Drill through anything (conductive) with Electrical Discharge Machining

today on Applied Science I'm going to show you how I built this EDM drilling machine now it's not electronic dance music that actually electrical discharge machining and it can do some pretty cool things one of the key features of the EDM process is that the drill or the machining electrode doesn't exert any pressure on the thing that it's machining so you can drill into the side of a round contour and the bit doesn't stray off like it would with a you know conventional drill bit also the hardness of the material is not much of a factor so you can drill through things like hardened steel bearings no problem drill bits even tungsten carbide which is pretty incredible this process is also very good for super high aspect ratio holes and so this is like a point seven millimeter hole that's about thirty millimeters deep very high aspect ratio using a drill bit to do this would be really difficult in fact I've been able to drill through every single conductive material that I've found in the shop so um someone has a suggestion for something else to try that's conductive just let me know you've probably done some electrical discharge machining and may not even know it if you've ever used a benchtop electrical power supply and brush the leads together and seen some sparks coming out you've actually been doing a little bit of machining on the leads there and so if we look at the alligator clip after I've brushed it against the other terminal a few times you can see that there's actually little craters little pits in the alligator clip and that is the result of EDM so when there's a spark bridging between the electrodes the spark is very very hot hot enough to melt or even vaporize a teeny tiny bit of the metal and those little craters are now left there because the metal has been either melted or vaporized the reason that your whole alligator clip doesn't disappear from you know striking it on the other terminal like this is that the amount of material removed is very tiny and once the spark is extinguished either because the two pieces of metal are in contact now then there's no more material removal so the trick to get EDM an efficient process if we actually want to use this to machine something is to basically turn the spark on and off very rapidly so that as the nest the bit near the thing that's eroding the material moves in the spark will form blow away a little bit material but then you want to extinguish the spark right away and then turn the power back on so that a spark forms somewhere else so that these little craters that material removal happen very smoothly across the whole surface so the trick is we need a a high current power supply at high frequency like about 30 kilohertz let's say that has good current regulation and also the ability to control how long the spark is on and how long the spark is off and that's what this is this is the arc generator on loan to me from Beck's EDM and as far as I know this is the first EDM power supply that is intended for small shops and potentially even hobbyists so you can build this into whatever kind of EDM machine you want today we're going to look at an EDM drill but another popular one that I'll probably do a future video on is wire EDM the next part of the system is the motion controller which is made by a company called Dyna motion and there's a specific reason that you want to use this particular motion controller in that it can control the CNC machine in the forwards and reverse feed rate direction and this becomes really important because in the EDM process occasionally the you let the electrode will bump into the workpiece and make a short-circuit and you actually have to go backwards to clear this short and start EDM machining again and there's very very few motion controllers that allow you to go backwards in your CNC profile so inside this computer case I've just bought the Dyna motion boards and you don't have to put them in a server rack like this I did this just cuz it's convenient for the actual CNC machine itself I used a kit from open builds this one's called the Sphinx because it has two y-axis motors and I can get my tub of water in the middle there without interfering with either axis and I've been kind of curious about this open build stuff the idea is that the company sends you a kit of parts including these aluminum extrusions and the motion feature the way that they make a slide out of this is to have plastic sort of skateboard wheels that ride in a track on the extrusion and I always was kind of skeptical about this but actually it works much better than I would have guessed also the kit does not have ball screws but the nut that the driveshaft runs in is like a Delrin nut and the fit is very tight so the backlash is very low I actually measured it myself at about half a thousand inch in most of the axes here I used the kit pretty much as designed and just made a few tweaks here and there that I thought improved the performance a little bit we'll talk about those later the drill head that I'm using was a bit of a lucky find initially I thought I was going to have to build this whole drill head myself from scratch and so I was designing it also lucky that the open builds thing is in fact open source and so I actually had the CAD for this so I sat down and started to do the CAD for a custom drill head and I realized that I was going to need some custom rubber seals this is actually what seals the high-pressure water into the drill which is hollow so I was searching like Alibaba and eBay and all that stuff for these rubber seals and to my surprise I actually found an entire complete EDM drill head on Aliexpress for like $60 I couldn't believe it I mean it was cheaper than the raw materials we're gonna cost me from McMaster buy a lot so I bought the whole drill head is sort of on spec and it showed up in a week or two and what do you know it's perfect so you'd be surprised