Milling Inserts

It is a known fact that in the advanced industrial scenario of optimum productivity, milling is one of the most promising methods of machining.

With the break through of CNC machines, milling activities are rapidly replacing other traditional machining operations in industries such as the mould and die making sectors, the automotive industries and the mining and machine tool sectors. These high-end machines are capable of removing heavy stock at faster rate than any other method and also with considerably higher tolerance. Moreover, PCD / CBN Cutting equipments have enabled many difficult-to-handle machine's applications to be performed with lot more ease. Thus, activities such as high speed milling of die blanks with form generation and high speed milling of Aluminium alloys, achieving surface finishes of 0.4 to 0.8 u in Ra value, are way more feasible with the use of these equipments on rigid machinery. Machine tool manufacturers, working along with the tool manufacturer, have given the required strength for machines to be available with more rigidness and higher spindle speed.

The goal of all the manufacturing enterprises is to attain utmost cost per piece or optimum production rate on a specified machining operation. This can be attained first by the adequate selection of the application activity and having chosen the process, the next step includes the correct selection of tooling and parameters.

PCD / CBN Tools have assisted in making this second step of selection way easier, requiring only an easy economic analysis of the machining activity to ascertain the highest cutting speed yields lowest cost per piece or utmost production rate.

PCD Tools compete directly against carbide in milling activities. Ceramic or silicon nitride is striving hard to bridge the gap between PCD and carbide, however PCD has a clear advantage over all other tooling material. The advantage seen in milling with PCD versus carbide on non-ferrous and non-metallic activities ,is enormous. An increase in tool life of up to 100 times is common. Some additional benefits comprise better tolerance control on the component, better surface finish and minimal burring, and the likes. This translates into less scrap, more machine up time and superior tool cost justification.

PCD is leading and will continue to lead its importance with the introduction of new composite materials, which are being used in the aerospace, automotive and other ailed industries. Face milling, end milling, drilling and reaming are the activities majorly performed on this material. PCD is found to have enormous benefits in performance while machining the complex micro structures of the new composite materials.

Desired success can be achieved, while designing the PCD milling insert, paying close attention to the milling cutter and insert geometries. In several instances, when carbide is used in milling activities, high rake angles (>20°) and high clearance angles (>25°) are needed. These geometries are no longer required when using PCD. As a matter of fact in many cases,' the reduced rake angle of 5° and clearance angles of 10° have given a more rigid setup allowing for successful activities in milling of tough material with severe interrupted cuts.

All in all, PCD Milling inserts provide superior economy through an addition in tool life and by making it possible to attain optimum quality at high rate. Cutting speeds as high as 3000 mts/min, with feed of 2500 mm and depth of cut per pass -2.5 mm is possible. Dry running can easily be applied and the results are unmatched with surface finish of 0.8 to 0.4 in Ra and flatness within 30 microns. The economic advantages of using PCD are further contributed when considering the amount of time saved by obviating frequent machine-downtime processes like tool changing and indexing.

PCBN Milling inserts are normally used on cast iron and steel. The geometry of the milling cutter has a momentous impact on the performance of the PCBN tool. As regards the rake angle, that is measured from the center of the tool, negative axial-negative radial rake milling cutters are desired for PCBN activities. An significant benefits of such double negative cutter is that, the tools are able to withstand higher cutting forces without fracturing.

The edge preparation of the cutting tools is also important. An edge chamfer of 15° -20° for widths of 0.20-0.25 mm along with edge honing of the radius is a must, depending on the application and job materials. The combination of negative cutter geometry and chamfer will produce higher cutting forces and require more horsepower, generating very high temperatures. Although these types of maching conditions may not seem ideal, they are, in fact, exactly the right conditions while maching with PCBN. This is because PCBN works better near the eutectic temperature of the material and removes metal more efficiently. The results demonstrate that one has to reevaluate the machine processes in the context of the capabilities of PCBN tools. The use of PCBN tools in milling can be an effective method of increasing material removal rates and productivity while reducing overall machining cost.