Fast Hole EDM from Hacked Parts

Hi everyone, 

I have posted before and got a lot of help setting up my CNC machine. 

Now I am working on a hacked/bolt on component for said machine.  I am in desperate need of drilling some very small (.5-.8mm) holes in inconel of high aspect ratio.  I was able to do it with PCB drills but I break more drills then I succeed. So I want to use edm.  I would really appreciate it if anyone who knows about these things could weigh in on the probability of success.

Here is the plan:

I can buy a edm drill head from aliexpress that handles high pressure. I can use a low pressure pump to pump the dielectric through a water filter. Then I can tap the fluid to an airless paint sprayer to pressurize the dielectric fluid to send to the drilling head (the drilling rods are hollow for flushing debris away). I will also tap off from the pump to return to the fluid container (but first it will be directed at the cut as my work piece will not be submerged).  I am ok with replacing filters often. 

All of this was taken from Applied Science YouTube channel. Here is a link: 


What I am doing different from him and am more worried about:

For starters I am using oil as the dielectric.  I am doing this because I already have oil set up for doing traditional machining with. 

The biggest thing I am worried about is the power supply. You can buy these cheap EDM machines form aliexpress that are built for broken tap extraction.  I have a couple of concerns with this. First, is I am not sure if the power supply output power can be reduced low enough to drill very small holes.  I believe it is necessary to lower amperage for smaller holes.  Second, I would not have a feedback to know if the arc has shorted. My thought with this is that I could simply run my feedrate low enough that a short is unlikely to occur. Alternatively, I believe the power supply comes with a drill head on it that does not have through coolant so I would not use it.  However this drill head does have a servo on it and I think that it has feedback to detect a short and it retracts the drill if this occurs.  I could probably workout how to sense when this is ocurring and feed this into my control board. This would require me to modify my LinuxCNC to reverse if a short is detected, but I am sure this could be done? 

Alternatively, I could use the Powercore from RackRobotics.  This power supply seems more versatile and controllable. But I do not think it is shipping at this moment because they are having some troubles with the board. However, I believe that it does have a logic out for short detection. 


I am really hoping I can get something together. I would really love to hear everyones thoughts. I can provide more detail if needed. 

Here are some links to some of the parts I am considering:

www.aliexpress.us/item/3256806213357626....yOTE0OTY1MC4xMy4wLjA. 
 
<!--td {border: 1px solid #cccccc;}br {mso-data-placement:same-cell;}--> www.aliexpress.us/item/3256803997349850....ller%7Cquery_from%3A

<!--td {border: 1px solid #cccccc;}br {mso-data-placement:same-cell;}--> www.amazon.com/gp/product/B01CFOFZ08

<!--td {border: 1px solid #cccccc;}br {mso-data-placement:same-cell;}--> www.amazon.com/gp/product/B004Z2090U?th=1

Best,
-Dylan 

"I am in desperate need of drilling some very small (.5-.8mm) holes in inconel of high aspect ratio."

Sounds like an examination question to a "make or buy" decision.

holeflix or spotdrillfy?

The thing costs more than 4 k€. (probably more advanced than the Makerspace kickstarter for less than 10% of that)
I wonder what a 3rd hand machine would cost.

Maybe this link is useful.

www.homebuiltedmmachines.com/sand-box-rc-vs-pulse/

Timo - what is a holeflix and a spotdrillfy? Are those products? Also are you saying that a BAXEDM is 4k? That seems about right.  Which is out of my price range tommy...

 

It looks like I might be able to get my hands on a powercore from rackrobo. But if anyone has more thoughts on the powersupply please let me know. 

Can anyone speak to wether linuxcnc can be configured to run edm? Can it handle reverse feedrate? Are there any linuxcnc resources on running EDM? Thank you. 

The words "holeflix and spotdrillfy" I made up refering to streaming platforms.

What I wanted to say is that it might be a good idea to pay someone to do the EDM part of the project. Provided it is only about getting the job done and not so much about toying around and experimenting.

To get good results with the technology requires experimenting and constant process control. (from what I could find watching youtube, and from  conversations) For a tap removal they charge me 6-9 USD, too less even to justify a cheap tap remover EDM. One time the neighbor set his oil on fire when he was trying to help me to remove a carbide end mill. We stopped the exercise at this point. 

To keep a nominal accurate diameter with acurate positioning is obviously not so easy. I saw a EDM tap. To get it to make accurate threads is not trivial. The secret seems to be the shape of the electrodes.

@Tommy: I would be tempted to jump in, in some way. I saw some comments somewhere that sinker EDM requires higher current outputs than wire edm.

The power requirements seem to be different (guessing from comments) between sinker EDM, wire EDM and hole drilling. 

I think a CNC sinker EDM can be very useful. Work with partial electrodes. e.g. using a small square electrode to clean up corners in blind holes, doing undercuts, threading etc.

Greetings Timo

 

i would seriously consider your options before you buy the rack thing, and also buy more than one if you really want it that bad.

how deep are you actually going?

since its for work, i would stray away from kickstarter tier stuff. not being able to actually adjust your settings is going to be a painful experience for you, depending on the spec of your hole.

if someone wanna chime in and correct me, but i dont think a short detect is really a control loop.

To get good results with the technology requires experimenting and constant process control. (from what I could find watching youtube, and from  conversations)

 

it does, and its called fast hole, not precise hole. depends on the spec, but overburn, combined with not being able to adjust the settings, runout from the setup, excessive electrode wear