What exactly is "Input Shaper"?  

RE: What exactly is "Input Shaper"?

In advance of any replies (again, thank you), I have found an article which discusses the purpose of Input Shaping.

To those as confused/ill-informed as myself, IS is an attempt to counteract resonant frequencies which might cause defects during the print.  Specifically, it appears that "ghosting" defects are particularly targeted.  I still don't understand exactly how IS functions, technically.

In addition, it remains unclear to me as to how often the IS calibration or testing must be undertaken in order for IS to be effective.  For example, I have two MK4 printers, both with IS and all of my prints still exhibit the "ghosting" effects which are supposed to be removed by IS.  It appears that just having IS functionality on-board is not sufficient - some other calibration process must be required.

Would someone with more experience comment?

thanks,

Chris

RE:

My experience with input shaping comes from printers using Kipper firmware and as you pointed out, Klippers input shaping is an attempt to counteract resonance frequencies which might cause defects during the print. The intended integration of this method, is to affix an accelerometer onto your moving mass, i.e. the print head, and run a software routine that puts the mass thought a range of speed and direction changes while monitoring the resonance frequencies thought-out.  The software will determine the conditions (speeds / accelerations) causing the worst vibrations, with which you insert the provided values from that analysis  into your firmware settings. 

Now Prusa has decided, at least in interim, is to provide Input Shaping functionality,  with a configuration, based on what is probably a best fit for their print farm. Not perfect for any machine, but best overall.  This probably does improve the average MK series printer performance, but since it is impossible for the thousands of Prusa printers out there to have the same resonance profiles, this one size fits all approach is problematic.  If the threads I've read are any indication, it is already showing up as imperfect.  For the MK4  I use the IS profiles, when I want a low detail large print, but the non IS profiles when detail is more important. This is good advice, in all cases, but as a point of reference, on my voron printer, I get better speed and quality when printing fast, because I was able to tune the machine using an accelerometer and the Input Shaper software.   I suspect that many of the negative comments and reviews about the current IA functionality could be mitigated by allowing in-home IS calibrations

The buddy board has a connector for an accelerometer, and perhaps Prusa will  move forward in future to provide the necessary tools to fine tune our individual printers. 

RE: What exactly is "Input Shaper"?

But are you using the Input Shaper profiles in Prusa Slicer?

You can also check the settings with a test print.I once made a thread about this.

Prusa also uses the Klipper Input Shaper. So you can set everything the same way.

Although the original profiles now work very well.I print exclusively with them.

For a better understanding, I recommend the klipper documentation.

With Marlin, the procedure is slightly different but uses the same test pressure as klipper. This is explained in more detail in my thread.

RE: What exactly is "Input Shaper"?

In simple terms and in the specific  case  of the FDM  it is the attempt to introduce a change in movement algorithms so they will avoid generating vibration that causes printing artifacts.

There are several algorithms that we are able to use for that, and each of them works a little bit differently but overall:

First the resonance frequency of the specific movement mechanism is captured. It is usually done with accelerometer. Then the software calculates the frequencies of the resonance and applies one of those algorithms to reduce the vibrations. Because of the width of the "band pass filter" that is applied, the algorithms have a little bit of leniency and so there is nreason to calibrate this very often. You don't need to do this before each printin. In the case of well designed 3D printers such as Prusa and a little bit more lenient algorithm there is no need for accelerometer on the printer at least not that all the time. There is a video of Mihai designs interview with David Crocker from Duet3D where he explains the topic perfectly.

RE: What exactly is "Input Shaper"?

Posted by: @fullmetalnozzle

I've searched the forums and I apologize for not being able to extract the info I'm seeking, should it exist, such that I need to post a question which may have many duplicative predecessors. 

What, exactly, is the "Input Shaper" function?

For potential responders (thank you!), I'm asking a technical question:  exactly, technically, how does Input Shaping work?  And what is the purpose?

thanks very much to everyone -

Chris

wbr,

Karl