Different Methods For Over Molding

And the reason you don't mold an o-ring groove and use an o-ring?

Or run a bead of clear silicone sealer around it before assembly?

I thinks the cups are molded separately and bonded (maybe spin welded) together, metal lids, too.

Running a bead or FIM (foam in place) I have seen this before. Not an impressive method. Time consuming too. What do you think about the scissors? Is that a multi shot or a over molding. On a second thought is there a forum specifically for molding related discussions.

I suspect the scissors handles are dip-coated, not over-molded (one can buy liquid compounds for dipping tool handles and such in most hardware stores). Most of the pens like the ones shown that I have disassembled are pretty much put together from separate components, not over-molded (although there are probably as many different ways to accomplish the effect as there are products). The cups are generally manufactured as separate components, so that someone downstream can take them apart and insert their own private spam advertising message in the inner space. You can actually take these things apart and add your own custom decorations.

A picture of what you are actually trying to accomplish might be more helpful...

Simply not enough valid information.

1) What do you want to mould? Show us a picture or sketch.

2) What type of plastic, is it thermoset or not?

MORE INFO. MORE PICTURES.

CADone, a less expensive alternative to the multi-shot mold tool (i.e., one tool for both the rigid substrate resin and then the elastomeric overmold) is to use two sets of mold tools. The first mold tool is for the rigid substrate, then a second tool is used and the plastic part is placed in it like an insert mold and the elastomer is overmolded onto it. Much less expensive tooling than a true multi-shot.