Extrusion machine firm sees advantages of intelligent ac drives
1 min read
Extrusion, winding and coiling equipment manufacturer Meltech Engineering has taken the design of its semi-automatic plastics inline coiling equipment one step further, with the elimination of a separate PLC.
The Blackburn-based firm says its new design also reduces the need for maintenance, and is the result of switching from dc to an intelligent ac drives solution from Control Techniques.
Meltech engineering manager Andrew Procter explains that the Unidrive SP ac drives selected include PLC facilities on board. That cuts out the wiring between the PLC and the drives, cutting both build time and an area of potential weakness, so also enhancing machine reliability, he says.
"We were looking for ways to cut manufacturing costs while maintaining or improving reliability and decided to switch from dc to ac," says Procter. "Whilst the switch to ac has brought a number of benefits, the selection of Unidrive SP drives has brought even more."
In brief detail, the firms' semi-automatic plastic coiler includes two reels mounted on a transfer disc. When the active winder is full, the disc is rotated 180° and the extrusion automatically transferred and attached onto the empty reel to allow continuous uninterrupted operation of the extrusion line.
The winding drives are now both 1.1kW Unidrive SP ac drives in speed control; the transfer disc is controlled by a 1.5kW Unidrive SP in open-loop vector mode; and the traverse is controlled by a 0.37kW Unidrive SP in servo mode twinned with a Control Techniques Unimotor FM servo motor.
All four drives communicate with Control Techniques' high-speed CT-Net network, with an SM-Applications Plus modules in each drive. The entire machine application control program is on just one of these units.
"The feed for the winder drives is by slip rings," explains Procter. "We now only need six slip rings for the three phases on each motor – we needed eight before, which has cut build cost, improved reliability and cut some maintenance."
And he continues: "In our development phase, we considered whether we still needed encoder feedback for accurate speed control – but found that the Unidrive SP's open-loop vector mode performance enabled us to eliminate the encoders, again saving costs and improving reliability."
