MIM
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LOL.....
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runningbear
New member
In a short reply it's powder metal made molten, and injected into a mold to form a part.
It had a some what rocky beginning,but today it's used in about everything you buy.
You see it used in knife blades and Automotive parts and firearm parts.
It is here to stay and has proven to be as good as any other steel part.
Most people find if a MIM part in a firearm will it will fail quickly.
It had a some what rocky beginning,but today it's used in about everything you buy.
You see it used in knife blades and Automotive parts and firearm parts.
It is here to stay and has proven to be as good as any other steel part.
Most people find if a MIM part in a firearm will it will fail quickly.
runningbear
New member
Thank you Pat701. 
g.willikers
New member
There's also an element of high pressure involved.
But mostly MIM provides endless cause for discussion to help plump up forums.
But mostly MIM provides endless cause for discussion to help plump up forums.
Its just another form of manufacturing. Not all MIM is created equal. It can vary from a outstanding and more exacting quality parts to just a average part. Its like producing a plastic part. There are soooo many variables in materials and quality of manufacturing that you can't generalize the processes although some keyboard comandos like to do so. Mim parts are used in everything from turbine jet blades to kids toys so the process is here to stay and is trusted to be used in the most critical applications. Alot of small gun manufactures can't afford the machinery to produce a quality MIM part so they must use other methods.
The misinformation about the process tends to run rampant in the 1911 forums. I suspect many purposely perpetuate misinformation on purpose for ulterior motives.
This is why many just avoid the topic on gun forums all together.
The misinformation about the process tends to run rampant in the 1911 forums. I suspect many purposely perpetuate misinformation on purpose for ulterior motives.
This is why many just avoid the topic on gun forums all together.
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marine6680
New member
A quality MIM part is not a problem...
Ruger does MIM very well... And the MIM in the new Sig 320 is very well done as well.
But MIM parts that are not made well, either because of cost cutting (even farther than MIM does on its own) or due to engineers that are inexperienced in MIM, and designing parts that are not conducive to the technique... Well that can lead to poor quality and part failure.
When working with liquid flowing into molds, you not only need to know material science, but also fluid dynamics. Poor design leads to poor flow in the mold, and possible voids in the finished part.
MIM tends to be surface hardened only, so removing material and reshaping parts to "improve" trigger pull or other aspects, can lead to rapid part wear... So that is a caution specific to the gun world.
Ruger does MIM very well... And the MIM in the new Sig 320 is very well done as well.
But MIM parts that are not made well, either because of cost cutting (even farther than MIM does on its own) or due to engineers that are inexperienced in MIM, and designing parts that are not conducive to the technique... Well that can lead to poor quality and part failure.
When working with liquid flowing into molds, you not only need to know material science, but also fluid dynamics. Poor design leads to poor flow in the mold, and possible voids in the finished part.
MIM tends to be surface hardened only, so removing material and reshaping parts to "improve" trigger pull or other aspects, can lead to rapid part wear... So that is a caution specific to the gun world.
polyphemus
New member
A: Metal Injection Molding.
Have fun.
buckhorn_cortez
New member
No - if molten metal is injected into a mold that would be casting.
MIM is powdered metal plus a binder (wax or plastic) that makes a low temperature liquid that can be injected into a mold. As the low temperture liquid cools in the mold it hardens and makes a "green" part.
The green part is removed from the mold and part of the binder is removed in an oven, or with solvents, or through a combination of processes. The result is a porous part (voids from the binder removal) that is in the "brown" stage.
The porous metal part has to be "condensed" so it is put into a sintering furnace where it heated to a specific temperature up to about 2450 F. The metal particles bind together from the sintering process making a part that is between 96% - 99% solid.
At that point, the final part may be used as it comes out of the furnace or finished further through machining, plating, annealing, hardening, etc.
That is the condensed version of the MIM process...
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marine6680
New member
^^ good simple description of the process.
During the process, there are dimensional changes to the part as well. So the engineer has to calculate these changes to ensure the part is correct when finished.
