by Andrei Petrilin & Marcel Elkouby
Over the last few years, leading edge technology has resulted in multi-tasking machine tools and machining centres with impressive working possibilities. At the same time,
this progress in machine tool engineering is significantly changing metal cutting technology.
Multi-functional machine tools increasingly widen the range of machining operations that can be performed. Technological processes developed for these machines are oriented to maximize machining operation for one-setup manufacturing, creating a new source for more accurate and productive manufacturing. Milling gears and splines are one of the operations suitable for performing on the new machines.
Gear (and spline) making is a complicated process that involves milling, chamfering, grinding and other operations. With batch manufacturing, the majority is made on specific machines: gear hobbing, gear shaving, gear grinding and so on. Developments in technology have changed the limits of hardness for cutting and considerably increased operational accuracy. This in turn has reduced abrasive machining in gear making while decreasing rough cutting. The modern multi-functional machines, which meet the requirements of one-setup manufacturing, have proved to be perfect for various gear making operations.
These new machines require appropriate tooling and cutting tool manufacturers should prepare their response accordingly, which is why producers of general-purpose rotating cutting tools are reconsidering the role of gear-milling cutters in their program for standard product lines.
As an example, Iscar has a three-point program for form gear making tools:
- Milling cutters carrying indexable inserts
- Milling cutters with replaceable cutting heads based on the T-Slot concept
- Milling cutters with replaceable Multi-Master cutting heads
ModuGear, the family of indexable gear milling cutters, reflects a conventional design approach, comprising disk-type tools with tangentially clamped LNET inserts. The tangential clamping principle provides an extremely rigid and durable cutter structure that results in stable and precise enough machining tooth or spline profiles. Its principal application is producing involute gears of relatively low accuracy and rough gear milling operations that feature a 1 to 1.75 mm gear module range.
The cutters with replaceable heads have two advantages compared with gear milling tools carrying indexable inserts: they offer better precision and allow the design of gear milling cutters that are small in diameter, but feature quite a large number of teeth. The replaceable heads are mounted in bodies (shanks), which are standard line products suitable not only for the gear milling heads but for other types of heads (for milling slots and grooves, for example). This enables customers to increase operating efficiency of the versatile shanks and to reduce tool stock, providing added value.
The replaceable solid carbide heads of the T-Gear SD D32-M…-SP15 family are mounted in standard T-Slot SD-SP15 cylindrical shanks and transform the latter into 32 mm diameter gear milling cutters. The precise profile of the cutters’ teeth and the accurate and reliable SP-connection between the shank and the head define its range of use: milling involute gears featuring a 1-2 mm module.
Both types of milling cutters, indexable inserts and those with replaceable heads, meet the requirements of standard DIN 3972, basic profile II.
There are two types of Multi-Master spline and gear making solid carbide heads: MM SS heads for milling involute spline shafts, and MM SG heads for milling spur gears. The main application field for these heads is the efficient production of small to medium batches of spline and spur gears in various industrial branches.
The world of gears is very rich and multiform, embracing a wide variety of external and internal gears: spur, helical, bevel, hypoid, and more. Manufacturing these gears encompasses an entire, dynamic industrial sector with its own methods, equipment and tooling. The introduction of multi-tasking machines in gear milling as an alternative to a dedicated machine represents a new challenge to this sector, and producers of commonly used cutting tools should be ready for this significant change. SMT
Andrei Petrilin (left) is technical manager of indexable milling tools, and Marcel Elkouby (right) is material sciences R&D manager at Iscar Tools.