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phil-t

UM2 bed vibrations causing infill to self-destruct - SOLVED

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Hi,

I've just picked up a second hand UM2, and in the main I'm really impressed, but obviously there is a nice learning curve with these things!

Everything was going OK until I wanted to try a larger print (204 x 158 x 45mm), I spent a while trying to get the first layer to stick (it has 4 x M3 thread holes that are tricky to get started), but the actual issue that has caused me to abort after 5 hours is because of the in-fill..

At some point I had a small amount of stringing/under extrusion occur (no idea why, it seemed quite random), and this led to one or two strands that clumped, and when it tried to do some infill on this, the further away from the Z axis screw it gets, the more the head seemed to vibrate as it went over the clumps, the knock on effect is that causes more ripples by itself as the material instantly sets whilst the bed is vibrating and it slowly spirals into a worse and worse set of peaks and bumps with the infill being very rough vertically.

I am just trying it with no infill, but just wondering if there is anything I can try?

It was UM PLA green, 210/60C @50mm/s, infill 20%, 0.2mm wall thickness.

The other issue I had is the outer wall also slightly warped (the one to the front of the machine where the opening is, the back of the print was fine).I don't know if I need more or less temperature at the bed to help this, or whether a brim would help.

 

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.2mm wall thickness (or layer height)? I think you're supposed to use wall thickness in multiples of .4mm (nozzle diameter x #shells), not that it would help the infill problem.

One thing I do to some prints that starts vibration bad is to raise the temperature for a minute or 2 and slow it way down. The hot tip seems to soften the layers underneath and flatten out the high spots that are creating the vibrations. Obviously, as the head moves over bumps (several on an infill) it will push the bed down on each bump. 50 bumps in a row, at 50mm/s and it just goes crazy with bumps. If you heat up a bit, and slow it way down for a couple of layers, you can get back on track in future prints.

Making sure you have the right wall thickness set in Cura, as well as making sure you don't have any external airflow cooling the front of the part, should help with the front warping. An alternative would be to cover the front of the Ultimaker with something (lexan, cardboard, wood, etc). This should help keep the interior a little more uniform in temp.

if you posted a pic of what Cura shows you in Layer View, it might help to better understand what's going on.

EDIT: I had no idea the incorrect shell size would also affect infill as gr5 states below. I learned something today :)

 

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While printing if you get this vibration (I've never gotten it) slow down the print in the TUNE menu. Normally it prints at 100% but you can speed up or slow it down so that the "bumps" aren't happening right at the harmonic for the bed.

Wall thickness of .2mm is very bad. This means it will underextrude all the infill by 50%. So keep that at a multiple of your head diameter (as solid print states). The head diameter is .4mm.

The warping at the front - is it like this picture (5th picture down on the left)?

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide

Any problems not cleared up please post pictures next time as we may be giving you totally wrong advice and pictures are incredibly helpful.

Gloucester England? Or Gloucester Mass?

 

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Thanks for the help!

Sorry for the confusion, the wall thickness was 2mm (5 * .04mm, and only increased from standard as I wanted a little more meat around the 4 holes.)

The advice both of you have given is great, and I wish I'd have thought of that at the time! I'll bear that in mind.

The warping was just a little bit of lift at the base, and oddly when I printed it with 100% infill, there was zero lifting, quite impressive considering the footprint size of the item is quite large!

The good thing about printing it with 100% infill was I could use the tune menu to see how more/less temperature and speed affect things! and see what a happy medium is for the green PLA!

I will get some pictures posted in this thread, no doubt someone in the future might have the same issue, and it's nice when it's all documented! but for now, I think I can count this as 'solved'!

oh, and I'm in the UK, right inbetween Gloucester and Cheltenham!

 

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Just to follow up, this is the infill getting rougher and rougher as the vibrations caused by the head moving over it just escalated until I had to stop it.

As mentioned above, the best thing to do is slow it right down, up the nozzle temp to slowly melt through and smooth out for a few layers!

DSC08612 zoomed

 

I've just had a similar issue almost start with a bridged gap, and found slowing a 50mm/s @ 0.2 layer height down to 30% (15mm/s) (Nozzle is already @ 230 with PLA) seemed to do the job, bringing it all back into shape!

 

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