This article explores three knowledge points, hoping to inspire you.
1. Under what circumstances should G41G42 be used?
2. How to choose G41G42
3. Selection of tool tip orientation
1. Why do you need to use G41G42 when counting cars and programming
When processing workpieces with conical surfaces or arcs on CNC lathes, there will be dimensional errors between the correct program written and the actual processed parts.
This error is caused by the arc of the tool nose.
To explain this problem clearly, we need to start from the CNC car tool setting, please see the following schematic diagram:
We know that the tip of most turning tools will have an arc R, as shown in the figure above:
Tool setting in the Z-axis direction is when point A of the tool tip touches the end face of the part
The pair in the X-axis direction is that point B of the tool tip touches the outer circle of the part
When actually cutting the end face or outer circle, the Z-direction or X-direction size of the part is determined by point A or B. At this time, the rounded corner of the tool nose has no effect on the processing size.
However, when it is used to process workpieces with chamfers, conical surfaces or arcs, the actual cutting point of the tool is each tangent point on the arc AB of the tool tip, not point A or point B during tool setting. As shown below:
Then when processing parts with shapes such as conical surfaces or arcs, it is necessary to use G41/G42 tool nose radius compensation.
Ok, the principle is clear, and then proceed to the second knowledge point
2. How to choose G41 G42 when programming
For machine tools, it is divided into:
Front Tool Holder
Rear tool holder
For parts are divided into:
car shape
Inner Hole
Then these two classification methods can be combined into the following four situations. Please refer to the following two pictures carefully:
1. Rear tool holder: The tool cuts on the right side of the workpiece
2. Front tool post: The tool cuts on the left side of the workpiece
3. Rear tool holder: The tool cuts on the left side of the workpiece
4. Front tool holder: The tool cuts on the right side of the workpiece
picture
Remember the above picture carefully
simple?
This trick is really simple, but very useful!
Well, let’s take a finishing program example directly:
picture
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O0001
T0101
S500 M03
G0X60.Z2.
G01 G42 Z0 F0.1. (Tool arc radius compensation)
X120.Z-150.
X200.Z-180.
Z-260
G0G40X205.Z2. (Cancel radius compensation)
M30
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Third, the choice of tool tip orientation
During programming, (G41/G42) tool radius compensation is added to the program
By now, what questions might you have? ---How does the machine tool identify the tool radius compensation R?
This requires us not only to add G41 or G42 to the program, but also to input the tool nose arc R and tool nose orientation of the corresponding tool in the tool compensation panel.
picture
Here appeared the "knife tip orientation"
I intercepted the tool tip orientation diagram in the manual of several lathes, as follows:
picture
The specific application is as follows:
Outer circle front car
picture
Inner hole front car
picture
The above is our longest tool position number, that is to say:
Front car outer circle: 3
Front car inner hole: 2
We use G41 or G42 in the program, and enter the tool nose arc R and tool nose orientation of the corresponding tool in the tool compensation panel.
As in the O0001 program above, if the tool nose arc R=0.8, I need to input the tool nose arc R corresponding to the T0101 tool and the tool nose orientation in the tool compensation panel.
picture
In this way, if the O0001 program is run, the machine tool will use the G42 function to eliminate the phenomenon of over-cutting or cutting residue.
Well, the G41/G42 explanation of turning has come to an end.
Let me share a CNC macro program rough and fine turning ball case, and inform the precautions in programming of G41/G42
