Introduction

In 1914, when metal heating in Europe was still by means of coal, a young Swiss electrical engineer set about applying a discovery made during a four-year learning experience in the United States: resistance welding technology. Within two years, Hans A. Schlatter had set up a company that has gone on to inaugurate a series of innovative, cleaner, and increasingly more energy-, time-, and cost-efficient manufacturing processes, each adapted to contemporary needs. Now in its 89th year, H.A. Schlatter AG is an ISO-9001 certified market leader and exporter of state-of-the-art resistance welding plants. Its versatile product range has found customers in a number of markets including railway construction, automotive components, radiators, and wire products.

About electric resistance welding

Electric resistance welding is a versatile and highly dynamic joining method able to perform a large number of welds quickly, precisely, cleanly, economically, and with reproducible quality. The process connects metal parts in a material-locked joint by means of electric power to heat them to welding temperature while subjecting them simultaneously to a mechanical force. No filler material is used.

In a resistance welding machine, the parts must be fed to the welding station exactly and positioned precisely; welding current has to be controlled; and the process parameters - current flow, current intensity, welding time, and welding pressure - must all be controlled exactly. This requires optimum coordination of the system’s mechanics, electronics, and information technology by the machine builder. The Schlatter term for this is “mechatronics”, and it forms the basis of the company’s systems engineering, notably the development of complete solutions in which several individual machines work together in synchrony. The core expertise of H.A. Schlatter AG lies in the synergistic coordination of welding technology, mechatronics, and systems engineering.

A brief history

Today, two generations further on, the Schlatter family firm maintains its awareness of the needs of the day and strives to provide flexible and economical solutions to the challenges of closely controlled productivity. Schlatter was among those leading the advance from the inefficiency of coal into the age of the electric current-heated forge, developing heating machines for the production of shoe nails, screws, and pointing wire rod, and spot welding machines for the manufacture of products from light bulbs to 15mm thick steel sheet. In the aftermath of World War II came the major breakthrough that launched Schlatter on its core process today: crosswire welding.

The European construction sector had largely opted to rebuild devastated cities and structures using reinforced concrete. But the steel reinforcement bars of the time were still manually held in position and attached to one another with wire before being embedded. Hans Schlatter, having devised a method of welding a crosswire to hold these bars together, produced his first mesh welding machine. Initially, only pairs of line wires could be welded one by one with a single crosswire, and output was low. This led Schlatter to develop a pneumatically driven mesh welding machine integrating several transformers. This permits all line wires to be welded at once over the entire mesh width with one crosswire, an advance cylinder moving the mesh into subsequent welding positions.

Schlatter’s headquarters in Schlieren, Switzerland

Welding quality and manufacturing productivity were thereby much improved. Further developments such as double track mesh welding followed, forerunners to the modern, fully automatic turnkey production lines available today. These make welded mesh for all kinds of wire products: supermarket trolleys; shelves and racks for kitchen refrigerators and dishwashers; display racks; animal cages; livestock transport containers; reinforcement mesh for buildings and sound barriers along motorways, roads, and tunnels; riverbank and coastal gabions, and so on. The list is virtually endless.

The Posiweld system

Wire products, often shaped in three dimensions, are joined together by the electric resistance spot-welding method using the Schlatter Posiweld system, a flexible, reliable method of welding cells for frequent-lot production with process security for reproducible quality. With this system, bright, stainless, and galvanised steel wires can be processed. Wire products are manufactured in small, medium, and large series. Typical examples include roundmesh, three-dimensional wire articles, composite products, conical mesh, and special shapes. Welding is performed on an assortment of wire diameters, multi-layer composites, and close-netted mesh.

Posiweld system, type Orion

The Posiweld system features DC or low-frequency technique, mains voltage compensation, and state-of-the-art welding processor technology, offering constant parameters over the entire welding range. Nonrectangular wire positions, different diameters, or a combination of wire with tube or sheet metal materials in one work cycle are also possible. Typical products include storage baskets and shelves for home, office, and industry; merchandise stands and racks; bird and pet cages; griddles for cooking appliances; shopping trolleys and baskets; mesh crates and containers; shelf inserts for refrigerators and freezers, stainless mesh shelving; baskets for the food industry; decorative mesh; fan screens; and washing baskets.

