FULLY AUTOMATIC HANDLING AND TESTING OF DISC SPRINGS
A spring manufacturer recently commissioned servo press and automation specialist IEF-Werner GmbH to develop a complete solution that not only includes the fully automatic testing of punched disc springs for characteristic values, but subsequently separates good parts from bad and feeds them at high speed to further processing. The result is a system that consists almost entirely of IEF’s own automation components and runs reliably at high cycle rates around the clock. Solutions from IEF-Werner are available in the UK from value-added reseller, RARUK Automation.
Every machine and every device is born from an idea. In the development process, this idea takes shape and finally becomes a production-line reality. The engineers at IEF-Werner GmbH adopt this ethos for every project, in line with specific customer requirements and regardless of complexity.
“In many projects we’re on board from initial contact to final commissioning,” reports Frank Neugart, Product Manager for Servo Presses at IEF-Werner.
This strategy proved no different when a request arrived to provide a completely automated solution for the testing of disc springs.
Once the initial concept and design had been agreed, the test system was set up at IEF-Werner’s technical centre in Furtwangen, where the implementation process began in close co-operation with the customer.
Show of strength
One of the principal challenges in disc spring manufacture is that each spring can differ vastly in certain characteristic values, such as strength, hence the need for testing. On the customer’s production line, disc springs are punched from sheet metal at high cycle rates and fed into the IEF-Werner system according to type. There, the springs are transported via a conveyor system to a spiral bowl conveyor which separates them accordingly.
“For the pick and place mechanism we developed a vacuum gripper that picks up disc springs from the separation area,” explains Mr Neugart. “Springs are handled gently by the vacuum solution without imparting any additional force.”
The gripper places disc springs back on the conveyor system, for which IEF-Werner specified its euroLINE 120 linear direct-drive unit with four independent carriages that serve as pushers. The euroLINE 120 acts as an axis for transporting disc springs to the subsequent stations. Notably, several slides on the euroLINE 120 can be moved independently of each other, which means that several springs can be fed and discharged simultaneously in subsequent stations.
Pressed into shape
As springs are often deformed after punching, they must be pressed into shape prior to testing. Thus, when disc springs arrive at the testing system, a slide pushes and positions them under a servo press from IEF-Werner’s aiPRESS series. This press loads the spring with the force required to bring it into a defined shape.
Next, the second slide pushes two components in a double cycle to two further servo presses of the same series. These test presses conduct a defined measuring load between 16 and 32N, and then measure the height. Once complete, parameters are switched over to measure the test force (200 to 7,000N) depending on the previously captured height dimension.
IEF-Werner servo presses are ideally suited to this application because the drivetrain consists of a servo spindle with a matching servo drive integrated in a solid and torsion-resistant steel C-frame. Importantly, the system includes a direct optical-path measuring system on the press ram to avoid positioning errors.
In order to monitor the process and display the progress graphically, IEF-Werner has equipped its servo press series with the intelligent aiQ-CONTROL force-path monitoring system. Also integrated is aiLIGHT: energy-efficient, four-colour LED technology that clearly signals system status to plant operators. Control is via an industrial PC from Beckhoff, which communicates with a higher-level controller using the OPC-UA interface. Warning and fault messages with message number or time stamp are stored.
Measured values are transmitted to a QS system through a so-called Q-DAS interface. Parts are 100% checked, with results stored in random samples.
Sorting good from bad
In the case of bad parts, the machine distinguishes between rejects and disc springs that can be reworked. Springs exhibiting the correct measured values are transported by an IEF-Werner MINITRANS flat belt for further processing.
“With a few exceptions, all of the components come from our company, even the motors and encoder cables,” reports Neugart. “The customer not only gets a servo press but a complete process based entirely on our know-how. We relieve the client of any responsibility.”
IEF-Werner has also trained customer personnel and, according to the maintenance contract, comes twice a year to clean, check and (if necessary) calibrate the system. Today, the machine runs across three shifts, seven days a week.