· The mold cooling time has been reduced from 22 seconds to 10 seconds, a reduction of 55%;
· The temperature of the mold wall is lowered by 40 ° C to 70 ° C;
· The daily output of each injection molding machine increased from 1,496 to 2,101, and the efficiency increased by 40%.
If you are the owner of an injection molding factory, do you see these numbers, do you want to make your own factory achieve such an improvement?
Metal 3D printing technology can effectively shorten the mold cooling time and improve the production efficiency of the injection molding machine in the injection mold, which is now confirmed again.
On August 23, 2018, the Antarctic bear learned that Alfred Kärcher (Kärcher) of Germany used each of the plastic shell products by using a mold core with conformal cooling function (made of metal 3D printing) in its injection molding mold. Cooling time reduced by 55%, greatly improving the company's injection molding production efficiency. This special core is designed by Renishaw and produced using metal additive manufacturing technology.
△ injection molding machine is producing plastic shell
The high-pressure cleaners produced by Alfred Kärcher (Kärcher) in Germany have not only become the necessary cleaning equipment for many German households, but also are favored by users in the international market – the distinctive features of these washing machines are their bright and striking yellow outer casing. Thanks to the powerful features and good reputation of the Kärcher pressure washer, both indoors and outdoors, more and more people use Kärcher products in the daily cleaning of the home.
△High pressure cleaner produced by Alfred Kärcher (Kärcher), Germany
To meet the growing demands of the global market, Kärcher produces millions of compact washers every year. The annual shipment of K2 standard high-pressure cleaners at a factory in Obersontheim exceeds two million units. However, Even if such high production has been achieved, Kärcher is still unable to meet all market demand.
One of the most recognizable features of the Kärcher washing machine is its bright yellow outer casing, but the outer casing manufacturing is also one of the main bottlenecks in the production process. For example, the outer casing of the K2 series washing machine is produced by six injection molding machines, each The machine can make 1,496 outer casings per day, but this quantity is not enough for Kärcher. Because Kärcher has four assembly lines, the workers are produced in three shifts, so the daily K2 pressure washer can be assembled up to 12,000. station.
Obviously, one option is to add more injection molding machines. However, in the view of coordinator Leopold Hoffer, who is the head of the injection molding process at Kärcher's Obersontheim plant, he can increase the productivity by tapping the potential of existing equipment. 'Our goal is to shorten the molding cycle from the original 52 seconds to between 40 and 42 seconds,' he explained. To this end he contacted LBC Engineering, based in Pliezhausen (the company was commissioned in May 2013). Renishaw acquired), seeking ways to shorten the mold cooling time.
△ original mold design
'The first phase of the project is to obtain data on existing molds to determine if Kärcher's proposed objectives are feasible,' recalls Carlo Hüsken, project manager at Reneschau of Kärcher. Renishaw uses the data provided by Kärcher to create injection molding The thermographic image of the molding process was then analyzed using Cadmould® 3D-F simulation software. The results showed that the plastics had a melting temperature of 220 ° C and a release temperature of 100 ° C. During the entire molding cycle of 52 seconds, The cooling time is 22 seconds. The mold temperature is controlled by cooling water at a flow rate of 10 liters / minute and a temperature of 35 ° C. Next, Renishaw focuses on the hot spots detected during the thermal imaging process. Because these areas directly lead to an extension of the molding cycle, further analysis is required. Using these data, Renishaw completed a data simulation with 20 molding cycles, including analysis of the mold wall temperature.
△Improved mold design
According to Mr. Hüsken's suggestion, during the second simulation, Renishaw improved the temperature control on the nozzle side by adding two conventional cooling channels to the mold plate on the nozzle side to enlarge the mold plate. Cooling effect of beryllium copper threaded joints.
Subsequently, Renishaw conducted two additional simulations to evaluate the potential improvements that could be obtained when applying conformal cooling. Traditional mold cooling methods are drilling holes in the mold to form a mesh coolant channel. The geometry of the channel formed by the method is limited. For a simple mold, this cooling method can achieve the desired effect, but for more complicated molds, the cooling effect will be greatly reduced. The core with conformal cooling method, The metal additive manufacturing method is used, that is, the core is processed layer by layer by means of additive. The additive manufacturing method is very flexible, which means that the complexity of the coolant channel in the mold is almost unlimited. Under the mold, the conformal cooling passages in the mold can maintain the same distance from the mold wall, so the cooling effect is more uniform; or in the area where the hot spots in the mold are concentrated, the density of the conformal cooling passages can be increased, thereby providing the areas with the density. Faster cooling.
The simulation process shows that after the conformal cooling, the cooling efficiency of almost all hot spots can be effectively improved, and the temperature of the mold wall is reduced by up to 70 °C.
Finally, Kärcher skillfully improved the product design in the mold area where there is not enough space to set up the conformal cooling channels, thus alleviating the molding cooling problem.
Based on the simulation results, Renishaw proposed a comprehensive improvement for Kärcher, pointing out that conformal cooling can be used to improve the temperature control of hot spots in the mold, so that the cooling rate of each part is more uniform and the overall cooling time is reduced. The mold design incorporates two metal 3D printed cores that provide a conformal cooling function to a defined hot spot.
Renishaw used thermal imaging to check the effect of the modified mold design, confirming that the mold wall temperature can be lowered by 40 ° C to 70 ° C, and the cooling time can be reduced from 22 seconds to 10 seconds, a reduction of 55%. Kärcher injection molding The technical team's head, Volker Neu, also proved that the new mold design and the re-adjustment of some peripheral processes (filling system, processing system, etc.) can shorten the molding cycle from 52 seconds to 37 seconds. Now, The daily production capacity of each injection molding machine can be increased from 1,496 to 2,101.
Subsequently, Kärcher also improved the design of other molds. Renishaw used the additive manufacturing technology to produce these mold cores with conformal cooling. Mr. Hüsken provided active support for Renishaw during the manufacturing process.
Mr. Hoffer was initially skeptical about the project. Now he said: 'The results are better than expected. Renishaw sold us a complete improvement plan. They conducted a comprehensive inspection and analysis of the molds we used to help us. Achieve optimal production efficiency. '
Renishaw has always provided its customers with exclusive solutions based on a combination of various technical means. 'In our case, it involves both traditional cooling technology and conformal cooling technology, including cooling in the traditional way. The liquid channel, which also includes the core processed by additive manufacturing, also involves the vacuum brazing technology of the core,' he added. 'With all these technologies, we can work out the most suitable production solution.'
Through this project, Mr. Hoffer has gained important knowledge and experience. 'In the future, we will pay more attention to molding cooling efficiency in the design stage,' he said. 'At Kärcher, cooling efficiency calculation will become a key part of mold design. Using this information, we can decide whether to use a traditional cooling scheme or a conformal cooling scheme.
'Renishaw has provided us with perfect support. In this project, Renishaw is our right choice; in the future, when we need to design a closed contour temperature control scheme, I believe it will be our most suitable. Partner, Mr. Hoffer concluded.