Posted on 22nd Dec 2022

Deep Look Into Graphite Machining And Its Advantages

Despite its softness, graphite is one of the most challenging materials to process. When machining these parts, machinists must make several decisions regarding tools, coolant use, and personal safety. Graphite machining is the process of shaping, moulding, configuring, and cutting graphite material to create various parts and components for industrial purposes.

The types of tools utilized determine the success of graphite machining. To prevent chipping and breakouts, manufacturers utilize specifically developed cutting tools. In most situations, indexable carbide cutters with the most practical shapes for roughing at high rates of speed are employed. 
 

What is Graphite, And What Are Its Types?

Graphite is a kind of carbon that contains carbon atoms organized in layers, which gives it its distinct features. Natural graphite is mined all over the world, although most of it is found in China, Brazil, Canada, and Madagascar. It is located in metamorphic and igneous rocks and is generated when carbon in the earth's crust is exposed to high pressure and temperature.

The carbon in synthetic graphite is of great purity and can endure high temperatures and corrosion. Calcined petroleum coke and coal tar pitch, which contain graphitizable carbon, are the primary elements used to produce synthetic graphite. The combined ingredients are mixed, heat-treated, moulded, and baked throughout the production process.

Machining cast iron and machining graphite processes are identical. Swarf, or fine chips, are removed as a fine powder. The tools used in the procedure do not grip the workpiece but cut it like ploughing snow. The compressive strength of graphite is muscular and may be kept in place by clamping force.

Graphite components are used in various sectors due to their chemical and physical qualities. It has a low thermal expansion coefficient, can be machined to tight tolerances and has excellent stability at high temperatures. Each of these qualities makes it ideal for specialized production applications.

Graphite has a wide range of applications, from the substance in pencil to the liner of nuclear reactors. Electrodes, brushes, and plates for dry cell batteries are made from crystalline flake graphite. In addition, the use of graphite in constructing electric vehicles is a significant new discovery.

Some of the types of graphite parts include:

• Lubrication Blocks Made of Graphite

Lubrication blocks are utilized in situations when wet lubricants cannot be used. They're primarily found in rotating equipment, including trunnion rolls, riding rings, tyres, and insert seals. Because of their weight, they are constantly in touch with the rolling surface, producing a thin layer of graphite. The significant reasons graphite is utilized for lubricating blocks are its wear resistance and long service life.

• Bearings with Graphite

Bearings are manufactured to minimize friction between two surfaces. As a result, they provide load support when in touch with another moving item. Graphite is perfect for bearings because of its self-lubricating properties, extended service life, and ability to tolerate hostile conditions.

• Brushes with Low Porosity Graphite

Graphite brushes are square and are used to conduct electricity via electric motors. They provide a consistent current shift between commutator segments and wear to preserve its condition. They are made from natural or synthetic graphite with a pitch or resin binding agent. Environmental variables will not taint graphite brushes.

While there are various uses for graphite in multiple industries, it still requires careful matching to ensure the best possible results. Factors that should be considered are:

• The material is very conductive. Protecting electrical and electronic components against tiny graphite particles is a significant concern for machine tool makers.
• Machining graphite on a CNC machine necessitates particular modifications to handle graphite dust, which can cause costly damage and even void a warranty.
• If electrical parts are not correctly selected and safeguarded, graphite dust will collect on them and cause a short-circuit, irrevocably destroying the parts.
• Machines must have proper enclosures and protection and dust suction techniques because prolonged contact with graphite powder causes respiratory problems. These particles are very lubricative, and their deposition on the shop floor will make it slippery, leading people to fall.
• Special electrical cabinets and panel coolers for the control system and drives are necessary to safeguard the gadgets.
• Drive components require unique coverings.
• It is preferable to cut the graphite dry.

Machined Graphite Processes of Various Types

Machined graphite parts and components come in various shapes and sizes. The procedure utilized to machine them is determined by the specifications of the element being created. Extruding, isostatically pressing, vibrating, and moulding are all ways of machining graphite.

• Extrusion Method

Extruding is a typical procedure in the manufacturing of polymers. Graphite powder is combined with a binder, placed into a hopper, fed into the barrel of the extruder, and driven down the barrel to the die by a piston in the graphite production process. After leaving the extruder, the form is fired, impregnated, fired again, and graphitized at 2000C (3632F). Extruding graphite pieces is highly cost-effective.

• Isostatic Pressing 

Isostatic pressing delivers equal pressure on fine grain graphite powder. Workpieces are heat-treated after pressing to fully solidify, densify, alter, and purify them to create the final crystalline structure. The procedure can be carried out either cold or hot.

• Solidification and Vibrated Graphite

When high strength is not required, vibrated graphite processes large sizes of less dense graphite, making it a cost-effective production method. The finished product has a consistent structure and a low ash percentage. A pasty substance is poured into a mould, and a hefty plate is placed on top. The mould is vibrated until the pasty mass freezes to condense the material.

• Graphite Molding

The molding procedure for graphite machining yields components with qualities comparable to those obtained by isostatic pressing. A graphite powder mixture is consistently squeezed into a mould and maintained there for a lengthy period. The resultant products lack the high-quality qualities of isostatic pressing but are appropriate for significant volume manufacturing runs of tiny parts like washers.

If you are seeking graphite moulded parts with a specific requirement, WIDMA is the correct answer for you!

Here's what WIDMA provides:

Deep Hole Drilling Machines

 

• Drilling of holes in horizontal & vertical rows (Both Cylindrical & rectangular blocks) – Programmable Axis for any hole position
• Single Spindle & Multiple spindle options
• Pneumatic fixtures | Mechanical fixtures OPTIONS
• High-Speed Spindles
• CNC Rotary table Option for part Indexing – For Single Setup Machining
• Programmable Center distance between the spindles (For multi Spindle machines)

Vertical Turning Lathes (VTL)

• The rough graphite blocks are machined to shape as per requirement.
• Wilma provides a solution for graphite machining – 2-axis CNC VTL, 3-axis CNC Turn Mill, 5-axis Multi-tasking machines and deep hole drilling machines.
• The OD turning / ID turning / Boring / Step turning / profile turning/grooving operations can be performed on a 2-axis VTL machine.
• The 3-axis Turn-mill machines can perform all the above-mentioned turning operations and drilling and milling operations on top surfaces. The machine is equipped with VMC live spindle with ATC apart from the work spindle on the table.
• The 5-axis Multi-tasking machine is very versatile. The live spindle is capable of tilting from a vertical to a horizontal position. Any angle machining is possible between vertical and horizontal positions of the spindle. In the horizontal position of the spindle, all drilling and milling operations are possible, similar to HMC applications.
• WIDMA offers and recommends specially sealed chucks for component holding to prevent dust particles from entering the work spindle.
• A Compressed / Pressurized Air jet is provided at the machining area, which helps in driving away from the dust particles at the cutting zone.
• Stainless steel telescopic covers to avoid corrosion.
• Additional bellow covers to protect the ball screws and LM guides from fine dust.
• Wilma offers unique electrical cabinets which eliminate the use of panel AC.

Visit WIDMA and connect with them to find the right solution for your graphite part requirement!