The Kleiss Difference is in the Inspection

We’ve invested in the equipment and we developed the software

“The physical dimensions of polymer molded gears can be any shape, any size. When a mold cavity is constructed, shrinkage of the gear from the cavity walls is estimated, and the part is formed; but without our precision inspection, you never know what you have.” –Rod Kleiss

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Unique Gear Inspection

The president and founder of Kleiss Gears, Rod Kleiss, has been at the cutting edge of polymer gearing technology and advancements for over two decades. As a visionary, he developed unprecedented software that mathematically evaluates and determines the profile form error and concentricity, as well as base circle shrinkage error and actual tooth thickness of any gear, polymer or metal.

Illustration of shrinkage

Shrinkage in Molded Polymer Gears

As the molder we must:

Estimate shrinkage
Cut the cavity
Mold the gear
Determine how close we’ve come to the targeted dimensions.

These types of measurements are not trivial. The entire form of the gear, including the involute base circle and tooth thickness must be accurately measured. Since there is currently no standardized system for directly measuring gear shrinkage, Kleiss Gears has taken the lead in this technology.

Our Senior Engineer, Michael, inspecting a gear on our Legend CMM

Inspection System

Kleiss Gears has developed its own, unprecedented system for measuring shrinkage, and we take no short cuts.

Simple outside diameter measurements, or even roll testing with a calibrated master gear, cannot characterize plastic gear shrinkage – the involute form must be measured independently. Molded gears do not shrink in any simple fashion. There is a minimum of four distinct shrinkage rates for any gear.

Even simple features such as outside and root diameters must be carefully inspected. A simple caliper check will often miss important features. These diameters must be inspected for total form error as well as concentricity to the principle bore or datum.

We scan each tooth of your molded gear to determine the size and form error of the involute gear profile. Measurements are taken with the Coordinate Measurement Machine (CMM) probe at a constant rate with constant force from the root of the tooth to its tip. After the data is collected for all teeth, it is mathematically evaluated to determine profile form error and concentricity as well as base circle shrinkage error and actual tooth thickness. These errors are eliminated in the molding process or compensated for in the mold cavity.

Off the shelf versus Shape Molded Design

Here are two gear scan traces. The first report is for an actual measured gear that has significant shrinkage error. The second report is for a gear designed and molded at Kleiss as a replacement for the same application. The original, poorly molded gear had been purchased off-the-shelf from a commercial supply house.

Roll Testing

Gear profile inspection is quite laborious and time consuming. And it is absolutely required for properly sizing a gear. Gear Roll testing consists of the following:

Fabricating a perfect “Master Gear”.
Placing the production molded gear against it with a slight preload.
Rotating the gear set while under this light load.
Recording both actual center distance and variation of center distance for the production gear.

If it were a perfect gear, the center distance would be exactly where it is specified, and it should have no variation from that position. Eccentricity, lobbing and profile error will cause vertical distortions in that trace.

Shrink errors and correction

The results for a gear before and after shrink correction are shown here. The spikes in the left schematic show that shrinkage correction is needed. The schematic on the right, after gear correction, shows that after rolling ten gears the footprint of the gear is consistent. The shrink error was corrected and is now a properly formed gear.

The Arsenal We Call Our Lab

At Kleiss Gears we’ve invested in a multi-million dollar lab to inspect a ten cent gear. It is unique to the industry and it works.

Werth VideoIP Check CMM

The newest weapon in our Inspection Arsenal is the Werth Video IP Check Coordinate Measurement Machine (CMM). It has combined and integrated probe and vision capability. This machine provides improved performance for traditional gear scanning as well as vision scanning of micro-miniature gears. Werth has outfitted this machine with a 4th axis rotary table to facilitate Kleiss requirements for precision and versatility in gear measurement. This machine is expected to provide new insights into the study and manufacture of precision molded gears.

Legend CMM

Our Legend CMM directly measures each gear tooth with a probe to build a data base of information that can then be used to compare against the intended specifications. Measurements are taken at a constant rate with constant force from the root of the tooth to its tip. Molded gears do not shrink in any simple fashion. By using our CMM equipment we are able to correct shrinkage error efficiently. Accuracy of our equipment is calibrated annually to 40µ inches with NIST standards, and accurately measures to 2.5 microns – that’s pretty darn small.

Olympus Tool-Makers Microscope

We also have an Olympus Tool-Makers Microscope with magnification from 50x to 500x with Heidenhain scales on all axes. Sometimes nothing less than a tool scope focused and sighted by eye will do the required job.

Kleiss Gears, Inc., 390 Industrial Avenue, Grantsburg, Wisconsin 54840
715-463-5995
Please email info@kleissgears.com with any inquiries.