User report company Goletz
Perfect Cooling and Temperature Control
Thanks to systematic configuration and integration of temperature control technology from gwk, plastics processing specialist Walter Goletz was able to offer injection moulding as a cost-efficient alternative to thermoforming transport trays. Thanks to the combination of close-to-cavity temperature controlled integrat 4D mould inserts and the multi-circuit integrat direct temperature control system, the part quality was improved and cycle times were reduced – and the investment paid off within only ten months.
“When our customer approached us with the idea of injection moulding special transport packaging that they usually produced by thermoforming, we were very sceptical, as mould engineering would involve much higher costs. But miraculously it worked! We successfully reduced the customer’s production costs – and were able to outperform competing thermoforming companies,” Hendrik Baukloh, Head of Quality Management at Walter Goletz GmbH, Kierspe/Germany reports.
Miracles are generally very rare in the Sauerland region of Germany. In this case, it was more likely down to hard work and a certain pioneering spirit that the customer’s wish came true. The major tier-1 supplier to the automotive industry required trays for transporting distance sensors intended for integration into car bumpers, which were produced for several car manufacturers. These trays needed to withstand the final
cleaning and painting procedures and double as global shipping containers to avoid transhipping of the sensors.
Therefore, the trays had to be fitted with a cover (to protect those sensor components which were not to be painted) as well as with holes for draining excess water from the cleaning and painting processes. “When faced with these requirements, we found that injection moulding had clear advantages: thermoformed parts can only be produced without holes. The holes would have to be added by means of expensive post-production drilling procedures. In contrast, holes as well as delicate structures and undercuts can easily be produced in the mould cavity.” Baukloh knows from experience that in contrast to thermoforming, injection moulding is able to accommodate completely different forms and shapes.
At the same time, the electronic sensor interior had to be hermetically sealed against moisture. During the production of applications such as this, thermoformed trays are
usually fitted with a lip seal to protect the part from moisture when it is inserted. “As this seal is glued to the part, it can easily tear off when the sensors are removed from the tray. Two-component injection moulding however, allows us to create an ir onclad bond,” Baukloh explains.
High repeatability and suitability for robot handling
The automotive supplier had a third requirement: the tray must be suitable for robot lines. This meant that it had to strictly adhere to the set dimensions. Baukloh: “This is no problem for injection moulded parts. We only had to ensure a high repeatability of the injection moulding process.“ The team at Walter Goletz had already made first experiences with injection moulded trays as the company had been producing multifunctional transport trays for
car keys in several colours for suppliers who use distinctive coloured trays for different OEMs. “The colour selection is another benefit of injection moulding, as thermoforming only produces one colour: black,” Baukloh
Walter Goletz was faced with challenging specifications for their tray production. “Apart from the specification, the customer only provided a drawing - no drafts, no data,“ Ulrich Teetz, Project Manager at Walter Goletz
remembers. Therefore, the tray project was initially handed over to the company’s development department – with uncertain outcome. “But we realized very quickly that this could become a flagship project as well as a major operation. This became very clear after a meeting with Carsten Schmidt and Ulrich Rosenberg of gwk during which we discussed the options of close-to-cavity temperature control. I already assumed that we would need gwk to achieve the minimum cycle times required to make this project viable,“ Baukloh explains. Rosenberg is Head
of Mould Technology, while Schmidt is Head of Process Engineering Injection Moulding at gwk Gesellschaft Wärme Kältetechnik mbH, Kierspe/Germany. Schmidt also remembers this crucial meeting: “At this stage of the project, the trays were already intended to be produced in 36 cavities with deep contours. We had to provide cooling channels that run around each of these cavities in order to allow thin-wall, cost-efficient production of the trays. It was possible, but not an easy task – that much was clear.”
gwk was involved at an early stage of the project
Baukloh had one important question: Was it possible to achieve the envisaged cycle times by deploying integrat 4D inserts with close-to-cavity temperature control and the integrat direct multi-circuit temperature control system? Following a process engineering analysis, the team met again. This time, both sides wrote down the cycle times
they expected or considered possible on a covered piece of paper. “What was the result? There was a discrepancy of only two seconds. That is almost negligible when you are dealing with cycle times of 47 seconds,“ Schmidt said.
