Type Characteristics and Improvement Scheme of Metal Boring Technology

Boring refers to the further processing of forged, cast or drilled holes. Boring can enlarge the aperture, improve the accuracy, reduce the surface roughness, and better correct the deviation of the original hole axis. In the process of ultra-precision boring, in order to make the boring rod withdraw from the workpiece for loading and unloading the workpiece, a tool groove is set up in the rear guide. Following is an introduction to various aspects of Borun Petrochemical Company on the types of downhole boring technology and the ways to improve it.

(1) Boring machine has many parts which can work in feed motion, so that it has multi-function in technology and shows strong adaptability. It can not only process the surface of cylindrical hole, plane, groove, thread and central hole, but also process many kinds of parts, which is convenient to realize the processing of hole system.

(2) Boring process takes tool rotation as the main motion, which is especially suitable for processing large-scale parts with complex structure, such as box and frame, compared with workpiece rotation as the main motion.

(3) The greatest feature of boring is that it can correct the hole axis deviation and deviation caused by the previous process.

Types of Boring Technology

(1) Supporting Boring Method

Supporting boring method is a kind of cutting method which uses the supporting boring rod in the tailstock sleeve of boring machine. The characteristics of the support boring method are as follows:

Compared with the cantilever boring method, the rigidity of the boring bar is greatly enhanced.

(2) Suitable for the processing of coaxial holes. It can be equipped with a variety of high precision boring cutters, with high processing accuracy and guaranteed processing quality.

(3) It is difficult and time-consuming to fix and adjust the boring cutter. It is not easy to observe the processing situation. The operation of trial boring and measurement is not as intuitive and convenient as the cantilever boring method.

(2) Suspension Boring Method

A single overhanging boring tool bar is used to boring medium-sized and non-perforated coaxial holes. This method is called overhanging boring method. The main features of the cantilever boring method are as follows:

As the boring rod used in the cantilever boring is generally short, thick and rigid, the selection of cutting speed can be higher than that of the supporting boring rod, so the production efficiency is high.

(2) It is convenient to clamp and adjust the cutter on the overhanging boring rod, and it is also convenient to observe and measure in the process, which can save auxiliary time.

(3) When the spindle is fed into the cutting by the cantilever boring method, the deflection of the tool rod system is different due to the change of self-weight because the boring rod is continuously cantilevered with the spindle, and the axis of the hole is prone to bend when the longer inner hole is machined. As the spindle extends continuously, the rigidity of the whole tool bar system becomes worse and worse. Under the action of cutting force, the elastic deformation of the system increases gradually, which affects the boring accuracy of the hole and causes the cylindricity error of the machined hole.

II. Improvement of Boring Technology

In order to reduce cutting force, eliminate cutting vibration and improve machining efficiency, effective improvements can be made by adjusting cutting angle, improving tool material and selecting high-end cutting oil.

(1) Adjustment of cutting angle

It is generally believed that the negative rake angle should be used to increase the strength of cutting tools for processing brittle materials such as cast iron so as to prevent the tool from breaking. But the rake angle has the greatest influence on the cutting force among the geometric parameters of the tool. Without reducing the cutting parameters, it can effectively reduce the cutting force, not only make the cutting faster, but also effectively reduce the occurrence of cutting vibration.

(2) Installation method of blade

Ultra-hard blades such as cubic boron nitride and cermet with common clamping method can not make positive rake angle on the blade, but making positive rake angle on the tool will increase the difficulty of installation and adjustment of the blade. In most cases, the chip breaking effect of vertical inserts is better, the chip holding space is more reasonable, the chip removal is smoother, and the stable processing process is easier to obtain.

(3) Blade material and structure

Ceramic cutting tool is a new material tool in modern metal cutting. Its characteristics are high hardness, high strength, high red hardness, high wear resistance, excellent chemical stability and low friction coefficient. However, the boring process is continuous cutting, and there is no impact in the cutting process, so ceramic blades can also be used in rough boring.

(4) Selection of Boring Cutting Oil

The performance of cutting oil in boring technology directly determines the accuracy of workpiece, so when choosing cutting oil, the appropriate cutting oil is selected according to the different material of workpiece. For materials that are easy to cut, low viscosity is usually chosen to prevent burrs on the premise of cleanability of finished products. Harder workpieces should use boring oil containing sulfur-chlorine compound additives, but the problem of rust should be avoided by degreasing as soon as possible after processing.

These are the common types and improvement methods of boring technology. Reasonable use of equipment, tools and cutting oil can effectively reduce errors and improve workpiece accuracy.