Calibrating ASA on Bambu Lab X1-Carbon

Not only does ASA filament stink a lot less than ABS, I like ASA for its properties as a 3D printing filament for projects where I need stability after the print (no cold flow, moisture, or UV degradation). Polymaker’s PolyLite ASA is my weapon of choice. But how should you print this filament on a Bambu Lab X1-Carbon?

I actually had a lot of luck at first with ASA using the Generic ASA profile. I changed the nozzle and bed temperatures to 100°C and 265°C, respectively, and left everything else the same. But I never really pushed the capability of the material.

A guitar hanger

Among the many things I printed was this guitar hanger model on Printables. It turned out looking really great:

No wimpy part

Pretty nice, right? Here is how much it is beefed up with ten wall loops and 50% Gyroid infill. This print took about 6.5 hours to complete, with speeds turned down by about 50% across the board, among several other quality and strength-related settings that add to the time.

Toughness

But before hanging a roughly 8 lbs Stratocaster into those horns, I wanted to see how strong this was. So, I applied force pulling the horns apart. It was no immediate break at all, but I pushed it to the point of failure when I heard a crack and then pulled it apart to find this:

And, yes, before you yell at the screen, I did not follow the author’s recommendation to print horizontally (to align the layers with the likely stress for strength). This layer break is entirely expected under those conditions. Under the force of expanding the distance between the horns, the rigid material transmits the stress to this part area, flexes, and causes layer separation. But why did it break this way? What can we do better?

Learning from failure

While I was disappointed at how much strength I put in to cause this failure, this does give me a chance to examine the part closely. In the picture above, you can make out that while the layers above the failure seem flat, the layers below the failure do not appear to have enough ‘squish’: they are like ribbons laid down side-by-side. And the ‘unraveled’ filament extrusions in the break were almost like pulling the string in a woven fabric and watching it unravel. But shouldn’t the auto-calibration of the X1C catch this? Maybe. Is not enough filament being extruded to fill the voids and improve layer adhesion?

Adjusting the flow ratio

I should note that I started using the OrcaSlicer fork instead of Bambu Studio a short time ago, but in principle, the eventual outcome can be implemented in either. OrcaSlicer has handy built-in calibrations in the top menu bar since it’s made for more than just Bambu Lab printers.

Here’s the result of the first pass 1 with a flow ratio of 0.95 from the Generic ASA profile:

It may not look like much, but the +5 coupon surface feels a lot smoother than 0. My fingernail catches a lot less. The ripples on the picture of the surface of coupon +5 are largely an artifact of the light reflection. On either side of 5 or 0, it gets quickly worse.

The OrcaSlicer calibrations instructions say to use the following formula:

0.9975 is our new flow ratio for the filament settings. Let’s move on to pass 2 for fine-tuning with this setting:

Let’s take a closer look at -1 and -2. And whichever the fingernail test says is smoothest:

For me, personally, -1 wins; it is slightly more uniform front and back. Again, the formula:

0.9875 is the maximum precision for our new value for flow ratio that the slicer will accept.

Conclusion

I learned a lot from this exercise. Even if you think your prints are great and the automatic flow rate calibration works great, it might be worthwhile to go through this calibration exercise and see if you can do better. Especially if you notice print artifacts as I described above.

By the way, I repeated the entire calibration and ended up with the same result to double-check that this wasn’t a fluke. It is very consistent.

Please let me know if you have any feedback; all are welcome.

Please see below for what my modifications are to the Generic ASA profile and what I now use for all my PolyLite ASA filament: