Increasing Rockwell Hardness Increases Fine Grinder Jaw Lifespan

Prater manufactures the M-Series fine grinder for grinding dry, free flowing material as fine as 200 mesh (75 microns) with very tight distribution of particle size.

It is best suited for heat-sensitive materials such as resins, sugar, and powder coatings. Utilizing a high-speed impact principle, the feed material is metered into the center of the mill where it is impacted by the rotor.

The feed material is then thrown outward where it impacts with other particles, aiding in the reduction process. After initial impact, particles are projected across the screen and are sheared between the blades of the rotor and the sizing screen or jaws.

This action continues until the particles are properly sized and are discharged through the bottom of the mill.

Precision tolerances are maintained between the rotor blades and the stationary grinding surfaces (jaws) to allow for accurate control of finished particle size and distribution.

In some instances with certain products, this process can be very abrasive and shorten the life of the jaws considerably.

Example: Customer, who was once seeing 3 months out of a set of jaws, was now only getting 1.5 months use. An increase in part wear can be due many variables, i.e. change in raw material or system flow. Either way, they were demanding more life out of the jaws.

Next step was to put the Prater Engineering team to work and start brainstorming ideas for increased jaw life, while keeping the cost manageable.

In determining a better material, there were many key factors to keep in mind. If you increase the Rockwell hardness, can it still be machined to the high precision tolerances? Will the material warp once heat-treated? Will the cost of the material and machining make the ROI unfavorable?

Solution: The Prater Engineering team was able to increase the Rockwell hardness from 12-14, all the way to 48-52, while increasing ROI and maintaining precision tolerances. Instead of the jaws lasting only 1.5 months, the customer saw 4 months and lowered their yearly jaw cost by 17%.