Roller burnishing

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A Skive-Burnishing tool is used to achieve mirror surface finish in hydraulic cylinders. Skiving-Tool-And-Machine.jpg
A Skive-Burnishing tool is used to achieve mirror surface finish in hydraulic cylinders.

Roller burnishing is a surface finishing technique where hardened rollers cold work surface imperfections to reduce surface roughness. Roller burnishing differs from abrasive surface finishing techniques in that material is displaced rather than removed. The tooling typically consists of a hardened sphere or cylindrical roller. [1] The tooling is pressed into the surface of the part while it is rotated (in some applications, the tools are rotated instead of the part). The burnishing tool rolls against the surface of the part at a constant speed, producing a very consistent finish across the part. A surface finish of less than Ra 0.1 µm is achievable with roller burnishing. [1] A side effect is that the outer surface of the part is work hardened.

Surface finishing is a broad range of industrial processes that alter the surface of a manufactured item to achieve a certain property. Finishing processes may be employed to: improve appearance, adhesion or wettability, solderability, corrosion resistance, tarnish resistance, chemical resistance, wear resistance, hardness, modify electrical conductivity, remove burrs and other surface flaws, and control the surface friction. In limited cases some of these techniques can be used to restore original dimensions to salvage or repair an item. An unfinished surface is often called mill finish.

Work hardening strengthening of a metal by plastic deformation

Work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material. Many non-brittle metals with a reasonably high melting point as well as several polymers can be strengthened in this fashion. Alloys not amenable to heat treatment, including low-carbon steel, are often work-hardened. Some materials cannot be work-hardened at low temperatures, such as indium, however others can only be strengthened via work hardening, such as pure copper and aluminum.

Roller burnishing is used in the production of some crankshafts. A dual roller (cylindrical) tool is moved into the thrust bearing journal of a crankshaft, while the crankshaft is spinning the tool is indexed (so each roller is perpendicular to the thrust surface while backing each other up) deforming the surfaces. So the diameters of each roller added together (compensated for elastic deformation) equals the finish dimension of the thrust bearing.

Crankshaft

A crankshaft—related to crank—is a mechanical part able to perform a conversion between reciprocating motion and rotational motion. In a reciprocating engine, it translates reciprocating motion of the piston into rotational motion; whereas in a reciprocating compressor, it converts the rotational motion into reciprocating motion. In order to do the conversion between two motions, the crankshaft has "crank throws" or "crankpins", additional bearing surfaces whose axis is offset from that of the crank, to which the "big ends" of the connecting rods from each cylinder attach.

Thrust reaction force which expels or accelerates mass in one direction

Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction on that system. The force applied on a surface in a direction perpendicular or normal to the surface is also called thrust. Force, and thus thrust, is measured using the International System of Units (SI) in newtons, and represents the amount needed to accelerate 1 kilogram of mass at the rate of 1 meter per second per second. In mechanical engineering, force orthogonal to the main load is referred to as thrust.

In deep hole machining, a roller burnishing tool is often combined with skiving knives on the same tool. The skiving knives pass first, scraping the inside layer of metal, followed by the burnishing rollers, which cold work the tube to create a mirror surface finish. Skive-burnishing is often used in hydraulic cylinder applications. This process can happen on a deep hole drilling machine or a dedicated skiving machine.

Hydraulic cylinder

A hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment, manufacturing machinery, and civil engineering.

Skiving or scarfing machines cut material off in slices, usually metal, but also leather or laminates. The process is used instead of rolling the material to shape when the material must not be work hardened, or must not shed minute slivers of metal later which is common in cold rolling processes.

See also

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Metalworking production and processing of shaped workpieces made of metals

Metalworking is the process of working with metals to create individual parts, assemblies, or large-scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry. It therefore includes a correspondingly wide range of skills, processes, and tools.

Machining process in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process; manufacturing process

Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. The processes that have this common theme, controlled material removal, are today collectively known as subtractive manufacturing, in distinction from processes of controlled material addition, which are known as additive manufacturing. Exactly what the "controlled" part of the definition implies can vary, but it almost always implies the use of machine tools.

