GRINDING MACHINE

GRINDING MACHINE


A grinding machine is a machine tool used for producing very fine finishes or making very light cuts, using an abrasive wheel as the cutting device. This wheel can be made up of various sizes and types of stones, diamonds or of inorganic materials.

Construction Features:

The grinding machine consists of a power driven grinding wheel spinning at the required speed (which is determined by the wheels diameter and manufacturers rating, usually by a formula) and a bed with a fixture to guide and hold the work-piece. The grinding head can be controlled to travel across a fixed work piece or the work piece can be moved whilst the grind head stays in a fixed position. Very fine control of the grinding head or tables position is possible using a vernier calibrated hand wheel, or using the features of NC or CNC controls.
Grinding machines remove material from the work piece by abrasion which can generate substantial amounts of heat, they therefore incorporate a coolant to cool the work piece so that it does not overheat and go outside its tolerance, the coolant also benefits the machinist as the heat generated may cause burns in some cases. In very high-precision grinding machines (most cylindrical and surface grinders) the final grinding stages are usually set up so that they remove about 2/10000mm (less than 1/100000 in) per pass - this generates so little heat that even with no coolant, the temperature rise is negligible.

Types of grinding machine

These machines include the

• Belt grinder, which is usually used as a machining method to process metals and other materials, with the aid of coated abrasives. Sanding is the machining of wood, grinding is the common name for machining metals. Belt grinding is a versatile process suitable for all kind of applications like finishing, deburring and stock removal
• Bench grinder, which usually has two wheels of different grain sizes for roughing and finishing operations and is secured to a workbench. It is used for shaping tool bits or various tools that need to be made or repaired. Bench grinders are manually operated.
• Cylindrical grinder which includes the center less grinder. A cylindrical grinder may have multiple grinding wheels. The work piece is rotated and fed past the wheel/s to form a cylinder. It is used to make precision rods.
• Surface grinder which includes the wash grinder. A surface grinder has a "head" which is lowered, and the work piece is moved back and forth past the grinding wheel on a table that has a permanent magnet for use with magnetic stock. Surface grinders can be manually operated or have CNC controls.
• Tool and Cutter grinder and the D-bit grinder. These usually can perform the minor function of the drill bit grinder, or other specialist tool room grinding operations.
• Jig grinder, which as the name implies, has a variety of uses when finishing jigs, dies, and fixtures. Its primary function is in the realm of grinding holes and pins. It can also be used for complex surface grinding to finish work started on a mill.

HMT MCHINE TOOLS

HMT MCHINE TOOLS:

HMT Machine Tools’ expertise in machine tools has been honed to a point that it can design and develop any kind of machine. From simple lathes to multi-station transfer lines, from stand-along CNC machines to flexible manufacturing systems, leading to factory automation, HMT Machine Tools’ Products cover general purpose machines, special purpose machines and CNC machines to meet the application needs of every engineering industry. To date, over 80,000 machine tools on par with international standards in quality and performance, manufacture by HMT, are in use all over India. The Company also manufactures sheet fed offset printing machines in single, two, four, and five colours, programmable paper guillotines, ball screws, and CNC Control Systems.

HMT’s pioneering spirit and cutting-edge marketing abilities enable it to showcase its products and services to a worldwide clientele. The establishment of HMT (International) Limited leveraged the Company’s international trading experience. HMT(I) markets the products through a global network that extends over 40 countries to service its customers worldwide. HMT (I) has a diverse clientele with more than 14,000 machines in over 70 countries including the developed ones.

HMT Machine Tools, jointly with HMT(I) has been instrumental in executing various international turnkey projects in Algeria, Tanzania, Nigeria, Malaysia, Iraq, Mauritius, Indonesia, Kenya, Ethiopia, Iran, Maldieves, Senegal, Turkemenistan, Nepal, Zambia.

