Rexnord - Leading the Technological Change in Mill Pinion Manufacture
 The
Falk name has always been a leading innovator in the design and production of gearing, gear boxes, and couplings used in the power transmission industry.
Rexnord continues to invest in the latest production technology in order to offer customers the very best in quality and reliability. As evidence of this,
we have recently purchased and installed a 4 meter Hofler CNC pinion/gear tooth grinder. This machine has on-board inspection capability and is able to produce parts that meet or exceed AGMA Quality 12.
This acquisition finishes the final step in the complete upgrade of our Mill Pinion manufacturing capability. Mill Pinions are generally larger than 12 inches (0.3 meter) in diameter and up to 14 feet (4.3 meters) in length. Mill Pinions are used to drive the girth gears which Falk produces for the mining, cement, and power generation industries. Mill Pinions are also produced in sets for heavy steel and aluminum rolling mills.
We began upgrading its Mill Pinion production capability because of the need to control all manufacturing processes to the precise tolerances required by its customers, and to control the production scheduling of all the critical process steps. With over 5,000 gear and pinion sets in operation worldwide it is important to Falk to maintain and enhance its position as the industry leader.
The improvement process started in 1992 when we purchased a NC lathe capable of turning workpieces 70 inches (1.8 meters) in diameter by 33 feet (10 meters) in length to tolerances better than .001" (.00025 mm) on a consistent basis.
The next phase of the project was to purchase a large pit carburizer, quench system, and pit temper. This equipment is able to carburize and harden parts up to 70 inches (1.8 meters) in diameter by up to 18 feet (5.5 meters) in length. Pinions are carburized to a case depth up to .250" (6 mm) and a surface hardness of 55-60 HRC. Before the advent of the carburizing process, Mill Pinions could only be through hardened to a maximum hardness of 40 HRC. The carburizing process allows for a higher horsepower gear set which is critical as mills have increased in size. Carburized pinions are typically used on these high horsepower mill applications and to replace older pinions when customers want to upgrade their mill capacity. Adding in-house carburizing capacity was critical to ensure quality and establish total in-house control.
 The installation of the Hofler 4 meter grinder completed the upgrading process. Falk’s temperature controlled grinding room was enlarged and upgraded with new temperature controls to accommodate this machine. This has also enhanced the quality of the entire grinding department. The new Hofler supplements our existing 2.5 meter grinder which is still capable of producing close tolerance parts, but does not have on-board checking. The machine is a generating-type gear grinder with the capability to grind parts up to 157 inches (4 meters) in diameter, up to 61.4 inches (1.56 meters) in face width, between 0.6 DP (42 Module) and 8.5 DP (3 Module), and weighing up to 77,300 pounds (35,000 kilograms). The machine is CNC controlled with a CNC wheel dresser capable of making profile and lead modifications. The on-board inspection machine is a Klingelnberg TPF40 lead and profile checker with independent 2-axis movement. It utilizes only the machine table for rotation, which minimizes the bias of the inspections.
The two biggest innovations of the new machine, besides having a larger size capacity, is the use of a full CNC control and on-board checking. The CNC control allows the operator to program all critical tooth geometry to high levels of precision and thus maintain consistency from part to part. On-board checking means that the pinion does not have to be removed from the machine for tooth inspection. All lead, profile, and spacing checks can be done right in the machine. This saves considerable time because multiple set-ups are no longer required.
Before we had a grinder with on-board checking capability, the operator trued up
the part, ground one flank and checked it with a hand held instrument. If it was
good, the part would be removed and set up in our PFSU 2500 Klingelnberg checker, where the true up process was repeated. The part was then checked while the grinder was idle. After this inspection, the pinion was returned to the grinder and was trued up again. If the part was acceptable the operator was able to finish the cycle and return the completed piece for final inspection in the Klingelnberg (another set-up!). If the pinion failed inspection the operator would make an adjustment, grind one flank and repeat the inspection/grind process until an acceptable part was produced. With on-board inspection all of these additional steps are eliminated.
The first part ground on the new machine was a carburized Mill Pinion with 21 teeth and a 40” (1 meter) face width, as shown in Figure 2. Lead and profile checks exceeded the requirements of AGMA Q12. This clearly demonstrates that
we have achieved our goal of producing the highest quality Mill Pinions in the industry.
|
