Types of non return valves

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Choosing a Non Return Valve

Tips for the Injection Molder

How do you choose the best non-return valve for your injection molding machine? One valve is said to provides better shot control, another a lower compression ratio, yet another promises longer wear . . . which is the best for your job?

With hundreds of new resins and material combinations constantly entering the market, making the correct choice is not always a simple matter. A valve that provides accurate shot control may assure that parts are molded accurately and consistently, but might damage shear sensitive materials. A hi-flow valve may prevent shear damage but may not provide accurate shot control. An extended wear valve most likely will cost more initially but can significantly reduce labor costs. How do you make the right choice?

What you need to know?

While almost all injection molding applications require a non-return valve to prevent the flow of plastic back to the screw, the type of non-return valve chosen depends on a number of factors including

The type of resins being processed
Corrosive or abrasive properties of the resin
Any fillers that may be added to the resin
How often the valve will need to be cleaned due to color changes etc.
The temperature of the melt
How fast the screw rotates (screw RPM)

The answers to these questions will give a pretty good determination of what type of valve will work best for your operation . . . now the question is where to purchase it? When choosing a manufacturer, you’ll want to know some specific information about their operation.

How much experience do they have in non-return valve design?
Do they manufacture their own valves or do they have them made somewhere else?
What sort of customer service do they offer?
How well do they back up their product?

After all, it’s not just the cost of the valve you are considering, it is also the costs to install and service it, as well as well as the quality impact it will have on your final finished product.

Understanding what a non return valve does

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