Metallographic Grinding and Polishing Equipment Information

Metallographic grinding and polishing equipment includes grinders, sanders, polishers, grinder-polishers or other machines designed for metal, ceramic, mineral, composite and material surface preparation applications. The equipment provides a planar, polished surface enabling materials analysis using microscopy, spectrometry, hardness, nanoindentation and other techniques.

Most metallographic grinders, polishers or grinder-polishers are designed to hold a metal alloy or material sample embedded in a resin mount. Some grinding and polishing machines can accommodate or be adapted to handle complete parts or sectioned samples with irregular shaped for applications where specifics grain flow, manufactuPlanar Grinder imagering defects or other features need to be examined within the component.

Metallographic preparation machines use a series of coarse grit to very fine grit abrasive products. Coarse grit abrasive discs, abrasive belts or abrasive stones or grinding wheels are used to rough grind the sample and expose the sample within the mount. After coarse grinding is complete, wet grinding with a series of finer grit abrasive discs is used to refine the surface finish. Each abrasive is the series removed the scratches from the previous abrasive product. Finally, polishing is completed with a series of abrasive pastes, abrasive slurries or polishing compounds using a polishing cloth on the backing plate. Alternatively, some alloy samples are final polished and/or etched using an electropolisher-etcher.

Types

Grinder -- Grinders and grinding machines remove material and improve surface finish. Abrasive materials are bonded to abrasive stones, grinding wheels, abrasive belts, or abrasive discs.

Polisher -- Polishers, polishing lathes, and polishing machines are specialized machines that produce bright, smooth, or fine surface finishes. Polishing machines use loose abrasives, lapping compounds. or fixed fine-grit abrasive products such as abrasive films or discs. Polishing lathes include two tapered shafts that accept a variety of tool-holding chucks.

Grinder-Polisher -- Metallographic grinder polishers allow the metallographer to perform grinding and polishing on a single machine, which might be a selection consideration in metallographic laboratories with limited bench top space. Coarse abrasive grit particles must be cleaned out from the machine to avoid scratch generation during polishing steps with finer grit abrasives.

Metallographic Machine Configuration

Metallographic surfacing machines are available in a variety of configurations, which utilize a variety of specific abrasive types, electrochemicals and mechanical action.

Abrasive Disc Machine -- Abrasive disc machine use an abrasive disc held onto to a backing plate with a pressure sensitive adhesive or clamping ring.

Belt Machine -- Belt grinders and sanders consist of a driven contact wheel and a tensioning idler wheel or pulley. Abrasive belts are mounted on both the contact wheel and the idler wheel. Workpieces are ground or sanded against the abrasive belt. Contact wheels vary according to the degree of aggressiveness or finishing required. Smooth, soft, Variable Speed Polisher imagerubber-faced contact wheels are the least aggressive. Serrated, hard, rubber-faced wheels are more aggressive. Smooth metal or steel-faced wheels are the most aggressive.

Electropolisher-Etcher – Metallographic electropolishing machines use an electrochemical or electrolytic process to polish or refine the surface finish after abrasive grinding steps. The electrolytic action polishes by attacking and dissolving the higher peaks one the sample’s surface. Electropolishers can also etch metallographic samples to expose grain boundaries, phases or other metallurgical features. Electropolishing is useful for metallographic polishing of austenitic stainless steels, pure aluminum, aluminum alloys, pure copper and copper alloys.

Lapping Machine -- Lapping machines generate very flat surfaces (geometry refinement) with extremely fine finishes by using loose abrasives in a carrier fluid where parts are processed between one or two large flat lap plates or platens. Compared to grinding and honing, lapping removes much less material. Finishes are measured in micron and nanometer ranges.

Orbital / Planetary – Orbital or planetary metallographic preparation machines use an orbital or planetary motion during finishing or grinding. The orbital action can reduce the effects of any variation in the abrasive product or lapping surfaces.

Superfinishing Machine -- Superfinishing, microhoning, or microfinishing machines produce surfaces with a very fine or low roughness average (Ra). A very fine grit stone or several fine bonded stones are rubbed against the surface of the workpiece. Superfinishing is similar to honing, but finer or lower Ra finish is produced with limited stock removal. Superfinishing can not correct geometry to the same degree as honing.

Variable / Multi-speed – Variable speed machines allow adjusted of the motor speed. Variable speed adjustment can be continuous or discrete speeds within an operating range.

Vibratory / Oscillatory Machine – Vibratory metallographic machines use a vibratory or oscillatory motion during finishing.

Machine Mounting

Bench -- Bench or pedestal units are smaller machines commonly used in shop applications for sharpening, offhand finishing, and deburring.

Floor Mounted / Stationary -- Devices are floor-mounted and designed to be used in one location. They are not portable.

Handheld / None -- Devices are light enough to be held manually and applied to the work surface during grinding, finishing, polishing, or sanding.

Portable (Field / Plant) -- Devices are mobile or portable and can be carried or wheeled to a field or plant worksite. They are not necessarily handheld. Metkon provides a portable hand held grinder-polisher, MOBIPREP, for field applications.

Performance Specifications

Surface / Linear Speed (velocity, fpm) -- This is the surface or liner speed in feet per minute or inches per second of the grinding wheels, buffing pads, abrasive discs, polishing naps, abrasive products, or other rotary tools that can be mounted on and driven by the machine.

Rotary Speed (rpm) -- This is the rotary speed in revolutions per minute of the grinding wheels, buffing pads, abrasive discs, polishing naps, abrasive products, or other rotary tools that can be mounted on and driven by the machine.

Automation / Material Handling

None / Manual -- Metallographic preparation machine requires manual loading and then manual setup and operation. Users must change abrasive products and adjust machine parameters such as speed, applied load, and coolant/lubricant flow. The user interface may include push buttons, foot switches, pendants, a touchscreen, or a graphical user interface (GUI).Grinder-polisher image

Automatic / Indexing -- Metallographic preparation machine loads parts automatically and can be operated without user intervention. Machines change or adjust abrasive product, workpiece, and other parameters such as speed, applied load, or coolant/lubricant flow rate in a pre-programmed manner. They also index the cut depth or position to achieve the required material removal, geometry, and/or surface finish.

CNC -- Metallographic preparation machine includes automated computer numerical control (CNC) machine tools. These can be as simple as point-to-point linear controls or can perform highly complex algorithms that involve multiple axes of control.

PLC - Metallographic preparation machine includes a programmable logic controller (PLC) for programming and controlling a sequence of machine operations.

Windows / PC Control -- Metallographic preparation machine requires is controlled or programmed through a personal computer (PC) interface that uses an operating system such as Microsoft Windows®. Machines change or adjust grinding wheel or abrasive product, workpiece or other parameters such as speed, applied load, or coolant/lubricant flow rate in a pre-programmed manner.

Loader Arm / Robot -- Parts are loaded and presented to the abrasive tool with a loader or robotic arm.

Applications

  • Biomaterials (Tissue, Bones, Cells, etc.)
  • Ceramatography
  • Electronics (PCB, SMT)
  • Failure Analysis
  • Forensics
  • Metallography
  • Materialography
  • Mineralogy / Petrology
  • Optics / Lens
  • Porous Samples
  • Semiconductor / Microelectronics
  • Spectrographic / Spectrometry
  • Wafer / Substrate Analysis
  • Spectrographic / Spectrometry
  • Wafer / Substrate Analysis

Image credits:

Buehler, an ITW Company | Lapmaster® Wolters



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