gas assist question

[jbaredesign]

Any help here would be great. I'm an industrial designer learning more about molding as I go. First time I've posted here, looks like a good community to get some help from.

I was wondering if it's possible to have a hollow cavity created in gas assisted mold to be completely enclosed by the part material. Or will there always be a hole from where the gas is blown in and I'd need to do something post molding to create the sealed cavity. The goal here is to create a single part design that floats.

[tfrounfe]

That's a good question that I'm interested to know the answer to. I've only had very minimal experience with gas assist and they were molding kayak paddles which had to have an open end. I have used rotational molding to create parts that are completely sealed or used two mating parts and either vibration or sonic welded them together to get a hermatic seal.

[rickbatey]

All gas assist will leave an opening that will require post mold sealing. You can mold some plugs and ultrasonicaly weld the plug in.
Now a couple of questions for you: How large is the part you need to float? What resin? Many "shop" resins will float on their own. But there are blowing and chemical foaming agents that can create gas bubbles/voids in parts to reduce the weight. Some will not make great looking parts without painting(blowing); others will look good straight out of the mold. There is also small glass bubbles that can be added to the resin. These options can run on standard machines by using a weight blender and shut off nozzles.
Rick.

[Pilot]

Hi,
not only gas assist process can do this cavity. Are exist other processes, like water assist :-) But anyhow you will have the same issue with inlet and outlet :-(

[rusty]

I have had one gas injection tool that did self seal, the tool worked fairly well but none of us liked the tool design, too complicated for what it did.

[cinazhu]

There always be a hole from where the gas is blown in and out. You can design some plungs to seal the hole later. if you want to know more, please visit thelink below:http://www.cnmould.com/Gas-assisted-Injection-Mould.html

[MIOMY]

Not sure if this is relevant , but a few places I worked were considering using gas assist to core out some thick body side mouldings from the back side, but after tooling mods, equipment, training and the cost of licensing for gas assist ( a yearly cost to renew, not sure if this is still the case) it was decided easier to core out tools with steel and run straight injection. I understand this is different applications we are talking about, but cost is what I am bringing to light !

Good Luck
Ron