Industrial Composite Structures

Composite solutions for machine tool and automation

Composite design translates lightweight, high stiffness and damping material properties to improve machining, laser cutting and automation.

CompoTech has found itself in a unique position, bridging the gap between lightweight composite design and the ‘heavy’ metal industry. Using the properties of ultra-high modulus pitch fibre with our in-house automated fibre laying (AFL) and advanced winding technology.

Our team of engineers have designed and produced composite components in machine tool and automation applications for over 20 years. Today, we are one of the world’s foremost designers and producers of composite components for machine tool and automation applications. The application of light weight, high stiffness components for this sector is targeted at improving machine performance, efficiency, accuracy and lifetime cost.

Stiffness of Steel at 1/4 of the mass

CompoTech’s automated AFL process allows the optimal processing of brittle pitch fibres. Converting the fibre into a composite beam allows the replacement of the same section steel beam with potentially up to twice the axial stiffness at a quarter of the weight.

If you want to cut faster, you need to accelerate your machine tool more quickly. To achieve this with the same accuracy of the cut, the stiffness of the manipulating structure needs to increase. However, to improve the overall performance of a machining system, there is a more complex balance of natural frequency and damping to consider.

Natural frequency, a function of stiffness and weight

Using the low mass and high stiffness properties of pitch fibre results in high natural frequencies of a part. In machine tool design, the harmonic resonance often limits the operating speeds. Therefore, this point is vital to bringing the properties required to make a step-change in performance.

Vibration behaviour can be optimised in several ways. The part’s dimensions, internal structure, and wall thickness can be adjusted to tune its natural frequencies, but the main influence in primary frequencies is the fibre choice and lay-up design.

Damping during machining

One area of particular focus in machine tool design is optimising vibration-damping properties. Carbon composite parts already provide good vibration and damping characteristics compared with steel or aluminium alternatives. Vibration is crucial in many machining applications that it requires special attention during design.

Damping materials, including rubber and cork fillers, can be incorporated into the structure. The inclusion of internal high-density foam reinforcements improves the vibration stability of thin-walled parts. As an added benefit, the foam can dampen audible frequencies, delivering health and safety benefits for the machine operator.

Lightweighting machine tools

Reducing the weight of sizable moving components allows designers to select lower-rated ancillary elements. Once a machine tool goes into service, the reduction in energy costs or increased life span of such parts provided by this weight reduction can pay back any additional material costs, well within the machine’s lifetime. Specific components, especially tools, can offer new functions or increase a machine’s performance when machining structures that would typically be outside of its payload capacity.

Thermal expansion

A composite shaft or beam design allows zero thermal expansion in one direction as a function of the fibre properties. For high-speed milling, creating a hybrid steel-composite spindle to reduce thermal expansion considers the combination of steel parts and specific placement and angles of the fibre to be close to zero.

Testing has shown 75% less displacement on the shaft alone and a 30% decrease within the spindle motor. This difference can be significant for milling accuracy and the load on the bearings, and hence the life span, in spindle motors machines without coolant.