that there's actually not that many EDM drill designs out there in the world and so basically if you search for EDM EDM drill rubber seals or whatever they're pretty much all 9 millimeters in diameter or a lot of them are and they all are designed for the same type of spindle and everything so it's nice that it's rare enough where they kind of everything is almost the same because no one's really bothered to invent multiple versions of it the water system works like this there's one pump here and this draws water out of the tank and forces it through these two filters that are in series and these are just standard cheap water filters that I got off of Amazon then the clean water comes out here and goes into a tee and one end of the tee goes into this airless paint sprayer which is basically like a high pressure pump that's lower volume than a pressure washer but is otherwise fairly similar and the other end of the tea comes up here and goes back into the tank so depending what kind of operation we're doing we might want relatively low pressure flushing water just to get all the debris from the EDM process out or if we're doing EDM drilling we actually need a really high pressure source of water which is why we need that airless paint sprayer and the reason it needs to be so high pressure is that if the drill rod is you know six tenths of a millimeter in diameter there's actually a hole going down through the middle of this and it takes a lot of pressure to get water to flow through this long of a rod at once with such a tiny internal diameter so if you're way down at the bottom of a high aspect ratio hole you still need to have good flow in there to flush out all the chips and so that's why we need such a crazy high pressure it ends up being about a thousand psi or about you know sixty or seventy bar something like that I should add that in most professional EDM systems they make a big deal out of the water filtration if you are running like high volumes through all this the amount of debris that the EDM process causes will quickly clog up one of these household water filters and so they make basically EDM water filters that are much larger and just have more surface area to catch the dirt and then also you have to control the conductivity if the water if you're really doing this professionally so you don't want to use absolute pure distilled water because the conductivity is too low and you can't use tap water because the conductivity is too high so generally what the pros use is an ion-exchange filter and it measures the conductivity of the water and then sends that through this ion exchange filter to lower the conductivity well I don't have any of that running basically what I do is just get a tub of distilled water from the store and use that and as time goes on it will get into the right conductivity range and if you go long enough it'll probably become too conductive but it's easier to just throw the water out I mean water your plants with it and then dump a new jug of distilled water in and so far I've been running this for a couple of weeks and haven't had any problem so that's that's been working great the drill head also rotates just with this low-power gear motor and so you can see it kind of spins the drill rod around and that's not because there's any sort of cutting tines or anything on there it doesn't really matter that it's spinning this just helps keep the system as consistent as possible so when drilling through the electrode actually erodes away not as much as the workpiece hopefully but it does erode and if you're spinning around that makes the erosion much more even so the hole will come out more concentric and having this spin also helps with the flushing process so that there isn't like sort of a channel I can imagine like erosion on a hillside you don't want the water to keep flowing through the same side over and over so having this spin around just keeps everything more even this bracket here is 3d printed I imported the open-open builds CAD in and put all this together and then catted it up in fusion 360 and printed this on the form too and this is in durable resin so I could actually clamp down on this and it worked great I actually printed the threads direct in there so let's set up for a drill here let's let's cut something I'm gonna unscrew this so you can see how it's built and there's a Jacob's taper number zero which is actually holding the Chuck to the spindle so you can see how this is put together the drill shop really is clamping down on this so that as it spins it can positively drive it but the trick with this whole drill head is that we want a couple you know thousand psi water into the into the actual electrode but we don't want the water of course to get onto our Chuck or anything else so what I'm going to do is briefly turn on the water pump and it's going to force out the rubber seal that's currently jammed in there okay so you saw the the seal fall out and this is what I was talking about earlier it has these kind of weird-looking seals and the trick is it has to make a good seal with this tiny electrode or the tiny the drill rod basically for EDM and so it has this channel cut in the top so that the high-pressure water actually causes the seal to pinch down tighter onto the rod so when as thing is assembled it looks kind of like this and that's and this is where the water stops so the water never actually gets down to the chuck and then in the top side there's a rotating connection which couples the water from the stationary part to the spindle which is rotating so inside here there's obviously a part that's inside bearings and rotating and it's Hollow and filled with the high-pressure water okay so to set this up for a new cut I'm going to take the old rubber seal off I'm going to throw that one out although you can reuse them multiple times and I'm gonna undo the chuck hopefully I don't like this Chuck much at all anyway it's it's open so that's that's