PLA under extrusion on top of PVA support

[3DukeEngineering 2]

Hey guys, I have a odd one here with my UM3E. This seems to happen every time I print with PLA+PVA. Basically any PLA layer that is printed directly on top of a PVA support interface is extremely under extruded. Note its only the first layer thats under extruded, once it does the next layer up the extrusion rate is back to normal. For the life of me I can't figure out why, I haven't been able to find a relevant setting in Cura that relates to this specific layer and a google search hasn't helped me either.

 

Im wondering if it might be a firmware glitch so am about to try a update but this has really got me stumped.

 

Anyone have any thoughts?

[kmanstudios 1,120]

I have not had that happen on my machine (UM3E). After it is finished printing, does it show as an error on the parts? Also, which version of Cura are you using?

[3DukeEngineering 2]

Cura version 3.1.0

 

Not sure what you mean by "show as an error"? The printer doesn't realise its an error, but yes it is definitely an error. This happens with all files that require PVA support material

Edited February 5, 2018 by 3DukeEngineering

[kmanstudios 1,120]

Sorry for not being clear. What I meant was does the print look messed up when complete?

[3DukeEngineering 2]

Yep it sure does. I have tried to highlight it in the photos. One photo clearly shows the pva support interface. The other shows what the first layer looks like. Sorry the photo isn’t the greatest. But you can see in the area I have circled what the problem is (hopefully)

[kmanstudios 1,120]

Ack! Sorry, on my monitor it just looks black.

 

But, you say the PVA interface is showing in the print. Have you looked at your "support interface thickness" setting in the support area/tab? You may have to unhide it. I have always had everything unhidden and forget what it shown and not shown by default.

 

My support interface thickness, on the 0.2mm layer settings is at 0.6mm. Also, does your interface really sink into or seem to cook into the PLA?

 

One last question: What brand PLA and PVA are you using?

[3DukeEngineering 2]

Yeah sorry, the photo is a bit hard to understand without seeing the model.

 

support interface thickness is set to 0.6 at 0.1mm layer height. I have just ramped it up to 1.0mm to see if that makes any difference but I don’t imagine it will. The pva interface always looks nice and sharp and clean.

 

i have the z distance between model and support interface set to 0 is that correct? I have just tweaked it to 0.2 to see if that makes any distance. Perhaps having it set to 0 means the first pla layer is trying to print at the same layer height as the last layer of pva interface? (Surely this wouldn’t be the case?) would explain the underextrusion looking issue though...... although saying that if I put slight pressure on the build plate to lower it while it’s printing this layer, I can clearly see there is not enough material being pushed out the nozzle.

 

no issue with pva sticking onto the pla beneath it. But when the first layer of pla is put on top of the pva interface it doesn’t stick very well. I realise pla generally doesn’t stick well to pva but in my opinion it’s not sticking well because it’s under extruded.

 

i use locally purchased materials, unsure of brand as they are rebranded by the company who sells them. Been using them for a very long time without any issues.

 

have printed with the same material combinations before without any troubles but that would have been way back on the firmware out of the box when first purchased (12m+ ago)

[kmanstudios 1,120]

huh...if this is new and not something that happened before, I am going to have to defer to the real masters here.

 

Ramping up the layer height on the support interface will just make it more noticeable though.

[tinkergnome 927]

@3DukeEngineering Do you use 'active leveling'? Perhaps is the z-offset of the nozzles not correct?

I would carefully clean the nozzles, make a manual bed leveling and re-check it it makes a difference.

[3DukeEngineering 2]

Thanks @tinkergnome I hadn’t considered the nozzle offset, so maybe I have overlooked the obvious! I only ever manually level the bed as I found it to be much more exact.

 

let me check it out and report back

[3DukeEngineering 2]

Ok so now I’m dumbfounded... I updated the um3 to the latest firmware, and leveled the bed + callibrated the offset. Deleted all cura profiles and reverted back to all the stock settings. 

 

Using the std cura um3 .15 layer height profile I still seem to have the same problem ?

 

right now im totally lost. Perhaps it could potentially be something more sinister than firmware or slicing settings? The wifi board also seems to have failed as I cannot connect to wifi or run any update without a direct wan connection (this has been a problem for a long time though)

 

First image you can clearly see the neat and tidy pva layers.

 

second image you can see the pla it has attempted to print on top.

 

3rd and 4th images are close ups of what it tried to print on top of the pva, this looks like not enough material coming out of the nozzle to me.

 

any suggestions?

 

 

 

 

[kmanstudios 1,120]

OK, this I can see very clearly, I have run into this, The PVA is very caramel colored and does not look like UM PVA. What materials are you using (Brand)? If you covered this, I apologize, I did skim through the thread, but but just got up and having first cup o' tea.

 

When it happened to me, it was a couple of things:

1. Brand makes a difference, but it was the PLA that was the issue.

2. For the first few layers I had to heat up the PLA quite a bit more than the norm to really get it to lay down.

3. I also had to slow it down as it would want to drag it before it would cool into place. You can see tht your PLA is not even really sticking to itself.

4. Different PVA brands have different 'stickability' and do require fudging around a bit.

 

Instead of such a difficult print (lots of thin areas of 'screen' and then border.....try just making a quick border with no screen and use it to test the settings quickly until it is right.

 

Also, is your fan at 100%?

[tinkergnome 927]

in addition: have you checked the 3D model and the layer view?

 

Perhaps it is not printing one or another layer at all - and then tries to lay down the following layer in mid air...?

[3DukeEngineering 2]

13 minutes ago, kmanstudios said:

OK, this I can see very clearly, I have run into this, The PVA is very caramel colored and does not look like UM PVA. What materials are you using (Brand)? If you covered this, I apologize, I did skim through the thread, but but just got up and having first cup o' tea.

 

When it happened to me, it was a couple of things:

1. Brand makes a difference, but it was the PLA that was the issue.

2. For the first few layers I had to heat up the PLA quite a bit more than the norm to really get it to lay down.

3. I also had to slow it down as it would want to drag it before it would cool into place. You can see tht your PLA is not even really sticking to itself.

4. Different PVA brands have different 'stickability' and do require fudging around a bit.

 

Instead of such a difficult print (lots of thin areas of 'screen' and then border.....try just making a quick border with no screen and use it to test the settings quickly until it is right.

 

Also, is your fan at 100%?

 

Correct this is not UM PVA, but I don't know what brand it is (not labeled) as for the PLA im currently using, its made by Imagin Plastics (a local company reputable for high quality filaments)

 

This particular print is for a client, and time is ticking.... I have had to slice the model into seperate sections to avoid overhangs and I will glue them together.

 

I will draw up a small test piece in a couple of days and have a play with temps and speed. cheers!

[3DukeEngineering 2]

13 minutes ago, tinkergnome said:

in addition: have you checked the 3D model and the layer view?

 

Perhaps it is not printing one or another layer at all - and then tries to lay down the following layer in mid air...?

 

Yep, I always check the layer view. Layers look perfect in Cura.

 

When I put some pressure on the build plate so I can see the nozzle while it prints this problem layer, it actually looks like there is just not enough material coming out the nozzle (compared to any other layer).

 

Anyway bedtime here (New Zealand) so I will tinker with a test piece once I have this job finished.