core-piston
3D-printable piston to hold a sediment core in its barrel
Design by Bobby Schulz; documentation by Andy Wickert; testing and additional documentation by Alex Waheed. Please attribute following CC BY-SA 4.0 (see the license)
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This core piston is made to work with a Pylonex HTH Gravity Corer with a 70mm tube diamter. The honeycomb structure within the 3D print ensures that it floats when invariably dropped into the water.
Materials
- Plastic body
- Two 3D-printable components
- SUGGESTED FILL DENSITY? Get from PRUSA Slic3r with SD card gcode
- Suggested material: White or brightly colored ABS
- Rubber seal
- Rubber sheet: 1/8" thick, durometer 60A. Get a bigger one than this 6"x6" sheet if you want to make more, of course!
- Circular cutter and hole punch, unless you have a laser cutter. @awickert: give McMaster items once proving that they actually work. @bschulz1701: Diameter
- Fasteners
- Screws: 1-1/2" long 1/4"-20 flat head hex drive. You probably don't need the hex drive part ;) but the rest is important, as is the angle made by the bottom flat head (because our countersunk hole fits it).
- Threaded inserts: 1/4"-20 Pull-out-resistant.
Instructions
Here, "bottom" refers to the plastic part that is held by the user, and "top" refers to the plastic part that is in direct contact with the core. These are connected by screws once assembly is complete.
- Generate gCode for your 3D printer. We use Slic3r with a Prusa 3D printer.
- Print using ABS. We suggest a bright color that you can see amidst the muck.
- Cut rubber rounds diameter. We use a laser cutter, but a compass with a pen knife should work well too. @awickert: Add McMaster tools once verified
- Cut holes for the three screws (1/4") using the laser cutter or a punch @awickert: Same as above
- Install threaded inserts into the bottom printed component. @bschulz1701: installation method depends on type -- any info here?
- Place the top component atop the gasket and bottom component, sandwiching the gasket betweent the two plastic parts.
- Insert the three screws, piercing the rubber gasket in the process. @bschulz1701 or do you cut holes in the gasket beforehand? Ensure that these are tight
- Inspect your piston for any obvious problems, and test it in the lab with a core barrel.
Rendered images
Images from bottom to top in the direction from user's hand inserting the piston to top of core barrel.
Bottom
This bottom portion of the piston is counterintuitively called "Plug Top". Maybe we'll change the name.
Bottom plastic component of core piston. The thinner portion to the lower right is held to insert the piston into the core barrel in order to seal it and keep the core from falling out. Not visible is a hole that goes partway through the piston and can be used with a dowel to extrude the core out of the top of the barrel. On the upper left are three holes to hold threaded inserts for screws that connect the top half and bottom halves of the piston. A circular rubber gasket sits between these two halves, held in place by the screws.
Bottom side of top plastic component of core piston. Screws pass between the three holes shown here, through the rubber gasket, and into the bottom plastic component (shown above). The angled edges of this component force the rubber gasket to bend towards the bottom of the piston, pinning it to the mating angled faces on the bottom plastic component. This ensures that the piston may extrude the core, but locks it against sliding downwards.
Top
This top portion of the piston is counterintuitively called "Plug Base". Again, maybe we'll change the name. Or maybe not.
Top side of top plastic component of core piston. This side of the piston directly contacts the bottom of the core. The three countersunk holes hold the screws and ensure that their heads are flush with the remainder of the surface.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.