Hey Guys… are you ready for class?
I’m kind of busy so i rushed through this, hope it helps.
So Many Ways.
Vinyl/PVC toys like bath toys and the cheapest dog toys are usually rotocast in a bank of molds that get filled with liquid, pelletized or powdered raw materials. This goes in to a furnace, spins real fast and then comes out to cool off, the toys are ripped out of small opening in the mold which creates a sloppy area on the part and its usually trimmed and filled in with a molded plug that would house the squeaker. This can also be done in a slush casting process using a vinyl plastisol. In some cases you might rotocast liquid RTV materials. Most of these materials are not highly durable.
Latex is slush cast or slipcast just like ceramic in plaster molds. slightly more durable than vinyl depending on how you measure but with a much shorter lifespan.
TPE’s, a very wide class of Thermo PLastic Elastomers can be blow molded or injection molded. (in my experience vinyl and pvc used for blow molding is rigid and not the same low durometer “squeakable” stuff used in rotocasting). In blowmolding there is obviously no core but you have wall thickness limitations. When injection molding there is a core or mandrel suspended in the mold cavity. For minor undercuts you can use the ejection stroke to remove the mandrel if you design the tool right but in most cases of hollow parts its a manual process where the part and mandrel are removed after each shot, mounted on a fixture and either leveraged off with brute force or if there are no other openings in the part you can run an airline through the mandrel and blow compressed air through to launch the parts off like a rocket.
Thermosets or vulcanates like natural rubber can be compression molded, injection molded, or compression/injection molded.
Same process as above but natural rubber has a higher stress/strain than most TPE so you can pull enormous mandrels out of tiny holes.
And when it comes to elastomeric materials natural rubber is incredibly durable
on my first trip to China i saw a part from my company that was 8" in diameter with a .4" wall thickness that was molded over a steel core that was pulled out of a 1.5" opening in the part. The part had nearly a 10 minute cycle time, two cavity mold, when the parts came out 1 worker would pick up the core and part, and hang it from a fixture while two dudes with bulging biceps used tire spoons to wrestle that part off the mandrel. At this point there have been millions sold.
On my last trip to China i saw a pneumatic machine that i designed to help bring some automation and robot assistance to this process on the production line of every rubber supplier i visited, i only ever sent the plans to one supplier.
I’m sure there are more possible process but this is what i have experience with.