MIM requires an engineer competent in more fields than machined parts. The process is cheaper on the back end once the engineering is finished and the process set up... Parts can be mass produced quickly and with less time and labor...
Improper mix of binder to metal powder can lead to issues; poor mold design, poor part design can as well... Improper sintering and heat treat are other areas of concern.
MIM has a lot of potential and can do things that machine work has trouble doing or can't do at all... It just need to be done right.
During the process, there are dimensional changes to the part as well. So the engineer has to calculate these changes to ensure the part is correct when finished.
MIM requires an engineer competent in more fields than machined parts. The process is cheaper on the back end once the engineering is finished and the process set up... Parts can be mass produced quickly and with less time and labor...
Improper mix of binder to metal powder can lead to issues; poor mold design, poor part design can as well... Improper sintering and heat treat are other areas of concern.
MIM has a lot of potential and can do things that machine work has trouble doing or can't do at all... It just need to be done right.
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Jim Watson
New member
I didn't know Ruger did MIM. They certainly legitimized casting as a way to produce good firearms parts.
I guess it was Remington who got us used to stamped gun parts in the 870 and other 1950s guns.
Glock wasn't the first plastic pistol but they were the first really successful one.
I see two problems with MIM
First, it has generally been used to keep cost down. The mold and other equipment are expensive but once you are set up, you can turn out parts like doughnuts. Unfortunately, if you get something wrong, it will turn out scrap faster than ever before possible.
Second, it works better when the method is considered when the part is designed. The P320 mentioned above is a good example.
An example the other way is the name brand 1911 company that adopted MIM early on, substituting molded parts for machined. They sold a lot of guns with slide stops that could not be counted on to engage. I figured they got the detail shrinkage wrong, that is a complex little shape. They finally rectified that problem, probably with a new or modified mold. The next generation of slide stops engaged every time, sometimes when not wanted. At least that could be fixed by filing the lug so it was not bumped up by the next bullet, a fitting step sometimes needed by milled parts.
I guess it was Remington who got us used to stamped gun parts in the 870 and other 1950s guns.
Glock wasn't the first plastic pistol but they were the first really successful one.
I see two problems with MIM
First, it has generally been used to keep cost down. The mold and other equipment are expensive but once you are set up, you can turn out parts like doughnuts. Unfortunately, if you get something wrong, it will turn out scrap faster than ever before possible.
Second, it works better when the method is considered when the part is designed. The P320 mentioned above is a good example.
An example the other way is the name brand 1911 company that adopted MIM early on, substituting molded parts for machined. They sold a lot of guns with slide stops that could not be counted on to engage. I figured they got the detail shrinkage wrong, that is a complex little shape. They finally rectified that problem, probably with a new or modified mold. The next generation of slide stops engaged every time, sometimes when not wanted. At least that could be fixed by filing the lug so it was not bumped up by the next bullet, a fitting step sometimes needed by milled parts.
Aguila Blanca
Staff
I have toured a couple of firearms factories and seen MIM in the making. Buckhorn Cortez (above) offers a very good description of the process -- the closest to the mark of all the posts above.
Walt Sherrill
New member
Here's a more-technical explanation that I first saw on either this forum or The High Road, by a S&W expert. It's worth the read -- it agrees with some of the simpler explanations, above. I copied the information, and I should have copied the LINK as well. I didn't.
Here's a post from Mr. Herb Belin of S&W. He was (or is) the the Product Innovation Manager for Smith & Wesson Holding Corporation (He may still be with S&W, for all I Know. His name shows up many times when doing a search-engine check.
Here's a post from Mr. Herb Belin of S&W. He was (or is) the the Product Innovation Manager for Smith & Wesson Holding Corporation (He may still be with S&W, for all I Know. His name shows up many times when doing a search-engine check.
"I have read with much interest the many comments in this forum pertaining to MIM, MIM Parts and the use of same in a S&W product. So far I have come away with several impressions and they are "people in general don't like/trust MIM parts" and "no one has said why" I will take a stab at this issue and see where it goes.
