Share: CNC machining experience

Knowledge sharing by Guangdong Shunde Teamwork Model Technology Co., Ltd, whom with over 20 years rapid prototyping experience.

First, the general rules of the knife:

Open rough: Under the maximum load of the machine tool, in most cases, the largest possible knife should be used, and the maximum amount of feed should be fed as fast as possible. In the case of the same knife, the feed is inversely proportional to the amount of feed. Under normal circumstances, the load of the machine tool is not a problem. The principle of selecting the knife is mainly considered according to whether the two-dimensional angle of the product and the three-dimensional arc are too small. After selecting the knife, the length of the knife is determined. The principle is that the length of the knife is greater than the machining depth, and the large workpiece should consider whether the chuck has interference.

Light knife: The purpose of the light knife is to meet the processing requirements of meeting the surface finish of the workpiece and preserving the appropriate margin. Similarly, the light knife uses the largest possible knife, as fast as possible, because the fine knife takes a long time to use the most suitable feed and feed. Under the same feed, the transverse feed is larger and faster, and the amount of curved feed is related to the finished finish. The size of the feed is related to the shape of the surface of the surface. Leave the smallest margin without hurting the surface. Use the largest knife, the fastest speed, and the appropriate feed.

Second, the clamping method:

1. All the clips are horizontally long and short.

2. Vise clamping: The clamping height should not be lower than 10 mm. The height of the clamping and the processing height must be specified when machining the workpiece. The processing height should be about 5 mm above the plane of the vise, in order to ensure the firmness without damaging the vise. This type of clamping is a general clamping, and the clamping height is also related to the size of the workpiece. The larger the workpiece, the higher the clamping height.

3. Plywood clamping: The pallet is coded on the workbench, and the workpiece is screwed on the clamping plate. This clamping is suitable for workpieces with insufficient clamping height and large processing force. Generally, medium and large workpieces have better effect. .

4. Code iron clamping: When the workpiece is large, the clamping height is not enough, and the bottom wire is not allowed to lock, the code iron is used for clamping. This kind of clamping needs to be double-mounted, first code the four corners, process the other parts, and then code the four sides to process the four corners. When the secondary clamping is done, do not let the workpiece loose, first loosen the code. You can also code both sides and process the other two sides.

5, the clamping of the cutter: the diameter of 10mm or more, the clamping length is not less than 30mm; the diameter of 10mm or less, the clamping length is not less than 20mm. The tool should be clamped firmly to prevent the knife from being inserted directly into the workpiece.

Third, the classification of the tool and its scope of application:

1, by material:

White steel knife: easy to wear, used for copper and small steel material to open.
Tungsten steel knife: used for clear angle (especially steel) and light knife.
Alloy knife: similar to tungsten steel knife.
Purple knife; used for high speed cutting, not easy to wear.

2, according to the knife head:

Flat-bottomed knife: used for flat and straight sides, clear plane angle.
Ball Knife: Used for light and light knives in various curved surfaces.
Bull nose knife (single side, double side and five sides): used for steel material roughing (R0.8, R0.3, R0.5, R0.4).
Rough knives: used for roughing, pay attention to the remaining amount of retention (0.3).

3. Press the knife bar to divide:

Straight bar cutters: Straight bar cutters are available for all occasions.
Slant bar knife: It is not suitable for straight face and face with slope less than the slope of the bar.

4, according to the blade:

Two-blade, three-blade, four-blade, the more the number of blades, the better the effect, but the more work, the adjustment of the speed and feed, the long blade life and long life.

5, the difference between the ball knife and the flying knife light knife:

Ball knives: The concave ruler is smaller than the ball ruler, and when the plane ruler is smaller than the ball R, the light is not enough (clearing the corner).
Flying knife: The advantage is that the bottom angle can be cleared. Comparison of the same parameters: V=R*ω The speed is much faster (flying knife), the light is bright, the flying knife is used more for the contour, and sometimes the flying knife does not need the light. The disadvantage is that the concave size and the flat ruler are smaller than the diameter of the flying knife.

