Resonance in Print Bed UM2

[thefordprefect 0]

When printing at 100mm/s long items oriented front to back the print head touches a small printed lump above normal height the plate resonates.

This can be fixed by slow printing but 100mm/s usually prints ok

The initial oscillation obviosly causes further z axis height differences which the head then touches and this prolongs the oscillation. Eventually long sections of print get wavy.

this is a video at 240 frames/sec of the problem (printing at about 100mm/s)

www.youtube.com/embed/1GqTaTMnr6Y

the finished print looks like this:

Is there any simple cure for this other than printing below 70mm/s? some damping mechanism - perhaps a plate of gel under the bed heater!?

 

[illuminarti 18]

Perhaps you could try increasing, or decreasing, the tension on all three bed leveling springs (and then rerunning the leveling wizard), and see if that makes a difference?

 

[gr5 2,192]

this is a video at 240 frames/sec of the problem

 

So... 8X?

Well if the downard acceleartion gets above 1G (and I suspect it does) then you should be able to put a small box or bag of sand on the bed and that should dampen it quite a bit. If you use a box, you need to only fill it half way - it's important to have an air gap so the sand can fly up inside the box. The vibration energy should turn into extremely mild heating of the sand and dampen the movement drastically. If it doesn't dampen it fast enough then probably you need a bigger box of sand. It probably won't help at all once acceleration is damped to less than 1G.

 

[gr5 2,192]

You could use a liquid filled shock absorber. Or pneumatic shock absorber like those on screen doors. Connect it to the leading edge of the bed and to the floor of the bed. Seems drastic.

 

[anon4321 16]

if it is truly resonance, wouldn't adding weight to the bed lower the resonance frequency possibly avoiding the issue?