Advice for plastic invention product

[IAAM]

I have an idea for a new product dealing with plastic top covers. Can anyone provide any ideas and or suggestions how I could go about getting this idea created into a product for manufacturing? Taking into consideration the product is a success, should I have a prototype already in possession when I contact a plastic manufacturer or should I share the idea and if they see it as a success have them manufacturer it and I receive a percentage of the royalties?

[The Stealthy One]

Definitely have some prototypes made. There may be flaws in the design, which are not apparent on paper, but bothersome in reality. Plus, no manufacturer will give you the light of day without a tangible sample. Real-world use by a few testers would help, as well.

[jasaunders]

Find a mechanical engineer to work with. They will be able to help you determine what plastic material to use, how to manufacture it, and will create the CAD drawings necessary for manufacturing.
You can use www.emachineshop.com to make cheap prototypes yourself.

[Nigami Enterprise]

Defnatly get a prototype made either by a company or yourself depending on the product. Manufacturers only make things not design them. Check out ebay aswell you can buy some plastic beads which you can design things out of i find them great for prototypes so much better then clay