Page 1 of 4 123 ... LastLast
Results 1 to 10 of 37

Thread: Wire EDM problem and test cuts

  1. #1
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    3,256

    Default Wire EDM problem and test cuts (more pics at post #23)

    Hello again

    My DIY wire EDM project has entered cutting test stage in the recent week or so and the most recent video of a test cut is here (nothing special happening between 1:30-6:30):



    The cutting went nicely, but what is bothering me is the brass welding in to the already cut gap behind the wire. This makes a kind of tab that holds the cutoff portion in place. It can be loosened with fingers, but it shouldn't do this.

    Here you can see a picture of the problem, the nudge of brass at the upper edge:



    I'm interested in knowing what causes this kind of thing, as I haven't had much time or wire to do thorough testing of everything yet. Sometimes this kind of welding happens with 1 mm thick steel, sometimes it cuts without this issue and the last test with 40 mm thick steel non-submerged showed no welding.

    The best cutting speed I have measured to date was 8 mm˛/min. Not bad for first tests, as the worlds first commercial wire EDM cut with a rate of 21 mm˛/min.

    There are a lot of variables in this, I know, but if someone has come across this kind of problem with a commercial machine then please do tell what was wrong. Or just give your best guess

    Other than that cut issue, the project is going along fine. The Arduino microcontroller card that is in charge of gap sensing, driving the steppers, LCD and pumps etc. works wonderfully, just need to code more functions for datum search and such.

    On the mechanical side I'm soon doing updates, the wire pulling motor is going to be a better and stronger and will have a PWM driver for it, so that I can lower my wire speed with the Arduino.

    Also been designing a new power supply to replace this RC generator I'm using at the moment. The new one is basically a 100 VDC power supply that has adjustable current limit and can be PWM controlled to achieve pulsed output for better spark control. Nothing fancy, just an op-amp sensing the current and driving a group of MOSFET's heavily heat-sinked to limit the current and then a PWM input to control on/off for them (or something like that).

    Edit 13-09-2013: There is now lots of pictures starting from post #23.
    Last edited by Jaakko Fagerlund; 09-12-2013 at 06:52 PM. Reason: Added information about pictures
    Amount of experience is in direct proportion to the value of broken equipment.

  2. #2
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    3,256

    Default

    Okay, can't resist it anymore: 100 views and not a single reply? No WAG's? No "you are full of shlte Fin, go ef a polar bear"?
    Amount of experience is in direct proportion to the value of broken equipment.

  3. #3
    Join Date
    Aug 2006
    Location
    Beaverton, OR
    Posts
    8,473

    Default

    Sorry, no idea. I can ask the edm guys at work.

  4. #4
    Join Date
    Dec 2012
    Posts
    452

    Default

    I'd answer, but I know nothing about EDM.

    When you say the brass is welding on place, is the original piece that yu are cutting made of brass? Or, where is the brass coming from?

    BTW, I know we all use language differently, but every time I read one of your posts, I keep meaning to ask if you could explain what your signature line means.

  5. #5
    Join Date
    Jun 2011
    Location
    Wisconsin USA
    Posts
    98

    Default

    Do you have the correct polarity? If the brass is transferring to the steel maybe try reversing the polarity so the steel tries to plate to the brass wire as is flows away. I'm just spit-balling though. As someone who is thinking of making a homemade EDM or possible electro-chemical machining center I'm glad to see a well made successful unit like yours.

  6. #6
    Join Date
    Mar 2013
    Location
    Portugal
    Posts
    31

    Default

    Ehe, not many replies, quite true. I was wondering what you are using with the dielectric. I had "The EDM How-toBook", by Ben Fleming, rather old (2005). I guess it's rather obsolete. I was somewhat interested, but later on, waned quite a bit when Fleming described what you supposed to do and need: Arc suppressor, Deionization, Flash point, Lateral flushing, Rotating spindle, Servo head, Gear motor, Submergible pump, etc. etc. Lots of things I should to buy, and my interest dropped to zero when the dielectric was kerosene. It didn't help at all if there are alternative substances, like Rustlick EDM-30. It might be cheap and easily available - and as unobtainable as spaceflight fuel.
    In MadModder, there's awemawson's posts about things EDM (http://madmodder.net/index.php?actio...owposts;u=1959) and he mentions
    "it is the "IonoPlus IME-MH" on this page:
    http://www.oelheld.com/products/metal-working-fluids/dielectric/ionoplus-dielectric.html"
    Likely it's German. But I guess you already have more than enough dielectric, good and cheap.

