3D printing shenanigans

mfrench

Senior Member
How smooth, glossy, is the finished texture on the 3D items?

I have an odd whatsit that I need to get made, and, machinists just seem a bit proud of their craft, for what this thing is. This thread got me thinking of alternate directions. thanks.
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The finish on most 3D printed parts is not smooth or glossy. That will require secondary processing. Also, dimensional tolerances will be tough to hold. Is the part in the picture some kind of bushing or spacer? How tight are the required tolerances? What mechanical and chemical stress will it be subjected to? It's a very simple part to turn on a lathe. Should take but a few minutes. Your other option is to machine the part from nylon or delrin. Again, simple job - a few minutes.
 
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mfrench

Senior Member
My toughest thing in creating this myself is centering the stem.
It is a high pressure air valve for an air rifle; 2k.psi. The OE poppet does exactly as you suggest, and it distorts, and loses its seal (suggested as black delrin - white ebing the preferred for the guys doing their own replacements). I've tried all of the things I can think of in alternate fixes, and, have gotten some to hold for short term. But, repeated cycles breaks down my efforts rather quickly. Then its another 100 pumps with my hand pump, and, sweat.
I'm hoping that the company comes to the rescue, but, am also doubtful, as they'd have to admit to a faulty design, and I am just out of warranty (but this is the third valve failure in a year and a half). Their warranty tech is a sharp guy, and has a complete machinist shop available to him. I have a message out to him, but, am still looking for alterrnates.

where are my manners?
thanks for the primer on 3D printing!
 
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A 3D printed part will not be suitable for this application; It's not strong enough. If concentricity is a requirement, and, it needs to be smooth to provide a tight air seal, then, I would use nylon. Start with a small round blank, drill an undersized hole. Press the 1/4" steel stem into the hole. Chuck the thing on a small lathe and turn. Can't be more than 20 minutes of work total.
 

mfrench

Senior Member
Again, thanks.
Concentricity isn't crucial, at least on its sides, and the valves sides. The poppet has to seal at the point where the stem enters the poppet, and it mates to a milled flat face on the valve body. It appears to be a flat to flat interface. But the original oppet had a slight dimpling to it, leaving a ring around the edge.
/highjacking.
I appreciate your helping me. I've never looked into anything 3D. So, this was quite enlightening.
Presently waiting for the JB-Weld to harden, that is an attempt at adhering a nylon washer to the poppet face; attempt number 126 in a series.... (some random number)

followup result...
And, it quickly pressured up to 1200.psi, which is very encouraging. The nylon washer is held in place by a brass collar that is also JB-Weld'd to the stem. To pressure up this quickly was a good sign.
 
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This post is here as it has more to do with 3D printing than multicell horns.

I started out using wood filled PLA hoping that it will provide the look as well as the mechanical strength. Looked good. But, not strong enough. Wood color is the first design. Grey color is with the beefed up flanges.

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The throat piece were printed using ABS filament. Did not come out well. Difficult to control shrinkage and warping.
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Settled on grey PETG. Good and strong. The nuts and bolts were printed from the same material. The 3D printer needs to be able to print at 240C and above to use PETG.

The assembled horn is 20 1/2" wide, 8 1/2" tall and 15 1/2" deep. Each horn section took 25 hours to print. The throat took about 17 hours.
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The first one was louder and sounded better. But, it was directional. This one still has a bit of the "tinny" sound. But, overall was much warmer than just direct from the phone and you can walk around it. I tested it by calling and talked to my son in a different room. The sound was fine (not hifi of course). I was imagining having it sitting in the center of a small conference/kitchen table.
 

Audionut

Next Round Is On Me
The first one was louder and sounded better. But, it was directional. This one still has a bit of the "tinny" sound. But, overall was much warmer than just direct from the phone and you can walk around it. I tested it by calling and talked to my son in a different room. The sound was fine (not hifi of course). I was imagining having it sitting in the center of a small conference/kitchen table.
Maybe it needs mini/medium/large horns on the outlets?
 
Maybe it needs mini/medium/large horns on the outlets?
Spot on. For this go-around, I wanted to test the researchers' claim and the omni-directional property of such a design.

For sound amplification, instead of being flat, the top of the piece will follow a tractrix expansion. (Looking very much like an ash tray!) That's a project for a rainy day.

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MrEd

Senior Nobody
Waiting for the printers to print, the VDCH reflector to dry.... Might as well work on the vector file for the Altec man. It's such a cool graphic. Not sure what to do with him yet. :)

View attachment 19275
Oh yes..
I want one to put on my 421 OB sub when I fianaly paint it.
Your primting is amazing

I actually knew one of the folks that developed the technology.
My son was buds with his kid from around 5 to age 12
We used have bunch of cool printed trinkets he would make for the kids back then
 
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