A US-based processor is using what's dubbed as the world's largest long fiber injection system to manufacture a two-piece roof made of polyurethane for agricultural machinery. A long-lasting paint surface is applied directly in the mold using IMP (in-mold painting) in a fully automated process.
German machine builder KraussMaffei ((Munich) delivered the machinery which employs a double-shuttle mold carrier system, for manufacturing the ultra-large lightweight components to Romeo RIM (Romeo, MI).
Shuttle mold reduced overall cycle time to 9-10 minutes.
Five-square-meter farm-machinery rooftop weighs just 23 kg.
While boasting enormous dimensions of approximately 2.5 x 2.1 m (8 x 7 ft) and an area of over 5m2 (56 sq. ft.), the complete two-piece roof weighs less than 23 kg (50 lb) and meets all requirements regarding flexibility, durability, low weight, and cost-effective manufacturing. Another contribution is the option for functional integration on the rear side, where the dome and ribs are attached.
At the center of the system is the largest mold carrier built by KraussMaffei to date, with a mold clamping area of 3660 x 3660 mm (12 x 12 ft) on the molds and weight of up to 40 US tons (36 metric tons). The mold carrier with dimensions 22 x 9.5 x 5m and a clamping force of 400 tons is equipped with a "two-shuttle system," which alternately brings one of two bottom halves of the mold into the mold clamping unit. While the long fiber injection process and the reaction time are running in one mold, the second mold can be de-molded and prepared for the next cycle. Every 9 to 10 minutes, therefore, one of the two elements for the complete roof is formed.
The mold carrier is equipped with a hydraulic four-axis parallelism control for precise component thicknesses and reproducible processes, which also ensures parallel closing of the molds for asymmetric components or off-center mold clamping. "The new mold carrier will enable us to produce, for instance, even larger exterior body panels for all of the markets we service like the agricultural and heavy truck markets and to do it in a cost-competitive way," explains Condeelis.
Two industrial robots, each of which are equipped with a long fiber injection mixing head of, are moved over the mold to dispense the long fiber injection mixture. Beforehand, two additional industrial robots can be used to apply a layer of paint (in-mold painting) and a barrier layer into the bottom mold, which prevents the fibers from penetrating the visible surface. Consequently, completely painted components with excellent mechanical properties and premium quality surfaces are manufactured in a single pass. "The shuttle system incorporates appropriate explosion protection to prevent problems from arising in areas where paint evaporates," says Cord Hagenmeyer, project manager at KraussMaffei. "
And while the machinery may be gigantic, operability has not been compromised. This is provided for by a swivel device on the movable upper mold clamping platen. When the mold carrier is completely opened, the upper plate with the top mold can be swiveled out by 90 degrees.