[How to force Cura slicer to perform orthogonal travel paths only?]

We are trying to make a print mixing multiple filaments (the printer is a Zonestar M4 4-filament extruder). the model was sliced by cura.

 

After finishing the print, we noticed that the print show smearing between different color regions - see the print photo below (transilluminated by a light source under the print) - each circular and rectangular regions are supposed to have a different blackness, but they seem to spread out across the regions.

 

 

 

 

We are trying to identify reasons for this behavior. By rendering the print (before adding the color switching tower) in cura, I noticed that there are travel paths that across individual regions - drawing diagonal lines within each layer. see screenshot below (blue lines shows the travel paths - the Extruder 1 is not rendered to show these paths inside) - I suspect that such movement may contribute to the smearing between regions of materials.

 

 

i am wondering if there is a setting I can force cura to only perform orthogonal movement for travel paths - for example, when jumping from one corner of a region to another region, it always move to one of the edges and move along the edge - this way, we may have less cross talk between regions.

 

any suggestions how to minimize such cross path would be appreciated!