Electric Discharge Machines, CNC Engraving Machines, Tungsten Carbide Controllers, Micro Controller Based EDM Logic Controllers, Spark Controllers, Horizontal Sparking Attachment, India

Introduction to

Microcontroller based EDM Logic Controller

Micro controllers, as the name suggests, are small controllers. They are like single chip computers that can be interfaced to other devices, like Programmable Logic Controllers (PLCs), to function as processing / controlling units. This results in reduced number of components and hence lesser breakdowns. M/s SAVITA MACHINE TOOLS PVT. LTD. developed India’s First Micro Controller based EDM Logic Controller in 1999.

This development resulted in

Minimum breakdown involving very low servicing cost (maximum fault free working period)
Higher output from the machine.

There is generally a false notion that Imported Machines give better service Vis-à-vis Indian machines. It is not true in all the cases. It is the general experience that cheaper imported machines result in increased service expenses thus ultimately off-setting the advantage of initial lesser cost.

Also some manufacturers are able to sell their products on the ground that they have good servicing backup. But large servicing backup is really required when the manufacturer is not confident about the performance of his products and tries to make up for the deficiencies by boasting of good servicing setup.

Our corporate policy at SAVITA is to provide high quality machines that would not require servicing but give highest performance to the entire satisfaction of the customer and we can proudly say that our machines meet these requirements; though in case of problem we do provide services in the shortest time possible.

To achieve this aim of providing machines with minimum breakdown, we at SAVITA developed the Microcontroller based EDM Logic controller for our EDMs.

The EDM circuitry can be grouped in two parts

1. CONTROL CIRCUITRY
2. POWER CIRCUITRY

The control circuitry has been put into the microcontroller resulting in

Reduction of components that can go bad
Reduction in no. of PCBs
High speed signal processing giving high performance in cutting speed, surface finish and low electrode wear.

Control circuitry is coupled with power circuitry by opto-couplers to avoid the noise problems.

In power circuitry we are using mosfets (Metal-Oxide-Semiconductor Field-Effect-Transistor) for switching the current. The performance of the mosfet depends upon their driver circuitry. The poor quality of driver circuitry gives the problem in high frequency switching. Also in electronic circuitry, the process correction rate is very slow compared to a micro controller. These result in arcing or pitting in finishing.

To over-come these problems, we have developed a very strong driver circuitry that switches the Mosfet for 0.1micro sec. No noise is generated during switching of the mosfet itself. Further our feed back circuitry gives the exact information about the sparking process to micro controller, which takes instant corrective action to maintain the process parameters thus eliminating arcing or pitting.

With the feedback obtained from the users of our Micro controller based EDM Logic Controller during the last 5 years, we can confidently assure that:

Our machine does not require frequent servicing;
Output from the machine is higher compared to others;
Electrode (master) wear is low;
Finishing is much better & faster without arcing or pitting.

“BUY THE BEST”

Micro-Stepping Motors In Electric Discharge Machines

What is a stepper motor?
The stepper motor means, a motor, which rotates in step angle. Normally the stepper motors used in Electric Discharge Machines have step angle of 1.8˚. Considering the reduction gear ratio and pitch of the drive screw, it generally gives the linear displacement of 2.5 microns per step.

What is micro-stepping motor?
Micro-stepping means reducing the stepping angle of stepper motor with the help of micro-stepping motor drivers. Developing a micro-stepping driver is an independent branch of excellence.
To enhance the efficiency of our Electric Discharge Machines, we are procuring micro-stepping motors and their drivers from unique and best manufacturers of motors and drivers from USA even though they are quite costly.

Use in EDM process.

We specialize in Electric Discharge Machine circuitry and its technology. We are producing a spark that is generating the surface of 0.1 Ra, which is too small & if the motor is moving in step of 2.5 microns, then following errors are bound to occur:

---The lateral finish (wall finish) of the cavity would be rough even though the spark circuitry can produce
a spark smaller than 2.5 microns.

---Cutting speed in finishing would get reduced considerably because the gap voltage cannot be
maintained uniformly. If the gap voltage is more, it would reduce the cutting speed and if it is less than
required, it would increase the arcing tendency and wear of the master.

---Creates a vibration tendency in sparking.

After conducting a number of trials with micro stepping drivers and motors, we, at SAVITA, have been able to achieve optimum stepping angle where size of spark generated during sparking process and linear displacement due to step angle gets synchronized. Due to this achievement, following improvements take place in the sparking process in our machine:

Very good lateral finish (wall finish)
Uniform grain structure on the Electric Discharge Machined surface.
Controlled and uniform over cut.
Higher cutting rate in finishing.
Less electrode wear in finishing.
No arcing or pitting in finishing.
Better surface finish reducing time lost in lapping operation.
Improves the quality of the mould because of lesser manual work for lapping of the die. (extensive manual lapping operation may result in deshaping and waviness of the die surface)

“BUY THE BEST”

High Speed Auto Flushing Reduces Deep Cavity Problem .

Flushing, i.e. the correct circulation of dielectric fluid between electrode and work piece, is a very important factor in Electric Discharge Machining. Suitable flushing conditions are essential to obtain the highest efficiency. It must be adjusted carefully to contain the degree of contamination in the dielectric to obtain optimum results. Flushing is required to:

To cool the electrode periodically;

To flush out the carbon particles of sparking surface.

Injection flushing and side flushing, though useful up to 6 to 7mm depth, they start becoming ineffective beyond these depths since external flushing cannot reach and flush out the carbon particles from deeper cavities. And presence of carbon on the surfaces being machined decreases the sparking speed substantially. This happens because lot of sparking time is wasted in removing the carbon.

To over come form this problem we, at SAVITA, have developed high speed auto-flushing---PULSE FLUSHING SYNCHRONIZED WITH ELECTRODE MOVEMENT that is dielectric fluid under pressure flushes the gap only during the time the electrode is raised and there is no machining.

With this arrangement, z axis (Quill) moves rapidly up and down. When it goes up with high speed, small vacuum is generated near the sparking area and oil (electrolyte) around the electrode immediately enters the sparking surface. While the oil is loosening the carbon particles of sparking surface, quill comes down at high speed. Due to plunging motion of the electrode, the oil in the cavity gets thrown out along with the carbon particles. It helps the Electric Discharge Machine to generate spark directly onto the job without carbon, thus increasing the efficiency of the machine resulting in improved cutting speed and surface finish of machined part.