Over Molding Moving Parts

[sjoseph]

I want to have produced a small molded assembly ( 1 in x 1 in) that has one moving part. Think of the assembly as a flag with a rod at one end (first molded piece) where both ends of the rod are over molded such that the over mold is like a sleeve. The objective is that, after over molding, the flag/rod piece can still rotate inside the sleeve. Said another way, the over mold does NOT adhere to the rod/flag.

Think of this like one half of a saloon door where the door rod is INSIDE the wall rather than mounted on the side with a hinge. The post molding gap between the flag and sleeve needs to be less than ~1mm.

Is it possible to build such an assembly? I'm an electrical engineer and need to ascertain whether such a structure is possible before I move to the next phase of the design.

Thanks

Scott

[rickbatey]

Scott, I think you may need to change how this is manufactured. You can over-mold most anything but there are limitations. The insert needs to be robust enough so that the injection pressure doesn't distort or become damaged. You have to be able to support the insert so it doesn't move and you can seal off to keep the over-mold resin where you want it. Also all resins shrink as they cool, so your clearance might quickly be lost and the assembly lock together.
You can use different resins to keep them from adhering to one another. Also odds are this will have to be produced in several steps being over-molded in more than one press as not everyone has a two or three barreled press available.
Possible to do but you need to find an injection molding guy to assist you with this.
Rick.

[sjoseph]

Thanks Rick. I was afraid of that. I'm probably approaching the problem incorrectly. I've ripped apart a few products that have pivoting rods inside plastic, but they all appear to be multi-part assemblies (i.e. metal rods attached to plastic flags that are spring loaded into a metal sleeve attached to another piece of plastic). I was hoping to make this uncomplicated.