How the heck do they do...........

[00_buckshot]

the delta ring on a AR-15 rifle? I looked at my factory anodized delta ring and can find no area un-anodized. Where do they make the connection? My lower also shows no area un-anodized. I've heard that there is some imperfection somewhere but I cannot find it anywhere. Nothing that looks like it was a connection point anyway. Someone has to know the secret.

[FM]

I have noticed that AN hose fittings are the same, that is there is no area that shows a connection. I don't know the answer but would like to.

[M_D]

Although not parts I have done, I have seen literally hundreds of thousands of anodized parts if not millions, and sometimes the un-anodized spots are obvious, while some are very well concealed. A lot has to do with the racking style and skill used during the process, as well as the configuration of the part.

I'm not familiar with the rifle part, so I don’t know if it has a hole or not, but I am familiar with most all types of AN fittings. Most anodizers will rack the part using a hole if available, if appearance is important. Sometimes the marks are very small and hard to see, depending on the shape and condition of the titanium contacts, and if it is in a hole (especially a threaded hole) it can make it even harder to distinguish. I have seen some parts touched up with various types of markers, and depending on the texture of the part can make imperfections hard to see.

[Fibergeek]

M_D,
When you have a chance, could you expound on you observations of professional racking? There are many here who would find this interesting, myself included.

[M_D]

Fibergeek, while I have spent some time around a commercial anodizing business, I didn't pay as much attention as I now wish I would have. My observations have been primarily as a manufacturer who has parts anodized, looking at it from an appearance and parts damage standpoint rather than the anodizer’s side of it. I have discussed racking issues with anodizers some, mostly about where an acceptable point to rack a certain part was.

So, I have paid a fair amount of attention to racking scars and comprehend a few of the issues. One thing is with complex parts, including pockets, blind holes and small through holes, etc., it is necessary to think about trapped air pockets that prevent areas from not anodizing and plan the racking from there. The position of the part can also aid or hinder rinsing, and small blind holes are especially hard to rinse well, and then bleeding trapped solutions latter. Sometimes, if having a small hole left un-anodized is acceptable, it may be best to rack the part so an air pocket prevents most of the solutions from entering deep into the hole in the first place.

If the contact points are sharp and “bite” into the parts, it helps to make a good connection and maybe as importantly can better secure the parts and help prevent the part from slipping or shifting during the process, which may spoil the part not only because of a lost connection but from coming in contact with other parts which are often racked at a high density. Another issue is a rack style that makes it easiest to rack and remove the parts with the least amount of potential for scratching the surface.

Anyhow, that isn’t much information, and you and many others probably are aware of more than I am. At the moment, I still have as many questions as answers.

I had done some playing around with anodizing a few parts years ago, and it has only been recently I have decided to do a selected amount of our commercial products in house. I don’t know how large of a line we may end up with in the future, but for now we will keep it reasonably small, maybe upgrading to 60-80 gallons of anodizing solution in a month or so. At the present, it is only a 15-gallon tank while we learn the process. I have ordered a small quantity of titanium racks and racking equipment, and as we gain some experience I would be happy to share what ever we learn about racking, as we aren’t going to compete in the anodizing market.

The reason I have been reading this forum is to learn, I have been doing loads of research wherever possible. I have found this forum educational, and have proven to myself the LCD method works. The only draw back is time like the manual says, but I found the reduced fumes and safer concentration of acid appealing, in the interest of fitting in with our current facility. It took me a little while to understand it, and there has been and will continue to be a learning curve, but due to learning here about PAR and various other tips I am sure we are ahead of where we would have been otherwise. Thanks!

[Fibergeek]

Thanks for the info M_D.

Keep in mind that LCD was designed primarily for the amateur anodizer, where throughput is much less important than equipment costs. The low current densities used in LCD is the only way one can grow a layer to full potential thickness using a 12V battery charger. Recall that the coating resistance is proportional to coating thickness; although its current (not voltage) that does the actual anodizing, sufficient voltage must be available to overcome the coating resistance or the layer thickness can't be increased. Higher current densities require higher voltages. This is Ohm's Law.

In your commercial application you may find that a compromise is in order; increasing current density to speed things up, you will still be able to make profitable use of the process monitoring tool we call PAR.

Starting small scale is always shrewd, you will go through your learning curve at minimum cost.

they pinch mount the wire in the parts opening ... and professional racking ( isn't that like racking fries at mcdonalds

[00_buckshot]

Please explain pinch mounting.

[bp]

There is pinch mounting and what we call at our facility "finger racks". I purchase aluminum and titanium rack systems. Depending if the job is clear anodized or anodized and 2-step colored. (Titanium cannot go in the color tank). Our tanks are 31 feet long and 7 feet deep and typically a full set of racks on the beam at 11" will hold about 700 to 900 parts depending on square footage, of course. Just an example of well they can utilize area on a load and leave a minor mark that most people will never notice.
You will have to watch out with titanium finger racks though as they can have local burning on the parts if your ramp time on the rectifier is applied to quick.

[M_D]

BP, I didn't know titanium couldn't go in dye tanks. Why is that? I was hoping to be able to rack parts on titanium and not touch them untill they were done. I realize racks might add some difficulty in rinsing between solutions, but I get the idea there is more to you statement.

I haven't seen as much for aluminum racking components compared to titanium, would you mind mentioning some sources?

Those seem like some very large tanks you work with.