If you are planning to manufacture and sell your invention on your own, this is where your prototype and design plans will be really useful.
Manufacturing can be simplified when you have a working prototype of your invention. To start out, contact a manufacturer who is familiar with new product development. That way, you will have the benefit of designers and developers who can identify and fix design flaws. They may even offer a more effective design solution for your product.
If you are going to have your manufacturing outsourced, that is, manufactured by a foreign company, make sure you research the company very well. Look them up online, research them at the library, find out everything you can about them. Foreign sourcing is a big undertaking, and should not be taken lightly.
However, if you have a solid CAD design, a competent manufacturer can produce your product with little trouble. A CAD design will also make it easier to divide your plans among multiple manufacturers, to avoid giving the entire design to one manufacturer if you choose to do that.
You can contact the Thomas Register at 1-800-699-9822 or check out their website thomasnet.com to find thousands of manufacturers for everything you can possibly imagine. You can visit alibaba.com or made-in-china.com for lists of foreign manufacturers for your particular product.
When considering your product with manufacturers, always ask if they are open to reducing or waiving up-front production costs for a percentage of future profits, or sometimes some other deal that they may have in mind. Sometimes a manufacturer, seeing the potential in a new product, is willing to produce the product on more creative terms for a guarantee of future business, or a percentage of sales (sort of like royalties).
Be careful, however, with deals like this. Be sure to put a ceiling on the duration of this deal, otherwise, you can end up locking yourself into a lifetime partnership.
The deal should just be financially worth the manufacturer's effort. For instance, I may offer fifty percent of future sales up until production costs are covered, and then ten percent of sales for a year after, with a guarantee of the manufacturer remaining my exclusive provider for the next year. There are literally trillions of ways to put deals together; it's all in how you negotiate it.