Surface Modeling

CENTRAL TOOL ROOM, LUDHIANA

Sheet 1 of 35CHAPTER: A4 CNC EDM DIE SINKING

METAL WORKING TECHNIQUE WITH CNC MACHINE TOOLSCHAPTER OUTLINEA4.1 IntroductionA4.2 Definition, Description of main parts & featuresA4.3 Calculation of cutting parameters (structure of machined surfaces)A4.4 Operations on CNC EDMA4.5 Safety & Maintenance of machine

A4.1Introduction-TOPIC OUTLINEClassification of EDM machine

Introduction of CNC EDM-

Electrical Discharge Machining:Machining of hard material or hardened material is not simple. It is very difficult and maximum time consuming method. EDM has solved this problem, since it can cut hardened electrically conductive material to cut complicated shapes and geometrically difficult contours.

A4.1aClassification of EDM Machine-

It depends upon amperes used-16 ampere generator32 ampere generator64 ampere generator128 ampere generator

SUMMARYAt the end of this topic student shall be able to Explain the CNC EDM ProcessKnow the classification of the EDM machines

In the next topic students are going to learn about the description of the main parts and features of CNC EDM Machine.

QUESTION BANKQuestions: Describe CNC EDM process.Explain how CNC EDM Machines are classified.

A4.2Definition, Description of main parts & features-TOPIC OUTLINEDefinitionDescription of main partsTool holding devicesMachine parametersWork Holding devicesTools (Electrodes)

A4.2aDefinition of the Process-The process is characterized by the fact that removal of material is obtained by a succession of non-stationary electrical discharges, separated from each other in time, i.e. only one spark at a time is created. The discharges are produced by the voltage source (off-load voltage). EDM process is also known as spark erosion machining.

A4.2bDescription of main parts-

The machine-The machine consists of a frame to which the column is attached; these two parts, in ribbed cast iron, are highly rigid.

The frame supports a cross table consisting of an intermediate saddle and top saddle, coupled to the work table on which the part to be machined is mounted.

The work tank, which is coupled to the table, contains the dielectric fluid during machining. The work tank is equipped with the part flushing system.

The column supports the Z slide.The electrical equipment box is attached to the back of the column.

The remote control unit is used to engage the motors of the three axes manually in the positive or negative direction (together with the C-axis option).The machine rests on the dielectric reservoir.

Filtering-The dielectric from the work tank is drained into the reservoir through the drain panel. When the pump is started, the reservoir dielectric is driven into a filter battery attached to the back of the reservoir. A part of the clean dielectric is used to feed the flushing circuits, the rest being directed towards the cooler, before being returned to the reservoir.

Electrical equipment box-The electrical equipment box contains the machine electronic interfaces. The box also contains connection points for the various electrical circuits and machining cables.

Remote Control-In the manual mode, the remote control unit is used to start the motors of the 4 axes in the positive or negative directions. The rate of movement can be varied between a minimum and a maximum of 0 to 15 m/sec.

Work tank-The work tank is used to immerse the part to be machined. The front wall, which is hinged, is used as a door. Access to the table is thus facilitated for installation and clamping of the part and for adjustment operations prior to machining.

The work tank is filled and emptied manually.

The dielectric level is set manually by the operator. The temperature of the dielectric in the work tank is kept constant by means of two thermostats located under the cover, on the left hand side of the work tank.

Control Cabinet-The control cabinet contains the various control devices. It is fitted with two access doors.The front door supports the operator-machine dialogue system.Control panelKey board

The front door provides access to the various PCBs of the numerical control, to the generator power units and, at the bottom of the cabinet, to the contractors and thermal protective devices of the electrical part.

The rear door provides access to the power supply PCBs, to the various monitoring boards, to the control and machining cable connectors and to the transformers attached to the bottom of the cabinet.

Control Panel-The control panel, which is built into the cabinet front door, contains the operator-machine dialogue system, together with controls for the operation of the machine, i.e.

