Cost-efficient production with 18 synchronous NC axes
Third Quarter 2019, This Week's Editor's Pick, Electrical switching & drive systems & components
Swedish equipment manufacturer, Ecmec has developed a high-tech machine for a supplier to the automobile industry that can complete several process steps simultaneously without having to remount the part being worked on. The machining centre is designed for high volume production of up to 200 000 parts per year and performs its functions and processing steps simultaneously within the same cycle. The machine reduces the previous processing and conversion times by more than one third, while requiring less of the valuable shop floor space. Beckhoff supplies TwinCAT 3 automation software for the Ecmec machine’s PLC and NC operations as well as the main spindle and forward-feed drives.
Ecmec produces hydraulic and mechanical fixtures, accessories for robot grippers and customised machines for assembly, part handling and machining operations. The latest example is the newly developed Ecmec Special Purpose Machine (SPM) machining centre, which integrates and simultaneously executes all steps for processing up to 200 000 pressure die castings per year for the automotive industry.
From the drawing board to the finished machine in record time
When equipment manufacturers design a customer-specific machine, they must keep an eye not only on component costs but also on development expenses. For this reason, the time from first draft to delivery should be as short as possible. “Since we don’t build a machine of this magnitude every day, we looked for a partner who could supply control and drive components designed to meet customer requirements,” says Daniel Eklund, managing director of Ecmec.
The challenges were considerable. Parts that were previously made on two machine tools with three to five axes had to be processed by a single machine operating 18 NC axes simultaneously. Two main spindles are designed as four-axis units, meaning they can move freely along the X, Y and Z axes as well as rotate and tilt. Another three main spindles move as three-axis units supplemented by an additional one-axis main spindle. With this configuration, workpieces can be machined on all sides without having to be remounted. A tool changer with four different tools makes the design even more flexible.
“The Ecmec SPM employs a totally different set of processing methods compared to traditional machines and does everything much faster,” explains Eklund. “It processes the workpieces roughly 33 percent faster than conventional machines and requires less machine footprint.”
Precise motion control with faster response times
“Addressing all 18 axes simultaneously requires a fast and powerful control system, which is where Beckhoff came into play,” says Eklund. “Beckhoff was able to meet all the customer specifications. The flexible hardware design was another reason for the decision to select Beckhoff technology. The Beckhoff system is very powerful and easy to operate, which is something we truly appreciate. It is a prime example of German engineering.”
At the core of the machine is TwinCAT 3 NC I software, which controls the six mechanical spindles simultaneously. As a highly scalable system, PC-based control also provides the best possible hardware platform for this application. The TwinCAT real-time kernel and the ultra-fast system communication over EtherCAT offer ideal conditions for high-precision motion control. Eklund explains: “This platform provided very fast control properties and a much faster response time than the conventional PLCs we used in the past, which was one of the main reasons why we selected PC-based control technology from Beckhoff.”
Control and drive components from a single source
The Ecmec SPM is controlled and operated via a C6930 control cabinet Industrial PC with a custom-designed CP3921 multi-touch Control Panel featuring push-button extensions. The user interface is TwinCAT HMI for NC processing, which is easily programmable based on standards such as .NET. The axes and I/O channels are configured via TwinCAT Engineering with NC I functions.
The two main spindles are equipped with AM8000-series servomotors with speeds of up to 11 000 rpm. The other four spindles ensure a high degree of processing efficiency for downstream processing steps as well. The maximum feed rate is 30 m/min, and the maximum acceleration rate is 0,2 g. The six main spindles and 12 servomotors are controlled by Beckhoff AX5000 Servo Drives for exceptionally fast and dynamic positioning. In addition, One Cable Technology (OCT) saves a significant amount of installation space.
For more information contact Michelle Murphy, Beckhoff Automation, +27 11 795 2898, firstname.lastname@example.org, www.beckhoff.co.za