Help needed with Spark Erosion

[Raymond HodgesParticipant @raymondhodges20973]

[Raymond HodgesParticipant @raymondhodges20973]

Hello fellow members

In the web site called MikesWorkshop he describes the making of a very basic Spark Erosion Apparatus.

In the circuit diagram is a 470uF capacitor could someone tell me what voltage rating would be apropriate for this capacitor, the DC voltage used in this circuit is 21v.

The capacitor is conected between the anode and base.

I havn't much idea of electronics exept i am able to read a circuit diagram.

Thank you

Ray

Edited By Raymond Hodges on 19/11/2014 20:33:20

[AndyPParticipant @andyp13730]

I have built and used a simple spark eroder and although it is not the same the capacitors in mine that perform the same function are 2 off 150uF 220v electrolytics wired in parallel. Mine works best at around 36v but it is fed by a variac so that is a little vague.

Andy

[Raymond HodgesParticipant @raymondhodges20973]

Hello Andy

Thank you I'l keep that in mind.

Oh i forgot to mention, do i need to take any precautions against Radio and TV interference.

Ray

[Michael Cox 1Participant @michaelcox1]

Hi Ray,

I used 50V capacitors when I built the spark eroder. These have given no problems.

I hope this helps.

Mike (of mikesworkshop.weebly.com)

[AndyPParticipant @andyp13730]

I don't know about interference, it doesn't wreck the radio in the workshop unlike the 3d printer and the family haven't complained so maybe not.

Andy

[Raymond HodgesParticipant @raymondhodges20973]

Thanks Andy and Mike i now know what to do

Btw Mike your web site is very informative along with the Gadget Builder web site i am getting exelent ideas for my little workshop.

Again thank you both

Ray

[Michael Cox 1Participant @michaelcox1]

Hi Ray,

Thanks for the kind words about the website.

Mike

[Ian S CParticipant @iansc]

Ray, any thing from around 50V and up, usually depends on what you can find. If a component is specified, and you can't get that spec, go up, same with resistors, might be 1/2 Watt on diagram, but it doesn't matter if you use 5 Watts, but it could if you used 1/4 Watt.

You can see I'm a junk box electronics dabbler.

Ian S C

[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

just visited the website. There's an interesting usb shadowgraph / microscope on there. I quite fancy making that along with the spark eroder. I worked for several years as a chemical machinist. and whilst this isn't the same it will help with some interesting jobs like removing broken taps and drill etc. I can also see a use for getting broken bleed nipples out of brake callipers.

[Raymond HodgesParticipant @raymondhodges20973]

well Bodgit thats just why i aim to build one, i broke a 2mm tap,tried Alum and Citric acid had no luck so decided this was the solution.

I asume you are refering to Mikes web site for the shadowgraph / microscope.

Ray

[Ian S CParticipant @iansc]

Ray, did you try warming the Alum solution, and try to poke a thin bit of wire down the side of the tap to get the air out.

Ian S C

[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

Hi Ray

Yes I am referring to Mikes website. There's some really useful stuff there. Let us know how you get on.

[Raymond HodgesParticipant @raymondhodges20973]

Yes Ian and blew the hole through every day for a week.

The joke is i broke the tap removing it from the hole the thread was done.

The citric acid is working better but for the future i will make a simple spark eroder, 2mm an hour is better than a week or more waiting for a chemical to work.

Mikes website and gadgetmaker's website are great for mod's information.

Thanks everyone for your help

Ray

[Raymond HodgesParticipant @raymondhodges20973]

One last question on Mike,

does it matter if i use electrolitic condensers.

Ray

[Ian S CParticipant @iansc]

Ray, at that capacity, electrolitics are what you get, stick to the circuit diagram.

Ian S C

[Michael Cox 1Participant @michaelcox1]

Hi Ray,

As Ian says for that capacitance you are only likely to get electrolyics. The only thing to be aware of is that electrolytic capacitors are polarised with a '+' and a '- ' terminal/wire. It is important that they are connected in the circuit correctly or they will last only a few minutes and probably end their life with a bit of a bang and a lot of mess spattered over the circuit board.

Mike

[Raymond HodgesParticipant @raymondhodges20973]

Thank you Ian

Thank you Mike

I'l take care not to prove the big bank theory

Ray

[Neil WyattModerator @neilwyatt]

You can get 470uF tantalum bead capacitors. I wouldn't recommend them for this application, though one forum member may have a few he would like to quietly pass on…

Neil

[Ian S CParticipant @iansc]

I don't know it Tantalium caps have a high enough voltage rating.

Somewhere in my supply department I have some 400uf 300V Non polarised capacitors, I think they polarise them selves once they are installed, I'v never used them.

Ian S C

[mark costello 1Participant @markcostello1]

Have You tried turning the tap with a pair of small wires, not stated anywhere in a previous message? May not be all that tight.

[Raymond HodgesParticipant @raymondhodges20973]

Two needles and a pair of pliers was my first try but the tap was too tight.

Next i tried alum for a few days nothing happend, then 25% citic acid this eventualy worked and after a week the taped hole was free.

Now i am in the process of building a simple spark eroder as decribed by Mike Cox in his web site.

The acid is ok for non ferous parts but not for steel, hence the very simple EDM.

Thank you all for your advice.

Ray

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