Screen-

During machining, the operator can display all the information concerning the work performed by the machine: quality, progress, messages from the machine, etc.Diskette drive-

The diskette drive is used to enter the programs required for operation of the installation, part programs or data specific to a machining operation. It is also possible to retrieve data from the machine memory.The function command keys-

Starting of the pump is indicated by an indicator light, when:The dielectric setting level is reached: the light is onThe dielectric setting level is not reached: the light flashesThe pump is off: the indicator is offPush buttons-Power on Emergency stop (a 2nd emergency stop button is located on the machine head)

A4.2cTool Holding Devices-

Electrode Mounting System-The electrode mounting system is of primary importance for both the attainable degree of accuracy and the economy of the spark erosion process. The system should combine universal applicability with maximum stability and high tool change accuracy. A good electrode clamping system, also referred to as tool system should comprise a leveling attachment for precision adjustment of electrodes, a number of highly accurate quick clamping chucks and different electrode holders which enable the electrode to be machined on a machine tool and subsequently fitted to the spark erosion machine without re-clamping. Some tool systems also include equipment for rotary eroding.

The market offers several tool systems, which have in part been specially developed for EDM operations. The relatively high price, which is due to the high standard of quality, should not keep the users of spark erosion equipment from purchasing such a system. In practice, such an investment will pay its way very soon by saving in setup time and higher degrees of accuracy.Types of accessories with changer-

A4.2dMachine parameters-

The machining process is influenced by a number of parameters, which will have to be familiar to the user of spark erosion equipment, if optimum results are to be achieved.

A)Stock Removal Rate:By definition, stock removal rate is the volume of material removed from a work piece within a unit time. It is expressed in mm3/min when the same spark frequency is used, the stock removal rate will be increased by raising the energy level per spark. But on the other hand, the use of higher spark energy will result in larger craters and thus greater surface roughness. Generally speaking, maximum stock removal rates can only be achieved at the expense of surface finish values being below the generally acceptable standard. This means that roughing operations have to be followed by one or several finishing operations at reduced spark energy. But it should be appreciated that, in the interest of better surface finish, the stock removal rate would be substantially lower.

It will, of course, always attempted to use the highest possible stock removal rate also in finishing operations because this is a decisive factor for the total machining time.

A major advantage of the EDM process lies in the fact that the stock removal rate is practically independent of the hardness of the material. This makes it possible to machine hardened work piece thus avoid the danger of heat distortions fissures which are frequently encountered as a result of heat treatment after the finished cavity has already been produced. Although the hardness of a material is irrelevant for the stock removal rate in spark eroding different materials such as steel and sintered carbides nevertheless show certain differences in behavior. It should also be noted that the stock removal rate would decrease with increasing working depth. This is mainly due to reduced flushing action and thus less efficient removal of the eroded particles, which have a detrimental effect on the conditions in the spark gap. Flushing conditions can be improved by using a vibrator or by pulse flushing.

B)Relative Electrode Wear:The second important technological parameter of spark erosion is relative electrode wear. As pointed out above, surface erosion not only occurs on the work piece but also on the electrode, although, of course, on a lesser scale. Relative electrode wear is understood to mean the ratio between the stock removals from the work piece. It is expressed in percent. A value of 5%, for example, indicates that an amount of 5 mm3 is removed from the electrode while at the same time, 100 mm3 is removed from the work piece. In the course of eroding operation, the active portions of the electrode will more or less be deformed as a result of electrode wear. Unfortunately, this electrode wear is not strictly linear, otherwise it could be compensated for by an appropriate amount of Pre-distortion.

As a matter of fact, sharp edges and corners will be subject to accelerated wear due to the greater current density at these points. As a result, the volume of wear is greater than the length of wear.

Recent developments in the field of spark erosion generators have mainly concentrated on an increase in stock removal rate combined with a reduction of electrode wear. The successes of these efforts is evidenced by the fact that modern pulse generators, if used in conjunction with copper electrodes, have reduced relative electrode wear to less than 1% in roughing operations.