Connecting rod mechanical element that connect the piston to the crank or crankshaft.

A connecting rod is a rigid member which connects a piston to a crank or crankshaft in a reciprocating engine. Together with the crank, it forms a simple mechanism that converts reciprocating motion into rotating motion.

Drilling cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials

Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work-piece, cutting off chips (swarf) from the hole as it is drilled.

Babbitt (alloy) alloys used for the bearing surface in a plain bearing

Babbitt, also called Babbitt metal or bearing metal, is any of several alloys used for the bearing surface in a plain bearing.

Grinding machine power tool or machine tool used for grinding, which is a type of machining using an abrasive wheel as the cutting tool; mechanical hardware for grinding

A grinding machine, often shortened to grinder, is any of various power tools or machine tools used for grinding, which is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation.

Swaging is a forging process in which the dimensions of an item are altered using dies into which the item is forced. Swaging is usually a cold working process, but also may be hot worked.

Shot peening cold metal working process

Shot peening is a cold working process used to produce a compressive residual stress layer and modify mechanical properties of metals and composites. It entails impacting a surface with shot with force sufficient to create plastic deformation.

Boring (manufacturing) process of enlarging a hole that has already been drilled

In machining, boring is the process of enlarging a hole that has already been drilled by means of a single-point cutting tool, such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.

Deep rolling is a method of cold work deformation and burnishing of internal combustion engine crankshaft journal fillets to increase durability and design safety factors. Compressive residual stresses can be measured below the surface of a deep-rolled fillet. Other types of fillets on shafts or tubes can also benefit from this method. Cast iron crankshafts will experience the most improvement potentially doubling their fatigue life. Typically the crankshaft is machined with under-cut fillets as opposed to tangential radiused for ease of manufacture, although all types can be deep-rolled. Most automakers are currently utilizing this crankshaft technology including: General Motors LLC, Ford Motor Company, and Fiat Chrysler Automobiles (FCA) The North American-based Hegenscheidt-MFD Corporation in Sterling Heights, MI, was established in 1966. Ingersoll CM Systems of Midland, Michigan with Global HQ located in Dalian, China and European based SPMS in Évry, France, are the only major machine/tooling manufacturers of this application in Europe and North America, supplying a highly specialised product throughout the global manufacturing sectors.

Cylindrical grinder type of machine used to shape objects

The cylindrical grinder is a type of grinding machine used to shape the outside of an object. The cylindrical grinder can work on a variety of shapes, however the object must have a central axis of rotation. This includes but is not limited to such shapes as a cylinder, an ellipse, a cam, or a crankshaft.

Grinding (abrasive cutting) abrasive machining process that uses a grinding wheel as the cutting tool


Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.

Honing (metalworking) abrasive machining process that produces a precision surface

Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive stone against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but may also improve the surface texture.

Burnishing (metal)

Burnishing is the plastic deformation of a surface due to sliding contact with another object. Visually, burnishing smoothens the texture of a rough surface and makes it shinier. Burnishing may occur on any sliding surface if the contact stress locally exceeds the yield strength of the material.

Brinelling is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface. Brinelling is a process of wear in which similar marks are pressed into the surface of a moving part, such as bearings or hydraulic pistons. The brinelling is usually undesirable, as the parts often mate with other parts in very close proximity. The very small indentations can quickly lead to improper operation, like chattering or excess vibration, which in turn can accelerate other forms of wear, such as spalling and galling.

Low plasticity burnishing (LPB) is a method of metal improvement that provides deep, stable surface compressive residual stresses with little cold work for improved damage tolerance and metal fatigue life extension. Improved fretting fatigue and stress corrosion performance has been documented, even at elevated temperatures where the compression from other metal improvement processes relax. The resulting deep layer of compressive residual stress has also been shown to improve high cycle fatigue (HCF) and low cycle fatigue (LCF) performance.

Metal spinning

Metal spinning, also known as spin forming or spinning or metal turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe.

References

  1. 1 2 www.animationlabs.de, Animation Labs. "The Basic Principles of Roller Burnishing - ECOROLL". www.ecoroll.de. Retrieved 2018-01-30.


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