Big class now also in small

GIESSEREI PRAXIS 2020/1-2
Ad
Eirich
Manufacturing Processes
Moulding Materials
Process Engineering
Eirich now offers Evactherm® technology for moulding sand preparation from a capacity of 7.5 m³/h. The first small vacuum mixer was commissioned in October 2019 at ZMM Stomana, in Bulgaria.

The demands on castings are getting even higher. Therefore, a reproducible and accurate moulding sand quality is gaining in importance. More than 50 foundries worldwide already rely on the Evactherm ® process from Eirich for moulding sand preparation. Vacuum mixing ensures constant cooling to 40 °C with optimum preparation of the bentonite-bonded moulding sand - even under fluctuating initial and environmental conditions. Previously only available for a capacity range from 60 m3/h: Eirich now offers the Evactherm ® technology from a capacity of 7.5 m³/h. 

ZMM Stomana, now specialises in the manufacture of woodworking machines. The company also had a very old foundry. The production facilities were no longer state of the art and were now thoroughly modernized. The highest possible plant availability and a consistently first-class quality of its castings - these are the ambitious goals that the Silistra-based company and its foundry now want to achieve. In a first step, ZMM Stomana has invested in a Laempe LL30 core shooter and a HWS moulding machine HSP-1. Consequently, modernization of the moulding sand preparation system was now necessary. The order for this was placed with Maschinenfabrik Gustav Eirich GmbH & Co KG, which was able to offer an innovative and at the same time economical solution. 

For a maximum of economic efficiency
Up to now, the moulding material has been prepared in a pan mixer and eight vibrating press moulding machines have been provided. The returning used sand was initially stored temporarily in bunkers without cooling and moistening. This resulted in considerable quality problems, especially in the summer months. The fluctuating moulding sand qualities led to higher reject rates. The modernization of the moulding sand preparation system is now intended to ensure that the eight-vibrating press-moulding machines and the new HWS moulding machine are reliably supplied with moulding sand of reproducible quality that meets the exact requirements. ZMM Stomana was looking for a moulding sand preparation system that would achieve maximum economy by means of a modern technical solution and meet the following requirements: - innovative technical solutions 

  • Integration into the existing building envelope - Reuse of existing plant units
  • Cooling of the used sand to 40 °C
  • Plant availability greater than 98 percent
  • reproducible moulding material qualities
  • less emissions, higher environmental compatibility
  • autonomous, fully automatic production including quality monitoring/control In order to fully meet these requirements, Eirich has developed a new concept.

New worldwide: Evactherm® technology in modular design
The desired integration of the new moulding sand preparation system into the existing building shell presented a challenge. The installation of a cooler with downstream mixer was not feasible due to the limited space available. Eirich decided to take a new approach. The requirement profile with cooling of the used sand to 40 °C played a decisive role in this decision. In the development and project phase, a new plant concept was therefore developed together with ZMM Stomana: 

  • The existing used sand section including magnetic separation, screening and storage, as well as additive storage and dosing were reused or adapted by the customer. 
  • A solids scale was integrated in one of the module frames. Used sand, new sand, bentonite, coal dust and filter dust are dosed via dosing screws onto the solids scale.
  • The necessary aggregates for the vacuum periphery of the Evactherm® mixer for cooling the sand are arranged on the same module frame. 

Due to the modular design and the relatively small quantities of moulding sand required, Eirich developed a new vacuum periphery. The main vacuum components were combined in only two units, the condenser and the pumping station. The advantage is obvious: The costs for the vacuum periphery have been significantly reduced. This made the process more economical.  

The heart of the plant is the Eirich Evactherm® RV11VAC mixer with a capacity of 7.5 m³ of processed moulding sand per hour. In conjunction with the vacuum periphery, the mixer enables constant cooling to 40 °C with optimum preparation of the bentonite-bonded moulding sand. The switch cabinets for the power/control section of the plant were installed in the direct vicinity of the mixer. Below the mixer, a collecting tank mounted on load cells is installed for the processed moulding sand. This is equipped with a discharge belt conveyor. The Eirich Qualimaster AT1 ProfiPlus is installed above the belt conveyor for quality monitoring. As a further development of the QualiMaster AT1, this testing device offers new possibilities in addition to measuring and controlling compactability and shear strength. Greater reliability with regard to the correction factor for evaporation is achieved by a second temperature measurement in the inline tester. Furthermore, the springback is measured in per mille. This information value provides information about the springback during forming. As a control value, the AT1 ProfiPlus also measures the gas permeability. The QualiMaster SandExpert software solution not only continuously records, analyses and displays batch data, but also performs preventive moulding sand control based on the company-specific model database. Moulding sand preparation can be programmed depending on the model and run fully automatically. 

The prepared and quality-checked moulding sand is fed into the existing finished sand section via a further belt conveyor. It is distributed to the eight vibrating presses and the HWS moulding plant. 

A milestone in moulding sand preparation with the newly developed plant, Eirich is setting new standards in the field of moulding sand preparation - especially for plants of very low output classes. 

  • Minimum space requirement for three process steps: homogenizing, cooling, preparation
  • Ensuring constant, reproducible moulding material qualities despite fluctuating initial and environmental conditions
  • Optimal quantitative and qualitative disintegration of the bentonite in a technical vacuum
  • Systematic quality assurance through the Eirich control concept of continuous data integration, which ensures the networking of production and control parameters at all levels
  • Preservation of valuable materials in the moulding sand system (fines, slurry) through closed water circulation
  • Halving the amount of dedusting air by eliminating a separate cooling unit
  • Installation/commissioning with material in less than 14 days.

Eirich presented the Evactherm® technology with this small output to the interested public at GIFA 2019 in Düsseldorf. Thanks to the modular design, the system tailored to ZMM Stomana could be commissioned in Hardheim at the main plant of Maschinenfabrik Gustav Eirich. Assembly and commissioning in the foundry of the Bulgarian company took place in October 2019.