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nyb

extrmely violent PVA printing

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I can't understand how to reduce the violence with which UM3 prints the PVA support...

 

In the last print, where I used the recommended settings for PVA+PLA prints at T-2days for the model to finish (6 days) the bed have been catapulted out from its holding springs.

On top of that the magnetic pins holding the cooling fan of the print head opened down and started scratching against the print bed.

 

The only way I found to prevent this is not to use the "print support" option, but rather run a 2-materials print where I draw the support myself...

 

Also it seems that I cannot stop the print remotely anymore with the latest version of cura (3.3.1) which would be something extremely handy in these situations

P_20180528_230706.jpg

P_20180528_230740.jpg

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I personally find the default speed settings in Cura for the UM3 are all too violent for my liking.  I slow all of the settings down for both extruders.  It may take marginally longer to complete a job, but the machine isn't jerking and clunking about so violently.

 

605045683_SpeedSettings.JPG.5b03177799a7f06423487ac5e75cb0ac.JPG

 

Any particular reason why you are using the BB core in the 1 position and the AA core in the 2 position?

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I haven't had issues with the default PVA settings like this.

 

It looks like your magnets are still in place where they should be in the front bracket, so that's good.

 

From the looks of things, if I was going to guess, I think the bracket probably opened first, and then it would have hit the existing print, causing the bed to dislodge. (Rather than the bed dislodging and then the bracket opening.)

 

Is it possible your bracket is bent to more than 90 degrees? The metal is pretty soft and it won't hold a good connection if it's bent to more than 90 degrees. Quick video on fixing the bracke: 

 

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17 hours ago, XYZDesignPro said:

I personally find the default speed settings in Cura for the UM3 are all too violent for my liking.  I slow all of the settings down for both extruders.  It may take marginally longer to complete a job, but the machine isn't jerking and clunking about so violently.

 

605045683_SpeedSettings.JPG.5b03177799a7f06423487ac5e75cb0ac.JPG

 

Any particular reason why you are using the BB core in the 1 position and the AA core in the 2 position? 

 

Thanks for the tip, I will try slowing all speed settings down by 50% then.

 

Should BB and AA cores be inverted? I have this configuration because the PVA spool is in a custom box with controlled humidity, which is on the left with respect to the printer's front.

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Generally I'm more concerned with quality not speed or time in my projects.  In your case perhaps just the reduction in the Print Acceleration, Travel Acceleration, and Jerk settings will suffice.  Please post the results of your success / failures with the changes.

 

I suppose the position of the two cores can be switched so long as Cura knows which core is each location and the settings for each are correct.  I'd defer to Erin fbrc8-erin for the final verdict on that question.

https://community.ultimaker.com/profile/327452-fbrc8-erin/

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Switching the two Core positions is totally fine; I actually recommend it in a lot of cases during troubleshooting if we're trying to narrow down an issue along one of the feed paths.

 

I'm running a print right now with PVA in Feeder 1 and PLA in Feeder 2 because I'm using Faberdashery PLA (loose coils not on a spool) and it worked out better in my workroom that way. 

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On 5/31/2018 at 4:27 AM, nyb said:

I can't understand how to reduce the violence with which UM3 prints the PVA support...

 

In the last print, where I used the recommended settings for PVA+PLA prints at T-2days for the model to finish (6 days) the bed have been catapulted out from its holding springs.

On top of that the magnetic pins holding the cooling fan of the print head opened down and started scratching against the print bed.

 

The only way I found to prevent this is not to use the "print support" option, but rather run a 2-materials print where I draw the support myself...

 

Also it seems that I cannot stop the print remotely anymore with the latest version of cura (3.3.1) which would be something extremely handy in these situations

P_20180528_230706.jpg

P_20180528_230740.jpg

The plate getting knocked about like that I have had happen. But I have seen it happen and not just found it afterward. It happened to me when the printhead collided with a heavy duty curl that was strong enough to not bend. It was not moving super fast. Just very strongly as it moved across. I can also say it did happen when I did not lock down the clips properly for being in a hurry.

 

I can also say that my printing has gotten less shaky with the time I have used Cura. Shaky as in going "Wacka wacka wacka" even on areas that are tight or when going from an area of large travel to a series of shorter travels say, as it moves into areas that are thin or corners.

 

But, when I have seen it happen (One of the perks of working at home and the printer just a few feet away), I could hear the knocking sound get worse and turn around and watch it to see what was happening. In my experience, it has been just strong solid moves against a curl that had built up to be very strong.

 

The fan bracket thing I have no idea about and definitely defer to @fbrc8-erin's experience in this. I bent mine while trying to get it clear of a dreaded filament rise into the print head until it looked like the blob, or as @neotko called it, Cthulu.

 

I should also say that by and large, I am not tweaking a lot of parameters, so the speed for the most part has not been tampered with. This does not mean I do not do so, just not always.

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Lowering jerk and acceleration may make your printer last longer or scare you less but that will also lower print quality (but will improve ringing).  I like my acceleration as high as possible (mostly because I tend to care about dimensional accuracy of my parts).

 

Lowering speed will increase quality and scare you less.

 

If you are going to mess with acceleration be aware of the consequences.

 

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finally got time to run this print again, where for both PVA and PLA I changed the following (from default settings)

lowered print speed to 25 mm/s
lowered print acceleration to 2500 mm/s2
lowered print jerk to 15mm/s

 

the printer survived the full print and at the end the bed was less messy as well

 

thanks for the tips!

Image 2018-06-14 at 13.57.42.jpeg

Image 2018-06-15 at 13.12.35.jpeg

Image 2018-06-14 at 13.57.43.jpeg

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