An outstanding feature of the Posiweld system is its excellent welding quality for wire and sheet metal joints. AC, DC, or medium-frequency power sources can be installed. Several independent welding circuits can be incorporated in the same cell if required. The Posiweld system also offers high output, good operational reliability, and short changeover times.

Posiweld system, type Libra

Modular system concepts for industrial and reinforcing meshes

In road and tunnel construction and many building and civil engineering sectors, reinforcing mesh of cold or hot rolled wire is the usual choice, together with lattice beams and all types of three-dimensional reinforcement. These wire products are virtually indispensable for making not only foundations, ceilings, pillars, and columns, but also prefabricated concrete elements. Industrial mesh also sees service in such other applications as shop fittings, storage facilities, and household appliances. Most of these involve the use of flat mesh. Shopping trolleys, shopping baskets, display stands, shelves and mesh partitions in refrigerators, ovens and dishwashers are just some typical products made of welded wire.

Reinforcement mesh

Welding machines of the Posiweld system are normally chosen for the manufacture of round, three-dimensional, and multi-part mesh products. Other machines are preferred for flat mesh. The Schlatter MG series of mesh welding machines, including versions MG900, MG300, and MG200, is of modular design and available in various sizes. These machines are computer controlled and can be interlinked with an assortment of loading, feeding, straightening, cutting-to-length, and payoff units in an automatic production line. Wires can be welded crosswise, one on top of the other, in practically any arrangement. Exact, reproducible control of the electric current and force system according to amplitude and time is assured by the SWEP welding process control system, together with stabilization of network and voltage fluctuations. Mesh sheet geometry is entered at a process control system and can be checked on-screen. Using the parameters entered for the mesh width and wire sizes, the system calculates the individual welding values for each node, permitting the saved data to be called up and edited at any time. Central data input and monitoring are also possible, and the user-friendly features are rounded off by electronic diagnosis and production data acquisition systems.

The MG900 line for heavy industrial mesh

The MG 900 concept accommodates a wide array of uses for industrial mesh, extending from filigree birdcages to heavy-duty security fences with double-welded crosswires. This top-of-the-range industrial mesh welding line system can be used for small-batch or mass production of flat and very accurate mesh sheets, and accepts any length of bright steel, galvanised, antimagnetic, or stainless steel wire, of different line and crosswire diameters.

The system MG 900 for the manufacture of industrial wire mesh and wire products

Gap or disc-type feeders equipped with preloading devices or twin-gap feeders can automatically feed the crosswires at varying pre-set speed sequences in any one loading cycle. Mesh sheet is transported and positioned by the pneumatically operated gripping fingers of the linear mesh pull-out units or crank drives.

The system MG 900: a modular concept

Cutting heads are available for trimming and slitting with programmable cutting positions and angles for a clean, accurate cut on each individual crosswire and along line wires. The special-design SYROCUT straightening and cutting unit allows quick changeover to other wire diameters.

SYROCUT straightening and cutting unit

Rotating straightening elements and any of a whole range of optional components (transformers, electrode holders, single-spot and series simplex, duplex, or triplex weld presses) can be fitted to suit particular weld applications. Electrodes, electrode holders, thyristors, current cables, and transformers will last much longer due to the system’s integrated water cooling circuit. Efficient throughput without interrupted production is achieved by stacking units set up in a line, and automatic stacking devices for transferring the mesh sheets into different storage areas. The number of mesh sheets per stack can also be programmed in.

Conical mesh welding device to manufacture shopping carts

Crosswire bending unit directly integrated into the welding machine

Welding station to weld additional line wires onto the same base mesh

The MG 900 system is available with a large selection of accessories for the manufacture of a multiplicity of specialty products. A bending device for the production of column reinforcements is just one example.

