chengcg – Page 13 – CNC Machining & Turning, Milling, Metal parts

What is the speed of CNC lathe

With the improvement of the performance of the core processor of CNC system, the feed speed limit of high-speed machining center can reach 80m / min and the empty running speed can reach about 100m / min. At present, many automobile factories in the world, including China’s Shanghai General Motors Company, have adopted the production line composed of high-speed machining centers to partially replace the modular machine tools. The feeding speed limit of the hypermach machine tool of Cincinnati is 60m / min, the fast speed is 100M / min, the acceleration is 2G, and the spindle speed has reached 60000r / min. It takes only 30min to process a thin-walled aircraft part, while the same part takes 3 hours in general high-speed milling machine and 8 hours in general milling machine. Due to the specialization of the division of labor among the components of the mechanism, the high-speed spindle is becoming more and more popular with the development of professional spindle factories. In the past, the models used only for High-speed Automobile Industry (models with more than 15000 revolutions per minute) have become an essential element of mechanical products.

ken. tang@chengcg.com

The importance of CNC processing stability!

In the field of machining industry, the stability of parts processing on machine tools is very important. For example, for CNC machining, the stability of precision parts machining process is a prominent problem. The machining process must consider the material properties and external dimensions of parts. Now let’s look at the importance of precision CNC machining stability:

Machine tool: precision machining in order to meet the requirements of CNC machine tools, CNC machine tools mostly adopt the overall structure. Gray cast iron, artificial granite, steel plate weldment and other materials are used. The basic support of the whole CNC machine tool is generally used to place important parts such as guide rail and spindle box. In order to meet the machining accuracy of CNC machine tools, the machining accuracy reaches the range of production standards.
Procedure: the programming engineer formulates cutting parameters and CNC machining feed rate according to the part processing process steps. Suitable for rough machining or finish machining. Ensure the machining quality of precision parts.
Selection of cutting tools: parts with high material hardness have high requirements for cutting tools for precision machining. Because of the high-speed cutting hardness of the tool, the material is easy to wear and even break directly. Different materials need to be processed with selected tools.

The above is about the importance of stable CNC processing. For CNC processing manufacturers, it is very important to schedule the delivery date according to the normal production plan. The normal delivery date is often affected by unstable processing.

ken. tang@chengcg.com

Precision parameter control of CNC machining

In the mechanical processing industry, CNC processing is also known as computer gong processing. It refers to the processing steps completed by the NC command of the programmer. Now let’s take a look at the accuracy parameters of CNC machining, which is mainly determined by the level that the specific geometric parameters (specification, shape and position) of CNC parts are consistent with the ideal geometric parameters. Learn the following parameters in detail:

In the process of machining mechanical parts and small batch parts, CNC machining accuracy usually includes three level parameters: specification accuracy, shape accuracy and position accuracy.

Appearance specification parameters of CNC machining

The specific specification of the machined surface of CNC parts or the middle of the surface is consistent with the ideal part specification. The ideal part processing specification refers to the median value of the specification indicated on the part drawing.

Shape accuracy parameters of CNC machining

The specific shape of the machined surface of CNC parts is consistent with the ideal part surface shape. The ideal part surface shape refers to the definite surface geometry shape.

Precision parameters of machining parts of CNC parts

After machining, the specific parts on each surface of CNC parts are consistent with the parts between the surfaces of ideal parts. The position between the surfaces of an ideal part refers to the positive position between the surfaces.

The above is the accuracy parameter control of CNC machining. For different shapes, shapes, simplicity and complexity, it is necessary to select appropriate machining process parameters to improve CNC machining efficiency and ensure the machining accuracy of parts.

ken. tang@chengcg.com

Factors affecting CAC machining accuracy

As we all know, the reason why the machining of precision parts is called precision machining is precisely because its machining process and process requirements are very high, and the precision requirements for products are very high. The machining precision of precision parts includes the precision of position, size and shape. We summarize the following ten factors affecting the machining precision of precision parts:

(1) The rotation runout of the spindle of the machine tool can produce a certain error to the machining accuracy of the parts.

