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Line Boring Metal 3D Print
You'll likely hear the wrist pin play immediately 😄 Usually the OP disappears taking the solution with them. Lots of good suggestions by members here and I wanted to at least show a way it could be approached. If she lasts at WOT for a few seconds, I'll count it as a success lol -
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Line Boring Metal 3D Print
That's quite an imagination you got there. Who rides a 1975 XR75 100 miles with a 3D printed piston that may not last 100 ft? Why is this your comment on a machining forum?... -
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Line Boring Metal 3D Print
OD on the piston skirts is about 47.978 mm for a 48 mm cylinder bore. The wrist pin bores are out of line about .0011" end to end, but that should work in the short term. -
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Line Boring Metal 3D Print
Finally got around to machining this piston...decided to start with the oblong wrist pin bores. With a non-circular bore to start with, I turned down the fixture and then filed down 2 sides flat so the piston would just fit on. Used a 3D printed spacer to tighten the M10 nut against since... -
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Line Boring Metal 3D Print
Just took some test cuts on another DMLS print from the same alloy (AlSi10Mg). Left a really gritty finish - best results were from high spindle speed and slowly feeding by hand. The one face cleaned up much better than the rest? Tried carbide inserts with a radius and HSS tools and they both... -
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Line Boring Metal 3D Print
That's the one area where I would consider sanding down to match the OEM Honda piston ellipse shape. But it's very miniscule on the factory piston - 47.95 mm Dia at the thrust faces and 47.73 mm Dia 90 degrees to that, but at the same distance from the skirt bottom. There's also the fact that... -
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Line Boring Metal 3D Print
Considering this project now that I've printed it, I could've probably designed the part WITH an elliptical OD and tapered skirt - then just Skim the OD where it would only clean up the thrust surfaces. And leave the wrist pin holes SOLID, but with a center punch on the outside edge to help... -
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Line Boring Metal 3D Print
I considered adding a shaft to the top of the piston crown - like I mentioned before, that wouldn't required most of the piston to be printed on "support" material. This is the breakaway material that supports any over hangs. You can see the support material below on the Porsche/Mahle pistons... -
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Line Boring Metal 3D Print
Only problem with that is the pockets for the valves would now be filled up. Not something I could easily re-cut, but there is some porosity there which your idea might help! The piston crown is the beginning of the print and built vertically from there: Exactly. I planned to cut the bottom... -
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Line Boring Metal 3D Print
Then you have guys like this who have never wound back their torque wrenches (or used them 😆) but make pistons that must last long enough to keep customers...I respect them for making due with the bare minimum: Not to make this a YouTube thread, but in my "research" I've come across a lot of... -
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Line Boring Metal 3D Print
@implmex yeah I agree, he's a bit reckless with precision equipment (and the aluminum piston), but he was a pretty old school guy. I'm a lot less nonchalant when it comes to my stuff... -
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Line Boring Metal 3D Print
Thanks for the tip! I could just machine the stock until it just barely fits through both bores The pin bore is offset 1mm towards the thrust side. Not sure whether they have that pin bore shape, I imagine it must be a modern piston evolution. These are 1970's Honda XR75 pistons, but it's a... -
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Line Boring Metal 3D Print
Sent. Prepare to be blown away how cheap they are. I could see if US DMLS suppliers were double the price, but 10 times? I don't see how they can justify that. -
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Line Boring Metal 3D Print
I'm sure there were a few round pistons early-on that worked just fine. Might've slapped like crazy and didn't go for 200k mi, but didn't need diamond tooling and special cam profile cutting machinery. I actually wonder if the original Benz in 1886 had straight, round pistons? -
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Line Boring Metal 3D Print
Well said! :cheers: I worked with a guy at my last job; absolute mechanical savage - he had no engineering degree but he could design like nobodies business. He made a cycloidal gearbox, hobbed the worm gears and everything in his garage! It was about 90% correct but as a prototype it showed... -
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Line Boring Metal 3D Print
I can probably guess what "D" stands for in @DDoug :LOL: So only machinists can turn aluminum? 🤡 I might as well start taking bets on this now. If it's gummy, I'll heat treat it -
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Line Boring Metal 3D Print
Whether a generative designed, 3D printed piston will work right off the bat. Yes, I mentioned this in post #20 to avoid comments on it. Like the OEM piston, the ring groove area will be ~0.5mm smaller than the OD and ROUND. Seeing as the skirt is much shorter and narrower than stock, I will... -
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Line Boring Metal 3D Print
Absolutely not. Because I'll have saved hundreds on a prototype. If it needs "certs" or is a production part, maybe it needs to be made outside of Asia. -
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Line Boring Metal 3D Print
It boggles my mind the price they can make things and still turn a profit. I read this book while trying to figure it out. The part in my hand cost $45 to make from a type of maraging tool steel and is shot peened. It's the head for a breaker bar and I have taken it up to 276 ft-lbs without... -
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Line Boring Metal 3D Print
@implmex thanks for the detailed look at this project, regardless of how ridiculous it seems. The important thing is that the wrist pin bore is perpendicular to the OD of the piston. Otherwise, you'll destroy the bearing in the connecting rod in no time, and unnecessarily side load the piston...