Looking at this for a client and I’ve searched the internet. Any kid or pet toy that has a hollow center made out of soft durometer material. I figure it’s some sort of a blow molding process. Some toys have open ends on them but I wouldnt think you could pull a core out of it without ripping the material. Help anyone?
You answered your own question, it’s blow molding. Soft elastomer materials are pretty easy to yank tools out of, especially if the material is still warm. Theres also collapsing cores and other options.
If you have a particular part that is confusing you, post a picture.
Is it blow molding or roto molding?I always assumed roto and then they IP the squeaker and either insert mold it or assemble it post.
Blow molding is a good technique for molding these toys but mostly if the product has to have a relatively strong and lightweight outer shell. It also has a cycle time at least 10x faster than rotational molding. But the advantages of rotomolding are that it works for more types of polymers including soft PUs, tooling costs are much lower, and it is easy to experiment with production parameters. That is the reason why these toys are often rotationally molded.
Thanks guys. I wish there was a video of this process. Normally I can just youtube any manufacturing question and see it on youtube or on old clips of “how things are made”. I’m curious if they use a rotomolded process, they must do multiples of them and I envision they put these molds or mold (with multiple cavities) on a rotating 2-3 axis mechanism.
Haven’t done any squeeky toys myself, but for the dog toys I’m thinking of, I would have assumed blow molding since usually there is a good smooth finish and an obvious clamp mark for a gas injection point, plus the smaller size and surface finish.
For anything I’ve seen rotomolded I always felt like it was larger parts, poor exterior surface quality, and usually the higher cycle time makes it not great for super cheap stuff.
But I admit I could be wrong and just basing those assumption on samples I saw long ago. Never touched either process in my line of work.
forwarding this to a guy who has actually designed these… Hopefully we can get some insight.
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.
Here is a video:
I recommend vinyl because it looks great and can be downcycled into flooring.
You can look into extrusion blow molding TPE or EVA but it will likely require some R&D before the factory gets it right.
Wow, wonderful responses everyone! Very helpful!
You’ve got questions, we’ve got answers.
If you are thinking of importing PVC products, be aware that they can contain material that is prohibited for sale in California or prohibited for sale without labeling. The law is called Prop 65. The list of materials is available here: https://oehha.ca.gov/proposition-65/proposition-65-list As a designer, you can’t really validate this in your garage, but inspection services can. Some services are Bureau Veritas, SGS, MTS or contact a testing laboratory. Even in Canada, most labs have a prop 65 testing protocol.
I’ve always used roto casting too, with spray ops for any deco. Like Ray mentions, you really need to watch out for some of those materials, especially including Phthalates, which are commonly used to soften material used in roto casting.
You’ll also have to consider mould if you’re considering anything that goes anywhere near water.
As an aside to the manufacturing of the outer, if you’re looking for it to make any noise you can have some fun playing with different bellow sizes and different reeds for a great range of sounds! And they don’t all need to be reeds, they can be compression and even things that you bend that make unusual sounds! Great fun to play around with, really makes you feel like a kid!