It should be emphasized in this connection that the use of graphite for spark erosion electrodes is particularly advantageous because this material is easy to machine and provides wear ratings which even may be far below 1%.

C)Accuracy for Reproduction:Another important factor for the general applications of spark eroding machines is the accuracy of reproduction of the electrode shape, especially since the general advance of engineering calls for closer tolerance limits. For this reason, it should be carefully considered what geometrical and dimensional deviations are permissible, and what corrections can be incorporated in the electrode, because the final dimensions of a

spark eroded die or mould will never exactly correspond to the dimensions of the electrode.

Other reasons such as electrode wear and the necessary spark gap width, but may also be attributed to mechanical factors e.g. the stability of the machine and the guidance of the electrode. The spark gap width, which ranges from 0.01 to 0.05 mm (0.0005 to 0.02), always makes the die cavity in the work piece slightly larger than the electrode. The width of the gap is dependent or the electrode and work piece materials, the dielectric liquid, the required surface finish and thus, eventually, on the generator setting. In the case of deep holes with a small section, it should be borne in mind that, due to unsatisfactory flushing, there will be slight taper in a downward direction. Conditions can be improved by using sufficiently long and stepped electrodes or by employing button electrodes. Engraved patterns can only be produced with a high degree of accuracy by finishing the work piece with the aid of one or more finishing electrodes after the roughing operation.

It should be noted that electrode wear is greater along the edges than on flat surfaces. Obviously, the smallest obtainable today is roughly 0.01mm (0.0005). This value cannot be appreciably improved except with considerable efforts.

D) Surface Quality:The surface roughness on a spark eroded work piece is determined by the size of the overlapping craters.

Since a high stock removal rate requires the use of high energy sparks, such roughing operations will produce very rough surfaces. A smoother surface can be obtained by a subsequent finishing operation with a second electrode using substantially lower spark eroding operations is less than 1 m CLA fro sintered carbides and about 1m CLA for steel. This will probably be sufficient for the vast majority of machining operations. If this is not the case, spark eroding may afford other advantages, for example in applications where conventional cutting methods can not be used or where complicated profiles and contours can be produced much more economically by spark erosion, provided that final re-touching by hand is reduced to a minimum.

E) Effects on Microstructure:The points of impact of the electrical sparks are exposed to very high temperatures, which have marked effects on the microstructure of the material. In addition, a certain amount of carbon from the dielectric as well as traces of the electrode material enter the work piece surface by way of diffusion. Extensive tests have shown that the surface layer affected by such processes may have thickness of several hundredths of a millimeter (approximately a thousand of an inch). Since the effects on microstructure are largely dependent on the duration and energy of the sparks, it will be no problem to remove such adversely affected surface layers results especially from roughing work by a suitable finishing operation.Material removal rateElectrode wearSurface finishSpark GAPFlushing is the most vital element in the technology of EDM and flushing is used to remove the unwanted particles from the sparking process. Different types of flushing are used depending on the application.

All above parameters are inter-related and give best possible results with appropriate combination.Pressure flushing continuous flushing impose flushing combined flushing.Suction flushing Continuous flushing combined flushingSide set flushing Where flushing through job or electrode is impossibleMotion flushing Motion flushing gives higher efficiency of flushing with moving electrode.

Rotating electrode with rotary device guarantees best roundness, better surface finish and shorter erosion time. Vibratory movement of electrode. Auto flushing in combination with pressure flushing or impulse flushing.

Flushing improves the efficiency of sparking since it is useful:To insulate the gapTo flush wastagesCooling of work pieces and electrodeTo provide bridge between electrode and work piece.

