Dual head setup, how to merge two STL's?

Hi, in the Velleman user guide says about printing with two head you can either use:

  • one file with several closed non intersecting meshes
  • combine several STL’s that make perfect fit

I tried the first option, but my CAD program doesn’t generate compatible STL’s for repetier (non manifold, can’t split objects)
About the secind option: How can you import several stl’s into repetier and ‘merge’ them perfectly (tight, non overlapping?

Non Manifold means there is a hole in your drawing somewhere.
You can use Netfab to repair it.

You can merge two (latching) STL’s by grouping them together, basically you drag them onto one another in the object three.

I think you need to combine them to a group.

You can see how to do this in think link.

the link doesn’t show it, it shows the breaking up of a multi mesh file and the possiblility to assign different colours/extruders.

It doesn’t show how to ‘merge’ two STL’s.

On the repetier site it is shown (tutorial ‘how to make a multi colour print’); you indeed need to group them:

After they break it up they show how to merge them into one group.
That is where you need to start.