CASE STUDY: Grinding Ahead
June 1, 2011
As part of an ongoing effort to diversify its market base, C&B Machinery, Livonia, Mich., has developed and shipped a model CBV2-16-R/B double-disc grinding system equipped with diamond-impregnated grinding wheels arranged for grinding the faces of various ceramic discs used in the telecommunications and permanent magnet industries.
The C&B machine, a re-engineered system developed from a used machine, was purchased by Island Ceramic Grinding in Gilroy, Calif. The machine is designed to increase product quality and output, thereby reducing cost per piece. During runoff, the grinder achieved production rates of 300 parts per hour, effectively doubling output over previous grinding methods.
The ProcessDouble-disc grinding is the removal of material from a part with parallel surfaces. The stock removal takes place on both faces of the component simultaneously, with the grinding occurring on the faces of the grinding wheels. Disc wheels are attached to diametrically opposed spindles, each contained in a heavy-duty precision grinding head assembly. For this particular process, the spindles are vertically opposed and the parts are introduced to the grinding wheels via a rotary carrier system.
The challenge was to provide a solution that fit within the customer's budget. "A typical re-engineered grinding system means starting from a blank sheet of paper and completely stripping the machine of all commercial and most OEM components," said Chris Cox, vice president of Sales for C&B Machinery. "New state-of-the-art feed systems and CNC controls are adapted to the machine, along with newly designed tooling." The result is basically a new turnkey system at 20-30% lower cost than a comparable "new" machine.
Project SpecificsIn this case, the machine updates were scaled back in order to meet the customer's budget. A simple PLC control replaced old relay logic, and the mechanical wheel feed systems were remanufactured and re-utilized. Careful attention was paid to balancing the spindles, which is essential to grinding with superabrasives.
The grinding wheel spindles were outfitted with variable-frequency drives that allow the grinding wheel surface speed to be programmable. Changing the speed of the wheels, in essence, changes the "hardness" and cutting characteristics. This is a useful tool in adapting for changes in the material being ground and stock removal variation.
"Considering the expense of diamond grinding wheels, the ability to program the speed of the wheels allows easier and more cost-effective optimization of the grinding process," Cox said. "It limits the necessity to experiment with and stock multiple grades of grinding wheels."
The machine is also outfitted with new digital readout displays for the grinding axes. This allows the operator to make very small adjustments (0.000050-in. increments) for precise size control. In addition, precise alignment of the wheelheads and tooling provide for extremely flat and parallel parts when compared to more conventional surface grinding methods.
"The trick to grinding ceramic components on a double disc is not to be in a hurry," Cox said. "In other words, the stock removed from the part is very small, as compared to metal components. This is in order to keep the parts from chipping or even disintegrating when they enter the grinding wheels. Depending on the parent stock, multiple grinding passes may be required. Even still, this is a much faster method of producing higher quality parts than conventional surface grinding.
"It doesn't hurt to have hundreds of years of grinding experience either," he said.
For more information, call (734) 462-0600, email firstname.lastname@example.org or visit www.cbmachinery.com.