how much electrode is left that we can't really use because of the geometry of the system so we throw that one away these are what the electrodes look like bought new I got these off of ebay and they are purpose-built for EDM drills very common is to using brass electrodes and the reason for that is that the blend is copper and zinc that's what brass is and the copper is good because it has good electrical conductivity and the zinc is good because it vaporizes very easily so as this thing is drilling down into the material the electrode is being eroded as well as the workpiece and we don't want sort of gobs of molten metal sticking in there it would be much better if it vaporized and then sort of made like a smoke almost that the water carries away so the zinc is better at being turned into smoke so we'll put the electrode into the drill chuck I actually cut these electrodes in half just because this machine is not quite tall enough and I'm gonna use a new rubber seal and it's actually completely sealed at the top so it actually pierced through there I'm gonna stick this out just a little bit more so that the seal can basically go down to really small diameter drill rods in fact it's not uncommon to get down to like 300 micron that still have a hole down the middle it's really quite something so that's in there and then on the bottom side here this is the electrode interface er that I came up with myself which I don't know if this is really pro or not but it's basically just a piece of brass with a hole that's very very closely matched to the electrode diameter and it's sitting in a 3d printed piece of plastic and then the thing that is mounted in the plastic is actually a ceramic bushing which is purpose-built again for EDM drills and you'd think all this is like really specialized hard to get stuff but actually this also came from ebay in the same lot where I got these electrodes so it's easier to find some of this stuff than you might guess initially I tried different things to interface the use of the electrical connection from the art generator to this electrode and I had like spring fingers and stuff that were pinching it but the problem is that if you apply any force any side force to this drill rod it causes the thing to be wonky right like it's if you're going through here like this and you're applying force to it you will have concentricity problems so I eventually settled on a bushing which is perfectly concentric with the axis of this whole thing and it's conductive so you know even though there isn't like spring tension holding it on there I haven't had a problem with with a loss of conductivity so what we'll do is thread this through and the fit is tight enough where if there's even like a tiny burr on the end of this drill rod which there is I can feel it won't go through so let me clip the end of this I'm basically just going to cut a very slight taper on there and hopefully that'll help us thread through okay let's see if we can thread this through there we go so now it's threaded through the brass through the ceramic bushing and then I'm gonna head back up into the spindle here and tighten this down and this is not a it's not like it's tightening down to whatever I feel is tight it actually goes into a hard stop so once I've tightened that down it's it's basically bottomed out and that's it and now the machine is pretty much set up so let's drill something the cutting force is very close to 0 because the electrode actually never touches the workpiece it's only the electrical arcs that jump between them ideally but remember since we are blowing water through here at such high pressure there will be a little bit of force however the clamping requirements are basically nothing because there is so little force here and I have one lead connecting through the water just alligator clipped on and four small holes and stuff like this the electrical connection is really not that critical okay so what I'm going to do is jog down so that the electrode is just about to punch through and then we'll turn the water on and drill a hole the software that comes with the Dyna motion controller is really deep and full-featured you can program it to do almost anything you want and you can also program C programs and FPGA code that gets downloaded into the controller so you can literally create anything you want the downside of this is that the learning curve is really brutal luckily mike backs the creator of this arc generator has written his own c program that will control this controller as if it were a purpose-built EDM machine and sort of the main thing here is that when there's a short-circuit or when the arc length is getting very short like it was about to be a short-circuit it tells the controller to back off the feed rate and I mentioned that most controllers can do this right like imagine you're running a milling machine you have a knob where you can turn the feed rate from a hundred percent down to zero percent or two hundred percent or whatever you want but the trick is almost no controllers have negative percent feed rate it's almost unheard of it wouldn't make any sense for a milling machine but for EDM like I mentioned if there's a short-circuit you actually have to back up to clear that short and this happens you know occasionally like once every minute or once every 10 seconds depending what you're doing and the K motion controller does this by a analog link that goes from the art generator back to the motion controller so there's basically just a voltage that tells it how long the arc length is and when it gets too short or even if it's zero then it tells the machine to back up and so all that's been programmed in and you can just download it and set and get it going although there's still quite a bit of setup so we have controls over this and we can turn the arc on and off and run G code just like normal and in this case I'm just going to type the G commands in we can jog the machine like this