PVA stringing and Burning

[GFlow 0]

Hi,

 

     I just got my UM3 Extended and I did my first robot print and it turned out pretty good.  This was after setting the nozzle switch position, manually leveling the base, then performing the auto level, and calibrating the xy.  I am now printing my first actual print and I am getting stringing and burning with my PVA.  What should I do to fix this?  I used the standard fine settings @ .1mm layer height.  I have read I need to look at retractions and right now the settings are as follows Retraction Distance: 6.5mm, Retraction Speed: 25mm/s Retraction Retract Speed: 25mm/s.  These are all untouched.  I am printing PLA with PVA supports.  Please see the attached photos for the stringing.

 

     Is there a way to change just the second nozzle retraction?  Or is there only one setting for both. Lastly the humidity in the building is around 42% and the temp is 72.

 

Thanks in advance

[kmanstudios 1,120]

Does it pop and crackle when printing? The burn marks are usually from that happening when it burns off moisture and carbonizes around the nozzle exterior.

 

Stringiness could be affected by that. But you can also try temp reductions.

[GFlow 0]

I have heard a pop, but the unit is probably 80 feet from my desk.  The unit is brand new as is the material, so I would think that there shouldn't be much moisture.  Should I try to heat the material up to ensure there is no moisture?  Also would it be worth while to have a dehumidifier in the area?  I have some weatherproof bins with desiccant in them to store the material, but nothing for the actual unit printing.  I live in Louisiana so it is very humid down here on a daily basis.

 

 

[kmanstudios 1,120]

OK, very familiar with the Louisiana humidity. Year round. If you have lived there your whole life, you probably think the winter is dry. But, that is just a relative comparison.

 

It takes no time for PVA to gather moisture. You have to remember that this stuff is made to dissolve away in about 24 hours on most prints. Put it into a humid environment like that and it is really gonna get 'damp'. And it is not the only hygroscopic material to be used.

 

Dry Storage is a good idea. But it is only part of the solution. There are things you can buy or build for the rest.

 

On the build end of things, @rebekah_harper designed a great mod for a food dehydrator.  Here is the thread. If you use a food dehydrator that has temperature control, you can use that to dehydrate your filament with no issues. Bex even linked to her 3D files she made to mod the dehydrator.

 

For building a filament feeding drybox there are plans aplenty at all the major 3D printing download sites. Youmagine, Thingiverse, etc.

 

On the buy it and get going mode there is this critter for dehydrating filament.

And for keeping filament dry while feeding you can use this as well.

 

But, I do recommend using these setups in conjunction with each other. Especially in the deep south. And you are about to start getting into hot days and beaucoup humidity. And if you are anywhere near the bayous or deltas, well, yeah..... :) And, if you are going to print with some other materials, like nylons, then you really need to have a system to keep things dry during use.

 

I live in NYC and it is much drier here, but I have to use both the dehydrator and polybox. Here is a thread discussing it too.

[GFlow 0]

So I will probably just go ahead and buy either the poly box or the printdry system.  Do I need both or just one?  Also is one better than the other or should I just go with the cheaper material. I think I may have some humidity issues, but I don't think its that bad.  I lowered the print temp to 218 from 220 to see if that helps the burning.  So far it looks good.

[kmanstudios 1,120]

I use the printdry to dehydrate filaments and recharge desiccant and I have one polybox per printer. This allows me to dry other filaments that may have gotten moisture while I printed. While that may seem odd that it would still absorb moisture, once it leaves the box/attached bowden tube, moisture will still get in there. There is no way to keep it fully out, but, it does help greatly. I can fit two spools up to at least 1Kg each.

 

I also suggest getting color changing desiccant so you know when to change out.

 

Keep in mind the bowden tube will add additional friction so you will have to play with your feeder tensions to make sure it has enough pull. I put my printers on table corner stands with open sides and a bottom shelf. The bottom shelf is where the polyboxes go. It feeds very naturally there too.

 

This is a thread where I specifically detailed what I did with my setup and how I reduced the friction from polybox to printer. Took me a week to get it all sorted out.

 

[GFlow 0]

So I will totally get some the poly box. But I have a hard time believing that the filament could've gotten wet in 12 hours. I setup the machine the night before and then started my print 12 hours later. This was brand new ultimaker PVA.

 

Also would moisture cause the burning? Or maybe there are some settings to adjust in cura? 

[kmanstudios 1,120]

The moisture would cause the burning. And, you do not have to believe me about the time it takes for that stuff to absorb moisture. It is all relative to temp and humidity in your location. Only time will tell about that. But I have had it happen in NYC.

 

I also got some that apparently got a ding in the sealed package that as soon as it came out, it had moisture. So, it could have been damaged at manufacturing or shipping. Or just a humid location.

[GFlow 0]

I had an all out blowout on my PVA on the print I did last night, the material was stuck, ground to basically nothing in the feeder.  It took me 2 hours this morning to clean it all up.  I did however just get my Polybox installed before my next print..   now I have a new PVA spool with some PLA in my poly box.  Everything seems okay now except I am getting some issues with my fill on the PLA.  Why are only some of the fill parts solid?

 

 

[kmanstudios 1,120]

Infill is a bit of an oddity on the Cura way of doing things. It is basically treated as a reinforcement, but not a pretty one. To get the infill to be more solid, just go to the speed temps and slow down the infill. Now be warned, I have had every setting unhidden since day one. I do not remember if you have to unhide that or not i the preferences/settings dialogue.