¿Programas por secuencia? Así es como un FB por tipo de equipo te salva la ampliación — Transcript

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1. 0:00The first conveyor worked and everyone
2. 0:02was happy. The problem appeared when
3. 0:04they asked for another one just like it
4. 0:05and the logic was scattered everywhere.
5. 0:08There is a structural error that I see
6. 0:10repeated in Siemens PLC programs that
7. 0:12appear to work perfectly. Programming
8. 0:15according to the process sequence
9. 0:16instead of by equipment type. Let me
10. 0:19explain. When someone new starts
11. 0:20programming a line, they tend to think
12. 0:22in terms of verbs.
13. 0:23Start conveyor one, wait for sensor,
14. 0:25start conveyor two, activate piston,
15. 0:27retract piston, start conveyor three,
16. 0:29and they build a giant FC or several
17. 0:32chained FCs that execute that script
18. 0:34from top to bottom. It works during
19. 0:36commissioning. It even looks nice
20. 0:38because the technician sees the program
21. 0:40and understands the factory by reading
22. 0:42from top to bottom. The problem appears
23. 0:446 months later.
24. 0:45When the client asks for a second
25. 0:47conveyor just like the first one or when
26. 0:49maintenance calls you because motor 3
27. 0:51has stalled and they only want to know
28. 0:53about that motor, start, stop,
29. 0:54availability, and running hours.
30. 0:57And that is where the sequence-based
31. 0:59structure falls apart, because all the
32. 1:01motor logic is scattered in four
33. 1:03different places in the program, mixed
34. 1:05in with the previous and next conveyors
35. 1:07. I always structure by equipment type,
36. 1:09not by sequence. One FB for a motor, one
37. 1:12for a valve, one for a compressor. Each
38. 1:14one is applied with its own instance DB
39. 1:16. The sequence, the order in which they
40. 1:19activate one another, I solve separately
41. 1:21in a coordination block that simply
42. 1:23calls those FBs and manages the
43. 1:24transition conditions for each one.
44. 1:27This is what I gain with this change:
45. 1:29when the client asks for the second
46. 1:30conveyor, I don't rewrite anything, I
47. 1:32just call another instance of the same
48. 1:34motor FB with its own DB; when
49. 1:35maintenance asks about motor 3, I open a
50. 1:37single DB and everything related to it
51. 1:39is there, without having to trace three
52. 1:41different segments of the program; and a
53. 1:43programming error in the motor logic,
54. 1:44for example, a poorly calculated
55. 1:46anti-short-cycling, I correct once in
56. 1:48the FB and it is corrected in all the
57. 1:49motors of the installation at once.
58. 1:52With the sequence structure, you would
59. 1:54have that same error copied and pasted
60. 1:56as many times as you have motors.
61. 1:58And correcting it means going equipment
62. 2:00by equipment praying not to miss any.
63. 2:03With three or four pieces of equipment
64. 2:05of the same type, you can already tell
65. 2:06who programmed thinking about that day's
66. 2:08process and who programmed thinking that
67. 2:09someone will have to touch this in 2
68. 2:11years.
69. 2:12If you want to learn how to program
70. 2:14Siemens PLCs and HMIs, click the link in
71. 2:16my profile. Yeah.