chengcg – Page 26 – CNC Machining & Turning, Milling, Metal parts

CNC computer gong processing for the knife

In the case of the same tool, 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 will be determined. The principle is that the tool length is greater than the processing depth, and whether the chuck can be removed for large parts.

The purpose of light knife: to meet the workpiece processing requirements: finish, flying die allowance, copper male spark position, etc., at the same time, as large as possible, as fast as possible, because the precision knife takes a long time, with the most appropriate feed and feed, in the same feed, the larger the transverse feed, the faster. The surface feed is related to the finish after processing, and the feed size is related to the surface shape In the case of no damage to the surface, the minimum allowance should be left, the maximum knife should be used, the fastest Belt should be rotated, and the proper feeding should be carried out.

Clamping method:

All clamps are long horizontally and short vertically;
Vise clamping: the clamping height should not be less than 10 mm. When processing the workpiece, the clamping height and processing height must be specified. The processing height should be about 5 mm higher than the vise plane, so as to ensure the firmness and not damage the vise. This kind of clamping belongs to 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;
Splint clamping: the splint is fixed on the worktable with the code, and the workpiece is locked on the splint with the screw. This kind of clamping is suitable for the workpiece with insufficient clamping height and large processing force, generally medium and large workpieces, and the effect is very good.
When the workpiece is large, the clamping height is not enough, and it is not allowed to lock the thread at the bottom, it should be clamped with code iron. This kind of clamping needs to be clamped twice

a. First code the four corners, process the other parts, and then code the four sides and process the four corners. The principle is that during the second clamping, be very careful not to let the workpiece loose, code before loosening,

b. Also has first code two sides, processes other two sides

CNC computer gong processing

In the process of computer gong processing, the operator shall not leave the machine tool without authorization, and shall keep a high degree of concentration and observe the running state of the machine tool.
In case of abnormal phenomenon or accident, the program operation shall be terminated immediately, the power supply shall be cut off and the instructor shall be informed in time, and other operations shall not be carried out;
It is strictly forbidden to tap the control panel and touch screen. It is strictly forbidden to knock the worktable, dividing head, fixture and guide rail;
It is strictly forbidden to open the control cabinet of the numerical control system to watch and touch without permission;
Computer gong processing operators are not allowed to change the internal parameters of the machine tool at will. Interns are not allowed to call or modify other programs that are not compiled by themselves;
On the control microcomputer of machine tool, no other operation is allowed except program operation, transmission and program copy;
CNC milling machine belongs to large precision equipment. Except for the tooling and workpieces placed on the worktable, it is strictly forbidden to stack any tools, clamps, blades, measuring tools, workpieces and other debris on the computer gong processing machine;
It is forbidden to touch the blade tip and scrap iron with hands. Scrap iron must be cleaned with iron hook or brush;
It is forbidden to touch the rotating spindle, workpiece or other moving parts by hand or in any other way;
It is forbidden to measure the workpiece and change the speed manually in the process of processing. It is also forbidden to wipe the workpiece with cotton yarn and clean the machine tool;
Trial operation is forbidden;
When using the hand wheel or fast moving mode to move the position of each axis, make sure to see the “and -” signs in each direction of X, y and Z axes before moving. When moving, slowly turn the hand wheel to observe the correct direction of the machine before speeding up the movement.

CNC processing hand proofing

CNC hand proofing, so hand production in the new product development, product shape in the process of scrutiny is indispensable.

Check the structure design: because it can be assembled, CNC hand board, so it can directly reflect whether the structure is appropriate, installation will not trouble. It is convenient to find out the problem immediately.

To prevent the risk of directly opening the mold: because the cost of mold manufacturing is usually very high, the relatively large mold is probably several hundred thousand, some even several million, if in the process of opening the mold, it is found that the structure is not appropriate or other problems, its loss can be imagined.

