor drawings and small text on the surfaces. I use o.25mm nozzle 0.1mm layer heights.
At first I only used PLA but now I am learning how to use PETG and I like it better than PLA in many ways. Both materials can give me what I think looks like beautiful first layers. Both materials give me a funny effect on the first layer of the finished part. It is like the outside perimeter string of the first layer has nothing above it. I can use my fingernail or I could use tweezers to pull only the outermost perimeter string off the part and it appears that it is not in contact with the second layer because nothing was printed above that particular first layer perimeter bead of plastic.
Another PETG problem I see is the second layer can be very scabby in areas. I think this is random because I used Octoprint to get the heatbed leveled +/- 0.04mm. The best way I found to have a successful print is to run the first layer at 50% and then slow the second layer down to 35% speed. The scabby spots are still appearing on the second layer but then the third layer corrects it. Usually the scabby spots are covered up better with each layer put on top. At 0.70 mm for the seventh layer is when I no longer see any problem and I can turn up the speed to 100% for finishing the remaining print. I can't print PETG at 100% speed from the get go because the scabby second layer gets wild and whipped up into higher layers where it crunches in interference with the 3rd layer nozzle movement.
Does anyone know what I am doing wrong?
RE: Second layer issues
Not an MMU user, but folks won't be able to help much unless you post photos of what you are seeing. Be sure to use the drag and drop method, and set LINK TO : MEDIA FILE option before pressing INSERT INTO post.
RE: Second layer issues
I'll get pics for the next post. I have been thinking about this and I believe I have a more clear explanation of what is happening as far as the perimeter strings that are persistent on nearly every piece.
I think the first layer is placed flat. The second layer is placed on top as it should. Then additional layers above the second layer are curving up or "potato chipping". The first sign of the potato chip will rip the second layer off the perimeter string of the first layer. Then, as the part is building higher, the curving force is no longer pulling the second layer off the first. Rather it is slowly peeling the first layer off the heat bed.
This can be seen by inspecting the first layer finish on the final part. I'll try to get a good picture but it might be tricky
RE: Second layer issues
I pulled the loose first layer perimeter string out and laid it across the top of a nozzle purge strip laid across the part. That is what happens and it makes the part look like the second layer was never printed on top.
It is hard to capture in a picture. But the glossy finish is what stayed on the heat bed for the entire print. The dull areas show where the curvature has been slowly pulling the first layer up and off the heat bed. This happens on every part that is not very small.
RE: Second layer issues
This is what happens to my second layer run at 100% speed with PETG. I slow the speed down to 30 or 40% and the second layer looks bumpy. But the condition clears with additional layers and usually at .7mm or the seventh layer is when the print is smooth and the speed can be returned to 100%
RE: Second layer issues
Curling above infill is an issue with PLA, too. Making sure I have sufficient infill (less than 20% tends to make it worse), and slowing down the print speed for solid infill layers is how I deal with it; and it tends to be part specific. Some parts can print fast with stock profiles, other parts need to be slowed down. I have yet to find the magic formula for when slowing down is a good idea.
RE: Second layer issues
Did you manage to correct this issue? I've suddenly developed the exact same problem. The first layer is fine and layers 3 & above are fine. The second layer seems to be missing the outside perimeter leaving a gap between the external perimeters on the 1st & 3rd layers. I have examined the slices which have the correct number of perimeters so it's something in the printer settings not slicer. But what???
Try putting a small value in Print Settings > Advanced > Elephant foot compensation
Cheerio,
RE:
Thx Diem, I did adjust the elephant foot parameter which was set at .05 back to 0.00 with no effect at all. I originally had the same thought that the EF setting was off enough to cause the overhang but that was not it. I discovered that my recent install of Slicer v 2.5.0 seems to be the culprit. They defaulted the perimeter slicing to a new variable called ARACHNE perimeter slicing. Reverting to CLASSIC perimeter slicing seems to have fixed it but of course you lose the benefits of ARACHNE slicing.