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1、Int J Adv Manuf Technol (2001) 18:399–403 ? 2001 Springer-Verlag London LimitedA New NC Machine Tool Controller for Step-by-Step MillingJ. BalicUniversity of Maribor, Faculty of Mechanical Engineering, Intelligent Manufa

2、cturing Laboratory, Maribor, SloveniaThe paper describes the design solution, operation and analysis of a new NC controller for a new step-by-step milling pro- cedure. A step-by-step milling device ensures that the milli

3、ng of workpieces by end or conical milling cutters, where the ratio between the depth of milling a (mm) and the milling cutter diameter D (mm) is greater than 1.5 (a/D ? 1.5) results in the increased wear resistance of t

4、he cutting edge. Breaking of the milling cutter is minimised and is not frequent and the milling forces are reduced, which results in smaller deflections of the milling tool and higher accuracy of machining. The machine

5、tool use is better.Keywords: NC machine tool controller; Step-by-step milling1. IntroductionTechnological problems occur when machining some compo- nents using end or conical milling cutters of small diameters at large c

6、utting depths. According to the recommendation of tool manufacturers the depth of milling should be within the range of 1–1.5 × D, where D is the milling cutter diameter. Frequently, the depth of milling required fo

7、r the manufacture of the parts may be as much as 6D. This problem is particularly severe when machining parts (dies and moulds) with a conical milling cutter (cutting depths is 4D, conical angle 3° to 6°), wher

8、e rough milling with a special rough milling tool is not possible and in the case of machining dies (the material of the dies is steel according to DIN 1.2343–0.4% C, 1% Si, 5% Cr, 1.3% Mo, 1% V), for the extrusion of al

9、uminium bars, pipes, and beams.2. State of the Art and Existing SolutionsThe state-of-the-art technology in the area of machining offers satisfactory solutions for almost all types of machining. TheCorrespondence and off

10、print requests to: Professor J. Balic, Laboratory for Intelligent Manufacturing, University of Maribor, Faculty of Mech- anical Engineering, Smetanova 17, SI-2000, Maribor, Slovenia. E-mail: joze.balic?uni-mb.simain prob

11、lem arises when, for the industrial use, it is necessary to optimise the choice of technological solutions with respect to the manufacturing time, resistance to tool wear, quality of surface, geometrical precision and ma

12、nufacturing costs. The literature contains some solutions concerning this area for ensuring higher quality of NC milling [1–11]. That literature contains discussions of step-by-step milling carried out by tools of specia

13、l shapes. For each shape to be made by step-by-step milling, a specially shaped tool is used. In this process the programmed motion of the tool does not change, only the manufactured shape changes, influenced by the pred

14、eterminated step shape of the milling cutter. The US patent [12] proposes a very high-speed adiabatic face milling machine. The efficiency of the chip removal system is such that chip recutting is nearly eliminated and t

15、he tool life is improved. This solution required a new machine tool and a high investment. The above mentioned devices and methods for milling do not include the new solution for step-by-step milling described in the pap

16、er.3. Step-by-Step Milling MethodThe step-by-step milling method features the step motion of the milling cutter (f1) in the direction of cutting and the relatedFig. 1. Milling by the step-by-step procedure. a, depth of m

17、illing; f1, motion in the direction of machining; f2, motion in the direction opposite to machining; D, diameter of milling cutter.New NC Machine Tool Controller 401Fig. 5. Workpieces and direction of machining.The compu

18、ter model of the solution is based on the following assumptions and requirements:Machining without correction (G40).The programmer programs the NC machining “conventionally”; the start and the end of step-by-step machini

19、ng are determined by two records in text form.The program comprises the machining functions G17 and G18.The program recognises all the functions having an influence on the machining process (G90, G91, G54 – G59, G00, G01

20、, G02, G03).Fig. 6. Graphical representation of forces.The program includes simultaneous machining of all three coordinates (x, y, z).The program changes only the statements inside the marked block.Renumbering of stateme

21、nt numbers.Creation of output data file.The program contains checking of machining correction.The algorithm of operation for the computer program is shown in Fig. 3. Checking of the deviation from the desired positions i

22、s performed automatically.4.3 Methods of Incorporation into Existing NC Control UnitsThe control can be incorporated onto the milling machine in three ways (Fig. 4):Into the milling machine tool control unit, between the

23、 memory of positions and the interpolator as shown by position 9.1.Into the NC control unit closely behind the reading-in of data module, as shown by position 9.2.Before the NC control unit where it intercepts the input

24、data of the NC program and suitably processes them, as shown by position 9.3.5. Experiments and Tests5.1 GeneralTests with the step-by-step device were carried out for milling by the conventional and the new methods. The

25、 tests were executed in the laboratory [16] and in the real production of tools for the extrusion of aluminium [17]. A horizontal 4-axis machining centre (Heller BEA-05) with a pallet system and a tool magazine was used.

26、 Tool clamping was performed with ISO 50 clamping cones. Machining of workpieces was horizontal (G17). A Kistler measuring device for measuring cutting forces was fixed to the machining centre table. The measuring equipm

27、ent and the software used for processing the measurement results had been developed at the Faculty of Mechanical Engineering in Maribor [18, 19]. The test material was aluminium AlMgSil (AC30T6 – pro- ducer’s factory des

28、ignation) and steel with the designation according to DIN standard 1.2343.Table 1. Two planned tests for tool wear resistance for aluminium AlMgSil.Tool Depth Spindle Feed Stepof cut speed (mm min?1) (mm) (min?1) 10 6 20

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