Professional CNC hand proofing, CNC hand manufacturers_ Solve the problem of hand model for you

It requires a high degree of mechanical operation, manual carving and design ability for designers. For example, in the design of action tooth box, it is necessary to design toys with walking, running or flying effects according to the requirements of customers, which emphasizes the design ability.

The simulation driver board pays attention to the craftsmanship and the sense of the line of the photo, and is very familiar with the plastic and hardware mold, focusing on the manual carving and mold knowledge; The design of plaster and oil clay hand board by CNC hand board can be called handicraft sculpture independently. There are many hand board creation rooms. The next section will talk about it in detail. It takes a lot of interest and long working experience to do well in the front three kinds of hand boards, and many great masters have got through.

Most parts can reach ± 0. 01mm。 But there are some special problems. For example, when machining POM material with lathe, it can only reach ± 0.05mm. If the product is 1m long, the material is acrylic, no matter how precise the CNC machining machine is, the professional CNC hand proofing will expand, shrink and absorb water with the change of temperature. In that case, the tolerance may be about 1mm. What are the conditions of quotation? Accurate quotation is based on the drawings (can see the size, appearance and structure), materials, post-processing and other specific requirements to measure the price and delivery time.

Computer gong boring type processing

1、 Processing type:

Hole processing:
Drilling: before drilling on the machining center, the center drill must be used for positioning, and then the drill bit 0.5 ~ 2mm smaller than the drawing size shall be used for drilling, and finally the appropriate drill bit shall be used for finishing.
Reaming processing: when reaming the workpiece, it is also necessary to use the center drill to locate, then drill with a drill 0.5 ~ 0.3mm smaller than the drawing size, and finally ream with a reamer. When reaming, pay attention to control the spindle speed within 70 ~ 180rpm / min.
Boring: to boring the workpiece, first use the center drill to locate, then use the drill 1 ~ 2mm smaller than the drawing size to drill, then use the rough boring cutter (or milling cutter) to process to the left side of 0.3mm machining allowance, finally use the pre adjusted size of the fine boring cutter for fine boring, and the last fine boring allowance shall not be less than 0.1mm.
Direct numerical control (DNC) operation:
Before DNC NC machining, the workpiece should be clamped, the zero position should be set, and the parameters should be set.
Open the processing program to transfer data in the computer for checking, then let the computer enter DNC state, and input the file name of the correct processing program.
Press the tape key and the program start key on the machine tool, and the machine controller will flash LSK.
Press enter on the computer to process DNC data.

2、 Contents and scope of workers’ self inspection:

Before processing, the processor must see clearly the contents of the process card, know clearly the parts to be processed, the shape, the dimensions of the drawing and the processing contents of the next process.
Before the workpiece is clamped, the blank size should be measured to see if it meets the requirements of the drawing. When the workpiece is clamped, it must be carefully checked whether its placement is consistent with the programming operation instruction.
After rough machining, self inspection should be carried out in time to adjust the data with errors in time. The main content of self inspection is the position and size of the processing part.

(1) Whether the workpiece is loose or not;

(2) . whether the workpiece is correctly divided into parts;

(3) Whether the dimension from the processing part to the datum edge (datum point) meets the drawing requirements;

(4) The position and size of processing parts. After checking the position and size, measure the rough machined shape ruler (except arc).

Finish machining can only be carried out after rough machining and self checking. After finishing, the workers should carry out self inspection on the shape and size of the processing parts: check the basic length and width of the processing parts on the vertical plane; measure the base point size marked on the drawing for the processing parts on the inclined plane.

How to make precision parts

Numerical control tool is one of the preconditions to improve machining efficiency, its selection depends on the geometry of the machined parts, material state, fixture and machine tool rigidity. The following aspects should be considered:

(1) The cutting tool is selected according to the cutting performance of the part material. For example, turning or milling high strength steel, titanium alloy and stainless steel parts, it is recommended to choose indexable carbide tools with good wear resistance.

