Machining Center Zhang Bin

 

【Abstract】Thin wall parts have the characteristics of poor rigidity and low strength, and the processability is poor. It is easily deformed during processing, and it is difficult to guarantee the dimensional accuracy and shape accuracy of the parts. Taking the front cover of the company as an example, combined with the experience of personal processing, this paper introduces in detail how to improve the processing precision of the front end cover in the process.

 

Key words: thin-walled parts, fixture, positioning, clamping process

 

Foreword: Thin-walled parts refer to parts with a ratio of diameter to wall thickness greater than 15mm. The thin-walled parts commonly used in our company include: support frame, end cover, front end cover and so on. Thin-walled parts reduce the weight of parts and save material cost in the case of equal volume, but at the same time bring processing weaknesses in the manufacturing process, the rigidity of the parts is poor, and it is easy to deform during the clamping and processing of parts. , resulting in reduced machining accuracy of parts. The front end cover of the company's products also has such problems. In the process of processing, non-conforming products often appear, resulting in production waste. In view of this, it is necessary to solve some corresponding solutions according to the characteristics of such workpieces.

 

1. Main factors affecting the processing accuracy of the front end cover

 

There are many factors that affect the processing accuracy of thin-walled parts, but there are three main aspects in the following:

 

1.1 Force deformation

 

The second-stage machining of the front end cover is to drill the locating pin hole. The φ130 hole needs to be clamped during machining. Since the thickness of the front end cover wall is only 6mm, the pin hole shape tolerance will be deformed before and after the clamping under the clamping force, thus affecting the workpiece. Dimensional accuracy and subsequent processing steps.

 

1.2 Heat deformation

 

Due to the thinner workpiece, poor heat dissipation and poor machinability, the cutting heat will cause thermal deformation and redistribution of the workpiece, making the workpiece size difficult to control, easy to appear inner hole, roundness of the outer circle, warpage of the part plane.

 

1.3 vibration deformation

 

The front end cover three-step machining content is machining inner cavity, milling bottom surface and drilling tapping. When machining the inner cavity with φ20 end mill, the workpiece has vibration and the large cutting force due to large margin and large cutting force. Deformation, which affects the shape and position tolerance of the product.

 

2. How to improve the machining accuracy of thin-walled parts

 

Since the factors affecting the machining accuracy of the front end cover are found, how can we improve the machining accuracy of the front end cover? In order to better solve the problems in the process of front-end cover processing and ensure the smooth completion of qualified products, we comprehensively optimize the four aspects of workpiece clamping, process route, cutting amount and workpiece cooling in the actual production of the front cover. To solve or reduce the impact of the above factors.

 

2.1 workpiece clamping

 

The front cover part requires high dimensional accuracy and is not easy to guarantee. During the machining process, the influence of the workpiece deformation on the machining accuracy, that is, the clamping problem of the workpiece deformation process, should be considered. If the force is too large during the clamping, the stress of the workpiece will be deformed, resulting in the shape and position error of the part. If the clamp is not tight, it may cause the parts to loosen and be scrapped during processing. Specifically, the clamping force is controlled during processing to reduce the clamping deformation of the part. During the processing of the front end cover, it is usually fixed by the clamping method of directly tightening the φ130 hole by the bolt plate. Because the front end cover wall is thin, the magnitude of the tightening force will have a great influence on the workpiece (Fig. 1). The tightening force is large, the center distance of the pin hole becomes longer, and vice versa, it becomes shorter.