The proper disposal of punching scrap makes an important contribution to saving resources and energy. However, the demands on materials handling technology are constantly increasing – not least due to increasingly high-strength and thinner materials.
Mayfran International Europe is one of the world’s leading scrap handling companies with over 2,000 MWD (Metal Working Dry) systems installed. “Dry” is to be taken literally, as Division Manager Frans Herings explains: “Nowadays, punching plates are less and less wetted with oil, which means that the conveyor belt chains are no longer sufficiently lubricated. We respond to this with appropriate lubrication systems that meter exactly the right amount of lubricant.”
Razor Sharp Punch Scrap
And there are further challenges: Sheet metal, especially for bodywork and structural components, is becoming harder and thinner, which saves weight but “literally turns the punching waste into little knives,” as Herings explains. This is a contradiction to the “soft” steel that the conveyor belt should be made of, in order to put little stress on the belt hinges during production. However, this has not changed the already proverbial service life and low maintenance costs of Mayfran belts, some of which have been in use for decades.
Ralph Muhm, Head of Sales, Service and Marketing: “For more than 40 years, our disposal and conveying systems have been used mainly by all well-known manufacturers in the automotive industry and their suppliers – as currently again by BMW in China and Great Britain.”
Other important customers include manufacturers of white and brown goods as well as the sheet metal profile and foundry industries. “Increasingly important is the electrical industry, with its growing demand for stamped motor sheet for electromobility and, in the long term, the recycling of car batteries.”
Special construction guarantees a long life
The standard in this area is slat-band conveyors, which Mayfran supplies in numerous designs and sizes to suit the customer’s individual requirements. Widths of up to two metres (for example, divisible into two usable widths of approx. 900 millimetres) and lengths of up to 200 metres are possible. They can overcome gradients of up to 45 degrees and they can also be oil-tight. Reinforced chain guides made of wear-resistant material are available for particularly tough requirements.
There are reasons for the durability of the conveyors, as Frans Herings explains: “The design of our chains avoids relative movements and thus abrasion and wear of the chain links.”
Depending on the conveyor type, bent or welded “eyes” accommodate the tubes connecting the individual belt plates, which at the same time increase resistance to deflection and protect them. The chains absorb the tensile force alone, so that the hinge plates remain free of tensile force. The lateral guidance of the belt also protects the chain space from the penetration of parts.
The vibratory feeder systems, for which Mayfran holds a patent, promise particularly efficient transport. A special drive sets the belt in linear motion without transmitting vibrations to the press.
The trick: “A slow forward movement is followed by a fast, jerky retraction of the channel,” as Herings describes. Like the well-known magic trick of pulling a tablecloth out from under the dishes, the inertia of the goods being transported causes them to stick. Muhm adds, “This transport method is suitable for press scrap, chips, laser dust, bulk materials, household waste et cetera, whether dry or moist.”
Waste disposal in case of height differences
Such vibratory trough conveyors can be implemented as individual conveyors or as conveyor systems. The length of a single conveyor can reach up to about 100 meters, with each conveyor requiring only one drive. Oscillating channel conveyors are used as underfloor solutions and offer advantages especially in case of limited installation dimensions, as they require considerably less space than classic slat-band conveyors with their lateral rollers and the lower run.
However, Herings does not conceal their main disadvantage: “They can only be used horizontally, at best with a slight incline.” But there are solutions for this as well: Mayfran overcomes height differences by combining them with slat-band conveyors.
An alternative to underfloor conveying is a press-integrated system. It removes the press scrap and/or good parts above ground from the press table. Says Muhm, “The individual chutes are located directly in the press die, which allows the scrap to be disposed of directly at the point of origin.”
A single drive can move several troughs via a common shaft. Several crankshafts could also be rotated in different directions, allowing different parts to be transported in different directions.
“This allows a variable set-up of the drive, which greatly reduces changeover times for tool changes compared to other overhead solutions.” After all, this also saves a lot of energy compared to conventional compressed air systems.
Fit for Industry 4.0
The systems can be controlled via common controllers such as the S7-1500 from Siemens on the multifunctional CPU 1518(F)-4 PN/DP MFP platform. This allows the integration of high-level language functions, but also the creation and reuse of stand-alone applications. These tasks no longer need to be outsourced to a PC, which saves additional space.
“We use the open Industrial Ethernet standard ProfiNet as the communication standard, which means that nothing stands in the way of digital transformation and the world of Industry 4.0,” explains Herings.
At the field level, ProfiNet is used to connect the decentralized periphery and drive technology. “For easy operation and control, we use the visualization capabilities of Siemens’ TIA platform for displays on industrial PCs.” TIA stands for “Totally Integrated Automation” and allows complete access to the entire digitized automation.
In addition, an OPC UA interface is provided via TIA, which can be used to transfer data such as weight, material type, discharge time, etc. to higher-level Scada systems. This enables users to control their plants across locations and to collect, record and forward operating data.
Ralph Muhm: “By combining the open standards ProfiNet and OPC-UA, we pave the way for consistent communication in the automation and IT environment and combine the advantages within a single Industrial Ethernet network.”
Environmental concerns play an important role
In times of continuously increasing costs for CO2 certificates, high efficiency of all machine components is increasingly in demand. For example, there is an increasing demand for loading stations for railway wagons, which are replacing the climate-relevant trucks.
Material purity is ensured by two- or three-belt systems, with which the scrap can be sorted into steel and aluminium 5000 and 6000. Drives are equipped with frequency converters, which not only avoids unnecessary power consumption, but also has a positive effect on the service life.
Author: Michael Pyper, Wehrheim