Combined hard turning and grinding on the VLC 250 DS
18/07/2014 - Oliver Hagenlocher
The VLC 250 DS Turning and Grinding Center combines the advantages of vertical hard turning with those of grinding, making it possible for a workpiece to be complete-machined in a single setup. The result: a better quality workpiece at increased output rates.
The advantages of combining the hard turning and grinding processes include process consolidation, improved component quality and greater flexibility. This combination provides the benefit of shortened cycle times. Throughput, transport times and storage periods can be drastically reduced where all the hard fine-machining operations can be carried out on a single machine, Easy and fast machine set-up also saves time.
An important factor for combination machines is ensuring safe machining with an unhindered flow of the turning and grinding chips. The VLC 250 DS, with its vertical work spindle and tools positioned below the workpiece, offers optimal chip flow conditions. The vibration dampening properties of the MINERALIT® polymer concrete machine base create a mechanically sturdy machine module. The design of the work spindle, which forms an integral part of a sturdy quill that carries out its Z-axis movement on a high-precision, hydrostatic guideway also contributes to the highly effective vibration damping effect.
The tooling systems are firmly anchored in the machine base and provide a stable environment for the demanding turning and grinding operations. This is important for time-saving hard pre-turning work and for achieving the best surface finish with a hard finish-turning or grinding operation. Number and design of the stationary tooling systems can be chosen to suit the individual machining requirement and continuous monitoring of the machine’s temperature ensures a high degree of thermal stability. The operating temperature is quickly reached and maintained within strict limits of the ambient temperature by a powerful cooling unit. The pick-up technique employed on the VLC 250 DS Turning and Grinding Center allows the machine to load itself, making other cost-intensive loading devices that involve time-consuming resetting work and a larger footprint, such as gantry loaders, a thing of the past.
Integrated quality control
The VLC 250 DS is ideal for handling complex manufacturing processes, whether turning at high chip removal rates or a gentler grinding operation. The machine covers a wide range of applications and complete-machining in a single set-up; eliminating reclamping errors is the obvious advantage. Measuring operations, too, can be included to ensure optimal quality control integration into the overall process. The measuring probe is located between the machining area and pick-up station, where it is safe from chips and coolant. Since the workpiece remains clamped during the gauging process, intermediate measurements can also be taken.
VLC 250 DS in action
The manufacture of gearwheels is a typical example for successful combination machining. The end face is hard finish-turned while bore and cone are pre-turned and then finish-ground to ensure that their high quality requirements are met. For this purpose the machine is equipped with two grinding spindles, where one spindle machines the bores and the other carries out the external grinding work. As the amount to be ground is only a few hundredths of a millimeter, the grinding wheels need only be designed for finishing operations. This combination process is state-of-the-art and has, to a large extent, replaced grinders.
Advantages of the VLC 250 DS
- Vertical hard turning and finish-grinding on a single machine and in one set-up
- All sectors of the workpiece that can be turned with process integrity are hard finish-turned, and only those that demand high quality requirements and process integrity are ground after hard pre-turning.
- Improved workpiece quality and higher productivity rates as the workpiece is complete-machined in a single set-up, whereby the hard pre-turning process leaves an allowance of just a few microns for the subsequent grinding process.
- As the grinding process need only remove nominal material, the wear on the grinding wheel is minimal and requires it to be straightened infrequently, and then only by a fraction. This is a considerable advantage for cycle times.
- The grinding wheel specification can be set to a “finishing quality,” as only a very small allowance needs to be removed. This produces process-capable surface finishes in the Rz < 1.2 µm range.
- Unlike hard turning processes, the grinding operation will generate absolutely scroll-free surfaces on the same machine.
- The problem of rear end faces being difficult to reach with a grinding wheel is easily solved with hard turning.
- The cross-operational machine design provides exceptionally easy maintenance and service access.
|Chuck diameter||mm||250 / 315|
|Travel in X, max.||mm||1,600|
|Travel in Z||mm||300|
|Travel in Y (optional)||mm||± 100|
|Rapid traverse speed, X||m/min||60|
|Rapid traverse speed, Z / Y||m/min||30|