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mrgibbo
01-08-2002, 08:13 AM
Hello,
I am new to this forum. I can see the great value of having a discussion group like this. I am trying to find information on making an EDM I have my own design, however would like a real plan to make it from. Can anyone help me out.

SGW
01-08-2002, 08:57 AM
There was an EDM construction article in Home Shop Machinist a while ago. I think it's been published as a book. Take a look at the Home Shop Machinist piece of this web site, or send an e-mail to Neil.

There was also an EDM construction series in "Strictly I.C." magazine a while ago.

Oby1
01-08-2002, 11:30 PM
I made my EDM from the articles in the Home
Shop Machinest And it works good for home
made,but I'm spoiled by the two I use at work. What can I help you with?
Bob

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Bob Indiana

mrgibbo
01-09-2002, 09:16 AM
Could you please help me out with "Strictly I.C." magazine. Who publishes it and where is it available. I am very pleased to have revieved a reply from people willing to help.

Thanks.

Bob: I have started making my own and will proberbly finish it and also make the one from the "home shop mahcinist" plans. For my own, could you tell me the output voltage, current and Hz that I should aim for using a "resistance-capacitance circuit" I have some electrical engineers who can help me achieve that out put but don;t know what to aim for. Another thing I would like to know is what kind of feed I should be aiming for. e.g .005 inches per minute???? I have made a spindle with a 40 TPI thread which is turned very slowly as my feed.

Your help is most greatly appreciated, Iain.

Oby1
01-11-2002, 12:32 AM
I had about 60vac going to the rectifier,you will want 5amps continus rating
on transformer. As I recall I wsed a 15 ohm
250watt power resister.
To figur your own power resister,since your transformer is probley different,I derated
transformer 20% to 4AMP and devided that in to the 60V=15ohm.Then 4amp times 60V=240Watts. Use a TEST PROBE to mesure volts and amps,finger nails grow back too
slow. Hope that helps some,anybody want to
help me out here?
Bob

Bill Neufeld
01-11-2002, 10:24 PM
Most commercial Edm's use 80 to 92 volts. They use electronic switching circuits to turn off the voltage for varying times to get a good cutting action. The electrodes are brass tubing or graphite blocks cut to shape. The electrodes do get consumed in the cutting. The dielectric is either oil or deionized water. If you intend to use oil as a dielectric have plenty of ventilation, it will get very smelly and smoky.(not very good for your health even if you happen to be a smoker.)

mrgibbo
01-11-2002, 11:02 PM
G;day Guys.

I was planning on using Kerosene? How does that compare as a dielectric. I was avoiding water because of the rust factor.

What kind of feed range do Edm's work in.
I was going to make a feedback circuit so that when the current drops due to a too large gap then it will advance. Once feed is determined for a particular job I would know the feed rate and set it to repeat the job if it was to be done more than once.

Iain.

Bill Neufeld
01-18-2002, 11:06 PM
I dont think I would use kerosene. My reason for this is that kerosene is flammable. The cutting action of edm'ing develops high temperatures on the surface of the materials similar to welding.I think the dielectric oils on our machines at work use a castrol product. A clean light motor oil may work. As for rusting when using water; after you are finished burning wipe off the water and use a low pressure air supply to blow out any cavities.
Your idea of monitoring the current and feeding when low is the one that most edm mfr's use. The feed rate will vary because of factors such as size of your power supply, flush rate and pressure, the configuration of the burn surface.Roughing burns on a full surface as opposed to a finish burn are much slower.
Be safe.
Regards
Bill

mrgibbo
01-19-2002, 02:19 AM
THanks for your replies I greatly appreciate your help. Could anyone help me with the feed rate range? How are normal EDM'S fed?

I have started to make a fine threaded shaft about 40TPI that will turn very slowly to feed my machine.

Iain Gibson

Bill Neufeld
01-25-2002, 10:52 PM
Iain; Unlike regular mechanical machines such as lathes and mills; Etc. where the cutter removes a set amount of material depending on the revs and feed rate, the process of removing material in edm is by burning off the material of the part. Some of the factors I mentioned in my previous post affect feed rates. The machines I am familiar with use 2 methods to feed the electrode. One is a hydraulic system using servo valves, the other is a regular lead screw with a servo drive. I'm sorry that I cannot give you exact rates due to the variables and and finish required.
Be safe and regards
Bill

Thrud
01-26-2002, 04:05 AM
Iain

Have you thought about a ballscrew? If you go to all the trouble to build one it may be worth it to go all the way. Tne articles I have seen on home units used a feedback system to control burn rate. This could be based on current or voltage or both. I think current control would be more important than voltage. I am not entirely sure of that, but it makes sense to me.

Good Luck

Dave

RCS
01-27-2002, 12:37 AM
I am a little leary about using a ball screw due to arcing from nut to ball to screw. The electrical activity must be isolatd from ball screws as well as other spindle bearings to prevent erosion of the bearing surfaces. Ball screws are not cheap. I changed enough spindle bearings on Elox HRP-64's and others.


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Thrud
01-27-2002, 02:05 AM
If the screw is mounted in dielectric material on both ends that should not be an issue. High voltage insulators rated for 600V electrical work would be more than adequate as an alternate to a machined insulator. I have used these in custom and production electrical equipment and tested them with an Dielectic Breakdown Meter at 2500V & .1A and never had problems with them. The Canadian Electical Code requires a 1200V test for 1 second for a 1" inch spacing between a conductor and its surroundings and adjacent conductors. These meters will find out real quick if you have any creepage in your insulators. Since you are only looking at around 100V and much less than 100A this should protect what ever type of screw you use. Your plunge ram needs to be insulated from its frame anyway - so it should work.

I would as a safety measure, intall a GFI circuit breaker in your unit to prevent accidental electrocution.

Dave

Smoothie
02-05-2002, 09:44 PM
re: "I was planning on using Kerosene? How does that compare as a dielectric. I was avoiding water because of the rust factor."

I went to www.metacrawler.com (http://www.metacrawler.com) and entered a search on "edm oil". Try that. It'll give you a few sites to look at that carry the oil and other supplies.

Thrud
02-06-2002, 02:22 AM
www.thomasregister.com (http://www.thomasregister.com) if you can't find it there you might not be able to buy it anywhere.