A cut above

CompoTech says it has developed a new hybrid metal and carbon fibre (CF) composite milling cutting disk in collaboration with Hofmeister - Innovation. With an initial ambitious target of a 50% reduction in overall machining time, the final design exceeded the goal. The hybrid four-disc tool increased both the cutting speed and feed rate. The result is a high productivity hybrid milling tool that can operate 78% faster on the same milling centre than a standard steel two-disc cutter.

Key production benefits of the hybrid four-disc milling tool include: lower inertia moment, resulting in lower energy consumption cost savings; lower thermal-mechanical load on milling machines; better anti-vibration damping properties, increasing slot hole machining accuracy; smoother machine operation, enabling higher quality surface finish; significantly increased output rates and productivity. An added cost benefit for manufacturers is that the cutting edge durability of the hybrid tool - which has 40 extra cutting inserts - is almost five times greater.

Exceeding expectations

The milling tool collaboration project was initiated by Hofmeister after receiving an inquiry for a four-disc milling tool from a leading European chain manufacturer looking to improve output rates and reduce production costs. By using CompoTech’s carbon fibre technology in the design and production, a new lightweight CF composite and steel hybrid milling tool was successfully developed with two additional cutting discs. The four-disc hybrid tool was well within the specified Doosan Mecatec HM63H twin-pallet horizontal machining centre’s 25kg maximum weight limit; this was not achievable using four conventional metal disc cutters, which individually weigh 7.93kg.

To further boost machining performance, the hybrid tool design included additional cutting inserts per disc. The hybrid milling tool has a total of 64 cutting inserts on four discs compared with only 24 on the standard two-disc milling cutter. The net result was vastly superior machining performance, reducing the machining time of a forged steel chain link component from 45 to 10 seconds, exceeding expectations.

Proven R&D partnership

Hofmeister is an established privately-owned engineering company based in the Czech Republic, which specialises in the development of complete machining technologies. Hofmeister - Innovation is the R&D arm of the company.

Hofmeister - Innovation and CompoTech have a long-established partnership developing and manufacturing next-generation lightweight hybrid tooling. This proven collaboration between the R&D teams of the two companies combines CompoTech’s expertise in CF composite technology and production know-how with Hofmeister’s extensive range of specialist capabilities, providing the tool specification, technology and precision production of the finished tool.

CompoTech’s facilities are located in the south-west of the Czech Republic near to Hofmeister’s facilities in Pilsen. The company has a successful track record in replacing traditional metal parts on automated assembly lines and industrial systems. Over the last 15 years, CompoTech has focused on the development and production of CF beams for automotive robot assembly lines and CF beams for heavy metalcutting machinery.

In recent years, the strategic focus has extended to include accompanying components, such as CF rotary shafts, spindles and tools and toolholders, which the company sees as complementary and holistic for machine tool performance improvement. Critical investments made recently on 6-axis fibre placement technology and rapid in-house tool making capabilities using 3D printing, have both helped CompoTech to accelerate innovative CF tool component design and development.

Lightweight hybrid design

The hybrid tool design uses a lightweight epoxy composite with ultra-high modulus carbon fibres for the inner section of the individual milling discs. The proprietary continuous fibre manufacturing process developed by CompoTech enabled the production of fully-integrated hybrid milling discs with an outer band of 16 metalcutting inserts.

“We were able to find a solution for the CF composite disk interface between the steel hub and the steel ring which was able to transfer the loading during milling and provide sufficient rigidity,” explains head of analytical design for CompoTech, Robin Poul. “This was achieved using a combination of an interlocking shape design and steel bolts.”

The semi-finished CF composite components for the hybrid discs were produced and assembled by CompoTech using semi-finished steel components supplied by Hofmeister. The final machining of each hybrid cutting disc and assembly of the complete hybrid milling tool was also carried out by Hofmeister. The entire four-disc hybrid milling cutter weighs only 16.25kg, well within the maximum 25kg tool weight limit of the BT50 L 150mm master mandrel on the Doosan Mecatec HM63H.

Superior tool performance

Test milling of the 200mm diameter four-disc hybrid tool was undertaken on a forged high-strength steel connecting link using the Doosan Mecatec HM63H machining centre. The milling operation to accurately cut to tolerance the side and the bottom faces of the forged link was completed in just 10 seconds using the four-disc hybrid milling cutter - 35 seconds faster than the two-disc metal tool.

Measurements made on the vc and vf rates for both types of milling tools showed that the hybrid CF four-disc milling cutter had a 50% faster cutting speed and a 54% higher feed rate. Tool life durability data was also gathered, which recorded approximately 250 pieces machined before a tool change for the two-disc milling cutter, compared with more than 1,200 parts (>4.8 times more) produced using the new hybrid four-disc tool.

Comparative testing

The comparative testing carried out during the project demonstrated that the hybrid four-disc milling tool can be used for machining in precisely the same way as a conventional all-metal two-disc milling cutter, but with added machining speed and durability. These significant benefits more than justify the initial higher cost of the hybrid cutter, which Hofmeister has estimated has an investment payback period of only around three months for a high volume producer.

“This has been another excellent collaboration between the R&D teams from both companies,” comments Hofmeister’s head of R&D, Pavel Kožmín. “We have developed an even better performing milling tool than we originally expected thanks to the unique carbon fibre epoxy composite design and production capabilities of CompoTech. The new hybrid milling tool project has exceeded our customer’s expectations with the operational and commercial benefits provided.”

This hybrid four-disc milling cutter tool offers manufacturers the opportunity to save time and money by achieving significantly higher unit output volumes using existing CNC milling centres, with lower overall production costs. Business benefits from using the new hybrid tool include debottlenecking, improving profitability, and delaying or avoiding the need for further capital investment to achieve growth targets.

https://hofmeister.eu

www.compotech.com