vertical holes too small in cura

[chriswal 0]

Hi,

i know ..again the too small holes story :-(

i am using cura 3.6.0 now ....i know there are a lot of these threads already ..with overextrusion ... not round holes ...material shrinking ..

but cura does it in every version the same way ...same size ..outer measurements are ok but holes are too small

i am writing this now , because i am printing now with a nozzle size of 0.1mm so the overextrusion cant be the problem anymore, and if the material is shrinking it should be also seen on the outer measurements.

when i am using the horizontal expansion it also changes the outer measurements.

 

for me it looks like there is some correction done on the outline, but not on the holes?

any ideas how to correct this in the right way?

 

ANet A8

Marlin 1.6.0

 

[geert_2 558]

Probably this is not due to overextrusion, but due to the fact that when making a tight corner, the molten material is *pulled inwards* while still liquid. It's like trying to pull a rubber band around a hole: you pull it in the hole, not around.

 

What I do is or calculate that effect into the design, thus design the holes a bit bigger based on experience and trial and error. Or else go through it with a drill afterwards. Use only a manual drill for PLA, since electric drilling melts the PLA.

 

 

 

[chriswal 0]

hi,

yes it is possible to be pulled inwards, but due to the fact that it should be connected to the previous layer it should be a factor of the extrusion width. as the measurements are constant (between different nozzle sizes), it looks as if there is some shrinking compensation calculation going on in cura,because the outer measurement fits exactly. if there is a shrinking it should be smaller the expected. then i could upscale the object (and the holes would get bigger too).

 

 

 

[geert_2 558]

Slimy liquids do not really "connect" to anything. You should try this at home with liquid honey, yoghurt, or even mayonaise. Try to pull them into circles on top of each other, while pouring them.

 

It takes some time before the extruded sausage cools down and solidifies. In small holes, the nozzle is always too close to the rest, and keeps radiating 200°C, so that area does not really cool down at all.

 

The same happens with printing small cones, like this test. As soon as the diameter gets too small, the top surface can not be cooled anymore, stays liquid, and deforms. Printing a dummy block next to it helps, as does printing as cool as possible, but it does not eliminate the effect.

 

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[chriswal 0]

if i print a cylinder 5mm with walls first (thats the same as printing holes, because its the ring first)

then it should be the same like printing a 8mm cylinder with a 5mm hole(with walls first).

 

it lays a ring of material (5mm) ....outside or inside?