PETG Infill Rot

[pyronaught]

I'm giving it ABS+ another try. This time I'm using a six line brim where the z-stop is set to initially start with a super flattened out extrusion while printing the brim, then I dial the z-knob back a notch for the rest of the print to avoid the wave problem. Plus I've got the super thick ABS slurry on the plate. If that doesn't hold it then nothing will. Of course if it does hold it down it's going to take a freaking chisel to get it off the plate afterwards. Lately I've been bubbling my 5mil kapton trying to pull these parts off. Bubbling regular kapton doesn't take much, but this 5mil stuff can usually take a lot of abuse before bubbling.

ABS+ seems more flexible than regular ABS, and looks like it prints smoother surfaces. Still has the same stinky fumes though.

[pyronaught]

The brim really helps. It's not pulling away from the kapton surface now, but instead it's pulling the damn kapton right off the plate! So there is air bubbles under the kapton sheet at the corners where the kapton is pulling up. You just can't win.

I've never really understood how these films can be pulled off the plate. In order for there to be an air bubble that fills the void created when the film is pulled up, there has to be a way for the air to get in. It's like trying to open the door on a vacuum chamber. How can the air even get in? Especially with a 5mil thick sheet, it's not like air is going to pass through that sheet in a short amount of time. Maybe over a period of days or weeks it can, but inside of an hour?

[Jules]

You know corner points seem to be particularly problematic from a warping standpoint.....I wonder if designing in a slightly rounded corner wouldn't help.

(The idea's based on what we used to see with cutters - the blade had a turning radius that caused chads to form in tight corners. (The paper pulled up when the blade twisted in one spot.) We learned that rounding the corners just a little gave the blade time to turn, and resulted in a smoother cut.)

Granted this is squirting and not cutting, but a rapid direction change still might result in less adhesion at that one corner spot.....just enough to make the corner more "warp-prone". And once one spot starts to pull up, the rest tends to follow.

Anyway, it's something to think about. I've noticed that warping tends to start at corners and migrate from there. Don't think I've ever had warpage occur on a round print either....those are usually a beeyatch to make let go. Might just be coincidence.

[pyronaught]

I think it has to do with temperature gradients. A circular part loses heat at the same rate all around its perimeter, but part with corners loses heat faster at the corners.

What's weird about this current ABS+ print I'm doing is that the end that stayed attached to the kapton and then pulled the kapton film off the plate is warping worse than the end that just separated from the kapton. The part is symmetrical around the axis separating these two warp scenarios, so you would think it should warp the same on both ends.

[pyronaught]

I'm running the job on a spool of Maker Geek ABS that is looking promising. So far it has out performed ABS+ in warp resistance. Their website says they dry the raw resin for 4 to 10 hours before making the filament and that this helps with reducing warping. It is looking like a claim that might actually be true based on what I'm seeing.

[pyronaught]

pyro you need me to print parts for you yet?

There's a chance I might if this test goes well. I was talking to the guy I'm working for today and if these molds can be used to make acceptable carbon fiber parts they are going to want a lot of them to setup an assembly line. I think in the best case scenario it will take three printers about 24 hours to create one mold set. There are going to be four or more different sets, then they will probably want at least 10 of each, maybe more. They are not going to want to wait a month for these.