It may seem counter-intuitive, but one of the most important focal points for achieving better grinding results is not the machine, the control or the grinding wheel. It’s your dresser. Selecting a better dresser and using it appropriately can have a profound impact on the results you are looking for, even before you initiate any other process modifications. Here are three examples:
Longer CBN Wheel Life
A manufacturer was using vitrified CBN wheels to grind a series of steps on the outer diameter of a conical part. With a conventional metal-bond dresser the operation was producing 4-6 good pieces before stopping to dress. By switching to Meister’s cDD diamond dresser, the interval between dresses was increased by about 100% to 9-10 pieces between dressings. Wheel life for the process essentially doubled.
To understand how this is possible, consider the difference it makes when you carve your Thanksgiving turkey with a dull knife vs. one that is razor sharp. With a dull blade you have to work very hard to get the turkey carved. The job gets done in a fraction of the time with a sharp blade.
The same holds true for grinding wheels. Duller wheels have to be worked hard, with higher forces and more heat generation. The cDD dresser did a better job of sharpening the CBN wheel, allowing it to cut efficiently with less force and heat generation. As a result, the cost of CBN wheels used in this process was cut in half.
Improved Process Stability
A manufacturer was using a Meister CBN wheel for ID grinding of its hydraulic valve product line. The wheels were being dressed with a conventional metal bonded diamond dresser. Switching to a Meister hDD Hybrid Diamond Dresser resulted in several process improvements, including:
- Reduced part to part bore size variations,
- More consistent surface finish,
- Improved process stability, independent of operator intervention.
And all this while achieving modest increases in per-machine productivity.
Better dressing frequently results in systematic bore grinding process improvements because the sharper wheels minimize lateral forces that can cause vibration, quill deflection, and uneven wheel wear. The resulting improvement in dimensional consistency and surface finish, along with productivity improvements, are frequently encountered in an application like this one.
Low Cost Process Upgrade with Safety Improvement
A job shop specializing in aerospace manufacturing had a plasma coated titanium part that had to be ground to a surface finish between 0.2 and 0.4µm Ra. They were using large diameter resin bonded diamond wheels that had to be dressed aggressively by hand using a stick. This dressing approach was frequent, tedious, fatiguing and produced wheels that were inconsistently sharpened.
The shop would have preferred to use a vitrified bond diamond wheel because the porosity of the wheel would be much better adapted to cutting through the part’s plasma spray coating. Vitrified diamond wheels, however, are typically dressed automatically with a rotary dresser. This shop’s machine was not equipped with one.
Retrofitting the machine with a rotary dresser would have resolved these issues but the cost of this upgrade was prohibitive for a small shop that only did this kind of work occasionally. Using a conventional stationary diamond dresser was also out of the question because the large diameter diamond wheel would have ripped through the dressers just as aggressively as it tore into the plasma-coated titanium.
Meister helped the customer resolve this issue by providing them with a Meister vitrified diamond grinding wheel along with a stationary cDD diamond dresser that has a series of CVD inserts imbedded in a porous, diamond encrusted hybrid matrix that keeps the edge from breaking down, allowing for better dressing performance over longer periods of time. This allowed the customer to upgrade to a better performing grinding wheel technology for grinding parts faster, more efficiently at higher levels of quality. It also eliminated potential safety issues stemming from the excessive manual dressing required previously.
Of course, for higher volume applications, rotary dressing spindles equipped with rotary cDD dressing tools provide an optimal solution. The rotary dresser can remove a layer of material off the wheel more efficiently so that it is sharper, cuts faster, and lasts even longer. However, when upgrading to a rotary dresser is not a viable consideration, Meister’s advanced stationary dresser technology can bring the performance of conventional grinders up a notch.