Sheets of metal have to be lifted from a stack and placed on a pallet as part of a customer order or on the table of a sheet-metal cutting machine. With conventional solutions, this cannot be done without some damage to the surfaces of the metal sheets, even if they are protected by intermediate layers of paper or by adhesive films, as is often the case with stainless-steel sheets or sheets with brushed surfaces.
A further problem is the tendency of the sheets to stick together on the stack, which means that considerable mechanical forces must be applied to separate the sheets from each other. This can be done manually in the case of thin sheets, but thick sheets require the use of further aids. Even if such handling tasks occur only occasionally, they require the use of several people and additional aids, and the surfaces of the sheets are still not fully protected against damage.
It is thus necessary to look for a practical, safe and economical handling solution. The investment in a special handling device pays for itself by reducing the number of people needed for handling the parts, by decreasing the handling and transport times, by minimising the idle times of the sheet-metal cutting machines and by avoiding damage to the sheets, which can result in costly complaints from customers.
This is particularly true when commissioning metal sheets in a sheet-metal production firm or trading company, such as a renowned trading company for semi-finished products and sheet metal.
The product range includes various sheet metals (stainless steel, aluminium, brass, copper, honeycomb and checker plates, plastic-coated metal sheets) in various formats (large: 1500 x 3000mm, medium: 1250 x 2500mm, small: 1000 x 2000mm). The sheets are between 0.8 and 30mm (aluminium) thick, which means that they can weigh up to 400kg.
The task was to handle thin and thick, large and small metal sheets. Neither the thick sheets nor the thin ones can be handled and commissioned rationally by hand. In addition, the company has to commission between 30 and 50 orders for metal sheets per single-shift working day, something which cannot be achieved without a sufficient number of people.
For this reason, the company management decided to reorganise their handling of metal sheets and started to look for a practical solution to the problem. Schmalz, represented by Millsom Materials Handling in Australia and New Zealand, articulated-jib crane and a VacuMaster vacuum lifting device provided a suitable solution.
Users can optimise their material flow and production operations under difficult conditions, which exist on their premises. The advantage of the rigid articulated-jib crane is that it weighs 800kg, at its low overall height. It has a large working area and can be controlled easily and precisely, even when carrying a heavy load.
The articulated-jib crane permits ergonomical, longitudinal or transverse handling and is thus suitable for loading and unloading sheet-metal cutting machines, even if access from the top is restricted or impossible, and for removing sheets from stacks and placing them on pallets.
The articulated jib crane is 3.5m long and can be swung out laterally to cover a working area of about 20sqm. Equipped with a vacuum lifting device of the type VacuMaster 500-6, the crane is capable of lifting loads weighing up to 500kg.
The articulated jib crane system has an overall height of 3580mm and a lifting height of 1700mm, which means that it can master most of the material-flow requirements in a flexible manner.
The rigid load suspension system prevents the load from swinging, and reduces the removing and dropping times and simplifies precise positioning. The reliable friction clutch ensures the necessary safety in the case of an overload and is supported in this by the safety elements of the vacuum lifting device.
The new material-flow and commissioning solution at the company provides more efficiency and productivity in the processing of orders in the central stockroom. For this, the required metal sheets are transported in stacks to the commissioning area, using ground conveyors. An operator lifts a sheet from the stack with the articulated-jib crane and the vacuum lifting device and places it on a pallet, which rests on trestles. A sheet of paper is laid between the metal sheets to protect their surfaces against damage and the entire stack is wrapped in cardboard. The thin sheets are placed on the pallet first and the thicker sheets are placed on top of them in order to provide protection and stability.
In the past, two persons had to manhandle the sheets from the stack, a procedure which resulted in damage to their surfaces. Heavy sheets had to be separated with the aid of iron bars and then lifted, moved and deposited with the aid of a fork-lift truck, a process which also often caused damage.
Now, one person carries out the handling with the combined crane and vacuum handling system without causing any damage to the sheets.
Due to the fact that the six suction pads are spring-mounted and flexible and have special sealing lips, which leave almost no marks on the sheets, the handling of both thin, non-rigid sheets and thick sheets is easy and safe, particularly since the large vacuum reservoir and the electronic warning device ensure safe handling even in the case of a power failure.