Waves at Corners
Waves at Corners
I have noticed on most prints, especial those with 90° corners, waves form at the corner. The displacement direction is perpendicular to the plane of the given surface and the amplitude diminishes in a linear fashion as the distance from the corner increases. This looks very much like classic resonance ringing to a fully damped state. I see this condition in both the X and Y plane. I never see this on both faces of a single corner, or stated another way, only on one end of a given face. I believe I read somewhere that this is attributable to the floating bed design; i.e. the spider resting on three springs. Is acceleration or deceleration forces causing the bed mount system to oscillate? As I see no noticeable deviation in Z I conclude the bed is not "tipping", its merely translating in the X-Y plane. If there are way to eliminate this condition?
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- Waves at Corners
Re: Waves at Corners
Usually slowing down the acceleration cuts way down on that. Add this code into your Starting Script.
M201 X1000 Y1000 ; lower default accelerations
M201 X1000 Y1000 ; lower default accelerations
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Matt_Sharkey
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- Joined: Mon Oct 20, 2014 3:10 pm
Re: Waves at Corners
along with what Jules said, If you are designing the model yourself, put small fillets on every corner that is in the XY plane. a 0.5mm should suffice. That way when your printer is approaching the corner it isn't trying to come to a dead stop then take off again. Instead it will make a more fluid motion around the corner.
Re: Waves at Corners
In thinking more about it, I believe the problem is caused by deceleration rather than acceleration. Both of these suggestions should help. Thanks for the feedback. 
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Matt_Sharkey
- Posts: 347
- Joined: Mon Oct 20, 2014 3:10 pm
Re: Waves at Corners
Deceleration is just negative acceleration, it's calculated the same way.quaver wrote:In thinking more about it, I believe the problem is caused by deceleration rather than acceleration. Both of these suggestions should help. Thanks for the feedback.
Re: Waves at Corners
quaver, you wont eliminate that. just about every 3d printer will do that. some are better than others but for the most part its there. ive seen parts printed by a 80k stratasys machine and its just as bad as on the m2.
Re: Waves at Corners
Deceleration is just negative acceleration, it's calculated the same way.[/quote]
Change in velocity over time with polarity of the quotient establishing direction (accel or deccel); completely agree. But, its the deceleration event that sets up the oscillation that causes the waves. The waves are noticeable because the print path is in a direction that is perpendicular to the axis of the oscillation. While its true the waves are made while accelerating I think the oscillation is set up by the deceleration event at the corner.
Change in velocity over time with polarity of the quotient establishing direction (accel or deccel); completely agree. But, its the deceleration event that sets up the oscillation that causes the waves. The waves are noticeable because the print path is in a direction that is perpendicular to the axis of the oscillation. While its true the waves are made while accelerating I think the oscillation is set up by the deceleration event at the corner.
Re: Waves at Corners
If it has accelerated, it creates more pronounced ringing when it has to slow down. That code just limits how much accelerating it can do.
Whatever you call it....using the code helps somewhat.
Matt's right too, if you put a slight rounding into your 90° angle (and tighter) corners, it distributes the force around the curve. Problem is caused by instantaneous direction shifts. (We saw it with cutters, when the knife could not turn in one place easily).
The other thing that helps is installing the Nema 17 dampers if you are willing to spend an hour or two fiddling with it. (I've got them on my machines and although there is still a little ringing around one side of holes in the sides of a print, (still trying to figure out how to work around that), it's pretty much gotten rid of that corner ringing effect. (Of course, i tend to print at slower speeds too, so that might be helping.)
All of the above. Just depends on how far you want to take it.
Whatever you call it....using the code helps somewhat.
Matt's right too, if you put a slight rounding into your 90° angle (and tighter) corners, it distributes the force around the curve. Problem is caused by instantaneous direction shifts. (We saw it with cutters, when the knife could not turn in one place easily).
The other thing that helps is installing the Nema 17 dampers if you are willing to spend an hour or two fiddling with it. (I've got them on my machines and although there is still a little ringing around one side of holes in the sides of a print, (still trying to figure out how to work around that), it's pretty much gotten rid of that corner ringing effect. (Of course, i tend to print at slower speeds too, so that might be helping.)
All of the above. Just depends on how far you want to take it.
Re: Waves at Corners
The NEMA 17 dampers look promising, if for nothing more than the noise reduction. If the stepper frequencies happen to sweep over the natural frequency of the bed gantry and sprung bed I can see how it could cause print anomalies. Ordered dampers tonight.
In doing more research on the topic (referred to as "ringing" on several other websites) I found another suggestion to help minimize the condition. Orient the parts on the print bed so that perpendicular outside walls/faces lie at 45°angles to the travel X/Y axes. This makes sense as it would reduce the velocity in X or Y which in turn reduces deceleration forces.
In doing more research on the topic (referred to as "ringing" on several other websites) I found another suggestion to help minimize the condition. Orient the parts on the print bed so that perpendicular outside walls/faces lie at 45°angles to the travel X/Y axes. This makes sense as it would reduce the velocity in X or Y which in turn reduces deceleration forces.
