Can a parallel-jaw arm assemble its own gripper?

What it found

Exhaustive search over assembly orders of a seven-part toy gripper (axis-aligned boxes) by a modelled arm with a parallel-jaw grasp check, three approach-direction models and a swept jaw opening. No complete order exists below a 30 mm opening, the width of the widest part; above it, 384 of 720 orderings are valid when parts may be slid sideways and 120 when strictly top-down. Jaw-pad thickness from 2 to 10 mm changes nothing (a negative result for this geometry). Stylised single design, no reach, force or fasteners; simulation only.

Paper, code and results

• README and method
• White paper
• Experiments and results
• Code
• Tests

More in Robot manufacturing loops

• Can a printed gripper assemble its own next generation?Can a printed gripper assemble its own next generation? With fixed-size jaw pads a gripper builds a copy only at scale ≥ pad thickness in mm (4 mm pads: scale 4); a stroke cap of S mm needs 30·pad ≤ S; seeds of 130 and 140 mm sustain a chain, 60 and 100 mm decay. Largely algebraic given an assumed opening; stylised.
• How long an arm does it take to assemble its own toy gripper?How long an arm does it take to assemble its own toy gripper? A planar two-link arm needs 60–140 mm links as the tray moves 40–400 mm away, and a 90° elbow limit more than doubles it (stylised).
• Does the assembly order change the arm an arm needs to build its own gripper?Does the assembly order change the arm needed to build its own gripper? Across all 384 valid orders the shortest arm is identical in every setting tried (negative result, stylised).
• Can friction hold each printed part of a gripper?Can friction hold each printed part of the toy gripper? The simulated minimum jaw force matches the m·g/(2μ) bound to within 5% over 33 cases and is at most 0.1 N, so the jaw opening, not friction, is the constraint (stylised).
• Does arm torque or jaw friction limit how fast an arm carries a printed part?Does arm torque or jaw friction limit how fast an arm carries a printed part? With 0.12 m links and 5 N m the carries take 0.06–0.10 s and the cover needs 1.25 N per jaw (21× static); grip binds below about 0.5 N (stylised, bound extrapolated beyond 40 m/s²).
• How much carry time does a time-optimal move save over min-jerk, and what does it cost the jaws?How much carry time does a time-optimal move save over min-jerk, and what does it cost the jaws? On the robofab-armaccel arm the six-part total falls by 21 to 29% while the jaw-force bound rises 1.2 to 2.4 times (stylised, assumed parameters).

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.