Moire Patterns In Prints - How To Reduce?

[mitchfx]

I am guessing this is less of a specific S3D issue and probably more related to my printer hardware, but I'm discovering that the knowledge on this forum is better than any other 3d printing board I've found

My printer is a Dremel Idea Builder, which is a rebranded Flashforge Dreamer with a few modifications. Overall the prints I have been getting are really nice, but I'm occasionally finding pretty noticeable moire patterns when running certain models at medium to large sizes. What is interesting is that when I print very small and detailed objects this moire is MUCH less noticeable and sometimes completely absent. All of my tests have been at 100 mircons and basically use the same overall settings in terms of speed, etc.

Here are some photos showing the effect that I'm seeing. In the darker model you can see some wavy interference patterns that are absent in the smaller scale test. I have to wonder if the transport doesn't get a chance to get moving at full speed in the smaller print due to the short paths before direction change.

Print exhibiting the moire artifacts

Print exhibiting the moire artifacts

Smaller print showing no moire

Smaller print showing no moire

Size comparison

Size comparison

[bot]

The effect appears to be what is referred to as "ringing" in the 3d printing community. It is due to rebound in the toolpath movement when changing directions after doing a high-speed move. The momentum is not dissipated enough by the acceleration settings on your firmware.

I'd say you aren't seeing it on the smaller prints because with such smaller line segments to print, it never reaches "critical speed" to have the rebound ringing.

I'm not familiar with your hardware, but if you can tweak any "jerk" or "acceleration" values, try lowering the jerk value at first, as well as the acceleration value. The jerk setting specifies the minimum speed that the toolpath will jump to before applying acceleration (or deceleration).

[mitchfx]

Yep, just as I was suspecting in relation to object sizes. Good to know the actual term and mechanics behind it. I will have to investigate if the Dremel firmware allows such low-level tweaking. If not, there might be a way to hack it using Flashforge Dreamer setttings...dunno. Worst case I guess I can just lower my print speed overall. I'm sure this is a common thing people discover but it is becoming obvious that I need a 2nd printer due to having to wait so long for high quality prints

Thanks!