New materials often have a domino effect on aerospace processing.Environmental problems have forced material changes from traditional chromium plating to high-speed oxygenated fuel (HVOF) spraying, which in turn affects the choice of grinding wheel and ultimately the choice of grinding machine itself.

Move between the two lines

The use of HVOF coating materials on aviation parts has had a positive impact on the aviation industry.HVOF coating materials are not only more environmentally friendly, but also more resistant to wear and tear, thus lasting longer.During the migration there was also a shift in the grinding process used to produce the parts.Resin-bonded diamond wheels, however, were the old standard, and ceramic bonded diamond wheels are now more popular because there is no way to repair the wheels in the machine when bonded to resin.This poses a challenge to maintaining consistency.With a ceramic bonded diamond wheel, a rotary dresser and a rotating dressing diamond can be used on the spindle to trim the grinding wheel.This broke the situation that only diamond grains could be bonded in the grinding wheel and created a brand new cutting surface on the grinding wheel.The gluing operation can be performed online and during manufacturing

Technological leap

Recently an aerospace parts manufacturer started implementing these new technologies and managed to find a new process for producing parts.In this case, the part is the fuse pin that holds the aircraft engine to the wing.The fuse pins are HVOF stellite cobalt carbide, 2-1/2" diameter x 8" long, with a diameter deviation of 0.01", and require a surface finish of 8 ra.Previously, the manufacturer had chromed parts for its customers.After updating the material requirements, the manufacturer needs to develop a new HVOF spraying process.Initially the manufacturer knew that this required a tool grinder, which was a rigid machine - an experience that Okumas had known and had been using for years for equipment to grind chrome.So, along the way, the Okuma official company was called upon to cooperate and inject the team with HVOF grinding expertise that was not available within the manufacturer.

Originally, the resin bonded diamond wheel met the customer's specifications, but when Okuma's team demonstrated the benefits of using a ceramic diamond wheel, the customer allowed it as an alternative.The company has seen that ceramic diamond wheels offer greater productivity because you can trim the wheel on the machine without removing it from the machine, eliminating the step of offline operation.A superhard material co., LTD. 's ceramic diamond grinding wheel was selected for a 220 mesh, 24" diameter ×1-1/4" wide, and set up for operation under 6000sfm process.Okuma's gp-36fii x 1500 grinder is the preferred machine.

Key features

Now that HVOF materials and ceramic diamond grinding wheels have become the new standard, the capabilities of CNC grinding machines are more important than ever.Okuma's grinder has several important features and capabilities that should be taken into account when optimizing the process and maximizing productivity.Okuma's gp-36fii x 1500 grinding machine was selected based on its following features.

Rotate trim

With a ceramic diamond wheel, a more open and free-cutting wheel is created and allows for more active grinding when the diamond rotary dresser and wheel operate in a one-way rotation (relative rotation).The rotary dresser can also rotate in reverse, providing a higher surface finish.It is important to note that the grinding wheel is not very sharp in this case, which is why it gives a better surface finish.The ability to rotate the dressing provides a variety of ways to adjust the grinding wheel. However, resin bonded grinding wheels also require alumina dressing rods.This involves the operator taking the dressing rod and pushing it into the grinding wheel to expose the cutting area, thus introducing uncontrollable variables into the process.Depending on the operator, the dressing rod should be able to be applied under different pressures and create different conditions for the grinding wheel according to the length of time.By combining the ceramic diamond grinding wheel with the rotary dresser, a consistent quantity can be dressed at a constant feed rate, thus a stable result can be obtained.

Acoustic sensor

When the grinding wheel touches the rotary dresser, the sensor starts to detect, so the exact location and time of contact are known.This prevents overdressing and cutting off the grinding wheel.In the case of the fuse pin process, a grinding wheel of this size costs $6,000 to $7,000, so the ideal situation is to trim as little as possible to extend the life of the grinding wheel.The cost rationale is obvious.By minimizing the amount of dressing, one can reduce the cut to 0.0001" instead of 0.0005".This saves material.

Height of static and dynamic stiffness

The Okuma grinder provides static and dynamic stiffness with two key features.The first is the guide rail system, which is an open v-shaped and flat guide with extremely high stiffness and no slippage.The second is the hydrodynamic grinding wheel spindle, which has very good rigidity.The supporting force at the center is 1 ton, and the offset radial load is equivalent to about 1 muon per 100kg, with a rotational accuracy of 0.0000004".This provides a higher surface finish for diamond wheels, while rigidity prevents vibration in the system, which is necessary when grinding very hard materials such as stellite.

In the transition period driven by the demand for new materials for aerospace components, we have the opportunity to update the entire process.By adding the unique design capability of ceramic diamond grinding wheel and suitable grinding machine to the process flow, it is possible to obtain greater overall productivity.