As background to our decision to use MIM in some areas of our Mfg Process we took a long hard look at our "Life Time Service Policy". It was clear to us that any change in any of our products such as the use of MIM components had to show equivalent or better performance and durability to those components that were being replaced or the "Lifetime Service" would haunt us forever. The second consideration was to determine if the change was too radical a departure from S&W mainstream design.
For the performance and durability issues we decided that if MIM could be used for the fabrication of revolver hammers and triggers successfully this would truly be an "Acid Test". There is nothing more important to a revolvers feel than the all-important Single Action Sear that is established between the hammer and the trigger. Mechanically few places in a revolver work harder than at the point where the hammer and trigger bear against each other. If these surfaces wear or loose there "edge" the "feel" is lost. Initial testing was on these two critical parts. Over time we arrived at a point where our best shooters could not tell the difference between a revolver with the old style hammer and trigger and the new MIM components. Special attention was given to their endurance when used in our very light Magnum J frames such as the early prototype 340 & 360 Sc's. None of our revolvers work their components harder than these small magnum revolvers. Throughout this testing MIM held strong and finally we determined that this change judged on the basis of durability and feel was a good one.
The second area of concern to S&W was our customer’s reaction to this departure from the traditional. Many heated, intense discussions resulted but in the end the decision was made to move ahead with MIM. The issue of cost was only one of the considerations in making this decision. Equally as important was the issue of part-to-part uniformity and the result of this of course is Revolver-to-Revolver consistency. We found that revolvers that used MIM hammers and triggers required almost no Fitter intervention in those areas during final assembly and final inspection and Trigger Pull Monitor rejection rates dropped markedly on finished guns. From an internal process point of view it appeared a "Winner".
Lets shift gears for a moment and talk about the MIM process. It is unclear to me as to the reason for many of the negative feelings on the forum concerning MIM. Typically when people complain and aren't specific in the reason why, the problem is often created by a departure from the "Traditional". Perhaps that is indeed what is bothering some people when they view MIM.
The term MIM stands for Metal Injection Molding. It holds some similarities to Plastic Injection Molding and many differences as well. To start we would take a finally divided metal powder. This could be stainless or carbon steel. Today even Titanium is being used in some MIM fabrications. We would mix the metal powder and a thermoplastic binder (generally a Wax) forming slurry of sorts when heated and inject this mix into a precision mold and finally form what is known as a “Green Part". This part is roughly 30% larger than the finished part it will become at the end of the process. Interestingly enough the Green Part at this stage can be snapped in two with simple finger pressure. The Green Parts are then placed in a Sintering furnace filled with dry Hydrogen gas and the temperature is brought almost to the melting point of the metal being used. Over time the "Wax" in the Green Part is evaporated, the metal fuses and the part shrinks 30% to it's final correct dimensions. At this stage of the process the MIM part has developed 98 to 99%of the density of the older wrought materials and a metallurgy that is almost identical. Dimensionally it is finished and no machining is required. However the job is not yet done and the MIM parts are brought to our Heat Treat facility for hardening and in the case of Hammers and Triggers, Case Hardening. Depending on the particular metal alloy that was used at the start of the process we apply a heat treat process that is the same as would be used if the material were the older wrought style. Final hardness, Case thickness and core hardness are for the most part identical to parts manufactured the older way.
Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn’t happen resulting in a rejected gun and rework or in the worst case an unhappy customer. With MIM parts you must still machine to very high tolerances and your cutters have to be perfect and your machinist has to be highly qualified but all of this only has to come together one time. That time is when the injection mold is made. Typically a mold for this process costs S&W between 30,000 and 50,000 dollars. Once it is perfect every part it makes mirrors this perfection and you have in my view a wonderful manufacturing process.
Hopefully this description will help us all better understand the MIM process. Please forgive the spelling errors and misplaced punctuation. I have no spell checker on this and the phone continues to ring!
