Parts tumbler issue.

[Jim F]

At work we have a vibratory tumbler, about 18x 36.
Tumbled steel handles all last week, everything was fine.
Today, first batch was Ok, second batch had a dark contaminant on them.
Added some SYM-C, it helped a little bit, not much.
Changed out the fluids and cleaned the tanks, scrubbed the tub with soapy water, next batch started showing signs after 10. min.

This happened a few mo.s ago, but it was with Al parts.
Cleaned everything and it has been fine since.

Any ideas ?

 

[pontiac428]

Was the media new? Did the media have any notable odor from manufacturing or offgassing of adhesives in the matrix? I'm just entertaining the consideration that an acidic manufacturing byproduct in the media stained your steel parts...

What did the dark contaminant look like? Did it wipe away, or was it a stain? Is it a wet process or a dry process?

 

[Jim F]

Was the media new? Did the media have any notable odor from manufacturing or offgassing of adhesives in the matrix? I'm just entertaining the consideration that an acidic manufacturing byproduct in the media stained your steel parts...

What did the dark contaminant look like? Did it wipe away, or was it a stain? Is it a wet process or a dry process?

Media was new after the Al incident.
It is a wet process, the contaminant smears when wet,
no odors , but I cannot smell or taste anything.

When this happened with the AL, they cleaned up with lacquer thinner.
Have not tried that with the steel.

 

[pontiac428]

I missed that it also happened with aluminum parts. In that case, it's not likely a chemical reaction. Some things blacken both alloy and steel, like selenium as an off-the-wall example, but the lines I was thinking along with an acid byproduct would have only stained the steel. I suppose totally flushing the bath system and doing a good pre-wash on new media batches would be a good way to ensure everything is clean and neutral to start. I don't think there's anything to examine with the additive, unless there are incompatible additives precipitating something like a black sulfate out of the solution that's sticking to the parts. There are definitely some off-the-shelf products out there that can mix to form a precipitate like that. But it would also be an easy possibility to eliminate, just tumble with clean water and see if the problem persists. If the black is from grease, oil, or rubber/plastics degrading (for whatever reason), you should be able to identify it on examination.

You've got me curious, so don't forget to post back when you get another look.

 

[Jim F]

Just to add, we add the same coolant from the surface grinders (7) to the tumbler, just not as strong.

 

[mmcmdl]

Some of the agents cause this . I had a salesman give me 55 gallon sample barrel for our large tumbler . It stained everything . It cost me many $$$$ to get it hauled out of the company .

 

[Jim F]

Some of the agents cause this . I had a salesman give me 55 gallon sample barrel for our large tumbler . It stained everything . It cost me many $$$$ to get it hauled out of the company .

We are thinking the liner is breaking down.