Testing Vevor 800W EDM For Removing a Broken #4-40 Tap

[@damienmiller]

amazed that something so comically simple can work so well

[@ArionRaine]

There is feedback, and it is a servo. The feedback just happens to come from the spark current, sensed by the driver board controlling the FET's. This is fundamentally how automatic EDM works. By controlling the spark gap, via a servo mechanism, to prevent a dead short, or open circuit, maintaining a spark. When a high current is sensed (verging on a dead short), the motor retracts the electrode, opening the gap. Then when current drops (verging on open circuit), the motor advances the electrode closing the gap. The sense mechanism this uses is basic, but works. Essentially only short and open circuit detection. A "servo" is not explicitly a motor. It just so happens most servo mechanisms use some sort of motor with a relatively directly coupled feedback mechanism, usually position feedback of some sort. A servo can be any mechanism that has closed loop control. A better driver board that has better current control could be developed fairly easily and would potentially make it much faster maintaining a more constant spark.

[@ColinOFlynn]

Thanks for the detailed background on the EDM, added a note for people to check your comment in the description! Makes more sense how it works (& seems to work fairly) well based on your description.

[@samykamkar]

Awesome! What do you think the thinnest "wire" it can work with is, really what is the thinnest hole it can leave in metal?

[@ColinOFlynn]

The smallest it comes with is a 1 mm electrode which was the first one I used. They tell you to not let too much extend as it will jitter with smaller diameters, so it's probably more a mechanical limit on how small you can get & having enough rigidity. The design of this machine has a solid chuck so you can easily feed a narrow piece through, but it wouldn't take a lot to just make a custom head to make it easier to feed out a bit at a time. The included chuck goes down to 0.8mm (claimed, didn't test), so if you don't want to change anything that is basically your limit!

[@samykamkar]

@@ColinOFlynn Ahh, very cool, thanks!

[@mirceagrau1568]

please tell me which electronic part generates the frequency pulse

[@NOBOX7]

how long did it take

[@ColinOFlynn]

Pretty fast, less than 5mins maybe? Most of the time was setup, and in my case realizing I needed to run again with a larger electrode. But the actual EDM procedure was pretty fast.

[@mirceagrau1568]

you are a great guy, it would be nice if you could draw an electrical diagram

[@mansoor.mmannu3360]

Hai sir can share some more details about electronic pcb motor control section

[@mansoor.mmannu3360]

4:08 please sir share more details about pcb

[@mirceagrau1568]

I studied many complicated electronic circuits on KZbin and I don't understand much anymore

[@robertomartin8731]

What's the power rating of the resistor?

[@ColinOFlynn]

Not sure - no markings on the resistor I could see, but with ~70V across it in theory you could dissipate 160W. They might have underrated it though since it's mostly pulses.

[@jheissjr]

How is the tap removed after it has the hole?

[@ColinOFlynn]

If the hole is big enough (why I needed to redo it with the larger electrode!) the tap should just kinda crumble out when you hit it. Basically you try to drill out the center part of the tap (at least with small taps, with larger taps can try to drill out one of the side flutes).

[@jheissjr]

So a hole is drill/EDM'ed big enough to disconnect the tap flutes from the center. Neat!

[@Graham_Wideman]

Huh, so it's pretty much a MIG welder with auto advance/retract.

[@ElationProductions]

I'd say more like TIG.

[@RajuAnsari-l8o]

Hii

[@mirceagrau1568]

maybe we should let the Chinese copy our technology, simplify it and then take it back😀😀😀