3d printed, blended Transfer port?

[aPpYe]

I recently got into 3d printing and some amateur CAD design.  I came across a rather good idea of remelting 3d prints while they are suspended in tightly packed, extremely fine powdered salt.  The idea is to strengthen the part by melting the layers together and producing what is essentially an injection molded part with all the strength that goes with it. 

I decided to give this a try so I put a box of salt through a blender, pulverizing it nice and fine.  After letting everything cool and digging the parts out of the salt powder, I rinsed them off in water.  The result was indeed a far stronger part that was equally strong in all directions regardless of the orientation it was in while it was being printed.  It had a nice matte finish and there was virtually zero dimensional change in any direction.

I then got the idea of printing a blended transfer port this way.  No dremeling required.  What's more, I was able to design one with exactly the dimensions I want, with the round valve port blending perfectly to the oblong barrel port.  I was even able to curve the path for the air to follow while it squeezes itself up into the barrel.

Thoughts?  I am thinking on what might be a good material to try this out with.  Hopefully you can see the screenshot below.  If not, I attached the file as well.

[Back_Roads]

 Not sure what plastic, but wonder if baking soda would also work and save all the blending as it is finer particles than salt already.

[aluminumfetish]

Popcorn salt ? If it works with PETG.. that would be cool. I have a lot if small PETG prints to test.

[nervoustrigger]

Hi Patrick, I like the idea of producing a blended transfer port in this manner.  I wouldn’t be inclined to put the time into it for a one-off but I can definitely see the appeal for consumable transfer ports where you want confident repeatability through multiple breakdowns/rebuilds over time or while tuning.  In terms of robustness, I wouldn’t have any qualms about using a 3D printed version anywhere it is constrained by surrounding metal parts, with or without the remelting process.  In other words, as long as a Rapid Unplanned Disassembly (RUD) doesn’t send plastic bits into my face, I’m for it.

[aPpYe]

Not sure what plastic, but wonder if baking soda would also work and save all the blending as it is finer particles than salt already.

I believe baking soda is not a viable option.  Something about releasing CO2 when heated that will cause it to ruin the part.

[aPpYe]

Hi Patrick, I like the idea of producing a blended transfer port in this manner.  I wouldn’t be inclined to put the time into it for a one-off but I can definitely see the appeal for consumable transfer ports where you want confident repeatability through multiple breakdowns/rebuilds over time or while tuning.  In terms of robustness, I wouldn’t have any qualms about using a 3D printed version anywhere it is constrained by surrounding metal parts, with or without the remelting process.  In other words, as long as a Rapid Unplanned Disassembly (RUD) doesn’t send plastic bits into my face, I’m for it.

Well, I don't know that I would trust the air pressure not to leak if I am using a non remelted one.  These prints can get pretty weak between layers, and the remelting goes a long way towards fixing that.  Of course, the part would likely be squished a bit between the barrel and the valve.

[ray1377]

Rapid Unplanned Disassembly (RUD).

Jason
You are the coolest of the cool

Ray

[aPpYe]

Lol.  I just caught that! 

Jason, didn't you provide a spreadsheet as some point years back that calculates the size I want my oblong barrel port to be, etc?

[nervoustrigger]

A copy of the porting spreadsheet is linked in this thread
https://www.gatewaytoairguns.org/GTA/index.php/topic,205566.msg156409489.html#msg156409489

[subscriber]

Patrick,

Your TP design is brilliant! 

My only concern with your extra sintering operation is that some salt my attach or imbed in the outer layer of the TP air passage.  Then be blown down the barrel later.

More specifically, my concern is the potential for rust.  That may be mitigated after completion by boiling the part in water, to dissolve and remove any superficial salt that might come loose later.

I understand why baking soda might be a bad idea; with sugar and other heat degrading crystals along with it. 

If my concerns are valid, and washing does not fully remove salt from the inside surface of the TP, then perhaps using some other powder for support might be considered.  Something like copper powder, as it would not rust or abrade the barrel if any residue were to be blow down the bore:
www.amazon.com/Copper-Powder-Metal-Inlay-Ounces/dp/B01G7XFR8S/

If the copper powder seems expensive for a one-off, I think your TP has enough potential that you could sell a bunch of them.  If I were in the market, copper powder sintering support would close the deal, while salt would make me pause for thought.

[subscriber]

One more thought; your port has the air travel backwards, before it sweeps forwards.  Could you not make the port travel down and forward, without also sweeping backwards? 

I have added red lines to your image to get my point across; although I think what I am showing is more exaggerated than necessary. 

Don't make the port any longer than what you have.  Just use that sweep to gain the most favorable angle of incidence with the barrel bore in the available space.  Sweeping backwards before forwards adds port length, without gaining the best entry angle possible for that port length and volume.

Or, you could make the port end at the same angle to the barrel, with the air travelling a shorter distance.

I am nit-picking here, as your port should flow smoothly and more predictably then one made by Dremel.

Perhaps your TP would be best suited to existing barrel posts that are placed opposite the receiver port, than when you start with an un-ported barrel; where you could place the barrel port slightly further forwards.  On the other hand, your TP implies opening the barrel port, and in doing so, that could be biased forwards, rather than keeping the center of the long slot opposite the valve port.

Food for thought, perhaps.

[rkr]

I like your port design and I would like to see a performance comparison against a straight port. It looks good but does the curved port provide any real life advantage?

[rsterne]

When I do an oblong barrel port, I blend from a circle to the longer, narrower port within the thickness of the barrel.... The transfer port then remains circular throughout....

I have the rear of the port vertical, the front angled forward (straight, not curved), and the sides taper inward from the width of the transfer port to the (narrower) barrel port.... Here is a dimensioned drawing of a .25 cal with full area barrel port that is only 80% of the calibre wide....



Basically to make this port, I machined a spot face on the bottom of the barrel that was 0.375" diameter, the same as the transfer port OD.... The ID of the transfer port was 0.250", the bore diameter.... I then plunged a 3/16" mill straight down into the barrel, flush with the back of the ID of the transfer port.... I then angled the miss 45 degrees forward, and plunged down so that the front of the barrel port was 1/4" long at the spot face where the transfer port sealed, but 0.313" (5/16" long) at the boreline.... I then ran a 60 degree countersink straight down, centered in line with the center of the transfer port, tapering the sides of the barrel port from 1/4" wide at the spot face to 3/16" wide at the bore.... Any remaining irregularities were smoothed with a Dremel bit....

The result is a barrel port that starts at 1/4" ID at the transfer port, narrows up to 3/16" wide at the bore line, while increasing in length from 1/4" to 5/16" at the boreline.... maintaining the same area, and angling the flow forward towards the bore.... If you have more thickness (ie using the transfer port depth), you could add a bit of shaping in the form of a convex front curve, but to maintain the same area halfway down, you would have to also curve the sides concave, which might lose you the flow gain you hoped to achieve by curving the front face.... All I know is that what I have been doing works for me!....

Bob