Rough cutting and light knife – processing experience summarized by CNC master

1、 General rules of knife path

1. Rough cutting

Under the maximum load of the machine tool, in most cases, the largest knife, the largest feed amount and the fastest feed should be selected. In the case of the same knife, the feed is inversely proportional to the feed. In general, the load of the machine tool is not a problem. The principle of tool selection mainly depends on whether the two-dimensional angle and three-dimensional arc of the product are too small. After the tool is selected, the tool length is determined. The principle is that the tool length is greater than the processing depth. For large workpieces, it is necessary to consider whether the collet has interference.

2. Light knife

The purpose of the smooth knife is to meet the processing requirements of workpiece surface finish and proper allowance. Similarly, the light knife should be as big as possible and take as long as possible, because the fine knife needs a long time, and the most appropriate feeding and feeding should be used. Under the same feed, the greater the transverse feed, the faster it will be. The feed amount of the curved surface is related to the finish after machining. The feed size is related to the surface shape. Without damaging the surface, the minimum allowance, the maximum tool, the fastest speed, and proper feed should be reserved.

2、 Clamping method

1. All clamps are horizontally long and vertically short.

2. vise clamping: the clamping height shall not be less than 10 mm, and the clamping height and processing height must be specified when processing the workpiece. The processing height shall be about 5mm higher than the vise plane to ensure the firmness and avoid damaging the vise. This kind of clamping is a general clamping, and the clamping height is also related to the size of the workpiece. The larger the workpiece is, the higher the clamping height will be.

3. Clamping of clamping plate: the clamping plate is placed on the workbench with a size code, and the workpiece is locked on the clamping plate with a screw. This kind of clamping is suitable for clamping workpieces with insufficient height and large processing force. Generally, medium and large workpieces have good effect.

4. Clamping with sizing iron: when the workpiece is large, the clamping height is not enough, and it is not allowed to lock the screw at the bottom, the sizing iron shall be used for clamping. This kind of clamping requires secondary clamping. First, code the four corners, process the other parts, and then code the four sides to process the four corners. During the second clamping, do not let the workpiece loose, code it first and then loosen it. You can also code the two sides first and process the other side.

5. Clamping of tools: the diameter is more than 10mm, and the clamping length is not less than 30mm; The clamping length shall not be less than 20mm if the diameter is less than 10mm. The clamping of the tool shall be firm, and the tool collision and direct insertion into the workpiece shall be strictly prevented.

3、 Classification of cutting tools and their application scope

1. By material

White steel knife: easy to wear, used for roughening copper and small steel.

Tungsten steel knife: used for angle cleaning (especially steel) and light knife.

Alloy knife: similar to tungsten steel knife.

Purple knife; Used for high-speed cutting, not easy to wear.

2. Divided by cutter head

Flat bottomed knife: used for plane and straight body side, clear plane angle.

Ball knife: used for light knife and light knife in various surfaces.

Bullnose knife (single side, double side and five side): used for steel roughening (R0.8, R0.3, R0.5, R0.4).

Rough knife: used for rough cutting, pay attention to the allowance (0.3).

3. Divide by cutter bar

Straight rod cutter: straight rod cutter is applicable to various occasions.

Inclined rod knife: but it is not applicable to the straight body surface and the surface whose slope is less than the rod slope.

4. Divided by blade

Two blade, three blade and four blade, the more the number of blades, the better the effect. But the more work is done, the speed and feed are adjusted accordingly, and the more the number of blades, the longer the service life.

5. Difference between ball knife and flying knife

Ball knife: when the concave ruler is smaller than the ball ruler and the plane ruler is smaller than the ball R, the light cannot reach (the bottom angle cannot be cleared).

Throwing knife: It has the advantage of clearing the bottom corner. Comparison of the same parameters: V=R* ω The speed is much faster (throwing knife), and the light is bright. Throwing knives are mostly used for contour shapes, and sometimes they do not need neutral light. The disadvantage is that the concave size and the plane ruler are less than the diameter of the flying knife.

4、 Practice of CNC with EDM and copper bar

1. Under what circumstances do you need to be a copper conductor

1) The knife can’t go down at all, so it needs to be made into a copper bar. There is still something that can’t go down in a copper bar, and the shape is convex, so it needs to be divided again.

2) The sabre can go down, but the one that is easy to break also needs to be made into copper, which depends on the actual situation.

