Gear cutting – milling – or planing – Milling – With means to control temperature or lubricate
Reexamination Certificate
1999-05-25
2001-07-03
Howell, Daniel W. (Department: 3722)
Gear cutting, milling, or planing
Milling
With means to control temperature or lubricate
C408S097000, C409S231000
Reexamination Certificate
active
06254321
ABSTRACT:
The present invention relates to a unit that includes a high-speed cutting tool, such as a milling tool or drilling tool.
The inventive tool forms part of a system, and the invention and the system components will therefore be described separately.
It is known that high cutting speeds provide a better result with regard to surface structure and tolerances than low cutting speeds. High cutting speeds normally result in faster removal of material from the workpiece, i.e. in a greater machining capacity.
Milling of lightweight metal parts in the aircraft industry to reduce their weight is one practical example in this respect. In this regard, it may be desired to leave material between the milled or machined part so as to form stiffening ribs or flanges. Besides being relatively time-consuming, it is not possible to form ribs of desirable thinness with the aid of present-day milling equipment. Circuit board machining operations are another practical example in this regard. The circuit boards are normally machined with the aid of so-called spiral drills which after having penetrated through the fibre board are moved in the plane of the board so as to form a groove therein.
Milling tools and the drilling tools are both subjected to bending stresses and axially acting forces in operation (due to the inclination of the milling tool and the drill bit). The tool is thus subjected to forces which, if the forces are constant and the rotary speed increased, will increase the machining power of the tool spindle. A tool spindle that rotates at 1,000 r.p.m. and a power of 10 kW generates the same tool cutting forces as a tool spindle that rotates at 100,000 r.p.m. with a machining power of 100 kW. However, a technical problem resides in the ability to take-up theses forces in bearings and journals at said high tool speeds. At present, the technical limit with respect to a typical tool spindle bearing comprised of hybrid ball bearings (steel rings and ceramic balls) is about 50,000 r.p.m. and 50 kW, wherewith a further problem resides in managing the critical speeds generated by the system.
The present invention, as defined in the characterizing clauses of respective claims, enables the tool to operate at speeds above 100,000 r.p.m. and at a power of 100 kW with very great precision and with rapid machining of the workpiece.
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Bjorn Lind Finance & Property
Howell Daniel W.
Intellectual Property Group
Pillsbury & Winthrop LLP
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