What’s new
Even the compaction behaviour of an old pan grinder can be controlled More transparency in the mixing process
RTC, the moulding material testing machine, set up close under the mixer
Slow increase in compaction during the mixing process
View into the inner workings of the RTC
Rapid compaction development with an intensive mixer
Sand removal hole for the RTC samples just above the mixer floor
Gießerei Radeberg GmbH decides to rejuvenate its sand preparation by means of a retrofit – datec delivers an immediately functioning plant in only 7 weeks
"We knew right from the start that it would be a challenge to install a new control system, new weighing technology and then our RTC automatic moulding sand tester on a pan grinder in such a short space of time." Said datec’s Managing Director Christian Ebert, speaking retrospectively about the swift retrofit project.
"We serve small series niches and we want to deliver quickly with good quality every time. It should not matter whether we need good sand first thing on Monday morning or Wednesday lunchtime or not until the end of the shift on Friday night", explains Managing Director Dirk Reinke on the aim of the investment project at Gießerei Radeberg GmbH. The measurement and control technology in the entire sand processing plant had become a weak point.
CEO Dirk Reinke left + Hendrik Schuster, Foundry Engineer
Gießerei Radeberg GmbH, which emerged from a centuries-old tradition of glass mould casting, is one of the few companies that still cast glass moulds, but that is no longer nearly enough. In the meantime, small batches are produced on two moulding lines. A hand moulding shop is also available for piece weights up to max. 1000 kg. In both areas, complex and core-intensive parts are the main focus. Due to relatively small melting furnaces, the company is able to produce more than 30 different casting qualities. A wide range of approvals for the marine industry and also the possibility of supplying completely machined parts round off the manufacturing possibilities.
It began with the replacement of the old contactor control circuit, still from GDR times, which was replaced by a modern PLC control system of the latest generation. To meet the requirements of unmanned operation, a central visualisation system was set up on the moulding line for monitoring "from a vantage point". From there, the system is operated; tasks such as changing the recipe selection or recording and acknowledging faults that occur. The multitude of measured values from the new measuring devices is displayed on the screen and later continuously documented in the batch report.
"That was a feat of strength because we had to take on the task of dealing with the main supply cables right at the beginning." adds Steffen Müller, Head of Maintenance. "We wanted to comprehensively improve operational safety and make sure there were no more crazy malfunctions. We managed to implement and achieve that in the space of a fortnight."
Steffen Müller, Head of Maintenance, in front of the new decentralised control system
With the aim of improving the uniformity of the moulding sand values, the sand preparation plant was equipped with new measuring technology. For example, the inlet of the bucket lift for the used sand dosing system was fitted with cutaway platform scales.
Weighing in the lift bucket by installing pressure cells in the entry shaft
Binder scales with 2 new dosing screws on the mixer
The big step forward was taken with the installation of the ROTOCONTROL RTC 107 automatic moulding material tester for continuous measurement of compaction and compressive strength. The special challenge was the mixer. A pan grinder of the old design with a minimum cycle time of six minutes required a modified control behaviour, as the development of compaction is significantly slower than with an intensive mixer.
"With the RTC, you now have an additional tool. It enables precise coordination of the moulding material and the model. By specifying a compactability in the recipe, you are very flexible and can achieve the target parameters in the shortest possible time," notes Hendrik Schuster, Head of Quality Assurance. "A discussion about the moisture content can be avoided in this way. You receive the data after each batch and are thus informed about the condition of the moulding material at all times. Subjective impressions can thus be matched immediately."
Now no uncontrolled parameter changes can be made by just anyone.
If it goes wrong, no one wants to be the one responsible - the classic worry of many production managers when things suddenly don't run according to plan and it turns out that important parameters have been nonsensically adjusted by unknown persons. As a protection against such unpleasant manipulations, in Radeberg the individual log-in to the operating and visualisation PC is carried out with an RFID chip, which is used by each company employee for personal time recording. Only authorised persons can access the menus and their access and parameter changes are documented. Especially the latter documentation is also useful for carrying out extensive trials in order to evaluate the changes in a targeted and systematic way.
Recording who has changed which parameters in the menus and
Logging in for menu operation via RFID_reader
Cooling water dosage behind the unpacking point brings the temperatures down significantly
In the overall package of this retrofit measure, the item - shake_out_cooling for a cooling water dosing system on the conveyor behind the unpacking station was rather insignificant, but the effect has been all the more remarkable. "It even surprised us just how much the used sand is cooled down and also how much moisture remains in the used sand." commented Tobias Herrwerth, a PLC programmer from Braunschweig, on the control system that he had installed. Sands with an unpacking temperature of over 100 °C are easily cooled down to temperatures below 50 °C. "Initially, we were not quite sure whether there would be a sufficient amount of air to carry away the evaporated water. In addition, we were unsure whether the evaporated water would not condense and then drip happily away somewhere."
