03/13/2023 - Added 1/32" bevel to flat bottom perimeter of rail to account for elephant's foot. Be sure to rotate before slicing so flat bottom is down. Slice with 4 wall passes, 50% infill, and gyroid infill pattern to improve shear strength in longitudinal direction as weak areas are around screw holes. This becomes critical when extending rail from supporting base as in the case of the Mossberg500 tube rail adapter, below, and in pictures.

Print yourself flat bottom Picatinny rail sections. Be sure to rotate the STL file before slicing so slots/rails are UP. Rail has middle slot so that flashlight holders align in the middle of the rail. The attached Fusion 360 file and STL file are for a 2" section but the Fusion 360 design can be extended to any length. Added STL and gcode for a 1.5" section and 3" section as well. Screw attachment points are 1 inch (25.4 mm) apart and are configured for #8 or 4 mm (M4) button head hex screws. NOTE that these designs support my Mossberg500 tube rail adapter, so hole placement may need to be altered for your design.

Mossberg500 tube rail adapter:
https://www.thingiverse.com/thing:5883726

Design was created in accordance with the 1913 Picatinny rail technical specification MIL-STD-1913 (attached) and is also compatible with NATO STANAG 4694. A well written concise explanation of the technical spec can be found at Thomas Mechanical Design here:

https://www.thomasmechanicaldesign.com/the-mitch-blog/picatinny-and-nato-rails-gdt

NOTE that the Fusion 360 files have been adjusted to account for shrinkage and expansion using IEMAI carbon fiber PETG extruded at 225/80 degrees from a 0.6 mm nozzle with 30% infill. Blanket shrinkage/expansion settings were not made in the CURA slicer program due to the small tolerances involved with the Picatinny rail. Hence you might need to use trial and error if you deviate from the material specifications that I used to print prototypes and finished products. Note that carbon fiber PETG can be tricky to use, especially when printing Picatinny rails, and you might need some post-procession trimming to eliminate even minor surface imperfections.

NOTE also that the screw placement on the 1.5" and 2" rail section preclude the use of the two side slots. This is because my other designs that use these rails use the center slot and a 1" center line to center line screw placement. You can alter the Fusion 360 file to not only add slots but to optimize 4mm screw placement for your own design.

Creality

Ender-3 v2

No

No

High

30 %

Temperature 225/80 with Magigoo on Creality Ender 3 V2 Neo removable bed. When slicing, try to avoid seam placement on rail tips! Using RANDOM seam placement seems to work best. Attached gcode file has been sliced accordingly, but to be sure you might want to start from the STL file and slice the way you prefer.