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Old 11-08-2013, 01:39 AM
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What are PMR's, or powdered metal in general? Unique answers here.

So to start off, I am a Quality Assurance tech for a company that deals with powdered metal, something I didn't even know existed when I started there. It's a very interesting process. We make gear carriers for GM, Ford, Toyota, washing machine parts, used to make main bearing caps ( big ones probably big diesel), and we make a carrier for the new ZF 8speed auto that Chrysler is getting.

These may be transmission parts ( mostly) but the powdered metal process for the rods in the late 7.3's and newer Ford motors, will be about the same just different mixes. I just figured maybe taking the time to show what the PMR's actually are, and why companies are using powdered metal might answer some questions.

So it starts off in big hoppers, looking like sand in various colours of black... I forgot to get a picture, and get's mixed according to whatever recipe of the batch is, different parts are mixed different, creating different alloy's.

First picture I started is the press. The powder is blown in and compacted into the shape. This is where a big advantage is over casting. Some parts ( like the new ZF) are compacted to tolerances as low as 0.005mm consistently.


This part goes in the GM 6L80, the output carrier. It's the part I chose to follow the whole process as I know it the best.





That's 2 of the 3 pieces required to make this, they are assembled and weld pellets put in specific locations. This part completed has 9.

After assembly they are ready to go into the belt furnace.


Also at this point, you can almost crush them in your hands, or easy snap the pieces, even picking up the assembled pieces wrong has caused the company huge problems.



After going through the furnace, which heats the parts to red hot, the first thing that happens is they are ultra sounded. With that we can check for internal cracks and density issues.



Completed part, starting the machining part of its process.



The machining is pretty basic and that's one huge advantage of this type of process, because of tight tolerances not possible with casting only bearing surfaces and pinion surfaces get machined, some parts get broached.

Part after it's second machining step, about to go to it's third. Being measured on one of our floor model CMM's.. These things stay accurate to with the ambient temperature to 45 degrees C... anybody that does machine work knows how significant that is.


This is the part I really wanted to show. The vast majority of our scrap is found with visual inspection, in some cases the parts are checked 4 times. Cracking and density issues are the biggest thing, and they would be a big reason why we see failures in connecting rods.

Common crack on these parts.


Similar part, the whole hub snapped off, ultrasound checks for that crack now but we didn't have it when this part was being made. That came OUT of a transmission... 6l45 (? I think) before my time there, apparently we got in big trouble over that.



Just another type of crack we see, if you tap that part on a concrete floor itll just snap right off in your hands.



My job is just to run these babies.... this thing cost more than most peoples houses.



The reason powdered metal is taking over. Start to finish in one shift 21 people make 1600pieces in 8 hours. To cast a part like this, then machine it, then finish it, at that volume would require 10x the equipment and manpower.

Powdered metal is also much much stronger than cast but it's biggest problem is the variance from one part to the next. Obviously we have it minimized but a little blip in the press can make the difference between one part failing at 30 000psi in the break test, and the very next one failing at 10. The best one though wouldn't compare to the same part forged though. Powdered metal is also very brittle, some parts have a copper infiltrate melted into them to soften them up to some degree. But a blow with a small brass hammer will break a 1/4" thick part fairly easily.


Just though maybe some people would like to know more about what the PMR's really are, and why the guys like me with early 7.3's are happy to have forged.

Last edited by schlutzer; 11-08-2013 at 04:34 AM.
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Old 11-08-2013, 05:53 AM
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Very cool! Thanks for sharing!
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Old 11-10-2013, 04:17 AM
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Gee tough crowd.... or ****ty section. I thought this would be popular maybe I should get it moved to the 7.3 forum
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Old 11-10-2013, 04:29 AM
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nice info period. No matter what section. Thanks for sharing!

