How to control spring knife, strike knife and overcut in CNC machining of precision parts?

In CNC machining, the problems often encountered are bouncing, hitting, overcutting, etc. This article discusses the solutions to these common problems, hoping to learn from each other.

1. Bounce

Bouncing tool refers to the large vibration of the tool due to excessive force. The hazard caused by the jumping tool is to cause the workpiece to be overcut and the tool to be damaged. When the tool diameter is small, the tool shaft is too long or the force is too large, the phenomenon of tool jumping will occur. If you use reasonable tools and processing methods, you can reduce the chance of tool jumping.

There are 3 main factors that affect tool deformation:

1) Tool length

2) Tool diameter

3) The force of the tool

1. Tool length

For the same diameter tool, when the tool length is doubled, its deformation will increase by 3 times. When machining, keep the tool length as short as possible to reduce the risk of bouncing the tool.

2. Tool diameter

For the same length of tool, when the diameter of the tool is reduced by 1 times, its deformation will increase by 4 times. When machining, choose a large diameter tool whenever possible or use a reinforced tool for machining to reduce the risk of tool bounce.

3. The force of the tool

The deformation of the tool is proportional to the force it experiences during machining. Reducing the force on the tool reduces the chance of the tool bouncing. In order to reduce the force on the tool, the contact area between the tool and the workpiece must be reduced.

2. Collision

Knives mean that the cutting amount of the tool is too large. In addition to the cutting edge, the shank also strikes the workpiece. The main reasons for tool collision are unreasonable setting of safety height or no safety height at all, improper selection of processing methods, improper use of tools, and the setting of the allowance for secondary roughing is smaller than the allowance for secondary roughing. First roughing settings, etc.

2.1cnc machining too much cutting amount

Solution:

Reduce stock removal. The smaller the tool diameter, the smaller the amount of cutting that should be taken. Under normal circumstances, the cutting amount of each rough opening of the mold is not more than 0.5mm, and the cutting amount of semi-finishing and finishing is small.

2.2 Improper cnc processing method

Change the profile milling mode to pocket milling mode. When the machining allowance is larger than the tool diameter, the contour milling method cannot be selected.

2.3 Improper safety height setting, hit the clamp when lifting the tool

Solution:

(1) The safety height should be greater than the clamping height.

(2) In most cases, except for special workpieces, the 'direct' tool advance and retreat method cannot be selected.

2.4 Improper setting of secondary cnc roughing allowance

The allowance of the second roughing should generally be 0.05mm larger than that of the first roughing. If the allowance of the first roughing is 0.3mm, the allowance of the second roughing should be 0.35mm. Otherwise, the toolbar can easily hit the upper side wall.

In addition to the above reasons, tool collision may occur when trimming the toolpath, so try not to trim the toolpath. The most direct consequence of hitting the tool is the damage to the tool and the workpiece, and more seriously, the damage to the machine tool spindle.

3. CNC machining over cutting

Overcut means that the tool also cuts the part that cannot be cut, causing damage to the workpiece. There are many reasons for the overcut of the workpiece, mainly including low machine tool precision, knife collision, spring knife, improper tool and so on. In addition, if the operator is not accurate with the knife, it may also cause overcutting.

When programming, you have to be careful and meticulous. After completing the program, the toolpath needs to be checked in detail to avoid gouges.

As a professional CNC processing manufacturer, DONGGUAN YIFENG METAL not only produces metal precision parts, but also provides plastic parts processing.

CNC machining service is the core business of DONGGUAN YIFENG METAL, from prototype machining to mass production, our professional 3/4/5 axis CNC machining centers, CNC lathe equipment, CNC turning and milling equipment, CNC grinding machines, etc., are all trained by Qualified personnel operating manufacturing engineers.



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