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Testers required for anti-resonance feature in Cura development builds

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Posted · Testers required for anti-resonance feature in Cura development builds

A user of my Cura builds asked about reducing the chance of resonance when printing areas of skin with short lines. I have therefore added a new setting "Avoid Frequency" that, when non-zero, specifies the resonant frequency to avoid. Skin, infill and support interface lines using the Lines and zig zag patterns that would be printed using hot end motion within +-/20% of that frequency will be slowed to move away from that frequency band.

 

Here's an example showing the speed reductions in the narrow(er) skin regions...

 

Screenshot_2019-12-26_12-35-20.thumb.png.7c43f2932dc1955079d46bc0621612a2.png

 

So if anyone uses a printer that has resonance issues and are willing to try out this feature, I would be grateful if you could give it a go and report back whether it is beneficial or not. Obviously, you will need to determine a suitable value for Avoid Frequency and that is going to be printer specific.

 

It may be that my simplistic approach to just avoiding frequencies within 20% of the specified value is not good enough and it may require either a bandwidth setting adding or upper and lower frequency limits.

 

As ever, my builds can be found at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0.

 

Please read the README.md file there. All feedback is welcome.


Thanks.

 

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Posted · Testers required for anti-resonance feature in Cura development builds

I don't have resonance problems (2x UM2 non-plus), so I can't test this. But I think this is an interesting approach.

 

The only question is: if people notice resonance, how are they going to find out which frequency it is exactly? If I feel a vibration, I can't tell if it is 5Hz, 7Hz, 10Hz,...? At least not without a known reference next to it. Further, it is very hard to feel/hear whether there are lower or higher harmonics on it, which could also trigger the resonance.

 

Maybe you could find a printing test pattern that "resonates well"? Or a printing pattern that causes vibrations at known frequencies, so that people can try this, and then can compare their own resonance to these standard patterns? I am thinking of a gcode-file with a sort of "frequency stepping scale" similar to the E24 resistor values in electronics? Where the actual resonant frequency is displayed on the front panel? And then, if that frequency resonates in the system, people can just read the value from the front panel, and enter that in Cura?

 

Could be interesting from a theoretical viewpoint, but I am not sure if it is worth the effort though, and if it would really result in better prints...?

 

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Posted · Testers required for anti-resonance feature in Cura development builds

Hi @geert_2, thanks for the input.

 

Yes, a test print could be useful. Perhaps just a region of skin that narrows. When the skin lines are printed, as the hotend reaches the area where the length of the skin lines is such that,  the hotend is switching direction at the resonant frequency, the user should notice the resonance and where it is occurring. They could then adjust the Avoid Frequency to reduce the print speed in that region. The layer view gives a crude indication of print speed so they just need to adjust the Avoid Frequency to move the lower speed (bluer) region to coincide with where the resonance occurred.

 

I would expect the resonance characteristics of a printer to be quite complex (i.e. different resonant frequencies in x and y and maybe multiple frequencies). So if I get any feedback that indicates that my current simple scheme isn't sufficient, I'll think about a more sophisticated solution.

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Posted · Testers required for anti-resonance feature in Cura development builds

there are smartphone apps that can measure sound frequency, which should make it possible to measure the print head's shaking frequency due to the sound it makes. I for example use such an app to tension my printer's belts to a certain value.

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