okay so I'm going to turn the water pumps on the main pump turn on the rotating spindle and I'm going to turn the high-pressure pump on so now we've got about a thousand psi and there's water flowing through the electrode and you'll notice that the spindle actually goes a little bit slower when the pressure is on it of course because that rotating seal has all the force on it now and you'll hear the pump turn on and off this is how airless paint sprayers work it actually has a pressure switch inside there and when it senses the pressure is too low it just runs long enough to get the pressure back up so that's totally normal okay so I'm going to run the code that initializes the machine and then sets the feed rate based on the arc length and I'm going to drill straight down I forgot to add that the art generator can be programmed with different currents and on times and off times like I mentioned that this is an important part of getting a good cut going so when I started that cut that power was way too low so I'm gonna turn this up to about 15 amps just kind of mid scale and put both of these at about mid scale so arc on time is like 15 microseconds off time 36 microseconds and that gives us a frequency of close to 20 kilohertz so when I say send config all this is downloaded to the arc generator and now when we go back to the screen here I'm gonna run that jeet kune around the g-code and it's going to use the new settings basically I mentioned that the arc length is reported from the arc generator to the motion controller via this analog voltage and so the voltage corresponds to the arc length when it gets too low that's when we go into this reverse feed rate control so you can see in some of the other cuts that I've made the machine doesn't just plow forward it actually can sense what's happening which is a critical part of this whole EDM so let's go back to the workpiece and I'll hit start you can see it in action and it will pick up speed as it notices that the arc is stable you can see some gas bubbles coming out there here's a shot from an earlier setup just so you can kind of see what it looks like in profile cutting speed can be pretty high especially in aluminum like this I haven't tried to find the limits but it can easily cut it maybe oh I don't know I've seen it go as fast as maybe about a millimeter per second at this certain setup so the electrode is all the way through and as it goes through it's making the hole slightly bigger because of you know lack of concentrated either' [Music] so as you can see I wasn't really paying attention there and the electrode it must have been bent or something because the hole that it created is much larger than the electrode itself and that will happen if there's a bend in it because we're spinning around nice and consistently the hole will always be round but it might be a slightly larger diameter than the electrode in this case since the thing was been - there was something out of a lie the whole is quite a bit larger however you might be thinking I wait a minute this is useful if you chuck up a big solid piece of brass like a quarter inch you could actually pretend like it's an end mill and that is in fact a thing that we'll look at in a future video EDM milling which can be really useful because your mill can be square if you aren't rotating it you can have a sharp edged thing and drive it into the corner of a box to get like a sharp internal edge and this is pretty common in sinker EDM which is yet another kind of EDM process one thing that you have to watch out for is electromagnetic interference the EDM process is inherently very electrically noisy like you've probably heard of spark-gap transmitters well this is one heck of a spark-gap transmitter it's got you know 15 amps going at and 30 kilohertz might be the switch frequency but the actual frequency content of the waveform is probably much higher than that and that will in fact cause interference with electronics and the dinah motion motion controller boards appear to me to be slightly more susceptible to EMI then sort of standard electronics I mean these are sort of custom-built Fords and so you have to be really careful and put ferrite beads on everything and ferrite toroid 's and make sure it's grounded and shielded and everything but what you see here is I would say medium effort I haven't gone completely nuts and ended up not having any problems so let's open up that electrical or let's open up the computer case there and I'll show you the Dyna motion boards okay so here we've got a 24 volt power supply that runs the stepper motors and the power supply goes into this stepper motor driver board and the stepper motors are connected through a db25 connector that comes off of here so this is actually the stepper motor controller that's also produced by Dyna motion and the stepper motor is driven through this cat5 cable this is like Stefan direction signals that come out of here and this converts it into the stepper motor actual drive current the actual Dyna motion controller is this board here and it's piggybacked on to an analog input board which is used for a few things but mainly it's that feed rate override control that I was mentioning so this is the actual 10 volt signal that describes how fast the machine should be going and if that signal is too low let's say 2 volts or whatever it actually goes into reverse feed rate so a pretty standard stuff I just got a 5 volt supply over here just to run the logic and there's a couple of auxiliary ins and outs to control things like water pumps and that sort of stuff but I haven't really hooked any of that up just yet ok like you say I'm probably going to do another video on wire EDM which is kind of like the complement to this if you use hole drilling EDM to make a hole in something you can then feed a wire through and then move the wire around to cut like a complex 2d shape out or even 3d okay hope you found that interesting see you next time bye

