Hole Popper leaves bad pitting around the Hole

[AGMantz]

Hey all,

So recently I've been playing around with our hole popper in the shop getting some experience with it. I've just been mainly removing taps and stuck drill bits from holes and occasionally putting in new start holes if I don't like how a block is setup for wire. Long story short whenever I am hole popping a tap or drill bit out of a hole I am getting really bad pitting around the hole. This also only tends to happen when I am running a larger electrode.(4.7MM) I am going by our manual for the settings and I've attempted lowering settings to reduce the power but I haven't had much luck getting rid of the pitting. I don't know much about hole popping in general so maybe this is just normal but I'd like to find a way around it if possible.

Thanks as always,
-AGMantz

 

[JZ.]

I have limited experience and non with a trode that size, but I'll offer some advice. Not sure what machine your running or condition of it, but I would check what the voltage is set at and maybe adjust your flushing gap. If you change you Voltage setting more than likely you will have to adjust others as well (on, off, ip, feed rate ect.). Sometimes if the gap between the guide and the part isn't set correctly you can get build up and what not on your part and guide itself.

 

[Madco]

Is there some kind of filtration unit on the machine?
Maybe your water is so conductive that it leads sparks to places where you don't want it.

 

[AGMantz]

I have limited experience and non with a trode that size, but I'll offer some advice. Not sure what machine your running or condition of it, but I would check what the voltage is set at and maybe adjust your flushing gap. If you change you Voltage setting more than likely you will have to adjust others as well (on, off, ip, feed rate ect.). Sometimes if the gap between the guide and the part isn't set correctly you can get build up and what not on your part and guide itself.

We have a EDMDrill ST300 I generally do monthly cleaning on it sometimes bi-monthly depending on how much I use it, seeing that I don't have much experience with it I usually go by what the book says and if I see it struggling I'll adjust my IP, On, and Off by a few values but beyond that I don't usually make big changes to the values as I'm not sure if I it'll cause even more problems on or around the hole.

 

[Bud Guitrau]

Hey all,

So recently I've been playing around with our hole popper in the shop getting some experience with it. I've just been mainly removing taps and stuck drill bits from holes and occasionally putting in new start holes if I don't like how a block is setup for wire. Long story short whenever I am hole popping a tap or drill bit out of a hole I am getting really bad pitting around the hole. This also only tends to happen when I am running a larger electrode.(4.7MM) I am going by our manual for the settings and I've attempted lowering settings to reduce the power but I haven't had much luck getting rid of the pitting. I don't know much about hole popping in general so maybe this is just normal but I'd like to find a way around it if possible.

Thanks as always,
-AGMantz

 

[Bud Guitrau]

AGM,
I'm going out on a limb here (I've done it many times), but I am curious as to know what kind of "hole-popper" you have (make/model/options), as 4.7mm is large for a hole-popper to my knowledge and I need to know more.

As for any "pitting" (again out on a limb), if you are referring to pitting on the top surface of your workpiece, simply protect it with a like-metal shim “sandwich” (at least .010" thick), clamped firmly atop the workpiece. This will mask the effects of initial ignition (imagine a volcano spewing molten bombs.)

"Sandwiched" with shims top-and-bottom, the edge-quality of both entrance and exit will be sharper and cleaner than without.

 

[eKretz]

Are hollow electrodes and coolant used on that machine? Did you build a dam around the hole with some plumbers putty so you get a little bit of a puddle? That usually did the trick for me.

 

[AGMantz]

AGM,
I'm going out on a limb here (I've done it many times), but I am curious as to know what kind of "hole-popper" you have (make/model/options), as 4.7mm is large for a hole-popper to my knowledge and I need to know more.

As for any "pitting" (again out on a limb), if you are referring to pitting on the top surface of your workpiece, simply protect it with a like-metal shim “sandwich” (at least .010" thick), clamped firmly atop the workpiece. This will mask the effects of initial ignition (imagine a volcano spewing molten bombs.)

"Sandwiched" with shims top-and-bottom, the edge-quality of both entrance and exit will be sharper and cleaner than without.

The hole popper model itself is a Current EDM MT40S. I was using a 4.7mm per request of the tool maker, I'd normally go at it with a electrode half that size and slowly break it down to get the bit out. The first time the "pitting" occurred it wasn't just around the hole, it had spread out 4-5 in. around the perimeter of the hole, which ended up being a real pain to clean up. Additionally the entrance point of the electrode hole wasn't sharp at all and it had rounded out the edges around the hole.

For protecting the top surface of my workpiece if I am understanding you right .010 shims circling around the hole and clamped down should help to reduce the damage? I generally never have problems with the exit point of the electrode that always comes out very clean and sharp.

Regards,
-AGMantz

 

[AGMantz]

Are hollow electrodes and coolant used on that machine? Did you build a dam around the hole with some plumbers putty so you get a little bit of a puddle? That usually did the trick for me.

No coolant is used on it, and I use coreless brass tubes for hole popping.

Regarding the plumbers putty around the hole, I've never tried that. I think an underlying problem is that my flushing isn't as optimal as it could be, and I'd assume(given I know what I'm talking about here) that a larger electrode requires better flushing. Would poor flushing be something that could cause "pitting" around the hole or even the hole having its edges rounded out instead of sharp?

Thanks,
-AGMantz

On a side note does anyone have any good recommendations for books, articles, or even other threads that have covered the general process of EDM drilling. I know the basics of how it works from the manual from our machine, but I want to take the next step in really understanding what is going on and better understand tips, tricks, and techniques you can use during the process.

 

[eKretz]

No coolant is used on it, and I use coreless brass tubes for hole popping.