3) Products with spark lines shall be made of copper.

4) If the copper pin cannot be made, the bone position is too thin and high, the pin is vulnerable to damage and deformation, deformation during processing and spark deformation, and inserts are required at this time.

5) The east and west surfaces (especially the surfaces will be smooth and even) machined by copper can overcome many problems in precision gongs and drawing.

6) When precise shape or large allowance is required, thick copper must be made.

2. Practice of copper bar

Select the surface to be made into the copper bar, complete the surface to be filled, or extend the extended surface, ensure that all edges of the copper bar are larger than the edge to be punched and do not damage the surface of other products, remove unnecessary plane angles that cannot be cleared (the intersection with the plane angle is a deeper glue position), and fill in the regular shape; Find out the maximum shape of the copper bar, use the side boundary and project it to the supporting surface; Determine the size of the reference frame, cut off the supporting surface, and the copper drawing is basically completed; Material preparation: length * width * height, length and width ≥ Ymax and Xmax are the reference frames. The length and width of the actual copper material must be greater than the reference frame on the drawing. Height ≥ theoretical dimension of copper bar+reference frame height+clamping height.

5、 Drawing Numbering

1. Under the condition that there is no ready machining surface, in the four sides of the plane, the center is to the origin, the top is to zero, and the top surface is not flat (in the case of copper bar), 0.1 allowance is left. That is, when the number of hits is 0 (z), the figure is 0.1 lower.

2. When there is a ready processing surface, make the ready surface on the drawing 0 (z), and if the plane can be divided into two parts, then it will be divided into two parts; otherwise, the actual height, width and length of the ready processing surface (single side) shall be checked for differences with the drawing, and the actual material shall be programmed. Generally, the dimensions on the drawing shall be processed first, and then the shapes on the drawing shall be processed.

3. When multiple bits are required for processing, the first bit (standard bit) should be used as the reference of the other bits. The length, width and height should be used as the reference. All the next processing reference should be based on the surface that has been processed in the previous time.

4. Positioning of insert: put it in the whole, pad the lower part to a certain height, and then raise the height in the drawing. The plane is divided into the middle according to the whole, and the height is locked with screws according to the drawing; If it is square and upright, it can be directly divided into middle; Roughly, the maximum profile can be used to divide; Cut a fixture, center it according to the fixture, determine the relative position between the insert drawing and the fixture, and then place the drawing origin at the center point of the fixture.

6、 Cutter path selection for roughening

1. Curved surface trenching

1) The key is the selection of range and face

The area of tool path processing is: the selected face within the selected range is the termination surface, and the principle is that all places where the tool can go down from the highest point to the lowest point. The selected face should preferably be a full face, while the boundary can only be the area to be machined. The distance of no face extension is less than half of the tool diameter. Because other faces have enough margin, they are automatically protected; It is better to extend the lowest line, because there is no R gong at the lowest point.

2) Selection of cutter: if the cutter cannot be fed by spiral or diagonal line, or the area that cannot be machined cannot be fed by cutter shall be sealed for secondary roughening.

3) Before the light knife, be sure to cut all the areas that are not cut thick, especially small corners, including two-dimensional angles, three-dimensional angles and sealed areas, otherwise the knife will break. Secondary roughening: generally, three-dimensional slotting is used to select the range, and flat end cutter is used for those that can use plane slotting and contour cutter path. Under the condition of not damaging other surfaces, the tool center reaches the selected boundary. Generally, the boundary is not refined. A fast two-way angle is used depending on the situation. The spiral feed angle is 1.5 degrees and the height is 1. When the groove is in a strip shape, if the spiral feed is not possible, the diagonal feed is used. Generally, the filter is turned on, especially when the curved surface is roughened. The feed plane should not be low to avoid knife collision. The safety height should not be low.

4) Retract tool: generally, it is not necessary to withdraw the tool relatively, but to withdraw the tool absolutely. When there is no island, it is necessary to withdraw the tool relatively.

2. Plane trenching

Milling all kinds of planes, concave and flat grooves. When milling some open planes, it is necessary to define the boundary. In principle, the tool can be fed (more than one tool diameter). The open part is more than half of the tool diameter, and the periphery is closed.

