For its new model GBH 36 V-LI Compact Professional especially lightweight and almost vibration-free cordless hammer drill, Bosch selected the resin Ultramid B3EG7, a particularly rigid and impact-resistant glass fiber-reinforced grade of polyamide 6 from BASF, that meets the demanding requirements for durability. The hammer drill weighs only 2.9 kg and, at 12 m/s2, has a low vibration value to minimize fatigue when working.
The two halves of the housing for the new Bosch Model GBH 36 V-LI Compact Professional cordless hammer drill are molded from Ultramid® B3EG7, a rigid and durable grade of polyamide 6 from BASF. It has to withstand the continuous vibrational loads where the two halves meet at the bottom, a requirement that professional-grade power tools must satisfy. Bosch employs the latest version of its patented vibration control technology in this hammer drill, which weighs only 2.9 kg: By using an elastomeric bellows (black) between the impact mechanism and the handle, transmission of vibrations to the operator’s hand is reduced to a minimum. Photo: BASF - The Chemical Company, 2009.
Low-vibration professional hammer drill with new technology
In the latest version of the cordless hammer drill with Bosch Vibration Control developed by Bosch, the front section of the impact mechanism is largely decoupled from the handle section at the back. While an elastomer bellows at the top cushions the motion of the impact mechanism, the plastic housing on the handle below provides a joining function.
Requirements for the resin
For this challenging application, Bosch looked for a resin that could withstand the continuous swinging load applied at the lower joint over a long period of time. In particular, the impact resistance and durability of Ultramid B3EG7 allow it to fulfill these requirements for the entire service life of the hammer drill. In addition, the resin is UL-listed (Underwriters Laboratories), thus it can be used in power tools intended for the American market. BASF's application engineers assisted in development of the product by conducting numerous investigations, including not only vibration tests on a shaker but also X-ray examinations to detect cracks, simulations for mold filling behavior as well as shrinkage and warpage test during the 3-component injection molding process, a challenging injection molding operation. The resin is available worldwide and is colored by BASF in the blue typical of Bosch products.
Vibration in power tools
For the European market, EU Directive 2002/44/EC dated 6 July 2002 governs the magnitude and duration of arm vibrations to which an individual may be subjected in the course of his/her daily work with power tools. The time that an employee may work with a vibrating power tool depends on how strongly the tool vibrates, among other factors. With its patented Bosch Vibration Control, the company has developed a method that largely decouples the impact mechanism and handle from one another and with the aid of which the vibrations reaching the arm are reduced to a minimum. The new cordless hammer drill made from Ultramid is one of these low-vibrations tools.