There are variables like on-time, off-time current etc. that contributes to achieve best possible results. With these variables the effects are shown in following table:

MrpElectrode WearSurface FinishGapCurrentIncreaseDecrease

On-timeIncreaseDecrease

Off-timeIncreaseDecrease

All the above are the variables available in the machine. Since the jobs can be of various materials like steel, carbide, aluminum, copper etc, various electrode materials are being used, viz-

Copper-electrode gradeGraphiteSteelCopper-TungstenCopper-Graphite

Depending upon the requirement of the job, these electrodes are selected. For electrodes, following properties are considered while selecting-

Electrical conductivityThermal stabilityMelting point

Grain structure and sizeMachinabilityDensityAvailability

Normally following combinations are used:

Job MaterialElectrode Material

Steel- Copper

- Graphite- Copper Tungsten- Steel

Non-Ferrous Metals- Copper

Carbide / Tungsten- Copper Tungsten

Carbide- Copper

With the general convention, copper or graphite are used as electrodes, being available with reasonable cost.

Graphite gives better material removal rate than copper since its thermal stability is more than copper. Hence more discharges are achieved from the same pulse.

Copper gives better surface finish than graphite since its grain structure is much more finer as compared with graphite.

Machine features and parameters-Every machine is divided into three major parts-

Machine ToolGenerator or pulse control unitDielectric unit

A) Machine Tool:

It consists of parts like-Work table and work tankSlidesServoSafety interlocks

Work table or work tank-Work table is used to keep the job on it. Work tank is used for filling up the dielectric during sparking operation. It is mounted on slides.

Slides-Slides are used of various types like slides with V-flat rollers, slides with needle roller bearings etc. Depending upon the requirements of accuracy, the slides are used. Needle roller bearings give better accuracy and life of slides, since wear and tear is less. These slides are driven by either lead screws or ball screws. Normally the slides are moved by hand wheel (for table movement). However in few cases motorized movements are used (Big EDMs, CNC EDM etc.)

Servo-

SERVO, the world itself means precious. It is essential element since every sparking operations is dependent on the SERVO movement. Various types of SERVO are use in the machine like Electromechanical

DC ServoDC Stepper SERVOAC SERVO

Hydraulic

In earlier generation machines Hydraulic SERVO was used, due to non-availability of electrical motors, which can lift higher weight electrodes.

Now a day with the advent of latest technology, various electrical motors are available and hence are preferred over hydraulic SERVO.

Now a days electromechanical SERVO is used since it has all the advantages of hydraulic SERVO with less maintenance required. Hydraulic SERVO needs periodical preventive maintenance against compared to electro mechanical SERVO.

Safety interlocks:

Various interlocks are used in the machine like A)Low level it prevents machine from fire. In case level goes down and sparking appears on the surface the fire accident takes place.Over Temperature- Due to continuous sparking operation the dielectric temperature increases. Due to increase in the temperature dielectric fires. This inter lock trips the machine before the flash point of dielectric.Preset depth this switch ensures the correct sparking depth. This prevents slide from over travel.Upper limit - This switch prevents the slides from over travel.

Apart from above interlocks other interlocks like over level, anti-arc switch etc. are used to ensure the safety of the machine and the operator.

B)Generator or pulse control unit:

It is a control unit, which controls all the functions of the machine. It consists of important sections like

Input-output section-Which controls the input commands and execution of output commands mainly it is an electrical section where under voltage / over voltage checking, output connections, contractors etc.

Current Section-The current is selected through this section. The current is applied with various devices like mosfet, transistors, variac etc. In recent times mosfets are used popularly since it can be operated with very high frequency range, which gives better surface finish.

Oscillator-Oscillator controls all the EDM technology hand in hand with current section. Oscillator provides settings for on time & off time. Oscillator can be of various types like EPROM, electronically controlled RC, LC or sometimes combination. In this EPROM oscillator is best choice since the data fed in does not change whereas in other cases it changes with duration hence calibration is needed.

Control Section-This section controls the movement of SERVO voltage of sparking anti-arcing sensing etc.

