Feature Request: First layer after infill speed

[Guest]

Hello,

 

I looked in the settings, but there didn't seem to be anything that jumped out at me to try.. other than to slow down the entire top surface skin speed, which would affect a number of layers and perhaps not even all the ones I'm interested in.

 

The reason for this request is so I can slow down the first skin layer that gets printed on any infill.  This to me is more like a bridge operation, especially when you have a low % of infill.  I've manually set my printer to 50% speed when I notice a skin being printed on infill and it comes out much better, leading to the following layers (which I reset to 100% speed again) to be completely defect free.  If I leave the speed at 100% for the whole job, I can see the skin gets better as each layer is applied, but my usual 3 layers for a skin is sometimes not enough to iron out all the kinks.  "Sometimes" meaning it depends on the material type and quality.  I could add one more layer too, I suppose, but I wouldn't have thought this one extra option for speed wouldn't be useful to others too?  (When there are already so many.)

 

Thanks.

[gr5 1,121]

I don't think this exists.  I was going to suggest going to 4 layers instead of 3 but you already suggested it.  🙂  Note that 4 layers instead of 3 will take the exact same amount of time as printing the first of the 3 layers at 50% (but a little more material).

[yellowshark 143]

personally I am not sure what the problem is; just add a layer or reduce the top layers speed; if you are printing fast enough so that the first of the top layers does not print well over the infill then you would probably want to reduce the speed of the top layers anyway to ensure a quality surface finish.

I have not used it but you could also use the option Gradual Infill Steps which, as I read it, seems to increase the infill density as you approach the top layers - indeed this may be a very good solution. But it is not a problem I have ever had as I always make sure I define enough top layers, which of course varies with layer thickness, to get a quality surface.

[kmanstudios 950]

I kinda wonder if turning on the 'bridge functions' in experimental would help with this. Kinda doubt it, but, you never know!

[yellowshark 143]

… plus also if you start varying the speed up and down at the top, you risk getting artefacts on the outer wall as the pressure keeps adjusting.

[mastory 35]

I like the idea.  A skin layer immediately over infill could be regarded as if it were a bridge layer.  To insure a smooth top with ABS, I have been printing a minimum of 6 top layers

[kmanstudios 950]

And, you could also use gradual infill steps towards a much denser support just below the first layer.

[Guest]

Thanks for the responses and suggestions, all.

[Guest]

SkinOnFillMaxSpeed.zip

 

@mastory (and anyone else interested):

 

Before I upload this to thingiverse, do you want to try out my first attempt to implement this feature (see attachment) as a post-processing script?  I think this one should be first in the list of scripts, to ensure the G code isn't first modified by other scripts which may pose unexpected issues.  Let me know if it bombs out, or you think I've forgotten anything.

 

I've got some other scripts too, if anyone's interested, basic instructions to install them are in the linked pages:

 

https://www.thingiverse.com/thing:3217695

https://www.thingiverse.com/thing:3260750

 

3217695 = Percentage complete - always goes last in the list of scripts to run

3260750 = Scalable Extra Prime (on retractions and combing)

 

Strange this site doesn't allow .py files to be attached (which is why I zipped it).

[Guest]

SkinOnFillMaxSpeed.zip

 

After printing a rather large item, the baker-cube from thingiverse, I noticed some problems (nothing went wrong with the print itself, it was just slower on a few layers, that I didn't expect to be slower).

 

The Public Domain routine I had used for detecting line segment overlaps was returning false positives.  E.G. Lines in diagonal quadrants said they overlapped.  So I changed that algorithm out for one I understand a bit better - which seems to work well now.  The new one says it doesn't detect when a line completely overlaps another - but this is desirable, as that one line can go full speed.

 

Also, I'm pretty sure if a skin line-end touches infill, it causes any skin layers after the initial one to also slow down.  I've added a configurable setting to trim skin line ends (I guess the nozzle size affects this too in Cura?) so the line needs to actually cross infill now..  The default of 0.7mm I've chosen seems to work well for me with a 0.4mm nozzle.

 

BTW: This test print only had two skin layers and it came out better than a lot of other prints I've done with 3 or 4.  I'm now far more confident lowing the infill % below 25% which was my go-to setting.  I'm not sticking to 2 skin layers though, 3 is fine.

[Guest]

https://www.thingiverse.com/thing:3314235

 

Thingiverse link, in case anyone wants it (185 people in the two days it's been there did).  Because I wasn't sure what the experimental bridging in Cura offers, there's also an additional version that allows you to slow skin layers over support.  I'd call it very experimental though, since it relies on there being 1 layer in-between where the infill stops (current layer tests support from two layers ago).  I'm guessing this isn't always the case depending on your settings for support?

 

You could fairly easily add extra support buffer arrays to make it work with your own settings though :)