  7. #7
    Join Date
    Dec 2007
    Location
    South Wales
    Posts
    6,653

    Default

    Try a different material, maybee brass is dooing some wierd zinc sublimation thing?, just guessing though as the only edm i have done was cutting tensile test peices years ago, all steel btw.
    Laser cutters get trouble with brass too, or so i have been told, requires extraction of fume from the cut?

    Mark
    Last edited by boslab; 09-08-2013 at 08:29 PM.

  8. #8
    Join Date
    May 2003
    Location
    Vancouver's Island
    Posts
    41,979

    Default

    I would love to help but EDM is out of my field. It's something I would very much like to try but right now I am limiting my projects to real short term items. I may not be around long enough to finish anything long term. Or I might. Or not.
    Free software for calculating bolt circles and similar: Click Here

  9. #9
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    3,256

    Default

    Kind of guessed right yesterday that my question might be a little too specific and that most probably don't have (wire) EDM experience. No wonder, it is a kind of rare machine to have.

    macona: Thanks, I appreciate if they can get some idea. I'll also ask from the wire EDM guys at my old work place once I have the time to go there, but what i used the Fanuc machines at that time didn't produce such results in workpieces, so I might not get lucky.

    andywander: The brass is coming from the wire, the workpiece material is HSS. I have had this same thing happen on steel also, but this was the only piccture I got of it at the moment. And about my signature line, it is a very bad machine translation of a 'wisdom' from my workplace

    robosilo: The polarity at the moment is positive at workpiece and negative at wire. If they are reversed, no cutting happens. There is no plating action going on I think, otherwise I would see the plating all around the workpiece too.

    cidrontmg: Yes, good and cheap dielectric - plain water It is the wire EDM's dielectric, just tap water to the machine and ran through deionisation resin to remove conductance (5-20 uS is preferred value). And if you think a sinker EDM has lots of work, then this wire EDM has nothing but. The thing is that there is no manuals or walk throughs to follow, you just have to make and test it with the best of your abilities and knowledge. This is kind of reinventing the wheel independently, as I know from the commercial machines what they do and how they function, but to achieve that in a home shop machine is a lot of work. And because this is a kind of pioneer work, I try to document everything by photos, video, postings and publich everything under CC-BY-SA and GPL so that everyone else can also try the things I've done without paying anyone for it

    boslab: I've tried HSS, steel and stainless steel. The stainless cuts nicely as does the steel and so does the HSS, but for some reason the brass from the wire welds itself like in the picture to the workpiece sometimes, especially if I try to cut 1 mm thick steel and sometimes with a 6 or 8 mm thick HSS, so it seems that the material I'm cutting doesn't play a role in it.

    Evan: Would love to see your brains working on a project like this and I hope all the best to you, hopefully you are around here for long

    What I'm thinking of the reasons for this brass from the wire welding itself to the workpiece is something to do with the flushing or the water quality or the power supply, as the material or the thickness doesn't seem to make a difference. But I've gotten this same result with flushing while non-submerged (dirty water or pure freshly deionised water), while flushing submerged (dirty and pure) and when cuting submerged with no flushing. Also tried different power settings on the machines RC generator, amps doesn't seem to affect it much, but haven't had components yet to test out adding capacitance (and now out of wire).
    Amount of experience is in direct proportion to the value of broken equipment.

  10. #10
    Join Date
    Apr 2010
    Location
    Tropical Milwaukee, Wisconsin
    Posts
    430

    Default

    Jaakko, you need good flushing. I'm only spit-balling here, but if I were to see that happen on my machine the first things I would check would be flushing quality, voltage gap, and wire speed. There is some degradation of the wire to be expected, but it is normally flushed from the cut and filtered out later. Check your top nozzle flushing pressure. In fact, increase it until you see the cut start degrading. This happens because the water jet pressure will make the wire bounce around, reducing cut quality. Also, you might want to increase the wire's speed so that there is not as much chance for the degradation. Lastly, the larger the voltage gap, the more power applied which will tie directly in to the previous two points. Try as smaller voltage gap. Disclaimer - I am not a WEDM technician or application engineer. Just a lame sod with a cavity of detritus sitting on my neck, who happens to own and run one most days of the week. Good luck, and great job thus far.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •