SPARK GAP

[leow_john]

View attachment 2572
Hi all

Refer to the picture, if I copy the surface and form one electrode and do the milling R5 Become R 4.9

But how I can apply spark gap and maintain radius same R5 without changing either part or electrode model.


Any parameter while do milling?
How others do when you want to finish one cavityEDM by orbiting method?

Thanks in advance.
LEOW

 

[MR_NC]

Spark gap is "often" handled by a factor of negative stock / material allowance. This is done at the time of toolpath creation.

I create all my electrodes at model / mold size. Then apply spark gap as a factor of negative stock allowance. Has worked well for a long time now.

Best regards,
Sean

 

[TonyJager]

Weadd a negative value value or in some instances a positive value for stock allowance while machining. Does work great.


We also have created the actual electrode by 'offsetting surfaces' or scaling the part for either sparkgap or shrinkage. So it would make sense that it would change the R5.0 to R4.9. This has worked great as well.


Regards


Tony
Edited by: TonyJager

 

[leow_john]

Hi
Thanks for the helps.

Usually I too apply spark gap by giving negative stock.
Then the result in this case will be R 4.9

But my requirement is R5.


How could I achieve it?

Thanks

 

[MR_NC]

Hi
Thanks for the helps.

Usually I too apply spark gap by giving negative stock.
Then the result in this case will be R 4.9

But my requirement is R5.

I am confused by your "requirement". If you want R5 on the finished part then in fact if you plan to use .01 spark on the EDM you DO have to cut the electrode to -.01 However, if your finish part "requirement" is R5 +.01 then in fact R5 on the electrode is correct. However, that is not what your picture leads one to understand. It is difficult for me to understand how the electrode can match the finish part size without having a 0 spark gap. I am unsure how well an EDM works with a 0 spark gap...

I am sorry for the lack of understanding of your "true" desired result & process.

Best regards,
Sean

 

[leow_john]

Hi
I think you all using the "conventional EDM"

If you talking about CNC EDM and Orbiting, surely you need to put R5 instead of R4.9

Thanks

 

[padraig]

The Problem here is the availability of different machining stratigies on different edm machines. Many if not all older machines would have an electrode made with 0.1 sg as shown and spark the cavity to the correct width and depth but the radius would be 4.9 not 5.0 as required. This is because as the machine works it uses less and less power as it goes through each stage and increase the machining orbit to compensate, thus giving the required surface finish.


This is most noticeable if tou try to machine a hemisphere, It will measure the correct diameter at the top and the correct depth, but there will be a slight rad at the bottom.


Newer machime have advanced orbiting to combat this, in other words you can use pro e with negative stock allowence and everything works perfect