(2) The tool is selected according to the processing stage of hardware parts. That is to say, the roughing stage is mainly to remove the allowance, and the tool with better rigidity and lower accuracy should be selected. The semi finishing and finishing stages are mainly to ensure the machining accuracy and product quality of the parts, and the tool with high durability and high accuracy should be selected. The precision of the tool used in the roughing stage is the lowest, while the precision of the tool used in the finishing stage is the highest. If the same tool is selected for rough machining and finish machining, it is suggested that the tool eliminated from finish machining should be selected for rough machining, because the wear of tool eliminated from finish machining is mostly slight edge wear, and the coating is worn and polished. Continued use will affect the machining quality of finish machining, but has less impact on rough machining.

(3) According to the characteristics of NC lathe processing area, the tool and geometric parameters are selected. If the structure of the part permits, the cutter with large diameter and small ratio of length to diameter should be selected; the end edge of the over center milling cutter for cutting thin and ultra-thin wall parts should have enough centripetal angle to reduce the cutting force of the cutter and cutting parts. When machining soft material parts such as aluminum and copper, the end mill with slightly larger rake angle should be selected, and the number of teeth should not exceed 4.

When selecting the cutting tool, the size of the cutting tool should be adapted to the surface size of the workpiece. In production, end milling cutter is often used to process the peripheral contour of plane parts; when milling plane, cemented carbide blade milling cutter should be selected; when machining boss and groove, high speed steel end milling cutter should be selected; when machining rough surface or rough hole, corn milling cutter with cemented carbide blade can be selected; Ball end milling cutter, ring milling cutter, cone milling cutter and disk milling cutter are often used to process some solid surface and variable angle profile.

In free-form surface machining, because the end cutting speed of ball end cutter is zero, in order to ensure the NC machining accuracy, the cutting line spacing is generally very small, so ball end milling cutter is suitable for surface finishing. The end milling cutter is much better than the ball end milling cutter both in the surface processing quality and processing efficiency. Therefore, on the premise of ensuring that the parts can not be cut, the end milling cutter should be selected as far as possible when rough machining and semi finish machining curved surface.

In the machining center, all the tools are pre installed in the tool library, and the corresponding tool change action is carried out through the tool selection and tool change instructions of the NC program.

Computer gong processing surface treatment:

In terms of appearance, the machined surface of the parts shall not have obvious defects such as scratches and scratches.
The surface of products processed by CNC lathe must be smooth, beautiful, no burr, no flash, etc
In terms of quality, the machined surface of parts must meet the requirements of corrosion resistance, wear resistance and hardness.

In order to meet the accuracy of parts processing, it must also meet the surface technical requirements and appearance requirements. The parts we process can’t appear to be full of burrs. Here we introduce the surface processing requirements of CNC lathe

In terms of appearance, the machined surface of the parts shall not have obvious defects such as scratches and scratches.
The surface of products processed by CNC lathe must be smooth, beautiful, no burr, no flash, etc
In terms of quality, the machined surface of parts must meet the requirements of corrosion resistance, wear resistance and hardness.
Selection principle of cutting parameters

According to the cutting requirements, first determine the back cutting amount AP, then look up the table to get the feed, and then look up the table to calculate the main cutting speed u through the formula.

In many cases, we can use empirical data to determine the value of these three elements.

Selection method of cutting parameters

Practice has proved that the selection of reasonable cutting parameters is related to many factors such as machine tool, cutting tool, workpiece and technology. The method of reasonable selection of processing amount is as follows:

In rough machining, it is necessary to ensure high production efficiency, so it is necessary to choose a larger back draft a. , larger feed rate,, low cutting speed u is selected.

When finishing, it is mainly to ensure the size and surface accuracy of the parts, so it is necessary to select smaller back feed AP, smaller feed, and higher cutting speed U.

