--- title: "GPSS manufacturing shop, conditional transfer" subject: "Simulation and Modeling" chapter: 9 key: "semester_8/simulation_and_modeling:gpss-manufacturing-shop" source: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/gpss-manufacturing-shop site: BCT Engineering --- # GPSS manufacturing shop, conditional transfer Simulation and Modeling · Chapter 9: Simulation software - Asked in: 2070 Magh, 5 marks - Video: [GPSS - Transfer Special - BOTH condition](https://www.youtube.com/watch?v=WDdERZYrbg4) — Shiva Gyawali - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/simulation_and_modeling/gpss-manufacturing-shop - Whole chapter: https://www.bctengineer.com/md/semester_8/simulation_and_modeling/chapter-9 ## Question Explain GPSS model for a general scenario of a manufacturing shop with conditional transfer. ## Short answer Parts are transactions. Conditional transfer uses TRANSFER BOTH to first try Lathe1, then Lathe2 if busy; statistical TRANSFER .10 sends 10% to rework after inspection. The model measures machine utilisation and rework count. ## Answer A GPSS model of a manufacturing shop represents parts as transactions that move through machines (facilities or storages). **Conditional transfer** sends a part to different blocks depending on the state of the system or on chance, using the `TRANSFER` block in its modes. #### Modes of TRANSFER - **Unconditional**: `TRANSFER ,PLACE` always goes to PLACE. - **Statistical**: `TRANSFER .25,A,B` sends 25% of the transactions to B and the rest to A (probabilities, for example for rework or inspection rejection). - **BOTH**: `TRANSFER BOTH,A,B` tries A first; if A is blocked (for example the machine is busy), tries B; if both are blocked, the transaction waits. - **ALL/PICK/FN** also exist, for choosing among many destinations. - **TEST/GATE**: `TEST L Q$LINE,5,OTHER` or `GATE NU DRILL,OTHER` sends the transaction elsewhere if a condition is false. #### Scenario Parts arrive at the shop about every 6 min (6 ± 2). They need turning. There are two lathes: Lathe 1 is preferred. If it is busy, the part goes to Lathe 2 (conditional transfer). After turning, 10% of the parts fail inspection and go for rework (statistical transfer), the rest leave. ```text GENERATE 6,2 TRANSFER BOTH,LATH1,LATH2 LATH1 SEIZE L1 ADVANCE 9,2 RELEASE L1 TRANSFER ,INSP LATH2 SEIZE L2 ADVANCE 10,2 RELEASE L2 INSP ADVANCE 2 TRANSFER .10,,REWRK TERMINATE 1 REWRK ADVANCE 5 TERMINATE 1 START 200 ``` #### Flow ```text GENERATE -> TRANSFER BOTH -> L1 --+ | +-> INSPECT -> TRANSFER .10 +-----------> L2 -+ | | TERMINATE REWORK ``` #### Explanation - `TRANSFER BOTH` first tries the label LATH1; if the facility cannot be seized, the transaction goes to LATH2. This gives load balancing without queuing at the first lathe. - Facilities L1 and L2 report utilisation and number of entries. - The statistical transfer models random rejects; `TERMINATE 1` with `START 200` stops after 200 parts. - Output: utilisation of each lathe, number of reworked parts, and total time in the shop (add MARK/TABULATE for this). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does TRANSFER BOTH,LATH1,LATH2 do? A. Sends half to each lathe B. Sends parts to both lathes at once C. Always sends to LATH2 D. Tries LATH1 first; if blocked, tries LATH2; if both are blocked the part waits Answer: D. BOTH mode tries the first destination, then the second, giving load balancing without queuing at lathe 1. (Key point: TRANSFER BOTH) 2. What does TRANSFER .10,,REWRK model? A. 10% of transactions go to REWRK (e.g. failed inspection) and the rest continue B. 90% go to REWRK C. Every tenth part waits D. A 10 time-unit delay Answer: A. Statistical mode sends the given fraction to the B destination; the rest go to A (next block when blank). (Key point: Statistical transfer) 3. How does the shop model end? A. After 200 time units B. When lathes are idle C. When rework is finished D. TERMINATE 1 decrements a counter set by START 200, so it stops after 200 parts Answer: D. Each terminated part reduces the counter; at zero the run stops. (Key point: Run termination) 4. Which block can send a transaction elsewhere if a condition (e.g. facility unavailable) is false? A. GENERATE B. ADVANCE C. GATE or TEST D. RELEASE Answer: C. TEST and GATE route transactions to an alternate label when the condition fails. 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