Common problems and improvement methods in CNC machining process, as well as how to select three important factors: speed, feed rate and cutting depth, for your reference.

1、 Workpiece overcut

1. The strength of the knife is not long enough or too small, resulting in knife snapping.

2. Improper operation by the operator.

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

4. Improper cutting parameters (such as excessive tolerance, SF setting too fast, etc.).

1. Tool use principle: it can be big but not small, short but not long.

2. Add angle cleaning procedure and try to maintain a uniform margin (the margin on the side and bottom is the same).

3. Reasonable adjustment of cutting parameters and large angle allowance rounding.

4. Use the SF operator of the machine tool to fine tune the speed to achieve the best cutting effect of the machine tool.

2、 Scoring problem

1. The manual operation of the operator is inaccurate.

2. There are burrs around the die.

3. The centring rod is magnetic.

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

1. Manual operation shall be checked repeatedly and carefully, and the points shall be at the same point and height as far as possible.

2. Clean the burrs around the mold with an oilstone or file, and finally confirm by hand.

3. Demagnetize the centering rod before mold centering (it can be used for ceramic centering rod or others).

4. Calibrate the meter and check whether the four sides of the die are vertical (large Perpendicularity Error requires fitter inspection scheme).

3、 Knife setting problem

1. The manual operation of the operator is inaccurate.

2. Tool error.

3. The blade on the throwing knife is wrong (the Throwing Knife itself has a certain error).

4. There is error between R knife and flat bottom knife and flying knife.

1. The manual operation shall be checked repeatedly and carefully, and the knife shall be the same as far as possible.

2. When the tool is clamped, blow it with an air gun or wipe it with rags.

3. The blade on the flying knife can be used to measure the tool bar and smooth bottom.

4. A separate tool setting program can avoid the error between R knife, flat knife and flying knife.

4、 Collision - Programming

1. The safety height is not enough or there is no setting (rapid feed) g knife or collet (hitting the workpiece at 00).

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

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

4. Depth z-axis retrieval of program list and actual z-axis retrieval of error.

5. Coordinate setting error during programming.

1. Accurately measuring the height of the workpiece also ensures the safe height of the workpiece.

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

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

4. In fact, take the data from Z axis on the workpiece and write it clearly on the program sheet. (this operation is generally manual and needs to be checked repeatedly).

5、 Collision - Operator

1. Depth z axis tool setting error.

2. The number of touches and operations are wrong (e.g. single side access, no feed radius, etc.).

3. Use the wrong knife (for example, D4 knife is processed with D ten knife).

4. Program error (for example, A7. NC has gone A9. NC).

5. During manual operation, the hand wheel shakes in the wrong direction.

6. Manual rapid feed in the wrong direction (for example: - x)   X）。

1. For depth z-axis tool setting, pay attention to where the tool is (bottom surface, top surface, analysis surface, etc.).

2. After the collision number and operation number are completed, it shall be checked repeatedly.

3. When clamping the tool, check it against the program sheet and program repeatedly, and then install it.

4. The procedures should be followed one by one.

5. When using manual operation, the operator shall strengthen the operation proficiency of the machine tool.

6. When moving rapidly manually, you can move up to the workpiece in the z-axis first.

6、 Surface accuracy

1. Unreasonable cutting parameters and rough workpiece surface.

2. The blade is not sharp.

3. The tool holder is too long and the blade is too long.

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

5. Program tool feeding mode (forward milling can be considered as far as possible).

6. The workpiece has burrs.

1. Cutting parameters, tolerance, allowance, speed and feed shall be set reasonably.

2. The tool requires the operator to check and replace it irregularly.

3. When clamping the tool, the operator is required to clamp it as much as possible to avoid the blade being too long.

4. For flat cutter, R blade and round nose cutter, the speed feed setting is reasonable.

5. Workpiece has burrs: it is directly related to our machine tool, cutting tool and tool feeding mode. Therefore, we need to understand the performance of the machine tool and supplement the edges of burrs.

Reasons and improvements:

1. Feed too fast

--Slow down to the appropriate feed rate

2. Feed too fast at the beginning of cutting

--Reduce the feed rate at the beginning of cutting

3. Loose clamping (tool)

4. Loose clamping (workpiece)

5. Insufficient rigidity (tool)

--Use the shortest allowable knife, clamp the handle deeper, and try forward milling

6. The cutting edge of the tool is too sharp

--Change the fragile cutting edge angle and the primary cutting edge

7. The rigidity of machine tool and tool handle is insufficient

--Use rigid machine tools and tool handles

Reasons and improvements:

1. The machine speed is too fast

--Slow down and add enough coolant

2. Hardened material

--Use advanced cutting tools, tool materials and increase surface treatment methods

3. Chip adhesion

--Change the feed rate and clean the chips with cooling oil or air gun

4. Improper feed speed (too low)

--Increase the feed speed and try down milling

5. Improper cutting angle

--Change to the appropriate cutting angle

6. The back angle of the tool is too small

--Become a larger back corner

Reasons and improvements:

1. Feed too fast

--Slow down the feed rate

2. Too much cutting

--Use a small amount of cutting per edge

3. The blade length and total length are too large

--Clamp the handle deeper, use a short knife and try to mill it forward

4. Too much wear

--Initial Regrinding

Reasons and improvements:

1. Feed and cutting speed is too fast

--Correct feed and cutting speed

2. Insufficient rigidity (machine tool and tool handle)

--Use better machine tools and tool shanks or change cutting conditions

3. The rear corner is too large

--Change to a smaller back angle and process the blade belt (grind the primary blade with an oilstone)

4. Loose clamping

--Clamping workpiece