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Old 11-10-2013, 04:31 AM
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I thought it was pretty cool. Thanks for sharing
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Old 11-10-2013, 05:13 AM
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Cool write up. Thanks
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Old 11-10-2013, 03:14 PM
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Thanks guys. Even my very own sticky! Lol

The PMR's in the 7.3 have gotten a really bad rap and it's only somewhat deserved. I bet a lot of the failures that are seen are due to density/handling issues. Most of the pictures of failed 7.3 rods I've seen fail near the wrist pin (which in fairness is a major stress point) or they seem to like to fail in the big meaty section which to me is somewhat odd. But both of those points would be suseptable to internal damage if the parts are laid on their side before they are put through a furnace

About 75% of the cracks/density issues we find are due to handling when parts are compacted but not yet put through the furnace. The rest are press/die issues, sometimes as simple as a pressure change.
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Old 12-05-2013, 04:41 AM
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Being an engineer for a diesel engine company i can tell you that PM is used in alot more stuff then you think. Also with some of you failure rates on those carriers can be solved by looking at those pictures you have showed us. PM is a very porious material aka like a sponge. if the enviroment around it is not controlled it will affect the outcome of the part itself. Most Rods are made in controlled enviroments and are acctually very strong in comparison to the forged ones. For a stock engine it makes sense for pm because of the cost but for the consumer aka "billy bob" that wants to add a tuner and pull with it its a deal breaker. But for the big rig industry were truck drivers just drive their trucks then they are fine.
Moreover, pm is very sensitive to the way it is heat treated. If you have cold zones in your furnace or oven that could be were your bad parts are consistantly comming form. Also it could be the way you are handling the parts before they are going into the ovens.
Powders metal has some very fine lines in the manufacturing world. IF you want to talk more technical on it then you can pm me and we can talk. But just from the pictures your should me they have some improvements to be made if your having that big of a fall out.
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Old 12-06-2013, 03:39 AM
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Quote:
Originally Posted by CNYWhiteDually View Post
Being an engineer for a diesel engine company i can tell you that PM is used in alot more stuff then you think. Also with some of you failure rates on those carriers can be solved by looking at those pictures you have showed us. PM is a very porious material aka like a sponge. if the enviroment around it is not controlled it will affect the outcome of the part itself. Most Rods are made in controlled enviroments and are acctually very strong in comparison to the forged ones. For a stock engine it makes sense for pm because of the cost but for the consumer aka "billy bob" that wants to add a tuner and pull with it its a deal breaker. But for the big rig industry were truck drivers just drive their trucks then they are fine.
Moreover, pm is very sensitive to the way it is heat treated. If you have cold zones in your furnace or oven that could be were your bad parts are consistantly comming form. Also it could be the way you are handling the parts before they are going into the ovens.
Powders metal has some very fine lines in the manufacturing world. IF you want to talk more technical on it then you can pm me and we can talk. But just from the pictures your should me they have some improvements to be made if your having that big of a fall out.
The majority of our scrap is due to press issues or handling...

We actually just updated our ultrasound method to check for other internal issues as we just had a brand new one that was caused by the press... completely undetectable by eye or any external measurement.... till the piece comes apart in the 40 ton broach. Something about some new core rods not my department.

Or the human factor, a Lazy operator doesn't watch weights and we get cracks, or doesn't check leg lengths and then windows are too small.

The kicker is with a part like what is shown, we've had 1 operator cause $60 000 in scrap in one press shift, nobody knows how it got missed that he wasn't doing his checks but his 1 part got assembled with 3 others, and sintered...x 3000. He runs one our the deburring tubs now.... lol

The furnace seems to be the one area we actually have down pat... probably because they almost never even get cooled down, they just go 7 days a week. Unless we have a power flicker or a rare start up our furnace techs have one of the easiest jobs in our plant.

We are just such high volume, on old equipment it's amazing that we do as well as we manage. We got shown what one of our sister companies in Japan looks like... The plant I work at might as well be in the dark ages.

I've always thought powdered metal needs to be run more with the machine shop mentality, but my work has managed to turn it into assembly line work...somehow. Huge profits, but the cost of a simple mistake can be unbelievable.

Being an engineer you likely know ten fold what I do about it, I know what I see, and much more about the machining aspect as that's where my QA responsibilities lie. I just wanted to show what it is because many people don't have a clue what PMR's actually are.
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