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.