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TwoDrunkOwls

Gyro PVA support problems

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I am having problems getting a successful PVA support print on my new UM3.  I decided to try the gyro because it came with the printer.  If anything was going to succeed it would be this, right?  Wrong.  All but one of my previous attempts using PVA had failed.  See this post.  I was getting gaps in the support where it failed to extrude.  The gyro support printed OK for many more layers than any previous attempt but then, in the last couple of hours of course, the support stopped extruding, as seen here:

IMG_0425.thumb.JPG.32a4e9e424163ec4518ac99aad767ae2.JPG

 

It looks to me that the support began extruding worse and worse until it failed:

 

IMG_0426.thumb.JPG.a9eb5d8e0feecfa8737252144f0c4228.JPGIMG_0445.thumb.JPG.c78383c0b5702fea96194265567094a2.JPG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

If you look closely you can see 'stripes' in what little PVA was being extruded:

 

IMG_0438_LI.thumb.jpg.628058e66c03877ea3e60800fbdab522.jpg

 

 

Has anyone seen this before? 

 

While I am not sure about the strange stripes I am thinking the extrusion problem is moisture related.  If this is moisture related, why does too much moisture in PVA stop printers from extruding?  I extruded a good two meters of PVA after I aborted the print.  There was no sign of cooked PVA but it had bubbles all through it and snapped a few times so the stuff was wet.  I am drying it  out on the print bed now as per Ultimaker's instructions.  It will be interesting to see if the desiccant turns color at all (turns green with moisture).  It did when I dried out PVA that came with the printer.

 

IMG_0415.thumb.JPG.15b3828727f962060352100dc73d8cb3.JPG

 

IMG_0417.thumb.JPG.b7ef92017f0ef67089863066d2f768c0.JPG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Any suggestions?  Words of wisdom?  What the heck are those stripes?  Why is the sky blue?

 

Regards,

TwoDrunkOwls

 

IMG_0419.JPG

Edited by TwoDrunkOwls
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The bubbles are humidity in the PVA. The cooking is not always visible, but the bubbles are a dead giveaway. And you may need to do a series of hot and cold pulls to clear out the nozzle. I am surprised you do not see charring on the outside of the nozzle, but probably is on the inside causing it to build up and clog the passage through the nozzle.

 

PVA is very, very hygroscopic. It can gain enough moisture in just a few hours of print even if dried out. Depends on your environment.

 

Once it starts to get squirrely, it goes very quickly.

 

If you do not have a dehumidifier to dry out the filament, putting it in the printer, with the bed temp about 50C for a few hours will help to dry it out.

 

The sky is blue because the atmosphere scatters the blue spectrum during the day when the distance through the atmosphere is at its thinnest. The other colours are passing through more efficiently. During the sunset, when the line of light traveling through the  atmosphere is its thickest, the blue spectrum is scattered out before it reaches you and leaves only the reds and yellows to be seen.

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3 hours ago, TwoDrunkOwls said:

What the heck are those stripes?

That most certainly is when the PVA is extruding again after not having printed for a while for what ever reason.

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Are you sure you're drying your PVA right? If you put it in a plastic bag while doing this, the moisture will stay inside...

 

See also the Ultimaker drying instructions:

  1. Put the filament spool in its original packaging (in a cardboard box, without the plastic bag), and place the box on the build plate.

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On 11/4/2018 at 12:58 AM, kmanstudios said:

The sky is blue because the atmosphere scatters the blue spectrum during the day when the distance through the atmosphere is at its thinnest. The other colours are passing through more efficiently. During the sunset, when the line of light traveling through the  atmosphere is its thickest, the blue spectrum is scattered out before it reaches you and leaves only the reds and yellows to be seen.

 

Wisenheimer. ?

Edited by TwoDrunkOwls
Added a stupid emoji. God I hate those things.

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On 11/4/2018 at 12:58 AM, kmanstudios said:

The bubbles are humidity in the PVA. The cooking is not always visible, but the bubbles are a dead giveaway. And you may need to do a series of hot and cold pulls to clear out the nozzle. I am surprised you do not see charring on the outside of the nozzle, but probably is on the inside causing it to build up and clog the passage through the nozzle.

 

PVA is very, very hygroscopic. It can gain enough moisture in just a few hours of print even if dried out. Depends on your environment.

 

Once it starts to get squirrely, it goes very quickly.

 

On 11/4/2018 at 12:59 AM, TMicke said:

That most certainly is when the PVA is extruding again after not having printed for a while for what ever reason.

 

I agree, humidity is the culprit for this print.  The PVA was out in the open the entire time.  Drying out the PVA some changed the printing characteristics.  My PVA support structure is stronger, less flexible, and looks clearer.  I still see a few bubbles in the extrusion but nothing like before.  I will try this print again when I know my PVA is dry.

 

I have resisted doing hot and cold pulls so far because the PVA always starts printing again after having been 'clogged' and I have seen no sign of charring.  It started printing again after this failure like it never had a problem.  I have been having intermittent PVA extrusion problems which may also be moisture related. (You can see my long winded posts hereThe problem has lessened some since I dried out my stuff but it still happens.  I do not understand how steam, in essence, could cause this.  I will attempt to find out though.

 

On 11/5/2018 at 4:11 AM, P3D said:

Are you sure you're drying your PVA right? If you put it in a plastic bag while doing this, the moisture will stay inside...

 

Seemed to make sense to me.  When the moisture content evens out inside the bag the descant will trap what it can.  Seemed better than trying to get the much cooler room air to absorb it.  I'll try it their way in the future.  For now I will dry material out on the printer bed, under a towel. I'll use a better way in the future.  Vacuum perhaps. 

 

When I print I'll use my old Prusa MMU spool holders inside a plastic bag.  The seal around the filament is not the greatest but it should let me print until I find something better.  Plenty of options out there.  At least I get to use something from that miserable first revision Prusa multi-material "upgrade".

 

IMG_20181109_144625611.thumb.jpg.583ebf7277522785feb03e4b48792f51.jpg

 

Thanks for your replies.

 

TRUST IN GOD BUT KEEP YOUR POWDER PVA DRY!

 

 

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