When is repairing a printer worth more than building a new one?

What it found

Follow-up to selfrep-wearout. Machines break down at a constant rate and the shop may spend spare-part vitamins to repair one instead of retiring it. A vitamin-balance formula predicts repair gives a bigger fleet exactly when the repair cost share is below the repair success probability; a discrete-event simulation with assumed inputs puts the crossing at that value, within about 9% of the formula in that sweep, but only when spares are held back from new builds (without a reserve the fleet was 70 against a formula value of 157). Repair also cuts die-out from one seed at short lifetimes (for example 55% against 100% at a mean life of 100 h) but does not remove it. Stylised: assumed inputs, memoryless breakdowns, repair returns the machine to new, no printed spares.

A figure from its own output

Paper, code and results

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

More in Self-replicating manufacturing

• How much does making its own spare parts cut the cost of repairing a printer?How much making its own spare parts cuts a printer shop's repair cost (stylised, assumed inputs): the printer alone makes none of the wear parts, so in-house spares barely move the fleet; the breakdown rate matters more.
• Does a printer shop lose its printed-bushing gain once a printed spare takes print hours?Does charging printed spares their print hours erase the printed-bushing gain (stylised, assumed inputs): the fleet ignores waits up to ~500 h per repair because it is import-limited, and the gain was within noise anyway.
• Is the lone-printer die-out an early birth-death accident?Exact Markov-chain test of why a lone replicating printer dies out (stylised, assumed inputs): about a fifth die before a fleet forms at 500 h mean life; wear-out lives remove it.
• Can a quasi-stationary approximation predict how long a small printer fleet lasts?Quasi-stationary approximation of how long a small replicating-printer fleet lasts (stylised, assumed inputs): within 5% of the exact mean time once a correction for early die-out is applied, poor for the shortest lives.
• Why do two exact extinction chains of the same printer shop disagree?Reconciles the two exact extinction chains of the lone printer shop (stylised, assumed inputs): the fleet-size chain is 1.5 to 7 times longer; adding the kit wait fixes small fleets but over-corrects large ones.
• Which part substitutions cut a printer's vitamins most, within a performance budget?Which assumed part substitutions (printed bushings and nuts, wooden rods) cut the Prusa Mendel's vitamins most under a penalty budget: all seven take closure from 43/22/16% to 60/36/48% (lines/mass/cost); best set depends on the assumed penalties. Stylised.

All 34 Self-replicating manufacturing projects →

Other research topics

Proper scoring & elicitation28Effort & peer prediction9Verification games & slashing19Detection & tolerances14Markets as routers13Prediction-market design9Paying contributors8Decentralised training systems23Digital twins & sim-to-real164LLM chip design loops40Robot manufacturing loops53Ambient AI assistant46Self-replicating manufacturing34Simulation-first design64Engineered clothing45Task-specific AI accelerators40Algorithmic chip-design loops42Open-source purpose-built robots44The software-engineering loop43Adversarial human imitation41Open-source residential construction41Autonomous multi-angle capture34Sensing, imaging and 3D31Energy supply and dense energy storage39Robot societies among people31Agentic co-design of low-cost robots27Laundry-hanging robots25Machine learning on qualitative data23Robots on the building site27Civilizations & group psychology1History & human sciences1

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.