A4.2eWork Holding devices-

1)Swivel base vice-May be bolted to the table or sub-plate. The swivel base enables the vice to be swiveled 3600 in a horizontal plane.2)Angle plates-Arc L-shaped pieces of cast iron or steel accurately machined to a 900 angle. They are made in a variety of sizes & have holes or slots, which provide a means for fastening the w/piece.3)V-blocks-Arc generally used in pairs to support round work piece. A U-shaped clamp may be used to fasten the work in a V-block.4)Step Blocks-Arc used to provide support for strap clamps when work is being fastened to the table or work holding device.5)Clamps or straps-Arc used to fasten work to the table, angle plate or fixture. They are made in a variety of sizes and are usually supported at the end by a step block and bolted to the table by a T-bolt.6)Support Jacks-Arc used to support the work piece to prevent distortion of work piece during Clamping.7)Parallels-Arc flat, square or rectangular pieces of metal used to support the work piece for set up.8)Sub-plates-Arc generally flat plates that may be fitted to the machine table to provide quick and accurate location of work pieces.

A4.2f Tools (Electrode)-

Material Classification-

Electrode material generally used can be classified as follows:

1)Metallic materials-Electrolytic CopperTellurium Or Chromium CopperCopper TungstenBrassTungsten CarbideAluminium

2)Non-Metallic: Graphite3)Combination of metallic & non-metallic materials: Copper Graphite

The Electrode-The purpose of any material used as an electrode in the EDM process is to convey the electrical machining pulses to allow erosion of work piece to take place with little or no erosion of electrode. In principle, any electrically conductive material may successfully be used to fabricate electrode. However, experience shows that depending upon the material to be machined and the type of generator used, certain materials are more suitable than others. The performance of electrode materials in any given condition is judged by its material removal rate, low wear and ability to accurately machine.

The basic requirements for a good electrode material are:

Good electric conductivity and low resistivityResistance to abrasionHigh melting and boiling pointsDimensional stability

High density and high modulus of elasticityGood heat diffusion and conductivity

The selection of proper electrode material is influenced by:

Size of electrode and volume of material to be removedSurface finish requiredTolerances desiredNature of coolant applications

The use of a suitable electrode is one of the main conditions for successful spark eroding. The selection of electrode material is also governed by the following factors:

AvailabilityReasonable priceEase of machiningMinimum wear combined with good stock removal rate

Graphite-

Graphite is an easily machinable material and has a very low wear characteristic especially when used for roughing operations. A variety of different graphite grades have been specially developed for electrical discharge machining. The cheapest and coarsest grain material are suitable for roughing work, while the more expensive fine grain material can be used for finishing. Fine grain graphite provides much higher heat conductivity and thus prevents local over heating of the electrode, which might lead to establishment of a continuous arc.

Copper-Apart from graphite, copper is probably the most frequently used electrode material, either in the form of electrolytic copper or cast copper. The material is universally used in both roughing and finishing operations, it is characterized by low wear and high stock removal and, in addition, is easy to machine on conventional machine tools.

Copper Tungsten-

This material is relativity expensive and thus only on a limited scale. It has excellent wear characteristics and particularly suitable for finishing operations. Copper Tungsten is specially used for machining cemented carbides.

Aluminium-

Aluminium used to be a very popular electrode material but is now employed very rarely. Its melting point is so low that the high electrode wear ratio makes most aluminium alloys uneconomical. Only very large electrodes with a correspondingly low current density provide for sufficient heat dissipation to reduce electrode wear to an acceptable level.

Brass-

This is a very popular and low priced electrode material, which was widely used in conjunction with earlier relaxation generations. Today it has only a limited range of applications, e.g. in machining titanium components, this requires negative polarity.

SUMMARYAt the end of this topic student shall be able to Identify the various parts of CNC EDM MachineKnow the tool mounting systems Know machine parameters Identify various tool holding devices and work holding devicesDescribe the cutting tool (Electrode)

In the next topic students are going to learn about calculation of cutting parameters (structure of machine surfaces).