Have a Great Weekend,
Herb"
As background to our decision to use MIM in some areas of our Mfg Process we took a long hard look at our "Life Time Service Policy". It was clear to us that any change in any of our products such as the use of MIM components had to show equivalent or better performance and durability to those components that were being replaced or the "Lifetime Service" would haunt us forever. The second consideration was to determine if the change was too radical a departure from S&W mainstream design.
For the performance and durability issues we decided that if MIM could be used for the fabrication of revolver hammers and triggers successfully this would truly be an "Acid Test". There is nothing more important to a revolvers feel than the all-important Single Action Sear that is established between the hammer and the trigger. Mechanically few places in a revolver work harder than at the point where the hammer and trigger bear against each other. If these surfaces wear or loose there "edge" the "feel" is lost. Initial testing was on these two critical parts. Over time we arrived at a point where our best shooters could not tell the difference between a revolver with the old style hammer and trigger and the new MIM components. Special attention was given to their endurance when used in our very light Magnum J frames such as the early prototype 340 & 360 Sc's. None of our revolvers work their components harder than these small magnum revolvers. Throughout this testing MIM held strong and finally we determined that this change judged on the basis of durability and feel was a good one.
The second area of concern to S&W was our customer’s reaction to this departure from the traditional. Many heated, intense discussions resulted but in the end the decision was made to move ahead with MIM. The issue of cost was only one of the considerations in making this decision. Equally as important was the issue of part-to-part uniformity and the result of this of course is Revolver-to-Revolver consistency. We found that revolvers that used MIM hammers and triggers required almost no Fitter intervention in those areas during final assembly and final inspection and Trigger Pull Monitor rejection rates dropped markedly on finished guns. From an internal process point of view it appeared a "Winner".
Lets shift gears for a moment and talk about the MIM process. It is unclear to me as to the reason for many of the negative feelings on the forum concerning MIM. Typically when people complain and aren't specific in the reason why, the problem is often created by a departure from the "Traditional". Perhaps that is indeed what is bothering some people when they view MIM.
The term MIM stands for Metal Injection Molding. It holds some similarities to Plastic Injection Molding and many differences as well. To start we would take a finally divided metal powder. This could be stainless or carbon steel. Today even Titanium is being used in some MIM fabrications. We would mix the metal powder and a thermoplastic binder (generally a Wax) forming slurry of sorts when heated and inject this mix into a precision mold and finally form what is known as a “Green Part". This part is roughly 30% larger than the finished part it will become at the end of the process. Interestingly enough the Green Part at this stage can be snapped in two with simple finger pressure. The Green Parts are then placed in a Sintering furnace filled with dry Hydrogen gas and the temperature is brought almost to the melting point of the metal being used. Over time the "Wax" in the Green Part is evaporated, the metal fuses and the part shrinks 30% to it's final correct dimensions. At this stage of the process the MIM part has developed 98 to 99%of the density of the older wrought materials and a metallurgy that is almost identical. Dimensionally it is finished and no machining is required. However the job is not yet done and the MIM parts are brought to our Heat Treat facility for hardening and in the case of Hammers and Triggers, Case Hardening. Depending on the particular metal alloy that was used at the start of the process we apply a heat treat process that is the same as would be used if the material were the older wrought style. Final hardness, Case thickness and core hardness are for the most part identical to parts manufactured the older way.
Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn’t happen resulting in a rejected gun and rework or in the worst case an unhappy customer. With MIM parts you must still machine to very high tolerances and your cutters have to be perfect and your machinist has to be highly qualified but all of this only has to come together one time. That time is when the injection mold is made. Typically a mold for this process costs S&W between 30,000 and 50,000 dollars. Once it is perfect every part it makes mirrors this perfection and you have in my view a wonderful manufacturing process.
Hopefully this description will help us all better understand the MIM process. Please forgive the spelling errors and misplaced punctuation. I have no spell checker on this and the phone continues to ring!
Have a Great Weekend,
Herb"
Jim Watson
New member
Do GE, P&W and RR get their parts from indo-MIM as I have seen advertise in gunzines?
Where does S&W get their MIM?
Where does S&W get their MIM?