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A PLC will feed parts into a pickup fixture when it is empty. The PLC will tell the robot when to pick up a part and load it using Devicenet.
Figure 28.16 Box Loading System
Solution: The following ladder logic will implement part of the control system for the system in Figure 28.16.
plc network -28.23
Figure 28.17 A Box Loading System
28.6 SUMMARY
* Networks come in a variety of topologies, but buses are most common on factory floors.
* The OSI model can help when describing network related hardware and software.
* Networks can be connected with a variety of routers, bridges, gateways, etc.
* Devicenet is designed for interfacing to a few inputs and outputs.
* Controlnet is designed for interfacing between controllers.
* Controlnet and devicenet are based on CANbus.
* Ethernet is common, and can be used for high speed communication.
* Profibus is another control network.
28.7 PRACTICE PROBLEMS
1. Explain why networks are important in manufacturing controls.
2. We will use a PLC to control a cereal box filling machine. For single runs the quantities of cereal types are controlled using timers. There are 6 different timers that control flow, and these result in different ratios of product. The values for the timer presets will be downloaded from another PLC using the DH+ network. Write the ladder logic for the PLC.
3.
a) We are developing ladder logic for an oven to be used in a baking facility. BACK | NEXT Easy Access To All Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106
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