Face milling enhanced
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Face milling enhanced
 
Article Introduction
In the beginning of february 2005, seco tools introduced a new type of face mill under the name quattromill. A new design, a revised choice of material for milling cutter bodies, new cutting-edge concept, and a new tool clamping principle meant that the quattromill stood out for simple, reliable machining of all materials with high productivity. Last year, extensive practical tests confirmed the claimed technical and economic advantages. With quattromill, seco tools is once again establishing a reputation for being one of the most innovative tool manufacturers.

Article Description
As early as the 60s of the last century, Seco Tools, set the standard for being the most innovative tool manufacturer with the introduction of mechanically clamped square inserts, the S25M carbide grade and an attack angle of 75-degree for the cutter. The positive cutting R257.1 face mill marked the beginning of modern milling. To the specialist, all the new characteristics of the recently introduced QuattroMill were immediately and clearly recognizable.

During the 1981 EMO in Paris, a second milestone was reached with the R220.13 face mill, which is the basic face mill that is still used by many companies. With this super-positive insert-milling cutter, Seco was the first to succeed in providing the inserts with an adequate coating. The T25M coating improved cutting properties and extended tool life. This further increased the productivity of the milling process.

In 1996, a new generation made its entrance with the OctoMill. As the name suggests, it is a milling cutter that makes use of octagonal inserts. In fact, it was not the shape, which impressed the technically well-informed public, as inserts of all basic geometric shapes (from circular to triangular, from diamond-shaped to hexagonal) were available in the market - each with their own logic. What appealed to them was its universal applicability for almost any milling process and method - face milling, slot milling, contour milling & pocket milling; linear, circular, helicoidal & trochoidal milling: axial & radial milling; copy milling (2-, 3-, and 5-axes). Then there was the advantage, in terms of cost price, of the octagonal cutting-edge. The last stage of the present face milling evolution was reached with the introduction of Hexamill, a very robust milling cutter with hexagonal cutting edges. This milling cutter was suitable for heavy as well as difficult milling work with high feed rates.

Contradictory interests
Since the launch of the very first type of face mill with indexable carbide inserts, the R257.1 face mill, Seco Tools have been consistently concerned with the question of how to further improve this tool. And, it is here that the designers were often confronted with the need to balance conflicting interests. For example one can fit coolant channels so that the milling cutter can be used at higher cutting speeds, but this weakens its structure. For a given diameter, one can also increase the number of teeth to increase the quantity of material to be cut per unit of time, but this results in small chip cavities and less support for the insert. The latter limits the maximum cutting forces and results in a lower feed rate. This posed a serious problem. However, as the QuattroMill uses a different type of material for the cutter body, it offers a way out of this dilemma. A much tougher material provides the possibility of keeping the area of the material support per tooth, smaller. In this case, increasing the number of teeth is a real option. If the higher chemical sensitivity of the tougher material is countered with an adequate coating, the circle is complete, and a major innovation has been achieved.

While designing the QuattroMill, several aspects, like the geometry and accuracy of the cutter body to the selection of the carbide grades for the inserts, and from the design of the insert clamping screw to the shape of the insert seats, were considered. This resulted in a strong, soft cutting, and user-friendly face mill, which could be used at high feed rates and/or cutting speeds. Besides, it is an innovative tool clamping system that improves the tool life of the cutting edges and minimises the runout of the milling cutter.

Accessiblity aspects
The QuattroMill is a face mill for use on modern milling machines and machining centres, available with two insert dimensions (12 and 9 mm), and with a diameter ranging from 20 mm to 200 mm. The user-friendliness is apparent, among other things, from the easy indexability of the inserts (compared, for example, with the octagonal OctoMill) and the simple, reliable clamping of the inserts in the milling cutter, and of the milling cutter on the machine. The QuattroMill is suitable for all face milling operations in all materials. However, it lacks the universal applicability of the OctoMill. On the other hand, the QuattroMill could be optimized for face milling work without compromise. The super-positive geometry, an effective rake angle of up to 35 (ultra-positive geometry), gets the most out of the available machine output. The robust, square inserts allow cutting depths of up to 6 mm.

The QuattroMills cutter body is manufactured on advanced CNC machines with a very high degree of accuracy. A special coating provides the cutter body, with its high degree of hardness of 800 Vickers (approximately 64 HRC), high wear-resistance and hence long tool life. Additionally, the corrosion- resistant properties ensure that the attractive appearance of the milling cutter is maintained for a very long time.

The insert seats, with their redefined geometry, have a positive 10-degree rake angle in the cutter body. The relatively thick, strong yet tough inserts, with integrated anvil - features that minimise the risk of insert breakage - are also manufactured within close tolerance limits. And, when the tool is used, it leads to high machining reliability. The inserts are available in seven different geometries, from flat inserts to inserts with a +25 cutting geometry. In addition, there are seven carbide grades (including the new T200M and T350M). Further, CBN inserts are also available. The letters LF in the insert code indicate that the inserts are of the complete full top type, which means that the complete full top layer is manufactured from CBN material. The wide range of inserts enable the user to machine steel, stainless steel, cast iron, hard materials and even super alloys very economically. Besides, being a new concept for the cutter body and the inserts, the QuattroMill system also incorporates the strong, special insert clamping screw, which Seco has developed in cooperation with the Swiss manufacturer, SFS. Therefore, the numbers of spare parts are limited (mainly because there are no separate anvils, which are now integrated in the inserts). Screw thread, length, choice of material, and the shape of the head have been specially selected with the user in mind. Indexing the inserts is a simple operation with the TorxPlusTM screw, and is also foolproof: it is impossible to clamp the insert in the wrong position. The inserts are secured according to the principle of central insert clamping (centrelock clamping). The screws need not be fully slackened to index the inserts, and indexing is even possible, while the milling cutter is located on the machine.

The user may opt for a normal, close or coarse pitch of the milling cutters. A relatively small number of teeth (coarse pitch) are used, among other things, where the machine capacity is limited, and close pitch is preferable while machining cast iron and other short-chip materials, if productivity (= high table feed) is important, and it also provides an economic solution when machining hard materials. Within the QuattroMill programme, one also finds smaller milling cutters with integrated shanks (diameters of 20-32 mm).

For all milling cutters with diameters of up to 125 mm, through coolant channels are standard and minimise the noise during production. Further, the extremely soft cutting ensures that the QuattroMill is a low-noise milling cutter par excellence.

Is user-friendliness worth the money?
Producing workpieces correctly and profitably is the basic objective of the machine shop. This is all very well in theory, but unfortunately it is not always that easy in practice. The basic advantages of the new QuattroMill milling cutter from Seco are that the milling cutter is safe, reliable, and user-friendly. The intrinsic characteristics of the milling cutter also render it less sensitive to irregularities (*) during production. However, the question is whether this is worth the money or helps increase productivity.

Finishing workpieces correctly (dimensional accuracy, shape accuracy, surface roughness, and material structure) depends on the expert knowledge of the operators. If this fails, workpieces are rejected, and this detracts considerably from the profitability of the company. If the operators are not well trained, it also - means that the company is unable to undertake difficult work, and it is obvious that this will seriously undermine its competitive position.

But even if well-trained production workers are available, profitability is not always automatic. The frequently heard remark, "Cant it be a little cheaper and faster?" speaks volumes. If the workpiece is not ready on time, the costs increase and the company also runs the risk of losing its customers).
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Posted : 9/5/2005

 
 
Face milling enhanced