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Common Problems and Solutions in CNC Machining

by: Jul 08,2022 961 Views 0 Comments Posted in CNC Machining

CNC Machining


Overcut

Reasons:

1.      The strength of the tool is not suitable, which causes the tool to bounce.

2.      Improper operation by operator.

3.      Uneven cutting allowance. (for example: leave 0.5 on the side of the curved surface and 0.15 on the bottom)

4.      Improper cutting parameters. (for example: the tolerance is too large or the SF is too fast)


Improvements:

1.      The principle of using tools: use big ones instead of small ones, use short ones instead of long ones.

2.      Add an inside corners sharping procedure, and the margin should be kept as uniform as possible.

3.      Reasonably adjust the cutting parameters and round the corners with large allowances.

4.      Take advantage of the SF function of the machine tool, fine-tune the speed to make the cutting of the machine tool achieve the best effect.


Problems in Determine the Center Position

Reasons:

1.      Inaccurate operation in manual operation.

2.      There are burrs around the mold.

3.      The optical edge finder is magnetic.

4.      The four sides of the mold are not vertical.

 

Improvements:

1.      Carefully check when operating manually, and the points should be at the same position.

2.      Use a whetstone or a file to deburr around the mold, wipe it with a rag and finally confirm it with hands.

3.      Demagnetize the optical edge finder before using.

4.      Check whether the four sides of the mold are vertical.


Problems in Determine the Coordinate of the Tool

Reasons:

1.      Inaccurate operation in manual operation.

2.      The tool is clamped incorrectly.

3.      The blade on the fly-cutter is not suitable. (the fly-cutter itself has certain error)

4.      There is an error between the R knife and the flat bottom knife and the fly-cutter.

 

Improvements:

1.      Carefully check when operating manually.

2.      Blow the toll with an air gun or wipe it with a rag when clamping.

3.      Use one blade when the blade on the fly-cutter needs to measure the shank and the smooth bottom surface.

4.      A separate tool program can avoid the error between the R knife and the flat knife and the fly-cutter.


Collision— Program

Reasons:

1.      The safety height is not enough. (the tool or chuck hits the workpiece during rapid feed G00)

2.      The tool on the program sheet and the actual program tool are wrongly written.

3.      The tool length (blade length) and the actual machining depth on the program sheet are wrongly written.

4.      The depth Z-axis value and the actual Z-axis value on the program sheet are wrongly written.

5.      The coordinate is wrong during programming.

 

Improvements:

1.      Accurately measure the height of the workpiece to ensure sufficient safety height.

2.      The tool on the program sheet should be consistent with the actual program tool. (try to use the automatic program list or the picture program list)

3.      Measure the actual processing depth on the workpiece, and write the length of the tool and the blade on the program sheet. (generally, the length of the tool holder is 2-3mm higher than the workpiece, and the length of the blade is 0.5-1.0mm)

4.      Take the actual number of Z axis on the workpiece and write it clearly on the program sheet. 


Collision— Operator

Reasons:

1.      There is an error in the depth Z axis when determining the coordinate of the tool.

2.      There are errors when determining the center position.

3.      Use the wrong tool.

4.      The program goes wrong.

5.      The handwheel is turned in the wrong direction during manual operation.

6.      Press the wrong direction during manual rapid feed.

 

Improvements:

1.      Pay attention to the Z axis when determining the coordinate of the tool.

2.      Repeatedly check when determining the center position.

3.      When clamping the tool, it is necessary to repeatedly check with the program sheet and program before installing it.

4.      The program should go one by one in order.

5.      The operator should strengthen the operating proficiency when operating by hand.

6.      First raise the Z axis to the workpiece when manually moving quickly.


Surface Precision

Reasons:

1.      The cutting parameters are unreasonable, and the surface of the workpiece is rough.

2.      The cutting edge of the tool is not sharp.

3.      The tool clamping and the blade avoidance is too long.

4.      Chip removal, air blowing, and oil flushing are not good.

5.      Program the tool cutting method. (consider down milling as much as possible)

6.      The workpiece has burrs.

 

Improvements:

1.      The cutting parameters, tolerances, allowances, and speed feed settings should be reasonable.

2.      Check and replace tools from time to time.

3.      When clamping the tool, try to clamp it as short as possible.

4.      For the lower cutting of flat knife, R knife and round nose knife, the speed and feed setting should be reasonable.

5.      Understand the performance of the machine tool and make up for the edge with burrs.


The pictures originate from theInternet.

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