Fourth, CNC with EDM, the practice of Tonggong:

1. Under what circumstances need to do the copper public:

The knife is not going to be a copper gong. It can't be done in a copper gong. The shape is convex and needs to be subdivided.
The knife can go down, but the knife is also easy to break, which depends on the actual situation.
Products requiring a fire pattern need to be made of copper.
If the copper can not be made, the bone position is too thin and too high, it is easy to damage and easy to deform, and the deformation and sparking deformation during processing require inserts.
The surface of the copper-made object (especially the surface will be very smooth and even) can overcome many problems in the fine and many problems in the drawing.
A thick copper must be made when a precise shape or margin is required.

2. The practice of Tonggong:

Select the surface to be copper, fill the surface of the patch, or extend the face to ensure that all edges of the copper are larger than the edge to be hit without harming the surface of other products, eliminating unnecessary The plane angle (which is a deeper glue position at the intersection of the plane angles), fills the regular shape; finds the largest shape of the copper, uses a boundary and then projects it onto the support; determines the size of the reference frame, cuts off the support, and The copper common diagram is basically completed; the preparation material: length * width * height, length and width ≥ Ymax and Xmax are the actual length of the copper material of the reference frame must be larger than the reference frame on the drawing. High ≥ copper male theoretical size + reference frame height + clamping height.

Five, the number of drawings:

1. In the absence of ready-made processing surface, the plane is divided into four sides, the center is opposite to the origin, the top is facing zero, and the top surface is uneven (in the case of copper), leaving a margin of 0.1, that is, when hitting the number, the actual pair is 0 (z ), the figure is 0.1 lower.

2. When there is a ready-made working surface, make the ready-made surface on the map face 0(z), and divide the plane energy into the middle, otherwise the actual surface height (width) should be checked with the ready-made edge number (single side). The length is different from the drawing and is programmed according to the actual material. In general, the shape on the graph is first processed into the dimensions on the graph.

3. When multiple bits are to be processed, the first bit (standard position) is to be smashed by the other bits. The length, width and height are all ambiguous. All the next processing benchmarks must be processed the same time. The standard shall prevail.

4, positioning of the insert: placed inside the whole, put a certain height below the bottom and then the drawing also raises the height, the plane is divided into the whole, the height is locked with the silk thread according to the figure below; In the middle; a rough point can be divided into the largest shape; cut a fixture, according to the fixture, the relative position of the insert and the fixture is determined and then the origin of the drawing is placed at the center of the fixture.

Sixth, open rough path selection:

1, surface grooving

The key is the choice of scope and choice of face.

The area where the tool path is machined is: the selected face in the selected range is the end face, and all the places where the tool can go from the highest point to the lowest point are the principle. The selected surface is preferably the whole surface, and the boundary can only be the area to be processed. The distance from the surface is less than half the radius of the tool. Because the other surface has sufficient margin, it is automatically protected; it is better to extend the lowest line because There is one R at the lowest point.

Knife selection: If the tool can't be screwed or slashed into the knife or the area that can't be processed can't enter the area of the knife, it will be left for the second time.

Before the light knife, be sure to open all the unopened areas, especially the small angles, including the two-dimensional angle, the three-dimensional angle and the sealed area, otherwise the knife will be broken. Secondary opening: Generally, the range is selected by three-dimensional digging, flat-bottomed knives, and can be used for plane grooving and shape knives. The tool center to the selected boundary without hurting other faces, generally does not refine the boundary, depending on the situation, the spiral direction is 1.5 degrees, the height is 1. When the shape of the groove is strip, it cannot be The spiral lower knife is fed with a diagonal line. Generally, the filter is opened, especially the curved surface is thick, and the plane of the feeding is not low, so as to avoid collision, the safety height cannot be low.

Retracting the knife: Generally, it is not necessary to retreat the knife. Absolute retraction is used. When there is no island, the relative retraction is used.

2, plane trenching: milling all kinds of planes, concave flat groove, when milling part of the open plane, you need to set the boundary, the principle can enter the knife (more than one tool diameter), the opening is more than half of the tool radius, closed Peripheral.