For water dosing, each unpacking of a box is signalled separately by the unpacking station in order to actually initiate the addition of the water for a short time and at the right moment. An infrared temperature measurement helps to determine the correct amount of water for the desired target temperature range.
Cool evaporation on the unpacking belt for simple but effective pre-cooling
Structure of the nozzle devices
The implementation of the retrofit measure for sand processing control system in the Dutch Aluminium Gieterij Oldenzaal in Oldenzaal
During discussions on the scope of renewal, all existing electrical equipment was placed under scrutiny. "We wanted to take a big step forward because what used to be sufficient is no longer good enough," Dennis Eekers, CEO at Dutch Aluminium Gieterij Oldenzaal in Oldenzaal, not far from the German border near Rheine, explained the motive for the investment. "No more disruptions and downtime, better sand quality and less waste, as well as much more transparency in the processes, and saving energy."
The beginning for the new control package Sandplant_control by datec GmbH was a new PLC, because the one still in use had long since been discontinued by the manufacturer. A new control cabinet was also envisaged, since contactors that are about 30 years old have a high probability of failure. At the same time, the manual operation system was completely renewed, as the central manual operation previously in use no longer corresponds to the current safety philosophy. Decentralised control boxes with a direct view of the aggregates being worked have significantly increased safety. A special failsafe concept also prevents the automatic control from being switched on centrally if the manual control is switched on decentrally.
The central manual control was replaced by local control boxes. It can only be operated in sight of the aggregates.
The core of the modernisation and quality improvement is state-of-the-art measuring technology. The two scales were equipped by datec with new electronics for more accurate dosing. Overrun optimization and automatic taring, as well as high resolution in the analog-to-digital value conversion, are the key features for improved dosing technology, especially for a binding material scale that is intended to weigh quantities of around 300 to 400 grams.
The scale electronics are part of the entire PLC network and are addressed directly via the PLC program.
"We now have a lot more data to help us with analytics and give us the visibility we need." A comprehensive batch report documents the large number of measured values and a special evaluation report helps with the analysis. With the use of statistical process control methods, the process can be analysed in detail and then also evaluated.
All relevant measured values, intermediate calculations, and menu values are documented in the batch report.
The evaluations are carried out from the large volume of data from the batch report, which is stored in a database for one year. With the eight-channel multi-diagram, 8 freely selected channels can be displayed simultaneously.
The EVA (Event Analysis) program is used to evaluate all fault messages in the archive. The primary concern here is the duration and number of faults. This information will help maintenance decide which problem to address as a priority.
Display of how often and how long in total which aggregate was in malfunction.
Display of how often and how long in total which aggregate was in malfunction.
In-house construction of the new control cabinet.
The continued use of the almost 30-year-old control cabinet was ultimately rejected because the probability of failure over the years was quite high and there were also gaps in the documentation.
"Of course, we pondered whether to go for a smaller or larger solution. We chose confidence - because things are looking up after the crisis and we then want to work through the orders without a handicap."
Energy efficiency
Initially, those responsible did not consider an energy efficiency control system, which automatically shuts down the sand preparation system when idling, to be necessary. But after a reference visit, the opinion changed, because then it was also seen at home how even with a foreseeable longer idle time, the system was not stopped manually. The system used to continue running through the break. Now the system switches off automatically and energy is saved. Energy consumption is recorded via a meter and later processed for sand production in an index calculation - kWh / 1 t moulding sand.
Hourly display of the sand quantity, energy consumption and the indicator kWh / t moulding sand.
You will find more information about our retrofit here.
You will find more information about the company Aluminium Gieterij Oldenzaal here.
Dutch aluminum foundry Gieterij Oldenzaal invests in sand processing
Hardly any modifications were made to the system itself during the investment; the new electrical equipment alone enabled significant improvements to be achieved. The original batch weight of 200 kg could be increased to 260 kg and at the same time the uniformity of the sand could be increased. The compressibility fluctuates only slightly, namely 1.5% in the 1st standard deviation.
In the spirit of the general energy-saving discussion, sand processing was also implemented with the Energy_control program module. An operating mode that automatically stops the sand processing when idling is detected and starts up again when sand is required. Although there are no long-term secured data with reliable findings, a conservative estimate is based on savings of at least 10%.
Key number chart
Dennis Eekers (li) and Danny Vreriks(re) ahead of the RTC at the Speedmullor
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