Extra Column During Dual Print

[cwsutherland 3]

When I print PLA with PVA support material (and maybe other combinations, that is just all the materials we have) this extra column gets printed as well. I assume it is some kind of transfer/cleaning process between material layers? I couldn't find reference to it anywhere.

[SandervG 1,155]

Hi @CwSutherland, welcome to the forums

What you are referring to is called a prime tower. In Cura if you go to advanced print set up and scroll down to Dual Extrusion you will see it enabled.

It is being used to wipe of any residue that might came out oozing. By printing a layer in the tower you create sufficient pressure in the printhead too, before your print core will be used to print in your model again and it is ready to go!

[cwsutherland 3]

Thanks @SandervG,

So if I were to turn that option off the side effects might be some unwanted residue from the opposing print core or material from the functioning core may not extrude immediately?

Edited November 16, 2016 by Guest

[ultiarjan 1,134]

Indeed, and on top in the case of PVA support the unwanted residue will leave holes in your print after dissolving. I would advice against turning it of for PVA support prints.

For PLA/PLA multicolor prints you can try turning it of. Specially if you also print with lower temperatures (less oozing) you can get good results without a tower.

[Zwakie 21]

Indeed, and on top in the case of PVA support the unwanted residue will leave holes in your print after dissolving.

 

Unless you want to tiny holes I discovered this phenomena myself the hard way recently, but instantly found a way that I benefit from this behavior in one of my prints: I just finished printing an iPad case using Innofil3D PET, which is to be mounted behind an airplane instrument panel.

For this application I definitely do not want the thing to be airtight because that would create pressure differences between the inner part of the print and ambient pressure at flying altitudes, which in the end would destroy structural strength due the tiny bits of flexing that would occur at each flight (think of it as metal fatigue).

So what I did was simple: used a rather thin line-width for the infill and used zero room between the PET and PVA. That this idea worked out perfectly was shown when I submerged the print in water: zillions of tiny little air-bubbles rose out of the print when it was slowly filled with water. Funny experience this print

Long story short: I guess what I am saying is that there might always be a good application for phenomena that in most cases are unwanted

[ultiarjan 1,134]

LOL that may not be very good for the part's strength.... guess I would prefect to model a few holes in CAD...

[Zwakie 21]

LOL that may not be very good for the part's strength.... guess I would prefect to model a few holes in CAD...

 

To be honest, I was afraid that it would have a noticeable effect on strength, so I just went ahead and tried to see if this idea would be viable. When the print was done I was pleasantly surprised that I could not feel/measure any decrease in strength or rigidity compared to a previous non-permeable print of the same case.

Of course time will tell how it will hold, but I am quite confident it will do just fine.

[Zwakie 21]

guess I would prefect to model a few holes in CAD...

 

I was holding off of designing those holes in because I did not feel like going through a very time-consuming exercise finding out how to make sure every cavity (or eat least most of them) within the infill gets a little 'leak'. Fortunately I discovered this phenomena around the same time and was able to make it to good use

[Zwakie 21]

OK, here is my 'miracle permeable' iPad Mini case mounted behind the panel. Material used is Innofil3D PET, used support was the 123-3D home-brand PVA.

Frontview with iPad Mini slide in from the left. The big plug right of the iPad (half visible at the right edge of the picture) is a 2xUSB plug which is held vertical by a 'bump' that is part of the case (see 3rd picture):

Front view of this case with no iPad inserted:

And finally, a behind-the-scenes peek of the test-fit:

The blue part is from a previous prototype and holds the lightning cable firmly in place. The bump underneath this blue part holds the usb-plug nicely vertical plus contains a built-in stain relief for the lightning cable. A little plug not visible on this picture ensure that the lightning plug is not pushed into the strain-relief when the iPad is inserted into the case.

Edited November 18, 2016 by Guest