(2) The inaccuracy of machine tool guide rail can also lead to the error of workpiece shape processed by precision parts.

(3) Transmission parts can also lead to workpiece machining errors, which is also the main factor of workpiece surface errors.

(4) Different types of cutting tools and fixtures will also have different degrees of impact on the accuracy of machining workpieces.

(5) In the process of machining and cutting, the change of the position of the force point will lead to the deformation of the system, resulting in differences, and can also cause varying degrees of errors in the accuracy of the workpiece.

(6) Different cutting force will also affect the workpiece accuracy.

(7) The deformation caused by the heating of the process system often affects the accuracy of the workpiece. The error caused by thermal deformation of the process system. During machining, the process system will produce certain thermal deformation under the action of various heat sources.

(8) The deformation of the machine tool due to heating will lead to the deformation of the workpiece.

(9) The thermal deformation of the tool will have a great impact on the workpiece.

(10) The thermal deformation of the workpiece itself is mainly caused by heating in the cutting process.

ken. tang@chengcg.com

Characteristics of CNC precision parts machining

In practical application, the higher the precision of precision parts, the more exquisite it is, the more it can reflect the machining level and quality. Therefore, generally speaking, NC machining has incomparable advantages and characteristics in machining, and its product quality is usually higher. What are the characteristics of NC precision parts machining?

NC precision parts processing plays an irreplaceable role in the development of new products. Generally speaking, parts with different complexity can be processed through programming, while the modification and updating design only need to change the program of the lathe, which can greatly shorten the R & D cycle of products.
The production efficiency of NC precision parts processing is higher. NC parts processing can process multiple surfaces at the same time. Compared with ordinary lathe processing, it can save a lot of processes and time, and the quality of parts processed by NC is much more stable than ordinary lathe.
The initial investment is larger than that of ordinary lathe, because the price of NC lathe is very high, and its maintenance cost and first preparation period for processing are long.
The automation of NC precision parts processing is very sufficient, which greatly reduces the physical labor intensity of workers. Workers do not need to operate the whole process like ordinary lathes in the processing process, but mainly observe and supervise lathes. However, the technical content of NC machining is higher than that of ordinary lathe, so it requires higher mental labor than ordinary lathe.

Familiar with the characteristics of NC precision parts processing, we can better operate NC precision parts processing and improve efficiency.

ken. tang@chengcg.com

Common methods of CNC precision machining

For the machinery industry, the substances they most often contact are a series of parts and components. No matter which style or type, they will be familiar with and know more or less. The staff in the relevant industry know what kind of parts are used in which structure or application position. However, no matter which configuration, it needs to go through certain processing steps before it can be implemented in specific mechanical equipment. Therefore, professionals call this step precision part machining.

There are many ways to process precision parts, such as heat treatment. Part refers to a single piece that cannot be separated in machinery. It is not only the basic element of the machine, but also the basic unit in the process of mechanical manufacturing. Its manufacturing process generally does not need assembly process. Such as bearing sleeve, bearing bush, nut, crankshaft, blade, gear, cam, connecting rod body, connecting rod head, etc.

1、 Precision parts machining. It mainly includes precision turning, mirror grinding and grinding. Micro turning is carried out on a precision lathe with a finely ground single crystal diamond turning tool. The cutting thickness is only about 1 micron. It is often used to process high-precision and highly smooth parts such as spherical, aspherical and planar mirrors of non-ferrous metal materials.

