Programmable Voltage Supply?

December 19, 2010

John asked:

Is there any value in a programmable(manual or C/C++) power supply for anodizing?

Say Vout=20+(110*N/(255)); // N=0,1,2,3,4,…255

Giving {20,20.4, 20.8,21.2…129.6, 130}

I can also make this power limited to approximately 13W(0.10A at 130VDC)

I am not selling anything! I am just wondering if this is a worth while adventure.

As a fellow electrical and programming geek, I see the appeal of the project. But practically speaking in terms of anodizing titanium, no. The color is determined by the final voltage, and the faster you get there, the better.

Also, I use down to 8 volts on occasion. And the lower voltages are more color sensitive than the higher, so it should either be 16 bit linear, or have exponential or quadratic output, as in

vOut = (((N/64)^2 + N) *120/255) + 5 // N={0…255}

But if you were to rig an x-y table to such a supply, one could then “print” in anodized colors. However, there is a limited palette. And also one would have trouble with certain adjacent colors, and have to adjust the lateral speed to be proportional to voltage, and maybe fluid flow through the dielectric cathode, and several other engineering considerations.

As such, it becomes fun and useful. But a lot more work. Then you would be able to share it on HackADay.com or Makezine.tv or some such.

In order to make such a project marketable, one would have to write the CADD end to prevent unfulfillable designs. Artists have to have limits imposed.


Is TSP/90 as Good as TSP for Anodizing?

December 13, 2010
TSP90
TSP 

James asked, “Will the TSP/90 Phosphate Free products work as well as the standard TSP brands?”

An excellent question. My first impulse is, “I doubt it.” But I am not sure. The folks at ReactiveMetals.com might have some insight (that I would share here if passed along).

TSP/90 is made with Sodium metasilicate and pentahydrate. So it is an alkali electrolyte with plenty of oxygen carriers in it. So far, so good. But as a cleanser it appears to suffer from leaving behind a film; a bad sign.

If you are concerned about the potential harm of artificial phosphates in the environment, anodizing is not a significant supply. I have been using the same 8 oz. box of actual TSP for the last dozen years. That’s equivalent to a few weeks of laundry. The same batch of electrolyte can keep on going for months, by adding distilled water (the part that is used up) and an occasional pinch of TSP crystals (to keep up the concentration from the drops removed by pulling out pieces). Occasionally, I filter out the dust and bring it to a boil to make sure it stays sterile.

If you want to be even more environmentally correct, use ammonium phosphate (lawn fertilizer) and then dispose of your old electrolyte by spraying it on your lawn. I used a box of this through the 1980’s and 1990’s.

One of these days, I’ll probably expound why the lingering phosphate meme of the 1970’s was somewhat misguided in the first place.


Q: Can I Stamp and Rivet with Titanium?

December 3, 2010

Kelley asks:

I make stamped jewelry and I have never worked with titanium before. Can titanium be stamped with a usual tool hardened steel stamp set? A client is wanting inspirational words stamped on a premade titanium bracelet.
Another question, would my usual method using a riveting hammer and a bench block do with titanium wire to create a rivet?

The short and qualified answer is, “Yes”.

Odds are that you are working with one of the less hard alloys or grades. Titanium behaves much like stainless steel, in that it takes more force to work it than do silver and other “normal” jewelry materials. Hit harder, maybe with a bigger hammer or mallet than you use to mark silver. I use normal steel stamps, myself  (as in this picture).

Where titanium gets its tough reputation from is that it is harder than steel under pressure. Stamps and especially cutting tools wear out faster because titanium, unlike steel, doesn’t get softer at a mere few thousand psi. Silver, gold, etc are softer to start with. I used a 20 oz. hammer to strike this stamp.

I have also used titanium wire to make rivets, using an ordinary little chasing hammer to set them. Nice, soft Grade #1 wire. Here is a List of Grades and their relative hardnesses.