Plastic and Metal Gear Selection

Ordinary plastic gears expand when they absorb moisture. Internal stresses are relaxed, and the tensile strength drops by 50% or more when fully saturated. Changes in internal stress can also cause plastic gears to lose their shape. When that happens, the weakened gears don't mesh smoothly, and teeth wear out prematurely, chip, or break.

The plastic composite outside layer of the Power-Core(TM) gear does not absorb moisture. It loses less than 10% of its tensile strength - and grows less than 0.2% (a negligible amount in gear design) - even when immersed in fluid, see graphs.

Adding to Power-Core's extreme dimensional stability is the rigid metal core, which absorbs and evenly distributes stresses when transmitting torque. It is firmly bonded to the outer composite, reducing thermal expansion of the gear by up to 50%.

In this second graph you can appreciate how well the Power-Core(TM) gear works to maintain tensile strength even when immersed in fluid.

When plastic gears don't retain dimensional stability, the spacing between the gears - backlash - also changes.

"Backlash" is the minimum clearance in the teeth mesh to allow gears to turn freely. To compensate for swelling caused by moisture, the backlash in plastic gears has to be increased, typically about double that of metal gears. Additional spacing is required to compensate for thermal expansion, and so the total backlash can be sizable.

Because Power-Core(TM) gears have minimum thermal expansion and are dimensionally stable in moisture, backlash compensation is reducing backlash to a minimum. Large backlash increases gear noise, affects shaft timing, and causes shock load on gear teeth during speed variations. In plastic gears that swell, the pitch diameter changes also, leading to increased wear. Changes in backlash will lower the gear's AGMA class.

Metal gears can be noisy. But with their self-lubricating composite outer ring, Power-Core(TM) gears run quietly, reducing noise levels by 6dB or more vs. metal gears. And when compared to other plastic gears, Power-Core gears run about 3 dB quieter because of the smaller backlash.

As for weight, Power-Core gears are 4 to 7 times lighter than equivalent steel gears.Lighter weight reduces drive power requirements and inertia. So Power-Core gears can accelerate, stop, and reverse direction more easily than steel gears.

Metal gears, enclosed in gear boxes or as open gearing, must be regularly lubricated to maintain smooth operation and to prevent wear. Oil leakage from housings and seals and loose grease can contaminate and ruin paper, pharmaceuticals, and other products.

With teeth made of a smooth plastic composite, Power-Core (TM) gears require no gear box or lubrication, eliminating oil leaks and reducing maintenance costs.

The Power-Core (TM) metal hub allows one-piece concentric machining. Pitch-line tolerance can be held to AGMA Class 10 or higher, a standard for gear tooth quality specified by the American Gear Manufacturers Association.

The gear blank is clamped onto the metal hub during machining, eliminating clamping stress that can cause pitch line distortion in all plastic gears. The pitch line is referenced from the precision bore in the metal.

The homogenous crystalline structure of the cast-on plastic ring provides uniform resistance to the cutting tool. This uniformity minimizes variations of the tooth surface, decreases pitch line runout, and enables narrow backlash tolerance.

Unlike other plastic gears, injection molded or machined, Power-Core's lack of internal stresses and greater dimensional stability allows the gears to retain the high AGMA class when installed.

The unique Power-Core (TM) technology enables our gears to perform under adverse conditions including harsh chemicals, moisture, shock loading, and extreme temperatures.

In corrosive or wash-down applications, the hub can be fabricated from stainless steel. When inertia must be kept to a minimum, an aluminium hub is used.

A unique combination of tensile and flexural properties allows Power-Core gears to absorb vibration and shock. The Power-Core gear retains strength over a wide temperature range from -50 to +200 degrees F. Tests show that the gear teeth become stronger at about 150 to 180 degrees F, long after other plastics failed.

Power-Core (TM) gears last up to 12 times longer than non-lubricated steel gears. The durable, long-wearing Power-Core technology eliminates problems of excessive wear, premature failure, and costly, unplanned down-time.

The non-hydroscopic, crystalline structure of the plastic composite reduces stress and increases the gear's wear life.

Intech's engineers perform special state-of-the-art engineering calculations for each gear design and application to ensure lasting performance where other gears break down.

Power-Core (TM) gears exhibit a high load sharing factor, an important quality when handling e-stops or shock loads. The load sharing factor, a measure of multiplying the load-bearing capacity of an individual tooth, is optimized for each application. Because the key way is cut into the metal hub and not the plastic, Power-Core eliminates the weak spot inherent in conventional plastic gears.

The metal hub absorbs all key way stresses, transferring maximum torque to the composite gear teeth. The teeth are made of a lightweight plastic composite, weighing just 0.037 pounds per cubic inch.

Torque of Power-Gear approximates that of cast iron, but without the brittleness, weight, lubrication, and teeth breakage. As a result, Power-Core gears can reach higher speeds, increasing the throughput of your equipment. We can precisely calculate torque capacity, allowing Power-Core gears to replace metal gears in many applications.

Power-Core gears can operate without lubrication at pitch line speeds up to 15 feet per second. Add our special friction-reducing coating, and you can double gear speed to 30 feet per second.

The outer plastic composite ring is gravity-cast onto the inner metal hub, creating a secure and permanent attachment. The metal hub permits more durable shaft attachment.

This eliminates the need for bolted metal flanges, a common design in conventional plastic gears. Bolts can stress and distort the plastic, causing dimensional instability and even breakage.

Power-Core (TM) gears available include spur, helical, bevel, spiral bevel, worm, rack, ring, and metric. Gears can be manufactured with outer diameters ranging from 0.5 inch to 36 inches or greater. Hubs are available in aluminium, carbon steel, and stainless steel.