Cura Flow

[recoil 0]

I recently calibrated flow in Cura making a 20mm cube with 2 pass walls at .8mm, the hollow cube is dead on at 92% flow the walls come out perfect at .8mm however when I print whole 20mm cube (not just a hollow cube without the top) the problems start I can see under extrusion on the top and scarring on the walls. If I increase the flow I lose the dimensional accuracy but fix the under extrusion, I tried going up from 92% in 1% increments and up to about 94% is around +.05-.08 above .8mm.

I tried playing around with increasing the flow to the outerwall only but still I can't get it right, anyone out there with some suggestions on what else to try? Thank you!

[peggyb 170]

Did you measure your accuracy in x and y as most important or also z?

For x and y you could play with 'horizontal expansion', using + or - values, then you can set your flow separately.

[recoil 0]

Hi Peggyb,

Yes I did calibrate the extruder and then the X , Y and Z axis. My 20mm cubes where coming out great. My last step was calibrating flow with .8mm walls.

I will look into horizontal expansion sound promising, would this allow me to leave the flow at lets say 100% while compensating a minus amount to reduce the size of the walls? I'll go research that option if it works as I hope it does that should resolve my issue,  thank you.

Do you think that the wall thickness in relation to the nozzle size has anything to do with it? My nozzle is .4mm hence it makes sense to do the wall thickness at .4 however I read ...

"Slicers typically will use 20% as the value of the extrusion width, this is due to an effect known as die swell. so for example, if you are using a 0.4mm nozzle the wall thickness, track width or extrusion width should be set to 0.48"

Does this sound correct to you? Once more thank you!

[peggyb 170]

Hope it works for you, let us know..

 

It is a complicated subject, I try to approach it rationally. To my knowledge, and I could be wrong of course, when you change the line width, less material comes out (less flow) and the wall is narrower (what you asked for).

When you set the flow higher, you get more material and the wall swells, resulting in a wider wall than your line width.

If you use less flow you end up to a point where there is not enough material resulting in under extrusion.

Using horizontal expansion shifts the wall in or out using the regular settings.

 

Every model is different and could benefit of the actions above, even different colors or materials act different.

For final object do some tests, print a part, a slice of the model. You can position your model with a -z in the bed to test a critical part and abort when you have enough information to skip time.

[ahoeben 1,948]

1 minute ago, peggyb said:

when you decrease the line width, less material comes out (less flow) and the wall is narrower.

 

These decreased-line-width-walls will also be placed closer to eachother, so given a layer that is entirely composed of walls (eg the bottom layer of a print) you get the same amount of material.

[recoil 0]

Thank you all for your help, I'll get to testing.