Channel: Applied Science

Views: 2,627,764

Rating: 4.8609805 out of 5

Keywords: EDM, electrical discharge machining, drill, drilling, machine, howto, DIY, baxedm, machining, applied science, ben krasnow, EDM drill, EDM drilling, hole popper, EDM hole popper, hole

Id: rpHYBz7ToII

Length: 24min 20sec (1460 seconds)

Published: Mon Mar 11 2019

Reddit Comments

[u/EricArtr]

Interesting to see a video of someone purposefully using EDM on a bearing.

I'm a bearing salesman and deal with this daily with my customers, electric motor repair facilities. EDM has become a big issue in industry due to the use of Variable Frequency Drives (VFD) on applications. The Pulse Width Modulation (PWM) of a VFD is used to vary the speed of the motor. PWM causes issues with excess current being stored in the motors instead of being used to spin the rotor. That current can build up enough to need to discharge, and the path of least resistance is the bearings as they connect the rotor to the outside frame of the motor, and then to ground.

Thousands of tiny discharges happen a second through the raceway of the bearings and rolling elements causing small EDM pits in the groove of the bearing. The little bits of debris get pressed into the raceway by the rolling elements of the bearing until it eventually leads to a full failure of the bearing. The failure is usually identified by either a dull grey surface by thousands of these microscopic pits or a ladder like formation knows as electrical fluting. Lots of products have come out in recent years to try and take these discharges safely away from the bearings through an easier path to ground.
Neat stuff!

[u/chocki305]

Very cool. I run a wire EDM machine. Awesome to see it going towards the hobby sector.

[u/TheGreenBastard2]

We use EDM for creating dies for aluminum extrusion.. Super tight tolerances. I think the tightest radius is 0.01", but from what I understand of the process we use, it doesn't drill, it's more like a jig saw through the initial hole to create the shape.

[u/yankeybeans]

Very nice video. Good pacing. You showed great ingenuity in construction and testing.

[u/logitech1212]

He sounds like Gabe from the Office

[u/plexxonic]

There is a Japanese Gameshow? that shows this method vs. regular that is a hell of a lot more interesting.

I'll see if I can find the link later.