Skip to main content

Why should CNC machining leave a machining allowance on the workpiece


　The thickness of the metal layer removed in each process of CNC turning is called the machining allowance between processes. For the torsion surface of the outer circle and the hole, the machining allowance is considered from the diameter, so it is called the symmetry allowance (that is, the bilateral allowance), that is, the thickness of the metal layer that is actually removed is the diameter of the machining allowance. half. The machining allowance of the plane is the unilateral allowance, which is the thickness of the metal layer that is actually removed

 

 

The goal of leaving a machining allowance on the workpiece is to remove the machining deviation and external defects left by the previous process, such as the chilled layer, pores, and sand layer on the outside of the casting, and the oxide scale, decarburized layer, and external cracks on the outside of the forging. , The internal stress layer and external roughness after cutting. Thereby improving the accuracy and surface roughness of the workpiece. The size of the machining allowance has a great influence on the processing quality and production efficiency.

 

　　The machining allowance is too large, which not only increases the labor of machining, reduces the productivity, but also increases the consumption of materials, objects and electricity. CNC medical machining increases the processing cost. If the machining allowance is too small, it will not be able to eliminate the various shortcomings and deviations of the previous process, nor can it compensate for the clamping deviation during the processing of this process, resulting in waste products. The selection criterion is to make the margin as small as possible under the premise of ensuring the quality of CNC machining. Generally speaking, the more finishing, the smaller the process margin.

 

　　When determining the CNC machining sequence, it is also necessary to clarify whether the parts need to be pre-processed before processing. Pre-processing is often done by ordinary machine tools. If the precision of the blank is higher, the positioning is more reliable, or the machining allowance is sufficient and uniform, it is not necessary to perform pre-processing, and directly process it on the CNC machine tool. At this time, the division of CNC machine processes should be considered according to the accuracy of the rough reference of the blank, which can be completed in one process or divided into several processes.


Comments

Post a Comment

Popular posts from this blog

Drive the preferential presetting of the spring frame of the vehicle

The secondary spring system of the original electric locomotive consists of 4 sets of the same ordinary cylindrical compression springs. Its parameters are: spring material diameter d=48mm, maximum working circle diameter D=230mm, effective working circle number n=6.6, free height H0= 528mm, working height H=431mm. The characteristic curve of the spring is approximately straight, with stable stiffness and simple structure. However, the spring stiffness is mainly along the axial direction, and its transverse shear and bending stiffness is very poor, and its anti-resonance ability is poor. After the train speeds up, its snake-like movement and shaking phenomenon intensify. Therefore, it is necessary to improve the spring system of electric locomotives. Improvement of the spring system. The improved spring parameters and characteristics take into account the special position of the secondary spring (between the bogie and the car body) and specific functions (s...
Post a Comment
Read more

Mitsubishi RM100HA-20F

# RM100HA-20F Mitsubishi RM100HA-20F New IGBT: 100A1000V, RM100HA-20F pictures, RM100HA-20F price, #RM100HA-20F supplier ------------------------------------------------------------------- Email: sales@shunlongwei.com https://www.slw-ele.com/rm100ha-20f.html ------------------------------------------------------------------- rm100ha-20f Description rm100ha-20f is a DIODE RECTIFIER BRIDGE SINGLE.   Target Applications rm100ha-20f Free wheel use, Welders IGBT: 100A1000V
Post a Comment
Read more

Elimination of Gear Backlash in CNC Machining Feed System

Elimination of Gear Backlash in CNC Machining Feed System   The transmission gear in the feed system of the CNC machining machine tool must eliminate the transmission gap between the meshing gears as much as possible, otherwise the motion will lag behind the command signal after each reversal of the feed system, which will affect the machining accuracy (accuracy) ). There are the following two common methods for CNC machining machine tools to eliminate the transmission gear gap.   1. Rigidity adjustment method   The rigid adjustment method is an adjustment method that cannot be automatically compensated for the tooth side clearance after adjustment. Therefore, the pitch tolerance and tooth thickness of the gear must be strictly controlled, otherwise the flexibility of the transmission will be affected. This adjustment method has a relatively simple structure and a better transmission rigidity.   (1) Eccentric shaft adjustment method   As shown in Figure 610, the...
Post a Comment
Read more