How to get rid of waves on outer walls without changing dimensional accuracy

[wieviele 0]

I am trying to get rid of those waves / ripples on the straight part of the outer wall of my print (see left print in image). I have partly succeded in doing so by disabling compensate wall overlaps, however this resulted in a slightly smaller gap (see right print in image). I need to fit the part on a second print, so the gap needs to be fairly accurate. I have also tried different combinations of:

- Line Width

- Compensate Outer Wall Overlaps

- Compensate Inner Wall Overlaps

- Horizontal Expansion

but I cant seem to get the right settings to have both a clean outer wall and the right size gap. 

 

[gr5 1,293]

Those ripples in the photo at left are underextruding.  And it's over extruding I think on that left corner.  What is happening is the printer slows down a lot for that corner and stops briefly and overextrudes then it slides to the right but it takes a while for the extruder to catch up and stabilize again.

 

Make sure "retract on layer change" is turned off.  Try printing much slower.  That way the speed change will be less dramatic at the corner versus the wall - try printing 1/2 speed - see how much that helps.

 

Most printers let you vary the "feedrate %" on the fly so you can try 5 layers at 100% and then 5 layers at 50% speed and 5 layers at 25% speed and experiment on this one part.

 

And again - make sure "retract on layer change" is off.

 

Also I recommend all printing speeds are the same and travel speed is super fast (like 200mm/s).  So make sure infill speeds, wall speeds are the same.  Speed changes cause over and underextrusion as well (speed up and it underextrudes, slow down and it overextrudes).

 

[wieviele 0]

Thank you for your help, gr5! 

 

"retract on layer change" was turned off already. I tried your suggestion varying the feedrate while printing and it turns out the ripples dissappear when tunring it down to 25%. At 50% they still appear. While this is good news, it also dramatically increases my printing times.

 

With my Speeds set around 25 mm/s, printing time was 40 Minutes for 5g of filament. Turned down to 25% its 2 h 30 minutes. Since I will have to print around 500g of filament to finish my project I am wondering if there is something else I could try. 

[gr5 1,293]

Increasing your layer height won't help as then you will need to cut the speed.

 

Get a better printer?  If this is an ultimaker then your printer is defective - if it's a UM2 series then you probably need to replace the teflon part which only lasts 200 to 1000 hours of printing.  It is expendable.  Like pencils.

 

The easiest and best upgrade is to get a larger nozzle.  Most 3d printers default to 0.4mm or 0.5mm.  Printing with 0.8mm nozzle is double the width but 4X the area and you can print 4X faster volume (because it prints lines twice as wide so you can do one pass on the wall and you can print twice as thick layer height).

 

What kind of printer do you have?  I sell nozzles for most printers out there.

[wieviele 0]

I think I found a solution for my problem.

 

This topic was particularly helpful: 

In the end what worked best for me was:

- outer before inner walls: off

- minimum wall flow: 33%

 

 

 

[yellowshark 148]

On ‎6‎/‎7‎/‎2019 at 3:24 AM, gr5 said:

...  Try printing much slower.  That way the speed change will be less dramatic at the corner versus the wall 

 

Also I recommend all printing speeds are the same and travel speed is super fast (like 200mm/s).  So make sure infill speeds, wall speeds are the same.  Speed changes cause over and underextrusion as well (speed up and it underextrudes, slow down and it overextrudes).

 

 

It amazes me that people still do not get this. Maybe it should be the opening banner on Cura so that newbies are aware. Something I tried fairly recently and is now standard for me, was to reduce the Cura standard print acceleration by 50%. It did not have any real impact on the print time although may partially be due to the geometry, so it is not a guarantee!

[LePaul 297]

I agree, the speed setting... I rarely print over 40/45 mm sec and I know a lot of people like to push their printers to the mechanical wall, going to 100 mm/sec or more.  My prints are usually large and can span a few days.  I'd rather get it right the first time...slowly.  Versus many attempts faster  🙂