CNC machining process common problem points and improvement methods
Starting from the actual production, this paper summarizes the common problems and improvement ways of CNC machining process, and how to choose the three important factors of speed, feed rate and cutting depth in different application fields
The workpiece is over-cut
The reason:
Knife, tool strength is not enough too long or too small, resulting in knife.
Improper operation by the operator.
Uneven cutting allowance (such as: 0.5 on the side of the surface, 0.15 on the bottom)
Improper cutting parameters (such as: tolerance is too large, SF setting too fast, etc.)
Improvements:
The principle of using a knife: can be big or small, can be short or not long.
Add the clearing procedure, and the margin is as even as possible (the margin on the side and the bottom is the same).
Reasonable adjustment of cutting parameters, large margin corner round.
With the SF function of the machine, the operator fine-tunes the speed to achieve the best cutting effect.
The central question
The reason:
Operator manual operation is not accurate.
There are burrs around the mold.
The center bar has magnetic field.
The four sides of the mold are not vertical.
Improvements:
Manual operation should be carefully checked repeatedly, and the points should be at the same point and height as far as possible.
Remove burrs with a whetstone or file around the mold, wipe clean with a rag, and finally confirm with your hand.
Demagnetize the dividing rod before dividing the mold (ceramic dividing rod or other).
Check whether the four sides of the mold are vertical (if the verticality error is large, it is necessary to review the plan with the fitter).
The knife problem
The reason:
Operator manual operation is not accurate.
Tool clamping error.
The blade on the knife is wrong (the knife itself has a certain error).
There is an error between R knife and flat knife and flying knife.
Improvements:
Manual operation should be carefully checked repeatedly, and the knife should be at the same point as possible.
Blow clean with air gun or wipe clean with rag when clamping the tool.
One blade can be used when the blade on the flying knife is to measure the rod and light the bottom surface.
A separate knife program can avoid the error between R knife flat knife flying knife.
The crash - programming
The reason:
The safety height is not enough or not set (the knife or chuck hits the workpiece when the fast feed G00).
The tool on the program list and the actual program tool are written wrong.
The tool length (blade length) and the actual machining depth on the program list are wrong.
The depth Z-axis fetch number and the actual Z-axis fetch number on the program are written incorrectly.
The coordinates are set incorrectly during programming.
Improvements:
Accurate measurement of the height of the workpiece also ensures that the safety height is above the workpiece.
The tool on the program list should be consistent with the actual program tool (try to use the automatic program list or use the picture program list).
Measure the actual depth of machining on the workpiece, write the length of the tool and the length of the blade on the program sheet (generally, the tool clip length is 2-3MM higher than the workpiece, and the blade length avoidance is 0.5-1.0MM).
Take the actual Z-axis number on the workpiece and write it clearly on the program sheet. (This operation is generally written manually to check repeatedly).
Crash machine - Operator
The reason:
Depth Z-axis alignment error ·
The number of touch and operation errors (such as: unilateral access without feed radius, etc.).
Use the wrong knife (such as: D4 knife with D10 knife to process).
The program goes wrong (for example: A7.NC goes A9.NC).
The hand wheel is rotated in the wrong direction during manual operation.
Press the wrong direction (for example, -X +X) during manual fast feed.
Improvements:
Depth Z-axis knife must pay attention to the position of the knife. (bottom, top, analysis, etc.).
Check the number of touch and operation repeatedly after completion.
When installing the tool, it should be installed after repeated check with the program list and the program.
The program should go one by one in order.
In the manual operation, the operator should strengthen the operation proficiency of the machine tool.
In the manual fast movement, you can first raise the Z axis to the workpiece above the move.
Surface accuracy
The reason:
The cutting parameters are unreasonable and the workpiece surface is rough.
The edge of the tool is not sharp.
The tool clamping is too long, and the blade is too long.
Chip removal, air blowing, oil flushing is not good.
Programming cutting mode, (you can try to consider going down milling).
The workpiece has burrs.
Improvements:
Cutting parameters, tolerances, allowance, speed feed Settings should be reasonable.
The tool requires the operator to check and replace it periodically.
When installing the tool, the operator is required to clip as short as possible, and the blade should not be too long.
For the lower cut of flat knife, R knife and round nose knife, the speed feed setting should be reasonable.
The workpiece has burrs: the root of our machine tools, tools, and cutting methods are directly related. Therefore, we need to understand the performance of the machine tool and repair the edge with burrs.
The blade is broken
Reasons and improvements:
1. Feed too fast
-- Slow down to a suitable feed speed
2. Feed too fast at the beginning of cutting
-- Slow down the feed rate at the beginning of cutting
3. Clamp loosely (knife)
-- Clamp
4. Clamping loose (workpiece)
-- Clamp
5. Insufficient rigidity (tool)
-- Use the shortest knife allowed, a little deeper in the grip, and try downmilling
6. The cutting edge of the tool is too sharp
- Change the fragile cutting edge Angle, one edge
7. Insufficient rigidity of machine tools and tool handles
-- Use a rigid machine tool and a tool handle
Wear and Tear
Reasons and improvements:
1. Machine speed is too fast
- Slow down and add enough coolant
2. Harden the material
-- Use advanced tools and tool materials to increase surface treatment
3. Chip adhesion
- Change the feed speed, chip size or clean the chip with cooling oil or air gun
4. Improper feed speed (too low)
-- Increase feed speed and try downmilling
5. The cutting Angle is not suitable
- Change to the appropriate cutting Angle
6. The first back corner of the knife is too small
-- Change to a larger back Angle
Destruction
Reasons and improvements:
1. Feed too fast
-- Slow down the feed rate
2. The cutting amount is too large
-- Use smaller cutting amounts per edge
3. Blade length and full length are too large
- Deep grip, with a short knife, try to mill down
4. Too much wear and tear
-- Regrind at an early stage
Vibration marks
Reasons and improvements:
1. Feed and cutting speed is too fast
- Correct feed and cutting speed
2. Insufficient rigidity (machine tools and tool handles)
- Use better machine tools and tool handles or change the cutting conditions
3. The rear Angle is too large
- Change to a smaller back Angle, machining the edge belt (oil stone grinding once)
4. Clamp loosely
-- Clamp the workpiece
◆ Consider speed, feed
The relationship between the three factors of speed, feed and cutting depth is the most important factor to determine the cutting effect, inappropriate feed and speed often lead to reduced production, poor workpiece quality, tool damage.
Use the low speed range for:
High hardness material
Headstrong big material
Hard to cut material
Heavy cut
Minimal tool wear
Maximum tool life
Use the high speed range for:
Soft material
Good surface quality
Smaller tool diameter
Light cut
Large brittle workpiece
Manual operation
Maximum processing efficiency
Non-metallic material
Use high feeds for:
Heavy, rough cutting
Rigid construction
Machinable material
Roughing tool
Surface cutting
Low tensile strength material
Coarse tooth milling cutter
Use a low feed for:
Light machining, fine cutting
Brittle structure
Difficult material
Small cutter
Deep vertical groove machining
High tensile strength material
Finishing tool
Honscn has more than ten years of cnc machining experience, specializing in cnc machining, hardware mechanical parts processing, automation equipment parts processing. Robot parts processing, UAV parts processing, bicycle parts processing, medical parts processing, etc. It is one of the high-quality suppliers of cnc machining. At present, the company has more than 20 sets of cnc machining centers, grinding machines, milling machines, high-quality high-precision testing equipment, to provide customers with precision and high-quality cnc spare parts processing services.Contact us