The main idea it’s to subtitute the very high cost of PCD tools by HSS+coating or Hard metal+coating for the construction of complex shape cutting tools to machine different type of wood materials.
In this way the very high cost PCD tool (but a very long life tool) passes from investment (the tool life of PCD is very, very long, and failure is usually for a bad use) to be a consumable. Here the innovation is not only technology, is a manner to understand the process, times and costs: PCD is the old practice, and use cheaper (but with sorter life) a new point of view in the wood sector. Three innovation aspects:
- Wood is a natural composite, therefore some ideas for CFRP, GFRP could be applied on wood
- Coating for this application could be different to metals: there is not scientific literature about it.
- Industry in Piamonte (Alps) and Basque Country (and close regions) are important, and demanding a dramatical reduction in production costs (Ikea is the Devil!!!!)
The objectives of the project are the development of innovative and efficient wood frames and furniture manufacturing to support wood industry.
The objective regards efficient and economically improved wood manufacturing, thanks to the development of specific PVD superhard nanostructured coatings for wood working tools and new machining cutting parameters.
In the wood industry, the improvement of performances during the last few years is mainly due to new developed machines and to the automation of the processes production. Nevertheless, innovative cutting tools were not developed, so that machines performances are at present limited by the tools performances. Those problems are more important in primary transformation of wood (sawmills, veneer manufacturers) where steel tools are used. The widespread use of steel tools is due to large dimensions of processed raw material and the balance between their hardness and resistance to shocks.
Besides, in the secondary wood transformation, steel tools are also used for specific operations like wood planing and shaping because of their low price and facility of re-sharpening. The industries that work in the transformation of wood, cut materials that contain a lot of knots, dust, sand, stones etc. Therefore the industries use large quantities of tools so they face the problem of tools blunting due to abrasion and breaks of the knife edge after contact with raw material and shock. That’s why they are interested to have improved tools. Those improved tools are also interesting for other sectors within the wood industry like: panels production (particle boards, fibre boards, Medium Density Fibreboard (MDF), …), decorative veneer production (veneer slicing), furniture and packaging industry.
It has been illustrated by many examples(ref) , that protecting tool substrates by means of thin PVD- (physical vapor deposition) or CVD- (chemical vapor deposition) coatings greatly enhances tool lifetime and allows for the use of faster, more productive processing parameters while maintaining the initial macro-geometry of the tool. Depending on the tool type, it will be commonly made from either tool steels (HSS, cold-working steel) or cemented carbides, where the focus of this project will be on carbide substrates for cutting tools and mould steel for die forging.
New cutting parameters will enhance productivity as well as precision and reduction of scraps. High spindle speeds will be allowed by advanced centering and alignment systems as well as by development of dedicated spindle and gripping devices. The project aims at re-launching the wood industry by allowing process efficiency enhancement and cost reduction with a consequent benefit for the wood and furniture sector.
The contribution of Meccanica Bicchi in this project was the complete design and drawing of the high speed electro spindle and the specific fixture to balance tools, plus the construction of both the prototype devices.
In particular, it has been committed in the following activities:
- Individuation of the best mechanical technology for the vibration reduction of the spindle rotor and the appropriate high speed bearings
- Sizing and selection of the adequate cooling system for the high speed electro spindle.
- Selection of the best clamping solution for the balancing fixture.
- Mechanical detailed design and drawing of the assemblies of both prototype devices, complete with the drawings of all components.
- Manufacturing (turning, milling and grinding) of all specific components.
- Purchase of all standard components.
- Purchase and assembly of the cooling system.
- Complete assembly of both prototype devices.
- Testing of functionality at high speed of the electro spindle.
- Testing of accuracy of the balancing fixture.
Although during the design have been used all the tricks of which we were aware, during testing at high speed, there were numerous failures of the main bearings. This was due to the shape of the rotor, which resonated to the critical speed of 50,000 rpm. Reconstructing the rotor with an appropriate shape, the engine has passed without problems the maximum speed of 60,000 rpm: speed that was set as a goal to achieve.
The construction of the tool centering fixture for the balancing operation, however, didn’t present particular unexpected problem, for the fact that it is based on a principle (retracting tapered elastic bush) that Meccanica Bicchi normally uses for other applications. Due to the particular accuracy with which were built the components of that fixture, positioning accuracy of the same has been verified (using calibrated master) within 0.005 mm Total Indicator Reading (TIR), therefore its use has allowed easy access to the balancing grade G1 on the tools used.