EDM: 3 solutions to avoid pitting problems

Estimated reading time: 4 minutes

Mold manufacturers have to deal with a very peculiar issue: avoid EDM pitting or DC arcing? While technology up-gradation has reduced the possibility of pitting, however for the most part, the problem persists and is very frustrating.

Imagine a scenario where you have spent weeks or even months designing the mold or cavity, CNC milling, grinding, etc. The only thing left to do is add the finishing touches using an EDM to add the details. The electrodes are ready, and you are prepared to program your EDM and setup the workpiece for the overnight operation since you are confident that everything is going as per plan.

“You need to see this!” mold manufacturer

The next morning when you give the workpiece to polish the mold to make it presentable and ready for dispatch, he/she says the most dreaded sentence any mold manufacturer would not want to hear, let alone first thing in the morning- ‘you need to see this.’

You guessed it right: DC arcs or microscopic holes in the deepest, most inaccessible part of the mold. Observing such a workpiece under the microscope makes you feel how every Indian must have felt looking at the lunar surface’s images when ISRO’s- Vikram lander was nowhere to be found- helpless and frustrated.

Quick-fix solution for the EDM pitting problem-

Most of the time, the entire mold will have to be scrapped and re-done. In some cases, you may have some creative space to explore. One of the innovative solutions may be to cut the pitted part and make an insert to replace it.

Permanent solution for the EDM pitting problem-

To solve the problem so that it never occurs, one must understand what exactly are these pits. The pits or holes are nothing but a poor surface finish phenomenon caused due to sludge deposition on the workpiece. The sludge acts as an electrode that causes arcing across the dielectric (mainly EDM oil), leaving its imprint on the surface.

 Three reasons for sludge deposition during EDM process-

1. Bad flushing of oil
2. Using incompatible/improper dielectric
3. Using unfiltered oil

Solutions for the above problems-

1. Bad flushing

Increasing the output flow of the pump solves the issue of bad flushing. Some latest machines ensure better flushing by retracting the electrode out of the cutting zone. Some have a high-speed oscillating effect that improves flushing.

2. Compatible dielectric (EDM oil)-

Dielectric is an essential parameter in EDM and plays a crucial role in determining high material removal rate (MRR) and surface finish. The dielectric fluid behaves as a medium that controls the electrical discharge and absorbs heat during the process. An ideal dielectric or EDM oil should have low viscosity (around 2 cst @ 40 deg C) and a high flashpoint.

3. Unfiltered oil

Dirty oil is a common culprit to DC arcing. Arcing happens because the filters are full or not sufficient to filter out the EDM sludge. EDM oil or dielectric should be one-micron filtered be to ensure no pitting due to dirty oil.

Solution for EDM oil filtration

Transor systems with their one-micron filtration technology prove very useful and add immense value for mold manufacturers. Mold manufacturers who use Transor systems get crystal clean oil consistently, which solves the pitting issues, improves their cutting speeds, and eliminates machine downtime. For more details regarding the Transor system for the EDM application, please click here.

Die & mold manufacturing can be a very satisfying and profitable business. With continuous improvements in machines and machining processes and by implementing lean manufacturing principles, mold manufacturers can improve their profit margins to a considerable extent.

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