In rough machining, it is necessary to give full play to the potential of NC lathe and the cutting ability of cutting tools. In the semi finish machining and finish machining of CNC lathe factory, how to ensure the machining quality should be considered, and on this basis, the productivity should be improved as much as possible. When selecting the cutting parameters, the CNC lathe factory should ensure that the cutting tool can complete a part or ensure that the durability of the cutting tool is not less than one working shift, at least not less than half a working shift. The specific value of CNC lathe factory should be selected according to the provisions in the machine tool manual, tool durability and practical experience.

(1) It’s a choice to take a knife on your back. The selection of back cutting amount should be determined according to the rigidity of machine tool, fixture, fixture and workpiece as well as the power of machine tool. In the case of the process system allows, as far as possible to choose a larger amount of back knife. In addition to the allowance left for the subsequent process, the rest of the rough machining allowance should be cut off as far as possible to minimize the number of tool runs.

Generally, on medium power machine tools, the back draft of rough machining is 8-10 mm (one side). The back feed of CNC lathe factory is 0.5-5 mm for semi finishing and 0.2-1.5 mm for finishing.

(2) The feed rate is determined. Feed rate refers to the change of tool feed direction in unit time. Numerical control lathe factory moving distance. The principle of determining the feed rate is: when the quality requirements of the workpiece can be guaranteed, in order to improve the productivity, a higher feed rate can be selected. When cutting, turning deep hole or finishing lathe, the CNC lathe factory should choose a lower feed speed. The feed speed should be adapted to the spindle speed and back feed.

Notes for computer gong processing:

Confirm the model, size and machining allowance of the blank according to the program sheet before operation, and remove sand and polish the blank
After operation, confirm the position of the workpiece and the processing sequence, and complete the table comparison
In the process of centring, if the “centring rod” is needed, the rotating speed is 501r / m. if the cutter is used, the rotating speed depends on the cutter. In this process, the data must be taken at the same height to ensure the accuracy of centring. After centring, the “G0 g54 x0 Y0” can be used for inspection
Before formal processing, check and confirm the position of the workpiece and whether the data is correct

Precautions during processing:

Before processing each program, it is necessary to strictly confirm whether the tool is consistent with the program
When loading the tool, it is necessary to confirm whether the length of the tool and the selected tool holder are suitable
In the same workpiece, each tool setting should be kept in the same area to ensure the accuracy of tool receiving
Try to blow with air in roughing procedure and spray oil in smooth knife procedure
Clean up the aluminum slag in the machine tool before light knife oil injection to prevent the aluminum slag from absorbing oil
During the self operation of the machine tool, the operator is not allowed to leave the machine tool or check the operation status of the machine tool regularly. If he / she needs to leave midway, he / she must appoint relevant personnel to check
If excessive machining allowance is found in the process of machining, it is necessary to use “single section” or “pause” to clear x, y and Z values, then mill them manually, and then swing them back to “zero” to let them run by themselves
In case of tool collision during machining, the operator must stop the machine immediately, such as pressing the “emergency stop” button or “reset” button or setting the “feed rate” to zero
Do not open the door when the machine tool is running to avoid flying knife or workpiece
The workpiece must be cleaned and deburred in time
At the end of work, the operator must make timely and accurate handover to ensure the normal follow-up processing
Before turning off the machine, make sure that the tool magazine is in the original position and the XYZ axis stops in the middle position. Turn off the power supply and the main power supply on the operation panel of the machine in turn

Introduction of CNC milling machine

The biggest difference between CNC milling machine and machining center is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, and a variety of machining functions can be realized.

CNC machining center is composed of mechanical equipment and CNC system, which is suitable for processing complex parts. CNC machining center is one of the most widely used CNC machine tools with the highest output in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after clamping at one time, and the processing accuracy is high. For the batch workpiece with medium processing difficulty, its efficiency is 5-10 times higher than that of ordinary equipment, especially it can complete the processing that many ordinary equipment can’t complete, and it is more suitable for single piece processing with complex shape and high precision requirements or small and medium batch multi variety production. It concentrates the functions of milling, boring, drilling, tapping and cutting threads on one equipment, so that it has a variety of technological means. Machining centers are classified into horizontal and vertical machining centers according to the spatial position of the spindle. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock.

