Bottom layer - poor infill quality

[art4242]

Newbie here, I just purchased a FlashForge Creator Pro and Simplify3D over the weekend.

Things are up and running, however I am seeing very poor bottom layer quality on the part:

It almost looks like there is not enough infill on the bottom layer, or that the bottom layer is too far off the support/raft and not melting together.
I’ve mainly been printing with raft/supports. If I print directly on the bed without a raft, the bottom layer is smoother as it compresses onto the bed.

I’ve tried adjusting 1st layer height and thickness, but this only seems to affect the 1st layer of the raft/support and not the 1st layer of the part itself. Also tried varying the raft offset and separation, but that does not seem to help either. I’m thinking it’s probably not a nozzle to bed offset issue since the 1st layer of the raft looks well formed.

Any ideas?

Thanks.

[CompoundCarl]

Idea #1 - don't use a raft! You have plenty of surface area on the bottom of those parts, so a raft would just be a waste of time. Even when I have small parts that need some extra adhesion for the first layer, I use a brim instead of a raft. Much quicker, easier to remove, and won't affect the bottom layers like the raft does. So if I were you, I would stop using a raft and only use a brim when absolutely necessary

Idea #2 - if your first layer looks like that, even when printing directly on the bed, then your nozzle is too far away. You can adjust that on the G-Code tab using the Z-axis gcode offset (for example, -0.1mm for the z-axis offset would move the nozzle 0.1mm CLOSER to the bed).

Idea #3 - if you really insist on using a raft for some reason, then you can adjust the gap between the raft and the part by changing the raft "separation distance". I'm guessing yours was too large since the layers looked like they were printed in thin air.

[art4242]

Ok, thanks for the tips. I’ve been playing around more and have found that decreasing the solid infill underspeed seems to help, as well as increasing the raft and support infill%.

1 . No raft is definitely better, decreasing the raft to part gap is also better (but of course makes the raft harder to separate).

2. The grey part definitely needs to build on support, as there is a small round boss protruding below the main body. Increasing the support density helps, but still seems to be printing partially in air. The best thing that worked was to change the support upper layer vertical separation from 1 to 0:

This results in a well filled bottom layer, but now of course the support essentially needs to be cut off. Is there any way to adjust the support to bottom layer gap in mm, similar to the raft to part gap?

I have used commercial level Stratasys machines for over a decade at work, and am used to the layer built on support being essentially similar in quality to top layers. This is of course possible since the Stratasys support is breakaway/dissolvable and can build directly on it without separation.

[JoeJ]

And also very possible here if you have a dual extruder machine with dissolvable support material

[barnwell]

Perhaps printing with raft and 1 layer space then printing the first layer of the model with a width of more than 100% (maybe 200%) and first layer speed much slower?

Just a thought.

[art4242]

And also very possible here if you have a dual extruder machine with dissolvable support material

Yep, I'm going to try that next. I have some HIPS on order and will try that using zero top layer separation and a dense support layer.

I did some more digging and it seems like this exact issue has already been mentioned before:

viewtopic.php?f=8&t=2746&p=11515&hilit= ... bad#p11515

viewtopic.php?f=8&t=2446&p=10044&hilit= ... ngs#p10044

I still think it would be helpful to have finer control of the distance between the top later of support and bottom later of the part, something like an actual distance in mm instead of number of layers.

[danielchoman]

Did you ever find a solution? I bought a flashforge pro 2 weeks ago and was running replicator g with no problems. last week I upgraded to simplify3d & I cant get anything to stick to the bed unless I use raft. Just like you were saying the 1st layer of raft will come out perfect on the bed.