PVA Layers not bonding strong enough

[toilet-ovule-add 0]

I am working on a prototype which has holes for leds. These holes are dimensioned in such that some pressure is needed to get en keep them in place.

The rim wherein the leds are placed is 4mm thick. In most places i am able to push in the leds without issues, but at other locations the layers are separating after pushing in the leds.
Material is Ultimaker Tough PLA, printing temperature 200c.

What is the best approach to increase the layer bonding ? 

[p-kimberley 4]

With holes as small as this, you might want to try printing without support - or if the other sections of the model require support, using the support blocker in Cura to avoid generating supports for the holes.

 

This will avoid nozzle switching, which can:

1. Cause contamination of support material, as shown in the white stringing and blobs in the second image
2. Weaken layer bonding by dropping the nozzle down to the "final" print temperature at the end of each layer. You can avoid support as mentioned to stop this, or adjust your temp settings to lessen the degree to which the temp is lowered towards the end of the layer.

 

You could also enable the "Prime tower" setting, which can help with contamination - though at the cost of additional filament, especially for tall structures.

Edited March 21, 2020 by p-kimberley

[toilet-ovule-add 0]

@p-kimberley

 

Ah contamination, did not expect this to be the issue. Wil try to use the support blocker at the position of these holes.

 

 

[geert_2 557]

I would say: make the holes slightly smaller, and drill them out manually with a drill that is still 0.1 or 0.2mm smaller than the desired size.

 

Maybe you could also design a simple 3D-printed retention clip into the case?

 

Try various dimensions on a small test piece first.

 

 

[toilet-ovule-add 0]

On 3/23/2020 at 11:52 AM, geert_2 said:

Try various dimensions on a small test piece first.

 

I always print small test pieces, but in the end it has to come together. There is where it failed here.

In the next full print i will try to use an ooze shield, to prevent contamination of the print by the support material. 
Will also try to prevent printing support material in the holes by changing the support overhang angle. If that fails i will see if i can print as simple clip in the holes which can be removed easily afterwards.

 

Thanks 

[Mari 36]

What is the recommended printing temperature given by the manufacturer?

 

The manufacturer of the PLA I use says: 195-215... I tried a lot of different temperatures, I get the best results at 210 (on my printer).

 

So try a little higher temperature en see what happens...

[toilet-ovule-add 0]

 

6 hours ago, Mari said:

What is the recommended printing temperature given by the manufacturer?

 

I use Ultimaker Tough PLA, use the adviced temperature of 210 and 215 for the first layer

 

Think p-kimberley did point me in the right direction which is contamination of the printing material by support material.

I am now revising the design, making testprints of parts of the design and then if all seems ok print it once again in full with an ooze shield and remove the support printing in the holes.