I'm wondering if someone can help... I have multiple vector drawings of outlines of fish (i.e. they're quite complex) and I want to create an outline that is 3mm away from each original then fill in the gap to essentially create a wide outline - it has to be 3mm as I'm exporting the shape as an svg to use for 3d printing. When I use scaling then cutting out it's hard to get them all lined up and in the right place and when I use offset path it all seems to go wrong. The svg corrupts or creates something really strange even when I move decimal up to 5 and get rid of minify/responsive.
Does anyone have a good auggestion as to how to do this efficiently?
Can you show something please (screenshot or example file)?
I would recommend adding an extra stroke (or fill) at the group or layer level by using the little circle right next to the name in the Layers Panel (means: "Target selection"). You need to open the Appearance Panel and a new effect: Offset Path on your added stroke (or fill).
(If you need real paths - you have to expand appearance afterwards.)
That's pretty much a terrible workflow in the first place. Consider learning Blender and exporting STLs from there. It has quite a few optimization tools for 3D printing, including a wall thickness tool that actualyl makes sense in this context and is able to fix self-intersections, spikes and loops.