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burtoogle

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

Hi burtoogle,

 

IMO. This is a very good idea, as all of us want an object to be printed as fast as possible, -with as less as possible quality issues, right?

 

This is very interesting and can be a tool for increasing a quality of the printed object, decreasing overall printing time and as well reduce wear and tear of the printer (bonus -less maintenance)!

 

Resonance’s, harmonics, upper, lower and multiple etc. you’ll name it. This is a big issue in the mechanic world. And sure, -an FDM 2D printer is part of this “world”.

 

The good thing is that we have printers that’s built the same, -and will behave the same for a given model to print. So if we have the “resonance data base” (let’s name it so) for our printer, we can predict speeds to be used for a given model in order to avoid resonance issues in printing this model. This is sure some part of Cura -to some extent, I’ll think.

 

Well, this is a big issue for sure, and may take some time to do..

 

However, your idea using known print to analyze print quality of your printer is very much in time, I’ll say. Because such print test object do not take very long and will ease finding failures in our 3D printers. A good printer will always perform as expected.

 

If our own model is analyzed for best printing speed during printing, we will be the winners.

I would love to have such a firmware..

 

Keep up the good work.

 

Regards

 

Torgeir.

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