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Additional features

Posted by cemkalyoncu 
Additional features
December 05, 2015 01:13PM
There are couple of features that I think can improve printing. These are all additional features not improvements to existing ones. I might do that in a different thread. I need to mention that I have only printed with PLA until now.

Speed limit by Z-height
Some objects are hard to print. Printing a thin axle for instance. Even when using brim, it falls of after a time. I took some time and noticed it happens when printing high speed regions and slowing everything down helps. But then the first half that has no problem at all would be slower. So a solution could be speed limiting based on height. Settings could be like following:
Slow down start height: 50%
Speed at top layer: 50%
So lets assume that we are doing perimeters at 50mm/s of a 100 layer print. At layer 50 speed would be 50mm/s but at 75 it would be 37.5, at 90 it would be 30.

Multi layer brim
I know I should use raft when adhesion is big issue. But rafts are hard to remove and brim does not always stick to the surface hard enough. A second layer on top of the brim would force it to the bed and make it stick stronger to the surface.

Temperature over bridges/overhangs
Lowering temperature reduces layer bonding, but increasing it causes issues in bridges/overhangs. Since Slic3r can detect them, it would be nice to set temperature of these cases separately.

Top layer fan speed
Full speed fan helps to smooth pillowing at top layer. It would be nice if we can set fan speed for top layers.

Pause after retraction reset
I find that my extruder takes a short while before it starts extruding again. A setting that allows a pause after retraction might be useful.

Extrusion multiplier for first level
My bed is almost perfectly at 0, almost. Extra extrusion at first layer can fill that missing part. Right now, there are very tiny gaps between lines which doesn't look very good. Additionally, I can easily tear the external perimeter of the first layer.

Disable retraction for first layer
Retraction on the first layer causes problems with tiny parts. Tiny bit under-extrusion caused by retraction can cause small perimeters to start too late. Creates serious problems.

Twin towers
I think that this is extremely hard to implement but will help immensely. Sometimes there are towering parts that are further apart. Instead of doing them one layer at a time, it would be much faster and less error prone (I will explain) if these towers could be done couple of layers for one them then the other. This would use Sequential printing settings for extruder clearance. Right now, moving from one tower to another sometimes causes extruder to touch the destination tower too hard and after a time knocks the object out of printing bed.

In-out perimeters
When there is no infill, instead of continuously doing inner perimeter then the outer, it would be much faster and cleaner to start from inner perimeter on a layer and start from the outer on the next. This means there will be no non-printing movement at all.

Internal brim
Sharp corners warp and bend easily, brim is there to fix it. But it is not generated for interior perimeters. It would be nice to have this as a setting.

Gradual bed cooling
I use high temperature (72) for first layer, than reduce it to to a low value (55) for PLA. I sometimes use Cura which does not support temperature change after first layer. Thus I do the same manually. I noticed, if I slowly reduce bed temperature the object sticks on the surface with much greater force. I even think that the high bed temperature should be kept for the second layer as well. This needs additional experimentation to be sure.

Edited 2 time(s). Last edit at 12/05/2015 01:18PM by cemkalyoncu.
Re: Additional features
December 06, 2015 08:48AM
A lot this can be done with modifiers. And I think the retraction issues can be fixed with "extra length on restart".

The thicker first layer is done simply by increase first layer height.

Thicker brim, and internal brim, can of course be modeled in.

The towers problem should not be occurring, if the previous layers were printed right. This might be another retraction problem; if not retracted enough, you will get a blob on the next tower which will snag the nozzle next time.

Bed cooling of course could be done by modifying the gcode.

The in-out perimeters is the only one that would seem to not be do-able another way, and would thus need to be a new feature.
Re: Additional features
December 06, 2015 09:23AM
I played with extra length, but it seems it causes over extrusion in the long run. Might give it another try.

Increasing the layer thickness increases the spacing between lines in the first layer.

I agree some features can easily be done (I do change gcode to get cooling right) and modify models to have internal brims. But same can be said for the supports. It is easier if Slic3r can handle them. Sometimes it is hard to find the right place in the gcode (for instance increasing fan speed for top layer) to modify.

Retraction is a hard thing to get it right, with a little help some of these extra features, it might not be that critical.
Re: Additional features
December 07, 2015 07:34AM
Multi-layer brim is easily set up by using the "skirt" with appropriate variables instead of "brim". Set skirt number of loops to a high number (= size of brim), set skirt distance to zero (so it becomes a brim instead of a skirt), and skirt height to 2 layers.

You could also set both skirt and brim - set a skirt as described above but with a skirt distance of (say) 0.5mm. Set a brim also. This should result in most of the brim being 2 layers, but with a small gap around the print on the second layer only, making it easier to remove (I've not tried it, but it seems like it should work that way).

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