The name pretty much sums up the business – Precision Roll Grinders Inc. But like all high art, it may look easy, but it is difficult to attain. Coming as close to perfection as they can – within 20 millionths of an inch or a 100th the thickness of a human hair – Precision Roll Grinders’ employees round out their work days providing some of the highest accuracy.
The number of industries that rely on faultless rotation include manufacturers of pulp and paper, steel, non-woven textiles, plastic, aluminum, rubber, turbines and compressors, forest and food products, flooring, film and even chocolate. Additionally, Precision Roll Grinders Inc. grinds shafts for wind and power generators, submarines and ships.
Founded in 1970 by the Syrbius and Schildge families – three of whose members are on the board of directors along with Chairman of the Board George Schildge – Precision Roll Grinders Inc. has relied on equipment from Waldrich Seigen since its founding.
“After the equipment purchase, we will go through a runoff protocol at that manufacturer,” President and CEO Jim Manley explains. “Theirs is the only equipment that is able to attain the tolerances and aspects that we have set throughout the purchase for the equipment. We just feel that Waldrich Seigen has provided us with the best equipment that gives us the best control in the grinding process for the tolerances that we are trying to obtain for our customers.”
As it does with many things, time wears everything. “Over time, in any continuous process industry, the product that is run between the rolls will wear the roll surface,” Manley concedes. “So the surface needs to be ground to reestablish the necessary surface finish, tolerances and profile on the roll again to perform satisfactorily.”
The universal grinding machines rotate the customers’ rolls past measuring instrumentation that verifies various geometric attributes of the rolls. “You’re looking to make sure the profile of the roll matches the target profile,” Manley explains. That includes whether the roll’s target profile is straight or if it has a concave, convex or compound crown.
“All rolls deflect,” Manley declares. “If you support a beam, on the ends it deflects in the center. A crown tries to compensate for that deflection based on the loading of the roll.” That crown may be as little as 2 or 3 thousandths of an inch on diameter. “We have seen crowns as high as 100 to 125 thousandths of an inch on diameter depending on the size of the rolls.”
Precision Roll Grinders’ method is to grinds rolls on the journals. “If you don’t grind from the journals, you’re grinding from the bearings and whatever inaccuracy that exists in the bearings,” Manley explains. “When you grind on the journal, you basically take all the variability of the bearings out of the equation.”
Round Out the Rolls
Computerization of equipment over the years has sped up the measuring process, storage and information transfer for reporting. The company’s 24-Point Spec Check puts rolls through 24 quality checkpoints to ensure they meet specifications. This generates documentation of the roll’s specs.
“Some mechanical and computerized modification to the equipment over time has enabled the process to be sped up,” Manley says. “The b axis – which is the face of the grinding wheel – can pivot left and right, so if you’re grinding a roll that has a concave or convex crown, the grinding wheel can pivot to stay parallel to the roll face as it travels up one side of the crown and down the other side. That technology was introduced in the mid-2000s.”
Precision Roll Grinders can grind rolls made of steel and stainless steel, chilled cast iron, forged steel, granite, copper and brass, or ones that are chrome-plated, engraved or coated with carbide or ceramic, or covered with rubber, composite or polyurethane. It has four locations – Allentown, Pa.; Carrollton, Ga.; Lewisport, Ky.; and Texarkana, Ark.; – and its customers are within a reasonable proximity of the plants. Transportation of the large rolls the company specializes in – which may measure up to 600 inches in length and up to 102 inches in diameter – is mostly by truck.
“We continue to look for new opportunities, not only opening new facilities, but the possibility of acquisition to maintain our focus on our core competencies – rotational components – and venturing off into new market segments we currently are not involved with,” Manley says. “Right now, we’re spending some time investigating the petrochemical industry. We are very early in the stage of the investigation. We’re spending additional time trying to understand the opportunities that may exist in the wind energy sector. That’s a relatively new market for us. We’ve been involved with that market for about two years now.”
When comparing rolls ground by different vendors, FPInnovations, a Canadian research firm specializing in paper industry quality improvement processes, has found that Precision Roll Grinders is the industry leader in uniformity of roll surfaces. Variations across the surface of a roll can result in uneven wear on the paper or other material being processed, creating an inconsistent final product and often causing equipment shutdowns.