Heavy Rust pitting, Quality of water and so on

I have been using an old Pratt & Whitney Wire CUT W1 for about 6 years now, it is a non-submersible machine.

2 Months ago we obtained a CHMER CW-643S Wire EDM that is submersible. The machine had fresh filters, resin, and distilled water put into it when we installed the machine.

I have cut many die blocks so far and the rust is incredible. Last week I cut a punch block that is 3.75" tall with some profile punches so the cutting time per punch is about 14-16 hours. After the cut the block is so rusted that the surface shows pitting on it and needs to be ground about 0.0010"-0.0015".

I've changed the resin and the filters but the rust still carries on. While cutting, the water in the tank is jet black from soot/slurry and rests on all surfaces. The machine cycles water based on the level sensor on the upper head.

Overall cutting speed seems fine to me compared to our older machine. on a 3.75" tall block I was getting a feed of about 0.050"/min.

Does the water in the main tank usually turn jet black after cutting for 1-2 hours?

The water coming out of the filter reservoir is crystal clear and it overflows into the exchange reservoir beside it, the water from the exchange reservoir cycles into the flooded tank and the jets shoot water in from the filtered tank.

Any advice?

Hi Sethrocon:
Two questions?
Have you checked the pH of your water?
Did you cut workpieces made from other materials than steel?
The reason I ask, is that corrosion like you describe is typically either from acidic water, or from galvanic corrosion caused by residues of materials in the tank with a different electrochemical potential interacting with your workpiece.
A third although more remote possibility with such a new machine, is that your DI resin is either poisoned or the conductivity probe is not triggering the dirty water to go through the resin bottle, so it's not actually decontaminating the water, leaving it more like a salt solution than like DI water.
Have you checked your conductivity probe to make sure it's OK?

If you cannot isolate the problem and make it go away, you'll have to coat your workpieces with something, at the expense of shorter resin life and a nuisance when you want to do precision clamping and touch offs.
Some people use Dykem, others use WD40.
It's also possible to add an anti-rusting agent to the water, but some claim it ruins the water.
The jury is out on that claim.

With regard to your question about the water colour after roughing, yes it'll be jet black if you're cutting at all aggressively, unless you're cutting aluminum in which case it'll go milky and have an unpleasant smell.
Cheers

Marcus
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining
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Thanks for your help

I purchased some test strips this morning and the pH shows it to be around 6.0-6.2, the water conductivity dial was reading 12K-ohm/cm, I am not certain as to what this meter tells me.

(This machine came with 2 poorly written manuals. 1 a quick start guide that does not explain every function the machine is capable of doing. The other manual shows samples of programs and what they do. It seems like I'm missing a key manual on maintenance and care of the machine, no diagrams on the upper or lower head or how often to change parts or resin or filters. King of left in the open)

I took a chance and bought some pH balancer and sure enough the pH is now at 7.2. I am performing a test cut at the moment to see if the rust situation improves.

The water conductivity also went from 12K-ohm.cm to 6 (which I'm not 100% certain on how to control the dial beside the meter, when you adjust it, the water will either cycle through the resin filter or not)

The only thing I've cut since I put fresh resin in and new filters/water is steel. 2 months ago I ran test cuts on Aluminium.

I am currently cutting 1/2" hardened A2 at 0.320"/minute

I've add a photo of the conductivity reading and adjustment dial.

I've tried coating the blocks with Lloyds AD2000 and it works great. Though it leaves an oil slick and coats the walls of the tank, there is limited rust by comparison. Soot does not stick to the side of the tank, and the cutting speed is unchanged.