metalworkingmag.com
07
'22
Written on Modified on
PH HORN News
Mastering processes: High feed milling
Tool systems manufactured by Paul Horn GmbH offer users the ability to design machining processes for high productivity and cost efficiency. Especially in tool and mould making, high feed milling can be used economically and productively. High performance milling is not only defined by high infeeds, but in high feed milling also by small infeeds coupled with high traverse speed of the cutter.
Machining applications have changed and challenges have become more complex and demanding. Shorter product life cycles and reduced development times dictate that several different components must be produced on one machine in shorter cycle times. For the tool manufacturer, this requires designing tool systems for the different applications. It means, for example, that a tool may not only be used for corner milling, but should also have the optional ability to plunge cut.
Another aspect is modern machine dynamics. The acceleration and deceleration of the axes as well as their synchronisation have been significantly optimised. For relatively new technologies such as trochoidal and high feed milling, tool systems must be able to withstand the high dynamic loads.
The DAH high feed milling system enables high metal removal at low infeed rates.
Low infeed - high metal removal rate
A few years ago, Horn introduced a system for high feed milling - DAH cutters for face milling. Due to the load being in the axial direction, the tool and spindle mainly experience compressive force and the shear forces are relatively low. Due to their low tendency to vibrate, the tools are able to withstand the high loads typically generated by a feed per tooth of fz = 1 mm at cutting depths ap up to 1.2 mm.
The large radius on the main cutting edge of the three-edged inserts creates a soft cut, ensuring an even distribution of the cutting forces and long tool life. On the inside, a small cutting edge radius ensures trouble-free and fast plunging. A primary and secondary clearance angle leads to a stable wedge angle and very good cutting edge stability. Due to significantly higher feed rates compared with conventional milling, metal removal rate in high feed milling is significantly increased, despite the lower infeed depths.
One Horn customer manufactures a component made from 42CrMo4, quenched and tempered to 1,000 N/mm2, 14 times faster than before. The challenge was to produce an axial recess in a round workpiece. The recess has an outer diameter of 240 mm, is 40 mm wide and has a depth of just under 90 mm without finishing allowance. Using a toroidal milling cutter with indexable inserts, the customer needed around 100 minutes to rough the recess. The life of the five-flute tool was 30 grooves per insert and the long process demanded optimisation.
Horn applications engineers changed the process to high feed milling. The cutting speed is programmed at vc = 150 m/min. The tool plunges helically into the workpiece with a continuous infeed depth of ap = 1 mm. The cutting feed rate (rotational speed of the component) is vf = 4,777 mm/min andthe feed per tooth is fz = 0.8 mm. The new time to machine the groove is only seven minutes,. while the life of the inserts has trebled to allow 90 components to be produced.
Helical infeed for roughing bores and pockets is also possible with the DAH milling system.
Eight usable cutting edges
In 2020, Horn presented a further development of the tool system for high feed milling. With its DAH82 and DAH84, the tool manufacturer introduced a new generation of tools for this milling process. The eight usable cutting edges of the precision-sintered insert offer a favourable price per cutting edge and hence economical production. Despite the negative mounting position, the positive cutting edge geometry ensures a soft and quiet cut as well as good chip flow.
Horn offers the inserts in the substrate SA4B, which is suitable for universal use with various materials. The large radius on the main cutting edge of the insert produces a soft cut, ensuring an even distribution of the cutting forces and thus long tool life. Maximum cutting depth is ap = 1.0 mm (DAH82) and ap = 1.5 mm (DAH84).
The tool system has been successfully launched onto the market. One application example in tool and mould making involved roughing of a mould. The user needed about 15 minutes to complete the machining process with the tool system for high feed milling previously used. With the DAH 82 system, Horn engineers were able to reduce the machining time to less than six minutes. This was achieved by increasing the feed speed from 2,500 mm/min to 6,900 mm/min. In addition to the reduced machining time, tool life per cutting edge also increased.
www.phorn.de
