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

1. Knife bounce

The 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 reasonable tools and processing methods are used, the probability of tool skipping can be reduced.

CNC machining

There are three main factors that affect tool deformation:

1) Tool length

2) Tool diameter

3) The force of the tool

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.

Tool diameter

For a tool of the same length, 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.

force of the tool

The deformation of the tool is proportional to the force it is subjected to 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.

collision

Punching means 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.

Too much cutting in CNC machining

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.

 Improper CNC machining 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.

Improper setting of safety height, 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.

 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.

CNC machining over cut

Overcutting 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, bounce 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 the program is complete, the toolpath needs to be checked in detail to avoid gouges.

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