Using different extruders for top/bottom infill?

So yeah, like the topic says. I have a dual extruder mendelmax and basically I'm trying to use one material for the entire "skin" of the object (perimeters + top fill + bottom fill) and another material for the "core" (infill). I can set infill and perimeters separately just fine, but the top and bottom patterns are always done with the same extruder as the infill. I want them done with the perimeter extruder. Is there a way to do this?

Thanks!

I'm incredibly new to this, but I've seen that it is possible to combine two STL files into one print. It may be that you need to split the top and bottom surfaces into a second file, and have that file print in the "skin" material. That top/bottom surface file would have no infill, and you would set the top/bottom surface "horizontal layers" to zero on the main file so that it doesnt print those features.

That is a good idea, but unfortunately it doesn't work from what I have seen. When you set a multi material part, it will print each part with the different extruders. To get what you want, you would need to shell the part, print the shell using one extruder, and the core with the other. Unfortunately there is no way to specify different print settings for each part though, so you would need to ensure that all of your settings are compatible with both extruders.

Update: you can do what you want to do now, just create a shell for one extruder, and the infill for the other. Then you will need to set the perimeters for the inner part to zero in the settings over rides for the part. Also, any changes to extrusion width or other things would need to be entered here. Not the ideal way to do it, but it will work for now. A lot more futzing than should be necessary, but you will get the desired result.

Actually a better way to do it rather than shelling it, is to make sections of the bottom and top that are as thick as you want the bottom and top layers to be. These would print completely with one extruder. Then print the central section with one extruder for perimeters, the other for infill...A little less work than my previous work around. Still not quite ideal, but should result in a better part. Shells tend to have problems with slic3r.