It's amazing how even a tiny amount of acceleration can completely remove the resonance. I have my machine on teacup printing 50mm/s and an accel of 10,000mm/s^2 and no visible ripples. Without the acceleration they are there, but have a very small amplitude.

Having a better handle on the PFD, REF and RC(x) settings and our electronic circuits could better tune the motors to remove some of the location/position ring. Remember that the motors as 'barrychuck' points out tend to oscillate between their steps. This will be during lingering at a stop or turn point and not so much during motion. But, this cube is in motion and the stop is nearly non-existent rather than momentary with a subsequent direction change. Much of the indications may be, as suggested, part of the mass, resonance and construction in our bots. --- Structural stiffening, damping (axis and between parts), electric hardware motor control, software control, electronic settings, device mounting, bot mounting to surface, etc... I had noticed our bots (MBI) are like stringed instruments with the ring through the wood.

It appears to me that this is exactly what you think it is: An undamped oscillation in the X-axis excited by the sudden bump in movement. If the Y-axis is moving at 40mm/s you can measure the period by measuring the distance from crest to crest or trough to trough. (Although it looks to me like there is some acceleration in Y after the bump.) The frequency is actually not important. What is important is that it continues undamped for several cycles. So going slower will not cure the problem it will just bunch it up near the bump. The cure is to find out what is vibrating
&
amp; damp it out. It should be easy to do. You should be able to see it or at least feel it with your finger tips. Something needs to be stiffened or cushioned. Stiffening will increase the frequency of the oscillation (also bunching it up) but lower its amplitude. Cushioning will dissipate the energy causing it to stop sooner. I don't know your rig so I don't know what is best but you should be able to figure out something appropriate. This is a good test part for this problem. Perhaps you will post the outcome with before
&
amp; afters on the test part. Good luck. - Dan

This is caused by the interplay of mass (inertia) stiffness of the system, and current on the stepper motors (they are essentially acting like springs). When you have a smaller mass (e.g. moving bowden toolhead printers), you can move it very rapidly, but the oscillations will have a higher frequency but lower amplitude. The correct belt tension is really important to get accurate prints.

Yes, very simple the waves show the slop or tolerance in the machines axis motions, due to belt tension, vibrations, and flexing of the bot. They are always greatly increased as feedrate is increased. So in other words-go slower and less artifacts in the print.

Also, a stepper motor basically acts at a spring-so again, when you have enough mass moving and try to stop it at a given position with a stepper, it will ring for a few microseconds afterwards, back and forth around the center position of the step.