Abrasive machining, sawing, and finishing

Manufacturing Engineering, Aug 2002

"Our manufacturing customers are demanding greater levels of flexibility in their grinders, along with the ability to quickly and easily reconfigure their processes to meet changing demands," says Dan Pheil, President of Landis Gardner, a UNOVA Company (Waynesboro, PA).

Landis Gardner has responded by developing more versatile machines and by combining multiple operations in a single machine. For example, the new Landis Crank Center grinds mains, pins, thrust faces, post, flange and oil seal diameters-operations that would typically require as many as four separate grinders-in one setup on one machine. It uses a single, narrow CBN grinding wheel to make multiple orbital-grinding passes and a final wiping of each eccentric-diameter crankpin. It can, therefore, process multiple shafts with different-width pins or mains without tooling changes.

"We've also successfully combined grinding of crankshaft thrustwall faces and ID grinding of pilot bores on a single CNC cylindrical grinder. For grinding cam and crank mains, the flexible, high-productivity Twin Wheelhead grinder has also replaced dedicated multiwheel plunge grinders in many applications.

We're also introducing a new angular centerless model of the Landis Cincinnati Viking line. This machine uses an angle-mounted regulating wheel and a formed grinding wheel to simultaneously infeed-grind the OD and flat surface of parts while maintaining submicron tolerances at high production rates. This grinder can handle a cylindrical part with a perpendicular shoulder or end, and is especially suited to the needs of fuel system manufacturers for high-production grinding of small injector parts with metering edges that have critical perpendicularity requirements."

Recent developments in grinding machine and CBN-wheel technology have now made highspeed finish grinding a practical reality. Landis uses specially designed CBN wheels; high-speed, high-power hydrostatic motorized spindles; high-speed wheel mounting and balancing systems; and linear motors and hydrostatic ways for stiffness, accuracy, and speed. The machines also have a sensor-based wheel truing/dressing system, and a high-speed open architecture control system.

"We are seeing an increased demand for flexibility in grinding," says Tim Leoni, National Sales Manager, Toyoda Machinery US, Grinding Machine Div. (Wixom, MI). In the past, machines were rather standardized and single purpose. Now there is more demand for more versatile, universal machines that can combine a number operations and do the job in a single chucking.

"Our universal machine, the GU4-100R, has a programmable pivoting wheelhead allowing multiple grinding operations to be performed with the wheelhead in a straight (plunge) configuration, as well as an angular (plunge, traverse, face) grinding configuration. This machine also has the ability to perform ID grinding operations with the optional ID grinding spindle mounted onto the back of the wheelhead. We also have an economical machine designated the GE 4 Select. It is basically an OD grinder with a single straight wheel that can be converted to angle head and also has an optional, swingdown ID attachment. This is aimed at the job shop that wants to get into grinding and wants one machine that will do a variety of jobs.

"We also note that more people are getting into CBN grinding, chiefly to take advantage of shorter cycle times, greater accuracy, and longer wheel life."

The limitation of CBN is surface footage. Most general purpose machines offer only 8500 fpm (45m/sec).

Typically, you need 12,000 fpm (60m/sec) or better to get the full benefit of CBN. Many grinding wheel manufactures may disagree, but Landis' experience in CBN grinding proves otherwise, according to Leoni. "It doesn't work on all machines. We offer dedicated CBN machines capable of wheel speeds up to 40,000 fpm (200m/sec).

"In today's market we have been providing more machine rebuilding and retrofitting services. We can take a carcass machine and retrofit it to customer order. It will have a custom control and as much flexibility as the customer wants."

Saw developments. Steve Manning, DoALL Co. (Des Plaines, IL) explains: "More and more carbide is being used in blades. For some time its applications were limited, but now it is commonly used on superalloys." Operators distrusted carbide because of problems with blade failure. Now, thanks to better controls, this problem has been reduced. But for most effective operation, carbide blades have to be used on very rigid saws.

"We are also seeing more use of material-handling options and controls," says Manning. "Automated storage and retrieval systems have been popular in Europe because of floor space problems and lack of personnel. Now these features are being demanded by US customers. These systems bring the material to the saw and control saw action based on material size, shape, and hardness. After the cut is made, the control keeps track of the remnants and material inventory. This type of part-- handling eliminates cranes and forklift trucks running through the plant."