2、 Precision parts processing. When the machining accuracy of precision parts is nano, or even finally atomic units (atomic lattice distance is 0.1 ~ 0.2 nm), the machining method of ultra precision parts can not adapt. It is necessary to use the machining method of special precision parts, that is, the application of chemical energy, electrochemical energy, thermal energy or electric energy to make these energy exceed the combined energy between atoms, So as to remove the adhesion, combination or lattice deformation between some atoms on the surface of the workpiece, so as to achieve the purpose of ultra precision machining. These processes include mechanochemical polishing, ion sputtering and ion implantation, electron beam exposure, laser beam processing, metal evaporation and molecular beam epitaxy.

ken. tang@chengcg.com

How to accept CNC machining center?

How should CNC machining center conduct acceptance? The acceptance of CNC machining center directly affects the operation of equipment manufacturers. The general factory acceptance standard is to process and test the workpiece directly. In fact, after the workpiece processing test, we can basically determine that the key parts of the CNC machining center meet the standards and have no problems in normal use. However, there are still some details. We should also pay attention to the acceptance. It is better for the manufacturer to have its own acceptance process or standard, so as to better ensure the quality and subsequent use of CNC machining center.

Performance and function inspection of NC machine tools

It is mainly to check whether the moving parts and auxiliary devices of CNC machining center have abnormal phenomena and noise during start, stop and operation, and whether the lubrication system, cooling system and fans work normally.

Machine tool performance test:

Spindle performance inspection

Select low, medium and high speeds. The spindle is started five times continuously, and then shut down to check the flexibility and reliability of its action. At the same time, check whether the power display on the load meter meets the requirements.
Manual data input and input can gradually increase the spindle from low speed to the maximum allowable speed. Check whether the rotating speed is normal. Generally, the allowable error shall not exceed 10%. Check the spindle speed at the same time. Observe whether the noise, vibration and temperature rise of the main shaft are normal. After high-speed operation for 2h, the temperature rise of main shaft is 15 “C
In order to check the flexibility and reliability of spindle action, the spindle can be stopped for more than 5 times continuously.

Mechanical zero point check

The reliability check of the soft and hard limit of the vertical machining center machine tool. The soft limit is generally determined by the system parameters, and the soft limit reliability can be completed by checking the system parameters. The hard limit is determined by the travel switch set at the limit position of each feed shaft, and the reliability of the hard limit is determined by the reliability of the travel switch.
Check the reliability and accuracy of zero return by returning to the original point, and check the zero return performance of each feed shaft.

Inspection of feed shaft

Manually operate the low, medium and high-speed feeding and rapid movement of each feed shaft to check whether the movement proportion is correct, whether the movement is stable and whether there is noise.
Manual data input mode (MDI) operation can detect whether the rapid movement and feed speed are normal through goo and gol command functions.

Inspection of tool change device

Carry out tool exchange step by step manually. Check whether the actions such as grasping, loading and pulling are accurate and appropriate. During the adjustment of CNC machining center, the calibration inspection method is used for inspection. In case of error, the stroke of the manipulator, the support of the manipulator or the position of the tool magazine can be adjusted.

ken. tang@chengcg.com

Large gantry computer gong processing

Large gantry computer gong processing is a common processing project in machinery, especially large-scale machining. There are still many technical problems in large-scale CNC processing. What requirements should be observed in terms of machining and technology?

Requirements for processing large gantry computer gongs

1、 Remove the oxide scale on the surface of the parts, and the machined surface of the parts shall be free of scratches, scratches and other defects that damage the surface of the parts. The tolerance of unmarked shape shall meet the requirements of gb1184-80, the standard tolerance of unmarked length shall be ± 0.5mm, and the casting tolerance zone shall be symmetrical with the basic standard equipment of blank.

2、 The rolling bearing of the device is allowed to be heated by oil for hot installation, and the oil temperature shall not exceed 100 ℃. Sealing filler or sealant is allowed to be used in the hydraulic system of the device, but it shall be avoided to enter the system. The parts and components entering the device must have the certificate of inspection before the device can be installed.

3、 Parts must be cleaned before installation, and there shall be no burrs, burrs, scale, rust, chips, oil, colorant, dust, etc. Before installation, recheck the main matching standards of parts, especially the interference matching standards and relevant accuracy.

