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The compressed air dryer uses air that is provided from an existing air compressor. The air passes through a heater before reaching the pellets. At the compressor, the air loses moisture and the dewpoint typically drops 25 degrees Celsius or 45 degrees Fahrenheit below the dewpoint of the ambient air within the room. Since the dewpoint is not as low that of a desiccant dryer, they are not commonly used for highly hygroscopic materials such as nylon and acrylic.

These dryers are growing in popularity with respect to two purposes:1) Small Batch Drying – although these dryers are not the most effective method of drying, they can be used to dry virtually all materials, but they often take as much as 50% more time to accomplish the task. 2) Supplemental Drying – although many molders are trending towards large centralized material delivery systems, the material resides at the hopper for a period of time. Small capacity, compressed air dryers are a helpful method of maintaining a dry material at the hopper, especially during a process interruption.

-Andy

I am using u-pvc injection molding for pvc pipe fittings.

When running a male addoptar which weight about .05 kg we are observing burning in the end of injection, what its cause?

In such cases, the cause is degraded material. PVC most often degrades whenever it either stagnates in the nozzle or adaptor or remains in the barrel too long.

PVC molders often have a habit of increasing the back
pressure above what is necessary to create a consistent melt. This tends to promote degradation and burning of the material.

-Andy

Hot air dryers are typically used to either remove surface moisture or preheat the polymer.Since they do not significantly reduce the dewpoint of the air, hot air dryers are not an effective method of removing moisture from hygroscopic polymers.

Even if you get the parts to mold, hydrolysis will occur and the parts will not have the strength and impact resistance to be effectively used.

When preparing such a highly hygroscopic material, it is critical that you use a low-dewpoint material dryer such as a desiccant or vacuum dryer.

-Andy

Shrinkage is a measurement based on change, and is a represented as either a ratio or as a percentage. The correct method is to determine the difference between the mold and part dimension and then divide that number by the mold dimensions.

ratio = (mold – part) / mold

% = (mold – part) (100%) / mold

The method used by your engineer is close for small shrinkage values, but the disparity becomes increasingly larger as shrinkage values and dimensions increase.

-Andy