[3D Printer] Improving Print Quality: Addressing Bottom Surface Roughness and Remodeling

Last time, I succeeded in creating a beautiful print using multi-color printing with the Bambu Lab A1 mini, but the bottom surface was rough and needed improvement.

This time, I reviewed the 3D print settings and the model, and attempted several improvements to enhance print accuracy.

Modifying the 3D model

The lower half of the polar bear model had a gentle curve, making it a difficult shape to 3D print.

Shapes like this that protrude like the bottom half of a sphere (overhangs) are prone to 3D printing failure because there is no support underneath. Since making it gentle makes it difficult, I will change the shape so that the bottom surface sits flat.

I will make the bottom surface circular and connect it smoothly to the main body.

I will connect the edge of the main body and the edge of the bottom surface using Bridge Edge.

I connected each as a G2 curve. Since I only know how to use auxiliary lines to connect with G2 other than Bridge, I thought this method would be easier.

After that, I will create a curved surface using XNurbs based on this curve.

Checking if it is connected smoothly

Increasing the density during export

Previously, I set the density to about 0.7 when outputting obj files, but since specifying a value of around 0.9 to 1.0 resulted in a cleaner finish, I decided to specify a higher value.

The figure imported into Bambu Studio.

It has become a little smoother than before.

Adding support material

In Bambu Studio, support was not enabled by default. Therefore, I will enable support from the left sidebar.

To state the conclusion first, enabling support provided the biggest improvement in this response. (Well, obviously...)

Specifying variable layer height

After referring to this article, it seems that one way to deal with overhangs is to increase the layer height.

In Bambu Studio, you can use variable layer height to specify different layer heights depending on the height, so I will set it to be thicker at the bottom and thinner at the top.

Since making it too thin seemed to significantly increase print time, I decided to change only the parts that I thought were necessary this time.

I made the top part finer so that the ears would be printed cleanly.

The layer height changes in the middle of the ears, and I didn't change the top of the head, but it seems it would be improved further if I also addressed the top of the head.

Seam control

3D printers generate seams at the start and end points of each layer.

I was a bit concerned about this. Therefore, I will specify the seam position to less noticeable areas such as around the ears and sides to improve the appearance quality.

In this model, the seam was behind the ear.

Using 'Seam Painting', I will specify it to wrap around the ears to make it as inconspicuous as possible. There is also a small seam on the lower back, so I will move this to the side.

I was able to move it to a less noticeable position.

3D print results and challenges

I tried printing with different settings several times this time.
When looking at them lined up from a distance, they don't look that different, so let's zoom in and take a look.

This is the case with and without seam specification. If not specified, the seam could end up in a conspicuous position as shown on the left.

I have been able to move it to a slightly less noticeable part, wrapping around the ear.

This is the difference when Density is set to 0.7 (presumably) and 0.9. You can tell from the preview before printing, but the one on the left has a faint line. The one on the right is printed cleanly.

This is a comparison of the differences in layer height. You can see that after changing the layer height, the top of the ear is cleaner because it is finer.

With the setting changes above, the overall quality turned out quite well.

However, while the critical bottom section did improve, it was not as much of an improvement as I had hoped for.

It is significantly better than when there was no support material, but changing the layer height did not lead to a major improvement this time.

Personally, I really want to finish this bottom section cleanly enough to hold it in my hand.

Future Strategy

There seem to be a few more things I can do to address the overhang, but for this model, I have decided to split the bottom and top sections and 3D print them separately. By taking this approach, I should be able to make the bottom spherical, whereas it was flat and circular this time.

I am just making a figure this time and not putting anything inside it, but eventually, I plan to create a space to house electronic components. Therefore, I need to be able to split it somewhere.

If I print the bottom section inverted, the overhang should be eliminated and the roughness issue should be resolved, so next time I will test the method of splitting the model into top and bottom parts and gluing them together later.