Salient Features:

• range of precision ball screws used in CNC machine tools and other various engineering applications where conversion of rotary motion in to linear movements and vice versa are required.
• High mechanical efficiency, superior positioning accuracy coupled with low wear and long life.
• Range covers ball screws in sizes from dia. 16 mm to dia. 80 mm with leads 3,4,5,5.08,6,6.35,8,10,12.7,16, 19 and 20 mm.
• Number of turns in nuts: 2, 3, 4, 5, 6, and 8 depending on size.
• length of up to 3500 mm is offered depending up on the size.
• applications in machine tools as mechanical feed elements, industrial robots, material handling equipment, nuclear reactors, rail road equipment, medical equipment, printing and paper machinery.
• also developed in-house patent design ball screw having unique stainless steel double start, self-locking and self-aligning yoke that is superior to existing conventional tube re-circulating type.
  

WIRE ELECTRO-DISCHARGE MACHINING

WIRE ELECTRO-DISCHARGE MACHINING

It is a process similar to the EDM except that a copper wire of diameter in the range of 0.20 0.50 rom is used for cutting through slots of required shape. Certain degree of draft cutting. (Cuttirig at an angle permissible around 7 degj side.). The process utilizes a predrilled hole to allow the cutting wire to pass through the hole then attached to the winding cylinder. The working chamber is filled with dielectric fluid distilled water. The wire sparks and melts the material in the region of spark gap usually 0.1 - 0.2 mm.

APPLICATIONS OF WEDM

The WEDM is widely used in the production of prototypes, small series of spare parts, stamping dies, drawing and extruding tools, templates, gauges, cam discs, electrodes for spark erosion, blanking dies, sintering dies, plastic molding dies etc.,

ADVANTAGES:

1. WEDM can machine any complicated through hole dies of electrically conductive materials.
2. The time utilization of WEDM is high as it can work right through out the day.
3. Small batch productions including prototypes can be economically machined as most of the programming is easily done. 4. The process leads to high surface finish.

WIRE-EDM MACHINE & ITS SPECIFICATION:

MAKE	ELCTRONICA
TABLE TRA VEL(mm)	400X300X250
D,V AXIS TRAVEL (mm)	+/-40
TABLE SIZE (mm)	660X440
MAX. WORKPIECE(mm)	500X400X250
MAX. WORKPIECE WEIGHT(Kg)	500
MAIN TABLE FEED RATE(mm/min)	900
WIRE FEED RATE(m/min)	0-15
WIRE TENSION (Kg£)	2.5
WIRE GUIDE DIA(mm)	0.25
	+ / - 30° /50mm LENGTH
TAPER CUTTING	+/-15° /100mm LENGTH

EDM MACHINES SPECIFICATIONS

EDM MACHINES SPECIFICATIONS

1. OSCARMAX ELECTRICAL DISCHARGE MACHINE

MODEL	S 325 ZNC
WORK T ANK(mm)	850X530X340
WORK T ABLE(mm)	600X300
TABLE TRA VEL(mm)	300X250
SERVO TRA VEL(mm)	150
WORK HEAD TRA VEL(mm)	200
MAX. ELCTRODE Wt. (Kg)	80
MAX. WORKPIECE Wt. (Kg)	400

2. ELEKTRA PLUS PS50

MOUNTING SURFACE(LXW)	550X350
MAX. WORKPIECE HEIGHT(mm)	250
MAX. JOB WEIGHT(Kg)	300
X-AXIS TRA VEL(mm)	300
Y-AXIS TRA VEL(mm)	200
LEAST COUNT OF HAND WHEEL	0.02
WITH VERNIER SCALE(mm)
MAX.T ABLE QUILL	515
DISTANCE(mm)
MIN.TABLE QUILL DISTANCE(mm)	265
WIDTH OF WORK TANK(mm)	820
DEPTH OF WORK T ANK(mm)	490
HEIGHT OF WORK TANK(mm)	325
MAX. OIL( Ltrs)	350

SERVOSYSTEM TO PROVIDE CONTROLLED FEED RATE

SERVOSYSTEM TO PROVIDE CONTROLLED FEED RATE

A servo system advances the tool electrode according to machining process. The feed controlled as to prevent the given¬
1. Too large gaps, which will prevents formation of sparks.
2. Short-circuits which will damage both the tool and the work piece.
The feed control system works by maintaining the constant gap voltage between the tool electrode and the work piece, hydraulically or electro mechanic all y.