Introduction of computer gong finishing

The feed route of finishing machining is basically carried out along the contour of the parts. Therefore, the key point of determining the feed route is to determine the feed route of rough machining and empty stroke. In the CNC lathe processing, the determination of the processing route should generally follow the following principles.

① It should be able to ensure the accuracy and surface roughness of the workpiece to be processed.

② The processing route is shortest, the idle travel time is reduced, and the processing efficiency is improved.

③ The workload of numerical calculation should be simplified as much as possible.

④ For some repeated programs, subroutines should be used.

Advantages and disadvantages of CNC CNC CNC machining has the following advantages:

① The number of tooling is greatly reduced, and complex tooling is not needed to process complex parts. If we want to change the shape and size of the parts, we only need to modify the processing program of the parts, which is suitable for the development and modification of new products.

② The machining quality is stable, the machining accuracy is high, and the repetition accuracy is high, which can meet the machining requirements of aircraft.

③ In the case of multi variety and small batch production, the production efficiency is high, which can reduce the time of production preparation, machine adjustment and process inspection, and reduce the cutting time due to the use of the best cutting quantity.

④ It can process complex surface which is difficult to be processed by conventional methods, and even process some parts which cannot be observed.

CNC machining center milling cutter

CNC machining center used on the milling cutter, should choose all cemented carbide, general milling machine used on the selection of white steel material. The hardness of white steel milling cutter is softer than that of cemented carbide milling cutter. Cemented carbide milling cutter has good thermal hardness, wear resistance, but poor impact resistance. The carbide is made by powder metallurgy. Its hardness can reach about 90hra and its thermal property can reach about 900-1000 degrees.

Number of milling cutter teeth

When selecting a milling cutter, the number of teeth should be considered. For example, the coarse tooth milling cutter with a diameter of 100 mm only needs 6 teeth, while the dense tooth milling cutter with a diameter of 100 mm can have 8 teeth. The size of pitch will determine the number of cutter teeth to be cut together in milling, which affects the smoothness of cutting and the requirement of cutting rate.

Chip holding tank

Coarse tooth milling cutter is mostly used for rough machining, because it has a large chip holding groove. Assuming that the chip holding groove is not large enough, it will make it difficult to roll the chip or the conflict between the chip and the tool body or workpiece aggravate. At the same feed rate, the cutting load of coarse tooth milling cutter is larger than that of dense tooth milling cutter.

Cutting depth

In finish milling, the cutting depth is shallow, generally 0.25-0.64mm. The cutting load of each tooth is small (about 0.05-0.15mm), and the power required is small. It is able to select dense tooth milling cutter, and it is able to select larger feed rate.

Application of rough milling

In heavy load rough milling, excessive cutting force can make the machine tool with poor rigidity vibrate. This kind of chatter will lead to the edge collapse of cemented carbide blade, and then shorten the tool life. Selecting coarse tooth milling cutter can reduce the requirement of machine power.

CNC machining center workpiece processing process is no longer like the traditional processing equipment, the need for uninterrupted control of the machine tool to end, control the function parts of the machine tool for messy and precise action, and then high-precision, efficient end of the processing process. The programming of workpiece processing is the key of workpiece processing in machining center. However, if the programming is not reasonable or the parameters are not set properly, the machining accuracy and power of the workpiece will be seriously affected, such as overcutting. Overcutting is a serious problem in workpiece processing, which can lead to the invalidation of workpiece. For some reason, the front-line processing personnel have worked out the processing program which is sure to be overcut. If the system can announce the alarm signal in advance in the working process, the overcut can be avoided.