New carrousel system for precast element production in China

The subject of industrialization in the field of residential construction has been gaining considerable significance in the People’s Republic of China during the last few years. In the country with a population of 1.35 billion people 45 locations for industrialized residential construction, so-called “National Residential Industrialization Bases”, will be established in future. These locations are supported by the Ministry of Housing. The city of Shenyang in Northeast China is part of this subsidy program, which is quite peculiar as 42 of these supported locations are companies. The city of Shenyang has 8.3 inhabitants and has exclusively been characterized by industry for 80 years. Owing to the climatic conditions prevailing in Shenyang with temperatures below -30 degree Celsius in winter months and the growing awareness in environmental protection, precast concrete construction qualifies for this city in particular and therefore the project shall be pushed forward here.

The construction company Shenyang Wanrong Modern Architecture Industry Co., Ltd. was founded in 2011 and is 45 % owned by the city of Shenyang. In the years that followed, the company implemented some major building projects for the purpose of the 2013 Chinese National Games. Between 2012 and 2014, they have realized the Security Command Center with 30 stories and an overall building area of 31,000 m² as well as the Nanke Plaza, a modern office building with 24 stories and an area of 41,100 m². Both construction projects were built by 70 % with precast concrete elements.

Complete carrousel system
for various precast concrete elements

In order to play a pioneer role in the precast concrete industry in Shenyang, Wanrong is aiming at improving the production of precast concrete elements and automating the same respectively. According to the company’s own statement, they concluded a contract with Ebawe Anlagentechnik, in early 2013, for the supply and installation of one of the most modern carrousel system throughout China. The scope of supply includes a complete carrousel system comprising 75 pallets having a gross size of 14 x 3.80 m, a pallet stacker and a curing chamber with 14 bays, a shuttering robot as well as turning equipment. The reinforcement machinery was supplied by Progress Maschinen & Automation, a sister company of Ebawe within the Progress group of companies. This includes a mesh welding machine, a machine for placing the wire meshes into the pallet, a lattice girder production machine and a robot for lattice girder placing. The factory, moreover, was equipped with a comprehensive software solution for work process planning, production and process analysis.

The new carrousel system is designed for the production of a wide variety of precast concrete products, such as precast floor slabs, double wall, sandwich and solid wall elements, which are used up in building of housing complexes. Before a new production cycle starts, the pallets are passing through stationary cleaning equipment for cleaning the shuttering surfaces. The formwork itself passes an appropriate device for cleaning and oiling. Afterwards, the storage robot returns them to the formwork magazine, where they are ready for the next production cycle.

The combined plotter and shuttering robot places the next element loading onto the shuttering surface. The reinforcement wire mesh required is manufactured just in time by means of the fully automated mesh welding machine type M-System Evolution using coils. This flexible machine is manufacturing wire meshes with a maximum size of 10 x 4 m, with every wire mesh being individually welded according to CAD data. The welding robot has six welding heads, which are welding the wire meshes with various blockouts and according to the grids specified. When the wire meshes are completely welded, a fully automated mesh bending machine provides for bending the longitudinal and cross bars, using a single wire bending system, if required. Subsequently, the reinforcement wire meshes are inserted into the prepared pallets by means of a magnetic crossbeam.

Just-in-time production of lattice girders

Wanrong uses a lattice girder welding machine of type VGA 215 for the production of lattice girders. This machine is manufacturing the lattice girders in the lengths required just in time in the company’s own factory. A robot carries the lattice girders made to an active and passive storage facility. Afterwards, a fully automated crossbeam is used to position the lattice girders on the pallets. The pallets are moved to the next work station. Here the concrete is poured with the aid of a concrete spreader with screw feeder system. For compacting the poured concrete a compacting unit with horizontal motion is available as well as two combined compacting units.

After the compacting process, the solid and sandwich elements respectively are troweled by means of a smoothing beam. A power trowel system can be used for fine smoothing the surface of the pre-hardened elements, when required.

For hardening, the pallets are moved into a rack unit consisting of five towers with 14 bays each, thus providing sufficient space for all pallets. It is moreover fitted with a heating and ventilation system.

For the production of double walls, the turnover of the first finished shell into the freshly concreted second shell is carried out by the turning equipment. As soon as the finished elements have left the rack unit, they are taken out of the pallets by transport racks for carry­ing them to the outdoor storage area using run-off carriages. There is a passable tilting device with mobile ladder available for lifting the wall elements.

In addition to the reinforcement machines integrated in the carrousel system, Progress Maschinen & Automation supplied a stirrup bending machine of the series EBA S 12, for making stirrups for internal and external job orders. Furthermore, Wanrong uses the Tunnel Master for manufacturing curved elements for the production of tunnel segments being used in tunnel construction. This machine is also included in the scope of supply provided by the Progress Group. Both machines as all systems of the Progress Maschinen & Automation product rang are directly fed from the coil.

Master control system for controlling,
monitoring and optimization

The Ebos universal master control system is used for controlling, monitoring and optimizing the entire precast element production process. This system was also developed by the Progress Group and it provides a comprehensive solution for work process planning, production and process analysis in the precast concrete industry. In this way, extensive interface problems are avoided, thus allowing the staff members to carry out their entire work processes in a single homogeneous and user-friendly system.

The technical department generates and provides the data of the elements for Ebos. For this purpose, they use the CAD program AcadPrecast of Idat GmbH, which is a very specific software being based on the market-leading CAD program AutoCAD. It supports the technical planner in all steps required for the element definition, being directly linked to Ebos via the CAD/CAM interface.

Using modern 3D technologies, the effort of the design draftsman spent in element planning is reduced to a minimum. AcadPrecast provides comprehensive automatisms for generating the geometry and reinforcement and for creating all necessary plans and drawings in a fully automatic way.

A special module for compiling the data for the mesh welding machine directly supports the user when preparing the mesh reinforcement per element in a machine-processable way. Furthermore, AcadPrecast determines all relevant billing data and transfers them to the customer’s internal accounting program via an open data interface.

From May 15 to 18, 2014, the opening ceremony of the new factory took place together with the trade fair “The Third China (Shenyang) International ­Modern Architecture Exposition”. More than 1,000 trade fair visitors came from all over China just on these four days in order to see the modern precast element production plant at Wanrong. In the course of the fair, the Ministry of Housing granted Wanrong the title of a “National Residential Industrialization Base” and in parallel the city of Shenyang gained in reputation by the title “­National Exemplar City of Residential Industrialization”.