QUESTION BANKQuestions:

Explain the machine basic construction.Describe the function of filtering unit.Write the elements present on the control panel on the machine.Explain relative electrode wear.What is the importance of servo in machine?Explain any two types of work holding devices used on CNC EDM Machine.

A4.3Calculations of Cutting Parameters (structure of machined surfaces)-

TOPIC OUTLINEStructure & characteristics of CNC EDM machined surfacesSurface finish

A 4.3aStructure & characteristics of CNC EDM Machined surfaces-

In EDM machining, removal of material is caused mainly by a thermal phenomenon. It is known that the temperature in a discharge is of the order of 80000 to 120000 C.

The effect of these high temperature discharges obviously affects the structure of the material used. This influence varies according to different materials (some do not show any modification of structure).

A metallographic inspection of the cross section of an eroded surface shows two layers of a different nature, shown in figure below:

A heterogeneous white layer, consisting of a mixture of carbon rich solid solutions, this latter coming on the one hand from steel and on the other hand from break down of the dielectric fluid (hydrocarbon) due to the effect of heat.

An intermediate layer located between the white layer and the metal that has not been subjected to the thermal effect. This layer appears only in heavy rough machining settings; it has not become molten. However, the metal has been raised to a relatively high temperature over a very short period of time and then suddenly cooled.

Depending on the temperature reached locally, this heat treatment produces a modification of the initial structure for steels susceptible to hardening, which can result:Either in hardening (hardening effect due to passage of the steel transformation points)Or in softening (super-tempered effect in the case of a hardened and tempered steel, if the heating is greater than the initial tempering temperature).

Generally, in practice hardening in the intermediate zone is observed, the eventual softened zone being located in the immediate vicinity of the metal not affected by erosion.The diagrams below show the relationships, which may be established, between maximum temperatures, which may be reached during erosion, micrographic structures, and hardness.

Curve of maximum temperatures reached erosion (along a line perpendicular to the surface).

Hardness curve resulting from temperature curve:1)Melted area white film2)Austenitized area hardened layer3)Super-tempered area only for hardened and tempered steelsThe thickness of the disturbed layers decreases simultaneously with the machining power level.

4.3bSurface Finish-

Testing of surface finishes is carried out using apparatus known as roughness meters.

Experience shows that measurement of surface finishes by visotactile comparison with a standard does not give an error of more than 2 class CH.

The roughness criteria are Ra (Europe) = CLA (UK) = AA (USA).

To obtain a roughness scale, Charmilles Technologies have defined a CH scale (similar to VDI 3400), which is, however comparable with the standards used.

Definition of roughness criteria:CH No.20 log (10 Ra) (m)

Significant rules and figures:1m Ra = CH2010m Ra = CH40if: Ra = Rax2CH = CH + 61m Ra = CH202MRA = CH26

The ratio between 2 successive CH units is 1.12

The difference between 2 successive CH units is 12.2%

Rt. is approximately equal to 8 x Ra. Mean Rt = 5 x value of Ra.

SUMMARYAt the end of this topic student shall be able to Explain the structure and the characteristics of EDM Machine surfacesClassify various surface finishes produce on CNC EDM Machine

In the next topic students are going to learn about various operations and features of the machine.

QUESTION BANKQuestions:Explain the structure and the characteristics of EDM Machine surfaces.Classify various surface finishes produce on CNC EDM Machine.

A4.4Operations on CNC EDM-Features of machine:On this machine complicated shapes and geometrically difficult contours can be made.Threading operation also done on this machineCutting independently in x, y, z axisHelical cuttingPath controlPlanetary motionMagazine facility

SUMMARYAt the end of this topic student shall be able to Know the various operations performed on CNC EDM machine.

In the next topic students are going to learn about the safety and maintenance of the machine.

QUESTION BANKQuestions:Explain the planetary motion on CNC EDM machine.List any two operations, which can be performed on the CNC EDM Machine.

