Interface pattern spacing - what is it?  

RE: Interface pattern spacing - what is it?

First of all it has no relation to infill.

Support is External to the model and supports the exterior surfaces, it is able to be removed after printing. Infill is internal and is used to fill up the interior spaces, it cant be removed afterwards as its inside.

External Support is made up of 2 to 3 parts.  This is the base layer, that can either be on the bed or on the exterior of a model part.  The main support which is printed upwards towards the external surface needing support and then the support interface, which is the bit between the support and the model itself.  If the support is on the model then there will also be a bottom interface layer.

If you slice a model in prusa slicer it takes you to the preview screen.  Learn to use it all the time.  It allows you to check that the slice is ok and by scrolling through the layers you can see potential problems before printing.  Of course spotting them takes experience.  The preview also has a colour coded key for the types of printing.  That key will show you support (a light green) and support interface (dark green).  So slice something that needs support and experiment with the settings and see what it changes on the preview.  Its the fastest way to learn the basics.

You can choose the spacing of both the support structure lines and the interface lines.  The idea is you use less material by spacing the lines further apart and the interface is more closely spaced.  

The amount of Infill depends entirely on what you are printing.  Firstly more perimeters makes a lot more difference to part strength than any increase in infill.  100% infill can actually cause issues in some cases.  You only really need enough infill to support the printed surfaces above.  This is less than you think.  Normally I go with 3-4 perimeters and 10-20% infill, usually cubic or one of its variants.  

Large flat top surfaces need more infill or they wont be printed very flat as they can sag.  In those cases I'll go up to as high as 60-70% in some cases.  Which is where something like support cubic or adaptive cubic is handy.  Again try different settings and using the preview and slider.

RE: Interface pattern spacing - what is it?

The interface is the section of the supports closest to your model, which can have different settings than the rest of the supports.  For best settings for supports, see https://projects.ttlexceeded.com/3dprinting_techniques_removable_supports.html

RE: Interface pattern spacing - what is it?

So let me see if I get this right - the support interface is what's in physical contact with the model, pattern spacing is the distance between the (light green) lines in the support structure, and interface pattern spacing is the distance between the (dark green) lines in the support interface? I think I used the term "infill" incorrectly, but I would guess that pattern spacing would be the best parameter for changing the density of the support structure? Sorry for the repeated requests for clarification, but in my generation a 5-1/4" floppy was something completely different from what the present generation has likely never heard of. 🙂

RE: Interface pattern spacing - what is it?

Yes  you have that correct. The interface section has a different function than the rest of the supports below that and so can have the option of different settings. The main part, below the interface does the structural work of supporting. The interface has more to do with ease of removal and perhaps the quality of the surface of the model directly above it. 

I remember 5.25 floppy disks, and reading huge trays of punch cards into a card reader.