Deep hole machining numerical control program optimization application

1. Process analysis of deep hole processing

(1) Characteristics of deep hole processing Generally, when the ratio of the hole depth L to the hole diameter D is greater than 5, that is, when L/D>5, it is called deep hole; when L/D≤5, it is called shallow hole. Deep hole machining is carried out in a closed or semi-closed state. The characteristics are as follows: Due to the fact that the operator cannot directly observe the cutting condition of the tool during deep hole machining, it is currently only possible to experience, listen to sound, see chips, touch vibration and other appearance phenomena. It is judged whether the process is normal; at the same time, the cutting heat is not easy to be dissipated, and 80% of the cutting heat in the general cutting process is taken away by the chips, and the deep hole machining tool itself has a large proportion, which is easy to overheat, the diffusion is late, the cutting distance is long, and the chips are discharged. Difficult, the tool is easy to wear and chipping; in addition, the deep hole processing technology system has poor rigidity, the long diameter of the hole is relatively large, the drill pipe is thin and long, easy to vibrate, the drilling is easy to go wrong, the hole processing precision and surface roughness are not easy Guarantee.

(2) Main problems to be solved in the development of deep hole parts processing technology 1 Selection of positioning reference: Selecting the positioning reference of deep hole machining is an important issue. Cone surface positioning is often used for drilling of rotary bodies, medium and small diameter deep hole parts, and tube blanking. The inner cone is positioned for medium diameter internal chip removal, and the outer cone is positioned for small diameter external chip removal or gun drilling systems. Large diameter deep holes, often with outer circle positioning. For non-rotating bodies, the mounting surface of the part is often used as the machining positioning reference. 2 Process analysis of deep hole processing: The choice of processing method determines the processing method and the number of passes according to the technical requirements of the deep hole surface. To achieve the common deep hole machining method and the processing range applicable to the tool. Another important factor in determining the processing method is the material properties of the part, such as the grinding of hardened steel, the difficulty of grinding of non-ferrous metals, and the finishing of diamonds or precision turning.

The chip breaking and chip removal of deep hole processing is an important problem, because the deep hole machining cutting heat is not easy to disperse, the chips are not easy to discharge, and forced cooling and forced chip removal must be carried out. At present, the commonly used method is to use high pressure to send the cutting fluid to the cutting area through the outside or inside of the drill pipe, and after the chips are cooled and lubricated, the chips are discharged from the outside or the inside of the drill pipe. Chip breaking is a guarantee for the smooth running of deep hole machining, which is closely related to the size of the chip breaking table, the cutting amount and the tool angle. The amount of cutting should match the size of the chipbreaker. If continuous cutting is found during processing, the speed should be reduced and the feed rate should be increased to achieve chip breaking. The main effect of the chip breaking effect is the rake angle of the tool, which reduces the rake angle and can achieve chip breaking.

In the process of the blank becoming a finished product, the total thickness of the metal layer cut off on a machined surface is referred to as the total surface finish. The machining allowance of deep hole parts is larger than that of general hole machining, because the shape and position error of the upper process is relatively large, and at the same time, in order to ensure a certain radial force, the guide is closely attached to the hole wall to stabilize the drilling. Different tools and different tool angles require different margins. For example, the single-edged reamer has a larger margin than the multi-blade reamer, and the larger the angling angle is than the reamer with a small main-angle angling; under the same conditions The larger the amount of cutting is than the required amount of small cutting amount; the worse the uniformity of the machining allowance left in the previous process, the larger the required margin; the machining allowance of the cutting fluid with anti-sticking property is smaller than other Machining allowance for cutting fluid.

2. Deep hole drilling programming instructions and analysis

(1) Deep hole drilling instruction instruction format:

G98/G99 G73 X_ Y_ Z_ R_ Q_ F_ K_

G98/G99 G83 X_ Y_ Z_ R_ Q_ F_ K_

Where X and Y are the positions of the holes to be processed; Z is the coordinate value of the bottom of the hole (if the through hole, the drill tip should exceed the bottom surface of the workpiece); R is the coordinate value of the reference point (R point is 2 to 5 mm above the top surface of the workpiece) ); Q is the machining depth of each time; F is the feed speed (mm/min); G98 is the initial plane after the drilling is completed; G99 is the reference plane (ie the plane of the R point) when the drilling is completed. If the Z, K, and Q movements are zero, the instruction is not executed.

For more information, please see Metalworking (Cold Processing), Issue 19, 2013 or download attachments:

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