4、 During the use of large gantry computer gong processing equipment, parts are not allowed to be knocked, bumped, scratched and rusted. When fastening screws, bolts and nuts, it is forbidden to use improper screwdriver and wrench for impact or use. After fastening, the screw groove, nut, screw, bolt head, etc. shall not be damaged due to large CNC processing. For fasteners that are tightened according to the specified torque requirements, a torque wrench shall be selected and tightened according to the specified tightening torque.

ken. tang@chengcg.com

Reasons for poor machining accuracy of CNC

The precision of hardware parts almost determines the quality of products. The more precise hardware parts are, the higher the requirements for precision are. So why does the machining accuracy of precision parts become worse? Here are the answers for you:

Precision parts processing

1、 The factor is the poor machining accuracy of the part itself. Generally speaking, if the dynamic error between shafts is not adjusted well during installation, or changes due to the wear of shaft transmission chain, the accuracy of parts will be affected. Generally, the accuracy of text search caused by such errors can be adjusted to compensate for the amount of resolution. If the error is too large or even an alarm occurs, it is necessary to check the servo motor and observe whether its speed is too high.

2、 The factor is that excessive operation will also affect the machining accuracy of the machine tool. This may be because the acceleration and deceleration time is too short, and the appropriate expansion and change time. Of course, it is also very likely that the link between the lead screw and the servo motor is loose.

3、 The reason is that the roundness out of tolerance caused by the linkage of the two shafts, the axial deformation of the circle formed by the machinery is not adjusted properly, the lead screw clearance compensation of the shaft is not correct, or the shaft positioning is offset, which may affect the accuracy of precision parts.

ken. tang@chengcg.com

Application method of CNC fast wire cutting

For the current processing industry, wire cutting is a very common cutting process. For fast cutting wire cutting, the same mechanical equipment will have certain differences in product quality after being operated in the hands of different people, which will also have a certain impact on the normal use of machine tools. Here, the methods for fast wire cutting will be briefly introduced. First, find the line you are cutting.

The line method is correct. If you are working on a multi-layer thin-walled sheet metal part because it will be affected by dimensions such as welding or blanking, the edges of the plate will not be neat. At this time, if the cutting accuracy is not high. In this case, it can be done by using the chemical fiber arrangement method or by manual method.

The alignment method of paper pattern is also a common method. When the multi-layer thin-walled bow and arrow is used for cutting shape processing, the inner contour or hole must be operated. Then, it is necessary to carry out silk pre threading in multiple places. At this time, we can paste one-to-one paper pattern on the workpiece to be processed, which will not only lead to the deviation of wire hole, but also lead to wire cutting. It will also become easier. Rapid cutting wire cutting is also a technology for cutting internal control, keyway or outer circle, which makes it possible to cut tooth shaped workpiece.

For the process hole to be corrected, many workpieces should be processed according to the machining steps. Generally, this process shall be carried out on the left and right sides of the plate and at the diagonal. At this time, the size or surface quality of the machined hole is a better case. You can use the corresponding hole on the bridge tool, and then use the position of the tip to perform alignment.

Universal table alignment is also a common alignment method using rapid cutting line cutting technology. The most important feature of this correction method is that the accuracy is relatively high, so the probability of using it is relatively large. Rapid cutting line is one of the cutting methods used at present. This cutting method requires higher cutting technology, but the cutting technology is actually based on cutting experience, so for the operator, we must accumulate some experience.

ken. tang@chengcg.com

Author Archive chengcg

What is the speed of CNC lathe

The importance of CNC processing stability!

Precision parameter control of CNC machining

Factors affecting CAC machining accuracy

Characteristics of CNC precision parts machining

Common methods of CNC precision machining

How to accept CNC machining center?

Large gantry computer gong processing

Reasons for poor machining accuracy of CNC

Application method of CNC fast wire cutting

CNC Machining parts

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