TexasCHLforum.com

The Annoyed Man wrote:

dicion wrote:

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

I thought that MIM was more of a sintering type process, where the metal is put into a mold in powdered form and then heated until it fuses. Molding liquid metal is casting, and casting is not necessarily bad. I once bought a set of cast 1mm overbore pistons from Yoshimura for my race bike, and they performed just fine, spinning at 11,500 rpm for hundreds of miles. It's hard to imagine a tougher environment than that.

According to Wikipedia:

The process involves combining fine metal powders with plastic binders which allow the metal to be injected into a mold using equipment similar to standard plastic injection molding machines. After the part is molded and before the binders are removed, the part is referred to as a 'green part'. The next step is to remove the binders with solvents and thermal processes. The resultant metal part is sintered at temperatures great enough to bind the particles but not melt the metal.

It's not exactly powdered, but its not a liquid either. it's mixed with plastic 'binders' that make it inject-able. Then it's injected into the mold, the binders are removed, and then it is sintered.

So you are correct that it is not melted together, but it is still injected into a mold sort of like a liquid. It's actually all quite fascinating to me how this stuff is made!

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

Some things to look for:

Parting lines and ejector marks
Stolen from another forum, so I'll quote it:

A parting line is a line that runs all the way around the part (where the mold closes). Ejector marks are (usually) little circles, all on the same ide of the part. They are left there by little punches used to force the part out of the tool. They may be disguised as counterbores around holes, at least that's how I always tried to hide them.

MIM parts also generally do not have tool marks on them, are dull, and actually sometimes look 'too' perfect.... but not all of these are always true.
Sometimes you can also see crystallization if you look closely.

Parting lines and ejector marks are normally cleaned up on high-end parts though.. so you may not be able to find them.

It's an art, being able to look at something and determine if it's MIM. I'm pretty good at it, but I'm not perfect.