A4.5 Safety & Maintenance of Machine-

TOPIC OUTLINESafety & MaintenanceGeneral recommendations

A4.5a Safety & Maintenance of Machine-

Introduction-In order to guarantee healthy and agreeable working conditions for persons working on EDM machines and for those present in the same premises, it is indispensable that some elementary hygiene and safety rules related to this machining process be respected. Operators, foremen and company directors are called upon to respect the rules mentioned below:

Training-Only persons trained on this type of machine and its equipment are authorized to use it.

Training sessions concerning hygiene and safety problems are to be held annually.

Premises-Freshening up of the ambient air of the premises must be guaranteed; this is done to avoid formation of a noxious and dangerous atmosphere, without omitting the volume of air evacuated by the smoke extractor, which must be replaced.The premises in which an EDM machine using a dielectric operates, in which the flash point is lower than 1000C, is considered a fire hazard.Therefore, the electrical installation on this premises must comply with the requirements of the standards in force.For Germany, standard VDE 0 100 T720.

Smoke-Essentially, emanations from the dielectric consist of gases and smoke produced by the thermal decomposition of the oil due to the spark erosion process.These emanations are of different kinds and comprise of:

Poly-cyclic aromatic hydrocarbons (PAH) in the solid or gas state,Aromatic hydrocarbon and paraffin vapors,Metal particlesVarious products which may result from the breakdown of additives

The following instructions must be respected:

The smoke sensor must be connected to a sufficiently powerful suction system capable of providing a suction rate, measured at the edge of the work tank, of more than 1 m/sec.The smoke suction-conduit must be non-inflammableIf the smoke suction, conduit has a metal armature the latter must be connected to ground

Comments-Some machines are equipped with a monitoring device in the smoke sensor, if suction is insufficient; it is impossible to start machining.

Fire-

Preventive measures:To avoid any over heating of the dielectric, the cooling system must be permanently in operation.Two safety thermostats control the dielectric temperature in the work tank; these will stop machining if the temperature becomes too high. (T>450)

Within a radius of 5 meters around the machine, the presence of flames and named light bulbs is prohibited.

Similarly, smoking is prohibited (no smoking signs)A extinguisher must be located in the immediate proximity of the machineIn the case of non-supervised machining operations, a fire extinguishing installation is to be set upWhen machining, the part must be covered with a minimum of 40mm of dielectric fluid, avoiding immersion of the electrode-holderGases generated by the machining process must not be allowed to form in the hollow parts of the machined part or the electrode (risk of explosion).

Protections-

All covers and protective paneling must be kept in place when working with the equipment.Protective material must not be neutralized.After an intervention, all protective devices must be installed before machining.In the event of an accident, and if the safety instructions have not been respected, Charmilles Technologies may disclaim all responsibility.There is no need to wear personal protection equipment when operating this machine.

Dielectric-

The dielectric used on EDM machines must be identifiable by its designation.

A plate affixed to the front of the work tank is used to inscribe the following information:Type of dielectricDielectric flash pointDermatological risksSafety instructions

Comment:The use of dielectrics of flash point less than 600 C is prohibited.

Hygiene instructions-

To prevent prolonged contact of the skin with the dielectric, gloves must be worn. \Wash your hands after any contact with the dielectricProtect the eyes against dielectric splashesDo not ingest dielectric

A4.5b General Recommendations-

If the dielectric overflows, this must not be allowed to soak into the ground or to be drained off through sewers.Contact the competent local authorities to acquaint yourself with the regulatory instructions concerning storage and elimination of waste.It should be noted that, in most cases, storage and elimination of waste imply sorting according to the nature of the pollutants (plastics, metal, etc.).Consult the standards in force concerning heavy, non-recyclable materials.

SUMMARYAt the end of this topic student shall be able to Know the various safety precautions followed on CNC EDM MachineKnow the general recommendations while working on the machine

In the next chapter students are going to learn about CNC High Speed Milling.

QUESTION BANKQuestions:List any two hygienic instructions to be followed while working on CNC EDM.What preventive measures to be taken to avoid fire of the machine?