3. Appearance

When the selected plane is suitable for contour layering, use contour layering to lift the tool (plane contour). When the tool lifting point is the same as the tool lowering point, it is not necessary to lift the tool. Generally, lift the tool on the z plane and try not to use relative height; The direction of correction is generally right (along the cutter).

4. Cutter path setting for mechanical correction

The number of correction is 21. Change the computer correction to mechanical correction. The feed is vertical. If the cutter cannot pass, increase the value of R without allowance.

5. Contour profile

It is suitable for walking on the closed face. If walking on the open face is four circles, it needs to seal the item face. If it is within or not four circles, it needs to select the range and height (certain arc feed roughening). It is used for roughening: the machining distance in any plane is less than one tool diameter, if it is greater than one tool diameter, it needs to use a larger tool or two contour shapes.

6. Curved streamline

With the best uniformity and dry brittleness, it is suitable for light knives to replace contour shapes in many cases.

7. Radiation knife path

Suitable for large holes in the middle (rarely used). Precautions: the knife is not sharp, the knife is too long, and the workpiece is too deep to go up and down; The surfaces on both sides of the sharp corner in the workpiece should be divided into two knife paths, which cannot be crossed. The edge of the light knife should be extended (use the arc to advance and retreat the knife).

7、 Angle cleaning

1. The corner clearing here is the two-dimensional dead corner, which is the part that has not been reached by the previous process. If the light knife needs to go to the place, the corner should be cleared first and then the light knife. If the angle is too small and deep, it can be cleared by several knives. Do not use a small knife to clear too many places.

2. Clear three-dimensional corners: open some small grooves and some three-dimensional corners.

3. If the cutter is easy to break, it must be considered that the cutter is thin, too long, and the processing amount is too large (mainly in the z direction and depth direction).

4. Cutter path: use two-dimensional shape, and only small angle (R0.8) and two-dimensional plane angle can be cleared; Use parallel knife path; Contour contour; There is a kind of place where the curved surface and the dead corner that cannot be reached by the knife should be sealed first, and then the corner should be cleaned. The small gap in the large surface should be sealed first.

8、 Midlight

1. Medium gloss: steel material and fine common gloss used as curved surface.

2. Principle: When the big knife is rough, there is more margin between layers, which is a process to get better effect when the light knife is open.

3. Features: quick removal, big knife and flying knife can also be used, large feed and large spacing; Do not worry about the surface quality; The flat workpiece does not need to be polished; The workpiece with contour does not need to be polished. When the contour is roughened, the two processes can be put together a little thinner. The thinner refers to the distance between the surface allowance and the layers; If the medium light is needed, another important factor is the working material. The harder the material is, the medium light will be considered; The processing direction of the medium light and the light knife should be better than that of the light knife.

9、 Light knife

Light knife is to meet the assembly requirements of various products and molds, so it is necessary to be very careful and give different knife path settings and parameter settings according to different requirements.

1. The cutting height and final height of the light knife are both changed to 0, and the tolerance is designed to be within 1 wire, without filtering (the smaller the workpiece, the smaller the tolerance, and the tolerance affects the appearance).

2. The front mold and parting surface should reach the best finish, the rear mold can be inferior, and other non matching and void avoidance positions can be rough.

3. Cutter path design is determined by the following factors:

1) Specific profiles (such as planes and other surfaces), steep surfaces and flat surfaces.

2) Whether the two sides are sharp corners (sharp corners are separated).

3) Whether the requirements for the two parts are different (whether to reserve allowance, how much allowance, and the requirements for finish are different).

4) The problem of protecting the surface in the light knife is a big problem. The machined surface must be protected from errors in the processing according to the requirements of the protective surface. Range protection, zero protection without error, height range and plane range; Protective surface protection.

5) The problem of tool path extension. In the light knife, it is better to make arc advance and retreat when the tool path is processed to the edge, otherwise the surface will be slightly extended in advance.

6) The problem of lifting the light knife. Lifting the knife wastes time, so try to avoid lifting the knife.

Method 1: Set knife lifting clearance (small gap)

Method 2: Cover and seal the knife (small gap)

Method 3: Avoid gaps (large gaps)

Method 4: Extend to the same height in contour

7) For the feed problem in the light knife, the first knife feed must be from the outside of the workpiece to avoid vibration and damage to the workpiece. All light knives must be equipped with feed.

8) Tool wear: when the workpiece is large, multiple tools are required to finish the same workpiece.