Latest Trends in Grinding Technology
Posted : September 27, 2004 at 9:20 am [IST]
Grinders are going multifunction
Customers are pushing to improve their capital investment payback through faster cycle times. Capital equipment cost and payback time is becoming critical.
Multifunction machines are becoming more common. There is a big move to incorporate grinding on turning centers, and turning or burnishing on grinders. Grinding is often introduced to improve dimensional accuracy or finish after turning.
Some sectors of the market are becoming mature for super-abrasives, such as cam and crank grinding, while other sectors are just waking up to this material’s potential. This includes through-feed centerless grinding with vitrified CBN, where falling grain prices are reducing the sticker shock of large wheels.
There is an upsurge in acceptance of oil coolant. This allows novel processing methods such as high-speed peel or contour grinding, common in Europe, to be introduced into the USA as a challenge to hard turning.
Major developments in the vitrified products area:
” The T2 bond technology which continues to make major performance improvements in an increasing number of applications.
” Dressing technology (rotary diamond dressers and motorized dresser spindles) to match the performance requirements of the wheels.
In conventional wheel developments
” Norton XPG.90 grinding wheels last up to 10 times longer than previous wheels on fluting, pointing, and punch grinding applications
Flexible grinding platforms that address both production and short-run needs are becoming more and more in demand. This requires innovations to both software and hardware on today’s grinding machines. This could be a machine with an easy to adjust loader. A loader, designed for the needs of small shops that want flexible automation, allows quick adjustment when the operator makes parts of differing lengths.
Another example is adding toolchangers to grinding machines. This allows an operator to fixture a part on a grinder, then walk away.
The new tool-changing technology increases the variety of applications to a great extent by increasing the number of operations that can be accomplished without operator interference. By limiting operator involvement and eliminating the need to move a part from machine to machine the new toolchanger enhances process control and results in consistent performance and quality parts. If the initial process parameters are correct, we can pretty much eliminate scrap as an issue. With this toolchanger, the operator can load all the tools required to finish a part — multiple abrasive types, conventional wheels, aluminum oxide, CBN, and, of course, drills, mills, and taps. The idea is to have the perfect abrasive or tool in the changer for a particular part. You can rough with one type of abrasive and finish with another. Perhaps you have a feature that requires a very well-defined wheel diameter, and perhaps plated CBN would be best. However, you may have other features on the same part where the stock is heavy and requires more conventional abrasives. With this design it’s possible to intermix tools and abrasives around the specific requirements of a given part and run that part complete, start to finish, in a single setup.
Typical applications include turbine vanes and blades, gear shifting shafts, rocker arms, small turbine and compressor blades, machining both sides of fir tree and root shank faces, shroud and Z-notch profiles — both sides and slots if required.
Part tolerances and processability requirements have become increasingly tighter in response to the demand for improved quality with lower cost. A manufacturer of fuel-system components, for example, now centerless grinds plungers at very high production rates to tolerances of 1 µm on diameter and 0.6 µm on taper at 1.33 Ppk. Many request to grind very tough materials such as Inconel bolts for aerospace and specialty alloy steel bars for various precision applications. Many part designs have become more complex, such as families of crankshafts with multiple throws or camshafts with multiple features that must be accommodated in finish grinding. And many manufacturers have been seeking to replace multi-operation, dedicated processes with more efficient grinding processes using fewer machines that combine operations.
The latest generation of flexible CNC production grinders from Landisi incorporates superabrasive wheels operating at very high speed and feature reliable, wear-free linear motor drives and the latest generation of PC-based open-architecture controls. Some of these new grinders can also minimize the number of machines in a process and reduce capital expenditure for our customers by combining multiple grinding operations in a single machine. For example, a typical five-machine crankshaft grinding process can now be reduced to only two machines by grinding crankshaft concentric diameters, including thrust-walls and eccentric crankpins, with an LT2 Twin Wheelhead grinder, one of the machines. Landis has also developed a machine for grinding crankshaft thrust-walls, flange face, pilot diameters, and reluctor ring all in one machine.
- Indra
Category: Machining |
Leave a Comment