What makes the zip-zip sound?
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@mrehorstdmd said in What makes the zip-zip sound?:
Video of printer running here: https://vimeo.com/279178750
This is a coreXY machine with GT2 belts and smooth, 22 mm diameter pulleys, 0.9 degree steppers. Interpolated ustepping is on. Print speed is 200 mm/sec for all features of the print (just testing- not a normal operating mode), X acceleration is 3k and Y acceleration is 2.4k mm/sec^2
Is the zip-zip sound caused by belt teeth hitting the smooth pulley surfaces, the drive pulley and belt interaction, the motor detents, or ...?
I've had that sound on my CoreXY too when experimenting with high speed printing and also at around 200 mm/sec. IIRC it was in a speed band of about 200 +_ 20 or so. Higher than that, or lower than that the sound disappears. Which makes me think it's the resonant frequency of the steppers or some such (seems to print fine despite the strange sound).
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@deckingman I'll try bumping the speed up and see if it goes away. I didn't really notice it much at lower speeds.
I've been pushing the machine to see what the limits are before it starts shifting layers. The Y axis is pretty heavy but no shifting yet. The machine is starting to shake a bit.
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@mrehorstdmd said in What makes the zip-zip sound?:
@deckingman I'll try bumping the speed up and see if it goes away. I didn't really notice it much at lower speeds.
I've been pushing the machine to see what the limits are before it starts shifting layers. The Y axis is pretty heavy but no shifting yet. The machine is starting to shake a bit.
I managed to get up to 300mm/sec by feeding 3 filaments into a Diamond hot end (3 melt chambers) and no sign of any layer shifting. That's with about 2Kg moving in Y per gantry. But yes, with a combined mass of around 4Kg (two gantries) at a height of a metre above the floor, being thrown around at those speeds I'd have to bolt the machine to the wall or something as the wooden floor that the machine stands on has a bit of "give". Funnily enough, all things considered, it didn't print too badly as everything rocked back and forth in harmony - somewhat alarming to watch though
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@deckingman My machine is maybe even taller, though the Y axis mass is about 1.5 kg. When the bed is up high, it shakes with the XY stage so there isn't any visible effect on the print quality, but as the bed gets lower, it will shake less that the XY stage and that will wreck print quality for tall prints.
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@mrehorstdmd Hmmmm. Interesting point that I hadn't considered. But isn't the case that, provided the frame is rigid, any rocking due to mass will be acting as if the entire thing is pivoting about the base. Therefore, the amplitude of movement will be higher at the top than say half way down. So the bed will as you say, only rock by half the amplitude of the gantry but the top of the part being printed will rock by the same amount as the gantry. This is all assuming that the XY gantry is fixed in Z and the bed moves in Z. Or have I misunderstood your comments?
Edit. Of course, if the frame flexes, then it will be an entirely different thing ( but you and I don't build flexible printers)️ -
@deckingman I try to build rigid, but I don't kid myself. When the frame is 1.5 m tall, and you throw 1.5 kg around with 5k m/sec^2 acceleration, its going to flex. I'll probably turn the acceleration back down to 1k or so for daily use and know that if I absolutely have to, I can crank it up.
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You could be right. Assuming you mean 5k mm/sec not 5k metres/sec for 1.5Kgs gives about 62Newtons of Force and plugging those numbers into my OpenBuilds calculator, for 40/40 extrusion would give 0.77mm deflection for a simply supported beam with a concentrated load applied. But if it was cantilevered beam, the deflection becomes 12.3mm. Difficult to work out really because the load isn't applied to the centre, but also assuming the frame is braced at the top, then the members aren't cantilevered either. And of course the load itself is dynamically varying due to direction changes. I guess most of the flex would come from movement in the joints, especially the contact between the bolt heads and the slot. As you say, it's all a bit hypothetical.
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Hey I love the setup, the print looks really pretty;
To your question, we make coreXY printers, and I believe the issue is mainly motor/driver noise at certain speeds. It's pretty normal when doing this kind of rapid accelerating.
I do want to make sure that the community is spreading information that is accurate, as inaccuracies propagate and create problems for others, like the manufacturing company I work for, which gets many requests saying things like "such and such person can print at 1000 mm/s why is your printer so slow" etc.
Just as the OP said, the setting is 200mm/s, but that doesn't imply the print is actually moving or averaging anywhere near 200mm/s. If timed it manually, one would see its probably averages around 60-80. The acceleration would either not let it reach 200mm/s over such short distances, or if it does, it would only be for a very brief period before it is decelerating again. This being the case, the infill is really beautiful, that's a lot of change in speed for extruder flow rates to keep up with.
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My build is about that tall too using 20X40 for the uprights. If I knock the frame it vibrates. No real surprise because the uprights are unsupported even with all the gussets. I intend to screw metal panels to the outside on 3 sides. On the front I want a sheet of 1/8" polycarb that has removable hinges on one edge so the door can be easily taken off. It will also have some thumb screws at the corners to tighten to frame. There is already a floor and partial top so mechanically this should make a closed box. Time will tell but this should be extremely ridged.
FWIW,
Mark Napier
@mrehorstdmd said in What makes the zip-zip sound?:
@deckingman I try to build rigid, but I don't kid myself. When the frame is 1.5 m tall, and you throw 1.5 kg around with 5k m/sec^2 acceleration, its going to flex. I'll probably turn the acceleration back down to 1k or so for daily use and know that if I absolutely have to, I can crank it up.
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I hear the zip zip too on my corexy at speeds above 200mm/s. Definitely sounds like it's coming from the motors over anything else.
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My printer will wake you up 3 rooms away with closed doors if I crank up the settings... Reducing speed and amperage is what makes the sound go away.
