From workpiece back to the tool: How a high-precision profile dressing roll can make the different.

When does one speak of a perfect process in our industry? When the result is within not only specifications, but also when the outcome spectacularly exceeds dimensional requirements.

Half a µ tolerance on the workpiece - that is record-breaking!

Not only the customer is amazed, but also our application engineers at Haas Schleifmaschinen, which are working with high precision applications on a daily basis. Test results have confirmed that the degree of optimization of each individual process step has been exhausted to the maximum. In our case, this involved grinding gears, worm shafts and compressor shafts.

Haas ensures precision in every step of the process. Let's start from the beginning.

The more precise the profile dressing roll, the more accurate the grinding wheel will be and therefore a more precise workpiece will be produced. The basic configuration of a perfect profile dressing roll is already contained in its high-precision base body. The production of the basic body of a CBN or diamond dressing rolle on the Multigrind® CA high-tech grinding machine is anything but trivial. During grinding of the basic body, made of hardened steel, forces are generated which must first be managed by a grinding machine. The Multicube design of the Multigrind® CA with its rigid, cube shaped cast mineral bed and symmetrical arrangement without mechanical interference was developed precisely for this purpose: For maximum stability, optimum vibration damping and unprecedented precision.

However, even small changes of general manufacturing conditions have an effect on achieving precision requirement: The heat given off by the machine, both the grinding wheel and the coolant oil, and even small temperature fluctuations or vibrations in a production environment have an impact on the result when working in the µ range. All of these factors need to be taken into account sufficiently, but they are not yet the key to splitting the a µ.

The magic formula: Compensation grinding with Multigrind® Horizon.

Every grinding process is associated with a constant mechanical load, especially at the grinding wheel prolife contour zone. This results in distortion of the workpiece, grinding wheel and grinding machine. This can result in a progressive inaccuracy and thus reduce the dimensional quality of the workpiece. In our case, the workpiece is the profile dressing roll.

An adjusting process control through an automated compensation process successfully prevents this loss of precision. Systematic and machine-specific deviations are determined by tactile measurement of the workpiece, on a coordinate measuring machine during the running process and the measuring result is constantly transmitted to Haas' own Multigrind® Horizon software. This software has a large number of compensation functions that complement each other perfectly. In this way, all dimensional deviations can be compensated within µ precision. Without compensating all process factors, the achievable tolerance would be 4 - 5 µ. Haas achieves the sensational tolerance of 0.6 µ in the described process.

The compensation process must continue and take place before the final grinding pass for finishing the workpiece: step 1 measuring of the workpiece, step 2 dressing of the grinding wheel, step 3 compensation grinding passes. In the dressing process, grinding wheels retain their high-precision shape and dimensional accuracy, which in turn is crucial for the high precision performance of less than 1 µ on the workpiece.

Our profile in profile dressing rolls.

"We adjust our grinding processes to the specific customer requirements, this applies generally to all cylindrical grinding applications and expressly to the production of high-precision diamond and CBN profile rolls." Thomas Bader, Managing Director of Haas Schleifmaschinen, knows these requirements clearly and with certainty. "Of course, these high-precision profile dressing roll are also used in our Multigrind® grinding machine, and in a figurative sense we are technology providers and users at the same time."

The Multigrind® grinding machines have the most flexible dressing unit on the market. In order to achieve grinding results in the quality of +/- 1µ, both the process and each individual component must make its contribution. This development will be of particular interest to the manufacturers of profile dressing rolls. In addition, the manufacturers of compressor shafts, gear wheels, bevel gears and worm shafts, because this is where the high precision profile dressing rolls are ultimately used.