Honing - Top Future Point

Honing is an abrasive machining process that produces a precise surface on a metal workpiece by scrubbing an abrasive grinding stone or grinding wheel along a controlled path . metalworking is mainly used to improve the geometric appearance of the surface, but can also improve the surface finish .

Typical applications are the finishing of cylinders for internal combustion engines , air bearing spindles and gears . There are many types of hones, but all consist of one or more abrasive stones that hold under the pressure of the surface they are working on.

Other similar processes are lapping and superfinishing .

Stone of honor

Uses a special tool grip, also called a honing stone or a honing , to obtain a precise surface. The hone is made of abrasive grains that are bonded together with an adhesive. Generally, honing grains are irregularly shaped and about 10 to 50 micrometers in diameter (300 to 1500 mesh grit). Smaller grain sizes produce a smoother surface on the workpiece.

A honing stone is similar to a grinding wheel in many ways, but honing stones are usually more friable , so that they conform to the shape of the workpiece during wear. To counteract their friability, honing stones can be treated with wax or sulfur. to improve life; Wax is generally preferred for environmental reasons.

Any abrasive material can be used to make a honing stone, but the most commonly used are corundum , silicon carbide , cubic boron nitride , and diamond . The choice of abrasive material is usually driven by the characteristics of the workpiece material. In most cases, corundum or silicon carbide are acceptable, but extremely hard workpiece materials must be honed using superabrasives. [1]

The hone is usually turned to the bore during moving in and out. Special cutting fluid is used to give a smooth cutting action and to remove material. Machines can be portable, simple manual machines or fully automatic with gauging depending on the application.

Modern advances in abrasives have made it possible to remove much larger quantities of material than previously thought. This has displaced grinding in many applications where “through machining” is possible. The outer hones do the same thing on the shaft.

Process mechanics

Since honing stones resemble grinding wheels, it is tempting to think of honing as low-stock removal grinding . Instead, it is better to think of it as a self-truing grinding process. [2]

In grinding, the wheel follows a simple path. For example, in grinding a shaft, the wheel moves toward the axis of the part, grinds it, and then backs out. As each piece of the wheel repeatedly contacts the same piece of workpiece, any inaccuracy in the geometric shape of the grinding wheel will be transferred onto the part. Therefore, the accuracy of the finished workpiece geometry is limited by the accuracy of the trueing dresser. As the grind wheel wears out, accuracy gets worse, so it must be truing periodically to reshape it.

In honing, the limitation of geometric accuracy is removed because the honing stone follows a complex path. For example, in bore honing, the stone moves along two paths simultaneously. The stones are pressed radially outwards to enlarge the hole while they simultaneously oscillate axially. Due to the oscillations, each piece of honing stone touches a larger area of the workpiece. Therefore, imperfections in the profile of the honing stone cannot be transferred to the bore. Instead, both the bore and the honing stone correspond to the average size of the motion of the honing stones, which in the case of bore honing is a cylinder. This averaging effect occurs in all respect processes; Both the workpiece and the stone wear out until they correspond to the average size of the cutting surface of the stones. As honing stones fade to a desired geometric shape, So there is no need to correct them. As a result of averaging effect, the accuracy of a honed component often exceeds the accuracy of the machine tool that made it.

Stone paths are not only a difference between grinding and honing machines, they also differ in the hardness of their construction. Honing machines are much more compliant than grinders. The purpose of grinding is to achieve a tight size tolerance. To do this, the grinding wheel must be moved to a precise position relative to the workpiece. Therefore, a grinding machine must be very rigid and its axes must move with very high precision.

A honing machine is relatively inaccurate and incomplete. Rather than relying on the precision of the machine tool, it relies on the average impact between the stone and the workpiece. Compliance is what a respectable machine needs to be of average impact. This leads to a clear difference between the two machines: in a grinder the stone is firmly attached to a slide, while the stone is driven by pneumatic or hydraulic pressure.

High-precision workpieces are usually ground and then honed. Grinding determines shape, and honing improves shape.

The difference between honing and grinding is always the same. Some grinders have complex movements and are self-truing, and some honing machines are equipped with in-process gauging for size control. Many through-feed grinding operations rely on the same averaging effect as honing.

Respect configuration configuration

bore honing
flat honor
OD Honing / Super Finish / Fine Finish (Taper & Straight)
round honor
track/raceway honors

Economics

Since honing is a high-precision process, it is also relatively expensive. Therefore, it is only used in components that demand the highest level of accuracy. This is usually the final manufacturing job before the parts are sent to the customer. The dimensional shape of the object is established by the preceding operations, the last of which is usually grinding. The part is then honed to improve a characteristic of the form, such as roundness, flatness, cylindricity, or sphericity.

Performance benefits of honed surfaces

Since honing is a relatively expensive manufacturing process, it can only be economically justified for applications that require very good form accuracy. Better sizing after honing can result in a quieter run or higher-precision component. Flexible honing equipment provides a relatively inexpensive honing process. This tool produces a controlled surface condition that cannot be achieved by any other method. This includes finishes, geometry and metallurgical structures. A high percentage plateau is produced free of cut, torn and bent metal. The flexible hone is a flexible, flexible honing tool with a soft sawing action. Each of the abrasive globules has an independent suspension that assures the tool is self-centering, self-aligning from the bore, and self-compensating for wear.

Cross-hatch finish

The cylinders use a “cross-hatch” pattern to retain oil or grease to ensure proper lubrication of the piston and ring seal. A smooth glazed cylinder wall can cause the piston ring and cylinder to scratch. The “cross-hatch” pattern is used on the brake rotors and flywheel.

Plateau finish

Featuring the removal of “peaks” in Plato finish metal while keeping the cross-hatch intact for oil retention. ^{[ citation needed ]} The plated finish increases the bearing area of the finish and does not require pistons or rings to “break” the cylinder walls.

Plateau Honor Specification: ^{[ citation needed ]}