Feature Request: Support Material on first layer / projection of upper perimeter

[stohn]

Currently I try to print (actually I printed it but i had to use crazy low speed) some objects which need a lot of support.

Some difficulties I had so far / some ideas:

using the rectlinear support pattern produces a lot of unconnected short extrusion.

• this is working ok except for the first layer. In order to extrude 1mm long lines only I need crazy low speed on first layer

Picture rotated, look from bottom:

Unfortunately the short perimeter is a bit to long and also seems not to be used for support extrusion.
==> In order to use this an "ultra short extrusion speed" could work (e.g. extrusions which move the head less than e.g. 3mm)
==> Or a projection of the upper perimeter (at least for the first layer) for the support material would help a lot

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Trying to print a complete face inside the air using support material is not working at all

• In order to print a face in the air I always have to add support manually in the 3d model since printing the perimeter for the face on the rectlinear support is not very good at the first face layer but it has to be good since the bridging really needs a good perimeter

The pictures (rotated, looking from the bottom) showing the original without support:


and with the 2 rings manually added by hand (rectlinear support by slic3r) to make it print

... One thing you might notice is that slic3r did not pay attention to the crossing of my thin wall support structure and it's own support. Surprisingly the print was working nice even that extrusion crossed the same point twice. The connected structure was very strong (maybe this could be a feature for strong infill ;-) ?)

==> I think it should be possible to make a projection of the perimeters which are required for bridging. this projection could be used as support material

Overall suggestions / ideas:

• It would be better to have adjustable speeds for first layer for all of the options separately. The factor is a bit annoying since I really have to extrude the perimeters on first layer very slow but the infill can be a lot faster (e.g. perimeter 20%, infill 60% of original speed). You could list the normal speed and the first layer speed next to each other and in case it's not filled the overall factor is used ... or something like this.
• dividing heated bed in 2 temperatures is not the best solution. I would like to have "first layer temp", "XX layer temp" (where XX is the layer number or % of the height) and "final temp". The temperature should be interpolated between the layers.
  E.g. printing the first layer need very high temp, the next 20 layer need high temp to avoid warping, the rest of the layers the bed needs just to be warm to keep the printed object on the table.

P.S. To give you an idea where I am at the moment... (0.3 nozzle, 0.1 layer height, 3mm PLA):

[alranel]

Hello and thank you for the precious feedback and ideas. I usually like to break things into multiple GH issues to track them more easily.

Regarding bed temperature, I do agree, there's already an issue here opened by rotorit and I will do it soon.

Regarding first layer speeds, my main concern is the abundance of config options which are already just too many and a bit scary. I'm considering implementing a per-layer rules system, which is getting requested a lot. This would allow for the speed customization you described.

Regarding support material, I need ideas :) your idea about projecting perimeters is good but.. perimeters are not enough for bridging. Bridges need anchors underneath, so perhaps we should also offset such perimeters to get something like a "concentric" support material...

[stohn]

Ok, focusing on support material (sorry for mixing up topics).

The bridging was working very nice for me by just using the single wall I added. I did not know about the anchors. But maybe the name "bridge" is wrong here since the rectlinear support pattern helped the bridges to make them "short bridges" which might need no anchors.

Concentric support was already in my mind when I looked at the printer printing the object. To have this option would be superior :-)

[alranel]

So, an update on this.

The issue about thin walls crossing support material is tracked in #771.

The problems about adhesion of support material to print bed were solved in the last months by the brim feature and by the solid base flange I recently introduced (available in next release).

First object perimeters will probably benefit from the recently introduced interface layers feature which allows to build a solid area between object and support material.

I'm closing this issue as there's no STL test object, but please do report your feedback as I'm very interested in improving support material by looking at test cases. Thank you!