3. Shape: When the selected plane is suitable for layering, use the shape layering knife (planar shape). When the knife point and the lower knife point are one point, it is not necessary to lift the knife plane to lift the knife. Try not to use the relative height. ; correct direction is generally right correction (shun knife).

4, the mechanical correction of the knife path setting: the correction number is 21, change the computer to correct the mechanical correction, the feed is a vertical feed, the knife can not pass the place to change the big R does not leave a margin.

5. Contour shape: suitable for walking closed surface. If the open surface is four turns, the surface should be sealed. If it is within four circles or not four, the range and height should be selected. ), for the case of thickening: the machining distance in any plane is less than one tool radius, and if it is larger than one tool diameter, a larger knife or two contours are used.

6, curved streamline: has the best uniformity and crispness, suitable for light knife can often replace contours.

7, radio knife path: suitable for the case of large holes in the middle (less use). Matters needing attention: the knives, the knives are not sharp, the knives are too long, the workpieces should not go up and down when the workpiece is too deep; the sides of the sharp corners in the workpiece should be divided into two paths, not the past, the edge of the light knife is best Extend (in and out of the knife with an arc).

Seven, clear angle:

1. The clear angle here is a two-dimensional dead angle, which is the part that has not been reached before. For example, if the light knife needs to go, the angle should be cleared first, then the angle of too small and deep can be divided into several pieces. Don't clear too many places with a knife.
2, clear three-dimensional angle: open some small grooves, some three-dimensional corners.
3, easy to cut the knife, must consider the case like a fine knife, too long, the processing volume is too large (mainly z-direction, depth direction).
4, knife path: use two-dimensional shape to walk, can only clear the small angle (R0.8) and two-dimensional plane angle; use parallel knife path; use contour shape; there is a place where the knife can not go to the surface and shape can not go The dead angle must be sealed first and then the knife is cleared. Finally, the small corners in the large face are generally sealed first.

Eight, Zhongguang:

1, Zhongguang: as a curved steel material and fine public light.
2. Principle: When the large knife is rough, the margin between the layer and the layer is more, in order to get a better effect when the light knife is used,
3, Features: rapid removal, large knife flying knife can also, large feed, large spacing; do not worry about surface quality; flat workpiece does not have to be light; contoured workpieces do not need medium light, contours can be thinner when thicker Putting the two processes together, the fine point refers to the surface margin and the distance between the layers; there is no need for medium light, and an important factor is the working material. The harder the material, the medium light; the processing of the medium light The direction and the light knife are rough, and the things processed in this way are better and evener.

Nine, light knife:

The light knife is to meet the assembly requirements of various products and molds, so it is very prudent to give different tool setting and parameter setting according to different requirements.

1. The lower knife height and the final height of the optical knife are changed to 0, the tolerance is designed within 1 wire, no need to filter (the smaller the workpiece, the smaller the tolerance, the tolerance affects the appearance).

2. The front mold and the parting surface should achieve the best finish, the back mold can be second, and the other non-cooperating and avoiding spaces can be rough.

3. The design of the tool path is determined by the following factors:
Specific shapes (such as planes and other faces), steep faces and flat surfaces.
Whether there is a sharp angle between the two sides (the angle is separated).
Whether the two parts are different (do not leave a margin, the amount of the margin, the requirements of the finish are different).
The problem of the protective surface in the light knife is a big problem. The processed surface must be protected against the error in the processing and protected according to the requirements of the protective surface. Range protection, 0 protection without error, height range and plane range; protection surface protection.
The problem of the extension of the knife path, in the light knife, it is best to make the arc advance and retreat when the knife path is machined to the edge, otherwise the surface is slightly extended in advance.
The problem of lifting the knife in the light knife. It is a waste of time, so try to avoid lifting the knife.
Method 1: Set the knife gap (small gap)
Method 2: Cover, seal the knife (small gap)
Method 3: Avoid gaps (large gaps)
Method 4: When the contour is increased, the problem of the feed to the same height is extended. The first knife must be moved from the workpiece to avoid vibration and damage to the workpiece. All the blades must be set.
Tool wear problem: When the workpiece is large, it is necessary to complete the same workpiece.