My luck is not good lately.

[Big Frank]

Metal Injection Molding.

[Solus]

Got my new front sight today!  Broke it Wed, got it today Sat.  That is pretty dang quick I must say.  Lets hope it stays on this time!

That is good. 

Any manufacturer can have a problem with their product....it's how they handle it that tells you what the company is about.

As long as the problem isn't reoccurring, that is.

[tombogan03884]

Metal Injection Molding.

It's a fine idea that can be used to make complex parts quickly and less expensively than traditional methods .
The draw back to it is that it leaves a granular molecular structure without grain unlike forging or casting and machining where the work stretches the molecules into  long, fiber like structures that give better resistance to breakage.

[MikeBjerum]

Metal Injection Molding.

In simplest terms it is metal powder put in a mold and pressed to bond it solid.  It comes out of the mold nearly a finished part.  However, like Tom said, it is grainy, and if you machine it you can remove the solid surface and compromise the integrity.

I have MIM hammers on two of my S&W revolvers.  I would like to bob the hammer on one, but I need to get a steel hammer before I do the deed.

[tombogan03884]

In simplest terms it is metal powder put in a mold and pressed to bond it solid.  It comes out of the mold nearly a finished part.  However, like Tom said, it is grainy, and if you machine it you can remove the solid surface and compromise the integrity.

I have MIM hammers on two of my S&W revolvers.  I would like to bob the hammer on one, but I need to get a steel hammer before I do the deed.

A sharp blow from a ball peen hammer should do the trick.   

[Sponsor]

[kmitch200]

Why wouldn't a bench grinder work?

[Solus]

Why wouldn't a bench grinder work?

I believe that would be like machining it...



....."and if you machine it you can remove the solid surface and compromise the integrity."

[kmitch200]

I believe that would be like machining it...

....."and if you machine it you can remove the solid surface and compromise the integrity."

The part that would be ground off isn't in contact with anything except air. 

And I'm not too sure of the 'factness' of the statement to begin with.
The "solid surface' on the outside should be the same as the internal hardness or you have added another step to the process which would negate why manufacturers went to MIM in the first place - to reduce steps.
Many, many, many MIM fire control parts have been tuned by gunsmiths for years with positive results.

[tombogan03884]

KMitch, does the outside of a muffin have the same texture as the inside ?
Or does it have a "smooth" surface ?
The smooth surface is from being pressed against the side of the muffin tin, it's the same as with the injected metal being against the sides of the mold.
The outer surface has a smooth shiny surface, while the interior structure is more like corn bread or sand.

[kmitch200]

In the sintering process the part is no longer in a mold. The mold is only used for the intial shape which is roughly 40% larger than the finished product. It is 'green' and still has binding agent in it.
(If you sinter a muffin at 1800+ deg it will indeed be one texture.)
Baking muffins aside, you can grind, polish, coin (cold deformation), tap, drill, plate, weld and machine MIM parts.
If you add too many steps though, you risk defeating the purpose of using MIM in the first place - reduction of steps and scrap.

Reducing the number of labor steps by using MIM, then adding steps costs more $$$ and adds material to the scrap pile. If you're not making thousands of parts (or hundreds of thousands) you might as well just machine it or cast it (if applicable) and not have to pay to run the ovens or for the mold to be made.