Download Free PDF
Automotive Product Finder Magazine | Lightweight with high performance
Lightweight with high performance
Lowering scrapping age for vehicles to have greater impact
TVS & Sudaram Clayton vows support of Rs 40 Cr to fight against COVID-19
The core bodies of grinding wheels are primarily made of steel. However, due to their weight, they have disadvantages for the grinding process. Lightweight core bodies represent an interesting alternative for numerous applications – in particular in the automotive sector. One solution for such applications is the use of lightweight composite fibre core bodies.
Grinding with high-performance grinding tools is essential for many users to manufacture components profitably, with high quality and at a high level of productivity. For this purpose, grinding wheels are used with a special core body, onto which the abrasive coating is applied. The core bodies are primarily made of steel. However, due to their weight, they have disadvantages for the grinding process.
Lightweight core bodies represent an interesting alternative for numerous applications – in particular in the automotive sector, the rolling bearing industry and for medical technology.
Highly productive grinding with CBN abrasives
Increasing the performance of grinding processes can often only be achieved with the use of high-hardness grinding wheels. However, CBN or diamond cutting materials used in these super-abrasives are significantly more expensive than conventional cutting materials, such as aluminium oxide or silicon carbide. For this reason, these tools have only a circumferential abrasive coating that is only a few millimetres thick and that is applied to a metallic or ceramic body. The core body must fulfil a number of requirements: Dampen vibrations, conduct heat and provide stability to the tool. As a result, grinding tool manufacturers such as Hermes Schleifmittel focus on the development and production of innovative and high-performance core bodies.
Steel core body – not always the best choice
For high-performance applications in the automotive industry, the rolling bearing industry or for medical technology, CBN grinding wheels rotate at cutting speeds of over 100 m/s. For this purpose, high mechanical loads, caused by the removal of material with high metal removal rates, act on the tool. For this reason, steel core bodies are used for these processes because they can ensure the required bursting safety and rigidity. A disadvantage, however, is their high specific weight, which makes handling difficult, especially for larger tools. Wheels weighing up to 100 kilogrammes and more can no longer be prepared and transported manually. Additional aids are necessary, and unproductive set-up times are increased considerably. In addition, the machine loads, in particular the loads on the spindles, rise significantly. The result is shortened service life of the spindle bearings and higher associated costs for maintenance. If the tool weight even exceeds the output power of the machine spindle, the grinding process is no longer safe as the spindle is unable to stably accelerate and decelerate the wheel due to inertia. Last but not least, more energy must be expended to get a heavy grinding wheel up to speed.
Lightweight body: the alternative today
One solution for such applications is the use of lightweight composite fibre core bodies. The advantage of these CFRP materials is the high specific strength combined with low density, eliminating the disadvantages of the significantly heavier steel core bodies. CBN tools with a CFRP core body (refer Figure 2) are used in a variety of ways for machining crank shafts or gear shafts, as soon as large wheel diameters are necessary or several grinding wheels are used in parallel – referred to as a wheel set – for example, in centreless machining.
The use of CFRP core bodies significantly reduces the tool weight by more than 70% compared to a steel core body. This not only facilitates handling, it also significantly reduces spindle loads. The CFRP core body also has better vibration damping and can compensate for negative process dynamic behaviour, which improves the surface qualities and this core body is also used in applications with a smaller tool diameter (for example, for medical technology applications).
Lightweight body of the future
The disadvantage of the use of CFRP basic bodies, however, is the low axial rigidity, and as a result, only processes with radial and tangential loads are possible. The use of acoustic emission (AE) sensors for contact detection or process monitoring is also not feasible with a CFRP core body. For these and other reasons, Hermes Schleifmittel has developed a completely new core body. The unique selling point of the Hermes Light Core is its application-specific design and the use of modern manufacturing processes. The process design of the planned grinding application is the basis for the estimation of future process loads. These are used to perform targeted strength analysis of different core body designs with the aid of FEM analyses. The result is a lightweight metal core body optimally designed for the specific load. Weight savings are thus achieved, just like a CFRP core body. At the same time, however, angular infeed grinding and other processes with axial load are possible, along with the use of AE sensor technology.
Hermes Schleifmittel is now able to offer its customers these individual analyses and tailor-made products. Hermes thus meets the high demands of the industry for the use of innovative materials, technologies and processes.
About the author:
Dr Tim Göttsching is the Head of Industry Management Bonded at Hermes Schleifmittel. He can be reached on email: T.Goettsching@hermes-schleifmittel.com Dr Florian Despang is the Head of Research & Development for bonded abrasives at Hermes Schleifmittel. He can be reached on email: firstname.lastname@example.org
Advertise Here [600 W x 90 H pixels]