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justin-woolich

Improving Surface Finish

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Hi, i have recently purchased a ultimaker 2, i have been working through various designs and i am trying to improve the surface finish of the top of one of my designs.

The print head seems to slice up the layer into triangular sections and this leaves visible lines on the surface. Is it possible to have a more consistent surface finish

x6ct.jpg

 

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Hi Justin, and welcome. What you've found is one of the biggest annoyances in Cura, for me. I wish it would treat exposed horizontal surfaces with more care, and do more to avoid making marks like that.

There's not a lot you can do, but tweaking your retraction settings in Cura's Expert settings may help. Set the minimum travel distance to a small amount - maybe 1mm. Turn off the 'enable combing' option. And set the minimal extrusion amount to 0.

This will ensure that it retracts the filament when making those positioning moves, so it will be less likely to ooze a trail of filament that then had to be covered over and leaves a scar.

I think it might also be a good idea to actually lift the head off the print for these finished surface moves, as even without oozing filament, there can be some scratching of

the surface, but I haven't tested that.

It might also help to increase your travel speed moves to something higher like 250mm/s, so the head has as little time as possible to ooze plastic during its move.

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If you got rid of those holes it would probably look better as Cura wouldn't have to go back so many times and fill in the gaps it didn't get yet. But I assume that's not an option. :)

You could also make the suface - not flat. Maybe make it curved? Add some interesting line patterns to it? Or hexagons or some cool pattern?

Also you can put the surface you want to look best on the bottom, set the temp very high e.g. 240C for the first layer and increase flow to 130% for the first layer. Then when first layer is done put everything back to normal.

Cura isn't perfect but it gets better every month.

 

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Yes, indeed. Although the slicer itself is going to have a much better handle on what is going on, and when it's doing flat areas of exposed solid infill. Trying to figure it out after the fact based on inspection of the gcode is going to be very hard.

And it's a very obvious artifact that reduces print quality, and gives the impression that UM printers produce 'ugly' prints. So I hope it will get some attention from Daid and the UM team.

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If you got rid of those holes it would probably look better as Cura wouldn't have to go back so many times and fill in the gaps it didn't get yet. But I assume that's not an option. :)

 

In theory the order of printing the fill areas could be better. However, this is a traveling-salesmen problem.

http://en.wikipedia.org/wiki/Travelling_salesman_problem

Right now the code just goes to the closest line it can find to print next. Gives decent results with a limited amount of long moves. But not always optimal.

Because I knew this can be optimized, I've put the implementation of this printing order in a separate file:

https://github.com/Ultimaker/CuraEngine/blob/master/pathOrderOptimizer.cpp

Now it's just waiting for some crazy person to optimize it. (I do not have the proper background in computer science)

 

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Thanks for the additional replies, i found that the settings suggested above seemed to clean up the top surface to a degree, i have also been experimenting with using acetone vapor to give a good final surface finish.

The settings i am using are:

Minimum Travel (mm) = 1

Enable combing = false

Minimal Extrusion before retracting (mm) 0

 

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As Christmas is close, I wrote a small present for all of you who wants to get rid of the combing lines on horizontal top surfaces.

https://github.com/Dim3nsioneer/Cura-Plugins/raw/master/RetractCombing.py inserts retraction for G0 movements (combing movements are G0 movements) on a specified height. You can specify the minimum and maximum height (e.g. it makes sense to set 0.49mm as minimum and 0.51mm as maximum if you want to have the plugin to work on your 0.5mm layer). You can specify a minimum distance under which no retraction will occur (default set to 2.0mm). Furthermore, retract distance and velocity have to be specified (the only possibility for prints with otherwise no retraction).

Optionally, you can also tell the plugin to lift the head (actually lower the z stage) during retraction.

I declared the plugin as test version and used the same version labeling scheme as Daid for Cura (hopefully, nobody will be confused by this...)

This plugin might also be combined with the TweakAtZ-plugin setting the speed to a lower value for the last layer...which gives especially nice prints...

 

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If just cura did a small z-lift on non-printing moves. Like 0.1-0.2mm then it would make a nice finish.

 

Actually that creates little vertical spikes. "non-printing" is harder than one would think.

 

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Actually that creates little vertical spikes. "non-printing" is harder than one would think.

 

The spike effect could be minimized with a low temperature (which you would anyway use for slow printing the last surface). And not all the PLA blends behave exactly the same...

But you are so right... this was my major finding when fighting with the dual extruder...

 

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i have also been experimenting with using acetone vapor t

 

This does nothing for PLA but works for ABS. Are you printing with ABS? If PLA, then THF can be used as a solvent. If you buy THF make sure you get it "with inhibitor".

Be careful with Acetone and THF as I believe these are quite toxic and quite flammable.

 

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