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All Springer/NP/PCP Air Gun Discussion General > 3D printing and files

Slim LDC

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subscriber:
Bruce,

If you are talking about a self supporting structure, then I taper the outer wall thickness from "heavy" at the rear, to "thin" at the front.  This makes sense to resist bending, and maintains sufficient burst resistance.

How heavy depends on the OD and length, and my estimate of muzzle pressure, based on FPE.  For a snug fitting insert, supported by a stronger outer tube, the outer wall of the insert can be made much thinner.

For my design you mentioned in the OP, I made the outer wall taper from 4 to 3 mm.  Could probably taper it down to 2 mm without any problems, assuming properly printed PETG.  The lighter the front, the less hard the rear has to work to prevent droop.

If you are using PLA, chances are that the material will creep over time, because that is the nature of PLA.

For the bore, I like a radial gap of 1 mm over pellet diameter.  Then increase that going towards the front by an additional 0.1 mm every 25 mm.  In some cases I might make it tighter, or looser, depending on confidence in concentricity and angularity relative to the barrel bore.

dan_house:

--- Quote from: TorqueMaster on June 05, 2023, 05:34:59 PM ---
Key constraints as in key dimensions, or something else?  Are you using Cura?  Either way I can offer specific or generic suggestions if you're interested.  Sometimes it is try, fail, modify, repeat...sometimes the first educated guess actually works!


--- End quote ---

Im interested..... Ive been using print/test/redraw for a long time, and if some or all of that could done in my slicer (Cura) then even better

subscriber:

--- Quote from: dan_house on June 05, 2023, 05:59:50 PM ---big prints.... can be broken down into smaller "bites" that dont take as long

depending on where the bits in question are, you can do some of that in your slicer

--- End quote ---

You can design a deliberate split into the part.  I designed an insert 13" long for Don (NVreloader).  I designed it as three separate parts that butt up against each other inside his super long shroud.  If your printed part is not an insert, but has to rely on its own stiffness, then how to join them takes a bit more consideration.

subscriber:
Dan,

Printing short section of the design containing the critical dimension to measure helps a lot.  Bob is an expert at that. 

I have created short generic test prints that might be useful for general calibration:  https://www.gatewaytoairguns.org/GTA/index.php?topic=204046.0

dan_house:
"then how to join them takes a bit more consideration."

ok, wasnt clear....

I should have said "for test printing purposes"....

I have a design for a "chassis system" for the Diana Chaser. I cut the part of the chassis that had the trigger inletting away from the rest (in my cad program), printed and test fit that piece to the trigger block. Changed the drawing, and repeated that. Then repeated that process until the backbone of the chassis fit correctly.  While that did take a couple of evenings, the end result was a part that fit the chaser correctly the first time the whole part was printed.

Once I had that part functioning correctly the rest of the design was a piece of cake

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