Conversion Coating vs Alodine & Iridite - What's the Difference?

Things are still a bit hectic for me.  I'm busy with a new job, and I'm preparing to start up a new class in Aircraft Fuel systems.

I guess I just can't sit still!

I did want to share a short post on a funny experience at work the other day.  Definitely a case of knowing more than I thought I did!

Many of the aircraft mechanics I know about refer to "Alodining" an aluminum part.  It's a common practice to prevent corrosion on components made of non-ferrous materials.

Alodined part.  From Chem Processing, Inc.

You can find some more great pictures of parts having been "Alodined" at this link from Avon Electro.

In my Aircraft Maintenance Studies at Mount San Antonio College, I haven't had much hands on experience with the Alodining process, so it's been relegated to the "I need to read about that later" file, in my mind.

In another life, my design work, I've also worked with the "Chemical Conversion coating" of Aluminum alloys.

I knew that it was a protective coating that prevented aluminum as well.  But there are many processes, and I knew what I needed to know to design parts.

Then one day, it all came together, with a bit of humor at my expense thrown in.

I had to read up on finishes for a totally separate process, and stumbled on to a document that spoke about chemical conversion coating shared by Chem Processing, Inc.

It was short, so I let my curiosity get the best of me, and read the article.

What was one of the first lines in the article?

"Chem Film, sometimes called Alodine or Iridite"

I had to laugh at myself.  All this time, I had been dealing with the same processes, but not even known it.  

Alodining, along with Iridite, are just trade names for chemical conversion!

Alodine image from Aircraft Spruce.

In one paragraph that I stumbled on to via a web search, I had connected the dots, and realized that I had known more than I had.  I was just missing one little link.

Ultimately, I found that I had known far more than I realized.

But what was the other big lesson I learned? Or perhaps, relearned?

Ask questions!  For years.  Yes, years!  I assumed that I knew enough about Alodine and chemicial conversion coating.

And in many ways, I did.  I could design fine with it, I hadn't used it "hands on" ye.

But if I had only asked one question... "What is Alodining".  I could have bridged those gaps a long time ago.

Instead of having adequate knowledge, I would have had knowledge that could have set me a part, if only in a small way.

So that's what I share with you.  Learn from my example, my mistake.

Ask questions.  It is true when it's said the only dumb question is the one you don't ask!

I'll certainly be taking this lesson to heart.

One final note.

If you want to read more about Chemical conviersion coating yourself.  Check out the article I found at Chem Processing, Inc here.

I learned a lot from it!

Showing Trimmed Edges in an Inventor Model

My father had many a humorous saying.  One I remember came from his days as an aircraft mechanic for over 40 years.

"Mark it with a micrometer, mark it with a chalk, cut it with an axe."

It was a humorous reference to the futility we all encounter in our careers, whatever it may be.

I was reminded of this saying when I was reproducing a part that had a note indicating that a piece of standard extrusion was going to be "trimmed to fit.".

Technical translation?  "Here's extra material, so you can make it fit in the field".

An example of "Trim to Fit"

But how do we represent that in the print?

In truth, there are several ways you could accomplish this.  The one I present here, is just one idea.

First, offset a work plane the desired distance from the edge to be trimmed, in this case, I chose the maximum of .093 inches.

The first step is creating the work plane.

After the work plane is created, choose the Split command, and chose the "Split Bodies" option from the dialog box.

Make sure to choose the work plane as your split tool.

Splitting the bracket

Once that is done, create your drawing as you normally would.  But you'll notice there's a bold line where the solid representing your bracket was split.

Now comes the trick!  I'm going to make the lines representing the trimmed section dashed.  This can be done by right clicking on the lines, and choosing "Properties".

Changing the lines from solid, to dashed

Once this is done, the part to be trimmed can be clearly seen!

The indicated lines are dashed! 

There's the trick, but why use it over several other methods, such as creating sketch lines in the model, or drawing or perhaps only splitting a face?

Here are my reasons, I only ask you to consider them.

1. Splitting the part doesn't create any extra files, this approach keeps everything in the part (*.ipt) file. 
2. Changing the lines is easy to do, the split creates a "natural break", which prevents having to create any sketch "trickery".
3. The split can be moved pretty easily, by changing the work plane's offset.  This let's you represent the geometry more accurately if you desire. 

So there are the reason I chose this method.  Feel free to see what you think, and use this tip should you ever need it!