Regarding the plumbers putty around the hole, I've never tried that. I think an underlying problem is that my flushing isn't as optimal as it could be, and I'd assume(given I know what I'm talking about here) that a larger electrode requires better flushing. Would poor flushing be something that could cause "pitting" around the hole or even the hole having its edges rounded out instead of sharp?

Thanks,
-AGMantz

You say no coolant (I should say dielectric, I really just meant a fluid) is used, then talk about flushing. I guess I'm a little confused. All the hole poppers I ever used ran fluid down through the tubes. Making a small dam around the hole with plumber's putty to keep some of that fluid puddled around the hole always helped contain any spatter/erosion for me.

Drilling and things like broken tap/drill erosion are quite different in terms of power applied and dielectric pressure and flow rate. For removing broken tools the power settings are higher in the interest of getting done quick and easy - with no care to how much damage is done around the hole to the tap. The tube size is generally selected so that only the central core of the tap or drill is removed and the flutes are left around it. Thus no damage to the parent material. For actual neat drilling of holes you want to set the power considerably lower - I should think those settings would be in your machine's manual.

This site has some decent intro videos and instructional material:

Free training videos for the EDM trade | Free Videos

20 training videos by Carl Sommer, tool and die maker, tool designer, operation manager, and president of Reliable EDM

reliableedm.com

 

[AGMantz]

You say no coolant (I should say dielectric, I really just meant a fluid) is used, then talk about flushing. I guess I'm a little confused. All the hole poppers I ever used ran fluid down through the tubes. Making a small dam around the hole with plumber's putty to keep some of that fluid puddled around the hole always helped contain any spatter/erosion for me.

Drilling and things like broken tap/drill erosion are quite different in terms of power applied and dielectric pressure and flow rate. For removing broken tools the power settings are higher in the interest of getting done quick and easy - with no care to how much damage is done around the hole to the tap. The tube size is generally selected so that only the central core of the tap or drill is removed and the flutes are left around it. Thus no damage to the parent material. For actual neat drilling of holes you want to set the power considerably lower - I should think those settings would be in your machine's manual.

This site has some decent intro videos and instructional material:

Free training videos for the EDM trade | Free Videos

20 training videos by Carl Sommer, tool and die maker, tool designer, operation manager, and president of Reliable EDM

reliableedm.com

Oop, my green is showing, to fully correct myself here and get rid of any confusion, there IS dielectric fluid that runs through the brass tubing during popping and additionally I have a small hose that pumps water around and inside the hole separate from the dielectric that runs through the brass tubing.(so yes there is fluid lol)

When I drill out taps I can't afford to have a lot of damage around the hole and need to keep it as clean as possible. That being said, if I want to neatly drill out a tap I should use the settings for drilling normal holes, right? Prior to reading your reply I really had no regard for picking out a electrode size that would only remove the core of the tap. I'll try out the all the advice given and see if it reduces the unwanted "pitting" around the hole.

Regards,
-AGMantz

Thanks for the intro videos, I'll give them a watch!

 

[eKretz]

Oop, my green is showing, to fully correct myself here and get rid of any confusion, there IS dielectric fluid that runs through the brass tubing during popping and additionally I have a small hose that pumps water around and inside the hole separate from the dielectric that runs through the brass tubing.(so yes there is fluid lol)

When I drill out taps I can't afford to have a lot of damage around the hole and need to keep it as clean as possible. That being said, if I want to neatly drill out a tap I should use the settings for drilling normal holes, right? Prior to reading your reply I really had no regard for picking out a electrode size that would only remove the core of the tap. I'll try out the all the advice given and see if it reduces the unwanted "pitting" around the hole.

Regards,
-AGMantz

Thanks for the intro videos, I'll give them a watch!

I would start by dropping that tube size down to the minimum necessary to core out the broken tool and adding a small fluid dam - it doesn't need to be high either, even ⅛" will probably do. See if that solves your problem first, it always worked for me. Dropping power will slow things down. If that doesn't work, I'd try using a small shim shield with a hole already punched in it that clears the electrode diameter. Drop power last.

 

[Bud Guitrau]

The shim acts as a "mask" to protect the upper surface. You will drill through the shim.

 

[eKretz]

The shim acts as a "mask" to protect the upper surface. You will drill through the shim.

He doesn't need to drill through the shim to core a drill or tap. Just needs a hole bigger than the tube. But that would work too.

 

[50BMG DUDE]

No offense Ekretz, but do you know who Bud is? He literally WROTE the book on EDM processes....This site is damned lucky to have some of the guys on here Bud Guitrau, Implemex, Richard King, etc.

Just felt the need to point that out.

Chris

 

[eKretz]

No offense Ekretz, but do you know who Bud is? He literally WROTE the book on EDM processes....This site is damned lucky to have some of the guys on here Bud Guitrau, Implemex, Richard King, etc.

Just felt the need to point that out.

Chris

That's great. Happy to have him here and I didn't say he was wrong, just that it doesn't necessarily need to be done that way for coring a tap... For drilling a hole that's to be a finished feature in a part I would agree with him 100%. I think @Bud Guitrau would probably agree with that as well.

And while it's nice to show props to guys that know what they're talking about, IME that kind of attitude (don't you know who this person is? You should worship his feet!) can sometimes prevent other people from giving an opinion or advice. This site is all about consultative collaboration. Since that sort of attitude can sometimes limit others from sharing, I generally tend to avoid it. I do the same when people say similar things about my advice - pointing out others and advising others to listen to ALL advice. There are a LOT of guys here with a LOT of experience. Most of us all have good advice to share.