Building an EDM machine. Part 1-some experiments

[Music] [Laughter] so edm uses an electrical arc to burn away material there is no cutting force applied to the workpiece and it can be used to machine parts that would be impossible with conventional machining eg very hard metals intricate geometry or very delicate work pieces this is the head from an old tap burning machine which i've been saving for years for a project like this it's old dirty and rusty and i don't have electronics or any other parts for it i'm going to reuse the micrometer screw and the precision slide which still works very nicely i need to find a suitable power supply to create the edm arc i have this old broken welder the transformer is still good and it can provide plenty of current but even with a capacitor across the output it only produces around 48 volts which is barely enough i also have this supply only 4 amps but 60 volts which is closer to what i need so i'm going to use this one this is the circuit i'm using for testing it's quite simple resistor r1 limits the maximum current drawn from the supply for this i'm using a heating element it has a resistance of a few ohms current through the resistor charges the spark capacitor this delivers short but very high current pulses to the electrode a low esr capacitor should be used for now i'm using an ordinary electrolytic one which works but it does get hot the current pulses are turned on and off using an igbt which is a type of transistor that can handle high voltages and current to drive the igbt i built a microcontroller circuit that allows me to adjust both the pulse width and frequency i found around five kilohertz at 10 duty works well i.e the pulse is on for 20 microseconds and off for 180 microseconds a spark will only occur if the electrode is close enough to the work piece but not touching otherwise a short circuit is created normally the workpiece is submerged in a dielectric fluid such as a special oil with the correct spark settings and careful selection of appropriate workpiece and electrode materials the workpiece will be eroded much faster than the electrode my [Music] a three millimeter hole made in 23 seconds is a metal removal rate of 18 millimeters cubed per minute which is much better than i was expecting the hole produced is perfectly clean and round on both sides for comparison here is the same size hole made with a hand grill the electrode itself has minimal wear some light pitting and the corners are slightly rounded so what next first i plan to add a stepper or servo motor to drive the screw and move the electrode at a controllable speed i need a way to measure the arc current and provide feedback to regulate the speed of the electrode the dark clouds seen here are particles of aluminium from the work piece these need flushing out of the cut to improve the surface finish this can be done with a jet or stream of fluid for prolonged use the fluid also needs filtering or constantly replacing to remove the particles i might also add some sort of compound table for the workpiece [Music] this is going to be a sync type edm rather than a wire edm but it will be useful to be able to accurately reposition the workpiece for taking multiple cuts in the future i might want to add a wire edm option this will require moving the work piece in the xy plane [Music] [Music] foreign

Channel: AndysMachines

Views: 64,660

Keywords: EDM, electrical discharge machining, spark erosion

Id: MZm-mvxa2qo

Length: 8min 26sec (506 seconds)

Published: Fri Feb 12 2021