PC-based controls and I/O modules give yarn true colors

In the controls field, accuracy is often a result of how fast you can secure data and make decisions. Package dye equipment, for example, requires especially precise control of numerous I/O variables to correctly dye large yarn spools in pressure vessels, or kiers, which range in size from those able to dye one 10-lb package to those that can handle 1,500 lb.

To accelerate existing dye processes, Cubex Inc. (Charlotte, N.C.) recently installed PC-based, open architecture control systems in package dye machines at two plants. The controls include a Microsoft Windows-based host system for batch procedure editing, machine scheduling, data collection, and batch reporting.

Cubex’s control system uses PC-based, flowchart-type control software on a 32-Mbyte Intel Pentium processor. This system is faster than the PLC-based systems that control many traditional dye applications, according to Richard Manley, Cubex’s vice president. Cubex’s system communicates via standard Ethernet between the Host PC and the machines’ computers. Cubex’s systems in the two dye processing plants use over 200 I/O modules. Fourteen of the modules have been operating for more than a year without failure.

“The open architecture allows us to use hardware from almost any manufacturer with minimum redesign. Most importantly, the open architecture gives the user flexibility when adding new modules or altering designs,” says Mr. Manley.

Once the spool cylinders are loaded into the pressure vessels, the dye solution is heated and pumped under pressure through the yarn packages. Flow rate or pump differential pressure, temperature, Kier pressure, salinity, and pH are monitored, alarmed, interlocked or otherwise managed. This data can then be used to control chemical additions, and drain and rinse cycles.

Batch sequence, number of steps, temperatures, dye-mix formulation, cycle times, and other specifications vary depending on types of yarn and dye required. These variables are downloaded to the control system from the host system to start a batch run on a particular machine.

I/O modules aid control

While creating the dye machine control system, Cubex’s designers found they needed a remote I/O subsystem to provide an open architecture interface to a PC-based control system. Mr. Manley says Cubex selected Entrelec’s (Irving, Tex.) remote I/O module with Profibus DP communications protocol because it allows communications to continue downstream of a failed module.

Entrelec’s rail-mounted, remote I/O devices operate at 24 V dc. Its digital I/O modules offer eight points each and are 1 in. (22.5 mm on the rail), 3 in. high, and 4 in. deep. Its analog and communication modules have four points each and are 2 in. wide (45 mm on the rail), 3 in. high, and 4 in. deep.

Typical dye machine have eight digital inputs, 16-32 digital outputs, four to eight analog inputs, and four analog outputs. Each machine control panel has an Entrelec Profibus DP communications module interfaced to the PC controlling the machine. A Profibus data highway connects the machines’ communications modules to the system-wide PC via a parallel twisted triaxial cable.

“This architecture allows additional remote I/O subsystems to be added at any time and tapped into the data highway cable at any point with little or no downtime,” adds Mr. Manley.

For more information visit www.controleng.com/info .

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