Mold cleaning is a challenge with a very small, 0.8 gram light injection-molded part with filigree contours. By using a dry ice cleaning system with MicroParticles, the Teltower Diehl Metal Applications GmbH in Germany optimized product quality, efficiently cleaned the mold and saved 400 hours of cleaning time per annum. This resulted in a 10% increase in plant availability as well as an increase in production capacity of 500,000 parts in plastic production.
Diehl Stiftung & Co. KG is an international technology group headquartered in Nürnberg, Germany. The company employs approximately 16,200 people worldwide in five business segments: metal, controls, defense, aerosystems and metering. Diehl Metal is one of the worldwide market leaders as a technology manufacturer of bars, pipes and profiles, synchronous rings made of special brass, steel and metal-plastic interconnection systems from its own value chain. Material development and production, sheet metal forming and forging technology, as well as surface, punching, press-in, injection molding and assembly technology are fully operated in their own company. Embedded in this business field, Diehl Metal Applications GmbH has specialized in innovative composite products made of metal and plastic materials.
At the plant in Teltow near Berlin, the company processes punched parts and approximately 850 tons of fiber-reinforced high-temperature-resistant plastics such as PPA, PBT, PEI, PPA and PA annually into complex multifunction parts for the automotive industry, communication industry, electronics and electrical engineering. For this purpose, the plastic production is equipped with 25 injection mold machines, on which the hybrid parts are extrusion-coated with the plastics at temperatures between 120 ° C and 400 ° C.
“Cleaning the injection molds has a decisive influence on the quality of our products,” explains Nicolas Hofmann, Process Engineer in Plastics Manufacturing, Diehl. “On the one hand, in order to meet the very narrow tolerances of only a few hundredths of a millimeter, on the other hand, the surface quality of the parts.”
In order to guarantee high product quality, the filigree forms were removed from the tool maintenance on an average of once a week. They were cleaned in an ultrasonic bath and then manually worked with brushes, re-assembled and finally were reinserted into the machines. This process involved about two shifts, which shut down production. In addition to the loss of production, two-day cleaning and an increased energy requirement led to the reheating of the injection molding machines. In addition, a short manual cleaning with brushes was carried out on each layer.
“With a very small and only 0.8 gram component of PPA, which is produced in a multiple form on three compartments, we had problems with the surface quality despite these time and personnel-intensive cleaning,” said Hofmann. “When, following multiple fault analyses and various tests, no solution was found with the plastic manufacturer. The material supplier recommended that we switch to the dry ice cleaning of Cold Jet dry.”
Just a short time later, the Teltow facility was testing the Cold Jet i3 MicroClean, a mobile dry ice cleaning device, in their plastic production. The i3 MicroClean is a compact, low-pressure, electrical blast system with patented MicroParticle shaving technology from dry ice blocks. It produces small, odorless MicroParticles which produce a more gentle clean than conventional dry ice pellets. MicroParticles are accelerated with compressed air to supersonic speed and can penetrate even into very delicate contours as well as cavities and ensures an effective but gentle treatment – even on surfaces that are prone to damage. On impact, a combination of kinetic, thermal shock and thermokinetic effects occur. The latter causes the dry ice to sublimate under ambient conditions – transferring from the solid directly to the gaseous phase. The dry ice expands within a few milliseconds to a volume of up to 700 times. At the impact point, this results in a microexplosion that spreads over the surface. This explosion wave has a very efficient lifting force, which reliably removes the deposits from the cavities.
In order to ensure that the MicroParticles do not damage filigree shapes, tests have also been carried out for abrasiveness. For this, identical metallic surfaces with sharp edges and corners were blasted with sand and MicroParticles over a defined period of time. No changes were observed with the dry ice treated surfaces.
“The results of the cleaning and abrasiveness tests were so convincing that we rented such a device at Cold Jet until the investment approval was granted by the company management in order to be able to work immediately,” said Hofmann.
The i3 MicroClean unit with various blast nozzles has been in use since May 2015 in the plastic production of Diehl Metal Applications in Teltow. They cleaned flat areas with two wide blast nozzles with 22 mm and 12 mm blast swaths. Dirt from undercuts, corners and edges is reliably cleaned with two different round nozzles. The applicator has a 360° rotary union so that all areas to be cleaned can be reached ergonomically. Integrated LED lights provide optimum illumination. The blast pressure and the quantity of dry ice can be individually adapted to the particular surface and degree of soiling, which ensures the most economical use of compressed air and dry ice.
“We can now clean the molds without dismantling them in the tempered state and achieve a perfect result,” said Hofmann.
The cleaning time has been reduced from 16 hours to one hour. And since it is now carried out directly in the plastic production, the staff of the tool maintenance department has more time for other tasks. The short manual brush cleaning per shift is completely omitted.
“We actually bought the device only for the application at the turntable machine,” said Hofmann. “Because of the increased personnel capacity in the tool maintenance department, the machine has already been paid off. Time saving is roughly 400 hours per year, resulting in a payback period of about 1.5 years.”
In addition, there is an increase in machine availability by about 10% as well as a productivity increase of approximately 500,000 parts per year. The plastic production facility in Teltow now uses the i3 MicroClean device, which is easy to transport from one machine to another, for mold cleaning at 10 injection molding machines for the production of three different components.