APPLICATIONS

The process can be used for the following applications on the work piece, which are good conductors of electricity.

1. For machining dies for forging, blanking, extrusions etc.
2. For drilling fine deep holes like in fuel ejecting nozzles.
3. Hydraulic valves spools can be machined.
4. It is possible to manufacture fragile components, which are difficult to machine through conventional methods because of high tool forces.

ADVANTAGES

1. Complicated geometrical shapes can be machined.
2. Toughness and hardness of the material are of no importance for the metal removal rate. So dies can be hardened before being shaped by EDM.
3. Possibly to do job which are impossible by conventional machining methods.

Electrical discharge machining (EDM)

Electrical discharge machining (EDM)

Electrical Discharge Machining (or EDM) is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques. One critical limitation, however, is that EDM only works with materials that are electrically conductive. EDM can cut small or odd-shaped angles, intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden them as well as exotic metals such as titanium, hastelloy, kovar, and inconel.

Sometimes referred to as spark machining or spark eroding, EDM is a non-traditional method of removing material by a series of rapidly recurring electric arcing discharges between an electrode (the cutting tool) and the workpiece, in the presence of an energetic electric field. The EDM cutting tool is guided along the desired path very close to the work but it does not touch the piece. Consecutive sparks produce a series of micro-craters on the work piece and remove material along the cutting path by melting and vaporization. The particles are washed away by the continuously flushing dielectric fluid. It is also important to note that a similar micro-crater is formed on the surface of the electrode, the debris from which must also be flushed away. These micro-craters result in the gradual erosion of the electrode, many times necessitating several different electrodes of varying tolerances to be used, or, in the case of wire EDM machining, constant replacement of the wire by feeding from a spool.

According to the Manufacturing Reference Guide by Robet H. Todd, Dell K. Allen, and Leo Alting, EDM grinding is a mass-reducing process that uses a rotating conductive wheel to remove electrically conductive material by means of controlled, repetitive spark discharges. A dielectric fluid is used to flush away the chips, regulate the discharge, and cool the wheel and the workpiece.
There are two main types of EDM machines: Sinker EDM (also called Conventional EDM and Ram EDM) and Wire EDM.
Advantages
Some of the advantages of EDM include machining of:
* complex shapes that would otherwise be difficult to produce with conventional cutting tools
* extremely hard material to very close tolerances
* very small work pieces where conventional cutting tools may damage the part from excess cutting tool pressure.

Disadvantages
Some of the disadvantages of EDM include:
* The inability to machine non-conductive materials.
* The slow rate of material removal.
* The additional time and cost used for creating electrodes for ram / Sinker EDM.
* Reproducing sharp corners on the workpiece is difficult due to electrode wear.
EDM is a chip less metal removal process that uses the principle of metal erosion by an interrupted electric spark discharge b/w the tool (cathode) and the work piece (anode) this process is also called liSP ARK EROSION II DIEELECTRIC FLUID

The common dielectric fluids used are paraffin oils transformer oil dematerialized water and kerosene. Dielectric fluids prevent particles of work piece adhering to the tool electrode and increases metal removal rate as compare with operating air. These fluids are hydrocarbons and hydrogen in these fluids provides de-ionizing action necessary for thee fluid to become an effective insulator after each discharge. It remains non conductive till break down occurs, breaks down rapidly when critical voltage is reached and then de-ionizes rapidly after the condenser as discharge. Low viscosity fluids make the flow easy.

A general guide to the selection of appropriate tool material for different

material is given below:

Electrode	Work piece
Copper	Aluminum
Copper	Brass
Copper	Steel
Copper Tungsten	Copper
Copper Tungsten	Steel
Copper Tungsten	Tungsten carbide
Graphite	Aluminum
Graphite	Steel
Graphite	Zinc alloy
Steel	Steel