The MG 300 system for large-batch production

Models of the MG 300 system will process wire drawn from coil or spool and straightened on the production line. This system is recommended for production of large batches in minimum time and with little manpower.

The Schlatter system MG for economical production of standard mesh

The MG 300 system can be used for medium and large batches or mass production of lightweight and heavy materials. Line wires are fed from the coil, and the crosswire from a rotary straightening unit with two integrated Syrocut straightening and cutting-to-length units. The MG 300 is capable of producing various dimensions without interruption.

System MG 303 for highly efficient production of medium-size batches

The MG 300 series is modular and readily expanded. It incorporates the MG 303 system featuring a disc-type feeder for the crosswires that allows for quick changeover to other wire diameters. The freely programmable roller advance unit contributes importantly to the excellent flexibility. The MG 303 system is thus a highly efficient production line, particularly for medium-size batches. This series also incorporates the MG 316 system, featuring a modular, extendible design that enables the mesh producer to adapt to changing market conditions at any time and at low cost. The possibility of combining crosswire feeding both off-spool and off-magazine opens up new market opportunities. In addition, the double-row MG 320 welding line operates reliably and accessibly even at high production speeds and in multi-shift operation.

Close-up of system MG 320

The MG 220 system for engineering welded wire fabric

The MG 200 system is suitable for the production of engineered structural mesh. Models in the series process cut-to-length line and crosswires. Various degrees of automation are available. High flexibility and short resetting times offer the competitive advantage of just-in-time production for direct delivery to the building site. The system’s quick changeover capabilities and high output of top quality welded wire fabric commend it to the manufacturer. It ensures economic production even with batch sizes of only one mesh sheet per order. The most elaborate design of engineered welded wire fabric can be produced fast and efficiently.

System MG 220 for small and medium batch production of
medium to heavy mesh panels, cold and hot rolled material

The MG 220 system is available in various designs and degrees of automatisation, from manual to fully automatic. It features:

• Processing of hot rolled and cold rolled material;
• Laterally stepless adjustable welding elements;
• Very large working range;
• Floating welding presses;
• Central, user-friendly input of production data through a process control system (PCS) with a management information system (MIS).

In the fully automatic version of the MG 220 system, prior to shifting of the elements the computer automatically determines their position and then calculates the shortest possible drive track. Changeover times are minimised as the welding heads do not have to be moved into a lateral initial position. Finally, the computer verifies the actual location of the repositioned elements, guaranteeing that even the first wire fabric produced fully meets specifications. Able to process line wires up to 26mm Ø and crosswires up to 16mm Ø, the MG 220 system covers a much broader working range than many other production lines. Mesh sheets can be produced in any desired width up to 3,6m and in lengths up to 13,7m. The system even handles sheets with displaced single- or double-line wires.

System MG 230

Process control

From very early on, H.A. Schlatter AG realised that a good machine can only become a leading product if it can offer good process control. The company has always been committed to in-house development of its controls, from electromagnetic relays to electronics. Now, in the age of mechatronics, Schlatter’s SWEP weld microprocessor control ensures reproducible, precise regulation of current, force, and time values. Mains voltage and frequency fluctuations are stabilised. And optimum linear phase shifting of the individual transformers allows constant, environment- and operator-friendly welding for excellent surface quality and strong, quality joints free of spatter and distortion. A central PCS data input facility offers diagnostic features, monitoring production and locating errors and interruptions, with all electronic variables stored in memory for instant recall on demand. CNC-axis controllers with AC servo-drives allow free and accurate programming to within one-tenth of a millimetre.

Meeting the individual need

H.A. Schlatter AG is a successful plant designer and developer with special skills in systems engineering, project management, and quality control, supported by a highly qualified team of experts. The company offers simple plant layout options, a compatible unit construction system, and modular software packages for extending or modifying existing production lines.

Schlatter’s test floor for machines and plants

A variety of machine widths is available. Components such as weld presses, electrode holders, and magnets are equipped with quick-clamping elements and plug connections for rapid exchange and adjustment. Components and equipment can be adjusted to accommodate initial investment outlays, while allowing for possible future extension.

The Megaflex System