detailed control over g-code generation?

[jbeale 0]

I am new to the Ultimaker system, having previously used a Makerbot with its own software MakerWare. On that device, when I print out a conical shape, I notice there is a visible seam along a radial line, where the head steps up to the next layer in the same relative position each time. I believe this is caused by the slicer software, since there is no such feature in the original CAD model (STL exported from OpenSCAD). See for example the photo here: http://www.thingiverse.com/thing:340161

I gather the Ultimaker machine runs on g-code generated by the Cura software. I have skimmed through the Cura manual, and downloaded and played briefly with the program, but I do not see many detailed controls. Is there a way to tell it to randomize the relative position where the head steps between layers, to avoid that straight radial line on the surface?

 

[illuminarti 18]

Cura doesn't allow you to specify the position of the z-scar, no. It is one of the controls which has been sacrificed in the interests of a simpler UI.

However you are free to any other 'generic gcode' slicers such as Kisslicer or Slic3r, or the commercial (and, IMHO, excellent) Simplify3D. Those provide more control over the layer start positions.

 

[Daid 301]

Currently Cura uses the last ending position on the previous layer as start position for the next layer.

It would actually only be a few lines of code to randomize this (for a quick solution). A proper solution would actually look at inner corners and put the Z-Scar there. (Maybe even randomizing if it finds different proper corners)

 

[gr5 1,872]

If you are patient you can make the Z scar almost non-existent by slowing it down to 20mm/sec because you don't get any oozing when you print that slow. Also it helps to crank up the Z acceleration to lower the time it sits there moving the Z.

Daid wouldn't it be even better to move the head to an "infill" region of the part during the Z move?

Most of my parts have no visible Z scar by the way (at 35mm/sec).

 

[Dim3nsioneer 556]

Currently Cura uses the last ending position on the previous layer as start position for the next layer.

It would actually only be a few lines of code to randomize this (for a quick solution). A proper solution would actually look at inner corners and put the Z-Scar there. (Maybe even randomizing if it finds different proper corners)

 

Do I read too much between the lines if I just saw the word 'currently'? :???:

How much effort would it be to realise the proper solution? I think the quick and dirty solution is not much better than the status quo.

The interesting question is how to deal with e.g. a cylindrical shape. How limited are you by patents?