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Stainless Steel Electrochemical Machining "CURRENT DENSITY" - Includes Gift!

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Victor Ramon:
Understood.

I will comply.  :-+

And thank you for the heads up on the Meanwell and TKD-Lambda. As an outsider, I did not know and so I thank you.

Ii will do as you say.

Much obliged.

T3sl4co1l:

--- Quote from: Victor Ramon on April 25, 2020, 08:20:39 am ---You've touched on so many of the most important aspects. It's obvious to me you've been working on electrochemistry at a very deep level. And I admire that. By the way you exposed your arguments so clean and clear, I couldn't tell if you're a chemist who is into power electronics, or an EE who is into electrochemistry. It'd be nice to know.
--- End quote ---

One of those rare times when an inclusive-or "yes" answer is appropriate. ;D

Professional EE, amateur chemist.  Haven't had a place to practice chemistry in quite some years, but I remember much.

I'm sure there are theoretical bases for what waveforms, additives and electrodes accomplish, but I'm quite happy waving my hand at "surface chemistry" and leaving it at that... the professionals and academics can handle it. :P

Have also heard that "high throw" copper plating (e.g. for PCBs) can be done with a partial reversal waveform, which apparently works by etching the peaks more rapidly (electropolishing).  Meanwhile, levelers and other additives encourage uniform deposition, even into narrow or blind holes.

A typical PCB is 1.6mm thick, and is drilled with 0.3mm holes -- a 5.3:1 aspect ratio -- which get plated with 35µm or so of copper.  The glass-epoxy laminate is treated with an activator, then electroless copper plated for initial coverage, then electroplated to finished thickness.  This is how they plate holes, edges, anywhere that isn't covered in copper foil to begin with.

(I've etched my own boards, once upon a time; never had the things together to try plated through holes (PTH) though.)



--- Quote ---I was thinking, naively, perhaps a half H bridge inverter with an IR2110 driver with 2 overkill mosfets in parallel could possibly work to chop the input current coming from a higher  SMPS. Something like this:
--- End quote ---

Well, two things --
0. If straight on-off is all you need, a single switch will do.  Simple!
1. If the buck converter is controllable, why not program its setpoint in the first place?  This gets you a multi-level, unipolar (always positive) waveform.
1a. If it's not controllable, it may be worth seeing if it can be hacked to do so.  Example: adjustable regulators have a feedback/sense pin, which connects to a resistor divider which senses the output voltage.  You can bleed in a small current (directly, or through a resistor from another voltage source) to offset the default value.  In this way, the regulator never loses control -- it's always in control of the load, no danger of confusing or destabilizing the control loop -- and the voltage can be controlled arbitrarily.  (Control might be from an Arduino with DAC shield, for instance.  DACs produce a digitally controlled output voltage.)
2. If the waveform should be bipolar (reversing), you can't use a half bridge anyway, but need a full bridge.  Which isn't to say you're on the wrong track -- a full bridge is just two put together, driven oppositely. :)

IR2110 style drivers have the downside that they must always be switching -- the high side driver is only powered when the low side turns on.  The rest of the time, a capacitor supplies its power, and this can only go for so long (milliseconds, seconds?), depending on its value of course.

So if you're driving a full on/full off waveform, or full on/full reverse, and it's switching at some minimum frequency or higher, a bridge will do fine, and bootstrap gate drivers will also do fine.

I would suggest opting for an off-the-shelf development board, as there are some details in bridge layout that would take some time to explain.


Also if you combine these approaches, you can do an asymmetrical reversing waveform, for example.  I don't know that that's helpful here, but it's apparently the kind of thing that's helpful for copper plating, so who knows.

Tim

coppercone2:
I don't have anything specific to add but if you are dealing with bare PSU modules keep in mind the chassis. You don't need EMI for this but it would help if they are splash proof and stuff. If you are making your own from the bricks and you are doing chassis you might want to make it a bit non standard with more complicated ventilation/splash control, i.e. blower fan with bends, mesh filters (not just perforations), etc.


The design of something for working around chemicals is different then a bench top lab power supply IMO.  Also corrosion, it might make sense to use potted electronics or to use conformal coat. Also use switches with coverings if you can afford them, in case you need to turn it off while wearing gloves (preferably add a EMO switch that you can slam)

good design around fluids will increase cost significantly. For low currents you might want to consider using batteries.

T3sl4co1l:
Speaking of chassis and ground, mind that a cell driven by full-bridge either needs to be isolated by itself (ungrounded), or the power supply does, or both.

Shouldn't be hard to get power supplies with non-grounded outputs, but keep this in mind if you're going to connect anything else to it as well (e.g., programming cable to Arduino board).

Tim

duak:
Victor, no, I didn't work in a plate making facility.  I'm an EE that worked in various R&D projects that often involved electro-optics.  My first major project there was in data storage. Some of the technology we developed was later used to expose silver halide film for printed circuit board fabrication and then for graphic arts, ie. lithographic printing plates.  We were one of the first companies to come up with Computer to Plate systems that bypassed silver halide and exposed the plates directly.  Early plates were sensitive to green wavelengths but we pushed thermal ie., IR sensitive.  Film and darkrooms were no longer needed although some plates still needed processing for longevity.  We did not develop or manufacture the plates ourselves but worked with plate media manufacturers like Kodak, 3M, etc. to improve and optimize their products.

I remember a lecture by one of the chemists from one of our large customers.  The chemistry of ink is complex and interesting - so many conflicting requirements like viscosity, miscibility, drying time, toxicity, etc.

Since gravure was a photo and chemical process, our Technology guru thought we we should look into some form of electro-erosion to make gravure plates.  I think it was a more difficult problem than expected as well as a market that was too small for us to continue.

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