Parametric Print-In-Place Bearing | PAX Designs

PAX Precision Print-In-Place Bearing — a premium parametric, print-in-place bearing/cage designed in OpenSCAD. The full model is single-part and prints assembled: inner race, outer race, ball pockets (rolling elements) and guidance features are all modelled so the balls are captured but free to rotate once printed.

Key model parameters

• Total height
• Inner radius
• Outer radius
• Ring fillet (edge_radius)
• Ball radius
• Ball corner fillet (ball_edge_radius)
• Radial clearance between ball and races (space_ball_rings)
• Minimum spacing between adjacent balls
• Vertical ball clearance (ball_height_space)
• Guides
• Calculated race radius for ball centers (ball_pos_radius)
• Calculated number of balls (num_balls)
• Ball angular step (ball_angle_step)

How it is print-in-place (what "print-in-place" means here)

• The model generates the balls and the surrounding race/cage as one continuous mesh so no manual assembly is required.
• The design provides radial and tangential clearances (space_ball_rings = 0.2 mm; min spacing between balls = 0.25 mm) so each printed ball is separated from the race and its neighbors by a small gap calculated to allow motion after printing.
• Guidance cutouts and guide_height lock the ball seating position axially while leaving enough contact area to function as a rolling element.
• The OpenSCAD uses rotate_extrude and repeated transforms to place and shape each ball pocket and ball cross-section so every ball is formed captive within its pocket during the print.

Functional behavior and intended use

• Designed for low-load, low-speed use or prototyping: suitable for robotics linkages, light hobby mechanisms, prototyping shafts, jigs, and demonstrators.
• The printed balls will rotate inside their pockets but will not match the low friction or wear resistance of precision steel bearings. Consider metal balls in the pockets for improved performance.
• The model includes small fillets and chamfer-like geometry to reduce stress concentrations and ease print removal of tiny artifacts.

Assembly, modification and customization

• No assembly required when kept as a print-in-place part. To use metal balls instead of printed balls: select standard ball diameter matching ball_radius = 2.0 mm or edit ball_radius in the OpenSCAD and re-render.
• To change shaft/bore size: edit inner_radius (half the desired bore diameter) and re-render.
• To adjust performance tradeoffs:
  • Increase space_ball_rings for freer motion and easier print release.
  • Decrease clearances for tighter fit (beware of fusion during print).
  • Increase height or outer_radius to house larger balls or more robust races.
  • Change guide_size_ratio / ball_guide_height to alter axial capture and steering of balls.
• The model already computes ball count automatically; changing radii or ball radius will re-evaluate num_balls.

Limitations and warnings

• This design is not a drop-in replacement for precision, lubricated steel bearings under high radial/axial loads or high RPMs.
• Print-in-place clearances can fuse on poorly tuned printers; verify a test print and adjust space_ball_rings upward if pockets fuse.
• Ball wear and race wear will be faster for printed balls or soft materials; for durability, use hardened balls and consider printed races as sacrificial or prototype parts.

Files, metadata and license

• Source: OpenSCAD parametric model (provided).
• Render modes: print_view = 1 produces the full print model; print_view = 0 produces a cut/preview view.
• Author and date: PAX Designs, 10/18/2025.
• License: Protected under the Standard Digital File License (included in repository).