“When I left gwk’s technical centre, I knew we could implement this project,“ Baukloh says. “This made me glad that we decided to involve gwk at an early stage of the project. In the past, we often thought about the potential
benefits of close-to-cavity temperature control channels in the mould, but by then it was too late for gwk to integrate them in any useful way.“
“This approach is a textbook example and allowed us to find the best possible solution in close cooperation with Walter Goletz,” Schmidt confirms. After the customer gave their go-ahead, the project managers were keen to develop the mould with gwk’s temperature controlled close-to-cavity temperature control inserts before it would be built by Goletz’ in-house mould engineering department. The result was a 2x2-cavity mould for the initial production of two tray shells as ABS hard components and subsequent insert moulding of a TPE seal for protecting the sensor’s electronic interior. This mould was equipped with four hot runners for each cavity to ensure even filling. Each hot runner was provided with its own temperature control circuit. In close cooperation with the responsible managers at Walter Goletz, gwk carried out the complex configuration of temperature controlled close-to-cavity mould inserts and developed the project-specific temperature control concept (see info box).
Three different water temperatures – prepared for every stage of the production cycle
The different water temperatures were selected so as to dissipate as much heat a possible from the tray after injection moulding. “And the same time, the trays needed to have a certain temperature when the soft component
was insert moulded at the second station so as to ensure that both parts form a tight bond,” Schmidt explains. It is not possible to predict the temperatures at different process stages, therefore the temperatures that occur during the injection moulding process need to be controlled.
There were extensive discussions about the number and position of required ejectors. As the 1.5 mm walls of the trays are very thin and may easily suffer damage during demoulding, the processor attached major importance
to this aspect. For gwk, this meant that the temperature control channels had to encircle the ejectors.
A closer look at the figures reveal the highly complex configuration of the temperature control channels: channels with a total length of 10 metres, 68 bends and a variety of risers are used for one of a total of eight mould inserts to ensure that all 36 cavities for the trays are cooled down evenly. “We virtually submerged the component in a
water bath. This mould contains more water than steel. I often wondered whether we used enough steel for this mould. Only the combination of temperature controlled close-to-cavity mould inserts with multi-circuit temperature-control system allowed us to implement this project in a cost-efficient and technically viable way,” Teetz explains.
The balance sheet shows an eight-second cycle time reduction
After a six-month production run, all members of the project team were convinced: it was well worth it! This year, Walter Goletz will produce 950,000 transport trays on a retrofitted Krauss Maffei two-component injection moulding machine with a clamping force of 8,000 kN.
The most important technical aspect is the easy, fast and smooth demoulding of the trays. With a cycle time of only 47 seconds including a 31-second cooling phase, the project is cost-efficient for Walter Goletz.
“Without gwk’s integrat 4D system, we would only have managed a total cooling time of 39 seconds, which would mean cycle times of 55 seconds,” Baukloh states. In sum total, the cycle time was reduced by 8 seconds, which
translates into 25%.
The project manager’s calculations demonstrate: every second less saves money for the company. During the production of 950,000 trays, which requires about 475,000 shots into a two-cavity mould, Walter Goletz saves machine operation hours to the value of EUR 59,000 a year – or Goletz can produce more trays within the same period of time. The investment costs of EUR 52,000 EUR for the temperature-controlled closecontour mould inserts and the multi-circuit temperature control system have paid off within ten months. The result corresponds with the preceding gwk feasibility study, which means that Goletz and gwk are right on course for success“, Baukloh concludes with satisfaction.
Integrated cooling concepts for all applications
In 2008 Walter Goletz created optimum conditions for the integration of temperature control technology when the company built their new facility: they installed a central cooling system with heat recovery and water treatment – also made by gwk – in order to make their production as cost-efficient as possible. The water treatment system provides an additional benefit for this project, as Schmidt explains: ”The standard water quality would not be sufficient to manage the winding passages of the circuit. The cooling channels would clog up and would have to be
cleaned all the time.” The installation of an energy-saving cooling system saves more than EUR 100,000 in energy costs every year. Heat recovery was another objective: Instead of installing a heating system, Goletz uses the thermal discharge of production machinery and ancillary equipment, which generates annual savings of more than EUR 20,000. Saving energy costs meant that the overall investment paid off within only 21 months.
This investment was well worth it, Baukloh concludes. The facility did not even require a heating system during the cold winter of 2011/2012: “There is a connection to the municipal gas grid somewhere in the corner. The public utility company forced us to install this connection because they would not believe that we would manage without gas. But we never used it. Again, the preceding gwk feasibility study turned out to be right. We now have the complete gwk system in operation and all components are perfectly tuned: we found the perfect partner for all
our cooling and heating tasks!“
Walter Goletz GmbH, D-58566 Kierspe, www.goletz-gmbh.de
gwk Gesellschaft Wärme Kältetechnik mbH, D-58540 Meinerzhagen, www.gwk.com