1 INTRODUCTION
The ability to components machined in the shortest possible time is a question that is nowadays of great importance. Therefore, when making any improvement tools, or methods that will allow for faster delivery, and at the same time and increase the quality of production must be taken very much into account. One way is to use high speed machining (High Speed ??Machining, HSM) strategies. Otherwise there is no unambiguous definition of what exactly should be HSM strategies in machining.
HSM can be any process on CNC milling machine in which use the higher frequency of rotation of the spindle, higher feed rate, and better processing technology, all for the purpose of increased productivity and faster production than that which can be achieved by conventional or previously developed treatment processes.
Modern technology in the treatment processes that developed at the present time has enabled the operators on the machines to access their work in a completely different way. Special tools have been developed for HSM strategy have totally different cutting characteristics of previous tools. While in the traditional method of programming is generally considered that the tool cuts from top to bottom, with modern HSM processing may also happen that the tool cuts from the bottom up.
When HSM strategies used various improved processing technology, such as:
? Shallow Depth of cut
? Large feed (up to 25.4 m / min)
? Greater frequency of rotation (up to 40,000 rev / min)
? Options CNC "by looking ahead" - determining the fastest feed, so it fits move into second and reduce processing time
When HSM processing spindle is the most important part of the machine and on it depends which kind of treatment, and the most critical parts of the bearings, which must be very much taken into account when dimensioning and construction of the spindle. The spindle must be designed to handle high frequency of rotation, and at the same time conveys sufficiently high power and torque, with not overly burdensome and as soon as longer life expectancy. Bearings that can be used in machines that are designed for HSM processing the ball, roller, hydrostatic or magnetic bearings, and the most popular solution for such spindles are angular contact ball bearings.
Plays a major role also toolholder. When HSM processing the most popular tool holder HSK (hollowshank taper), tapered shank tool which is characterized by precision inherent to the cone and rigidity that characterizes the flange.
2 HSM
2.1 History HSM strategies
HSM strategy has found its application in various industries. High speed processing is one of the advanced manufacturing technology with great potential in the future. However, as was the case in many other achievements of technological progress, for the conversion of basic knowledge when it produces results took a relatively long time. In this particular case, a period of about 60 years was not only due to the cautious attitude of industry, but also due to the fact that the existing manufacturing facilities that match the state of the art at that time were not able to meet the demands of HSM. Theoretical studies date back to the distant year 1931, when on the basis of previous research has been a very important conclusion that the temperature after a particular cutting speed starts to drop again. This is shown for the different materials in the following figure.
In the early 50's, again, was developing an interest in machines that will be able to work with high cutting speeds. Given the fact that machines with increased speeds of rotation were not available, began ballistic research. It was performed by passing or tools over the sample workpiece using a rocket or missile launch tubes in the shape of the workpiece with a stationary blade. From these tests were obtained by the realization that at high cutting speed cutting conditions created a fundamentally different than a conventional method of cutting. Various American studies done in the early 60's has shown that productivity increases dramatically and one can expect to reduce the cost of production and processing of the product if it can overcome the difficult spending machine, tool or excessive vibration .. In a research project in 1978 showed that the speeds Cutting above 6500m / min opens new interesting aspects for aluminum processing. 1977 during a ballistic test showed that the high surface quality significantly improved with increasing speed rezanja.Tek 80-ies of these theoretical considerations have had the chance to take hold in reality, because then made the first machines that could meet the demands of HSM -a, and since then the HSM strategies on a constant rise. Procez development HSM included not only the development of machines, VAC II also further development of tools and materials for processing, and also the development of the CAD / CAM system.
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