Monthly Archive May 10, 2021

Calculation method of CNC processing fee

In the mechanical processing industry, the price of general parts processing is calculated through the standard formula, and the processing cost will be appropriately increased in case of complex parts. There is a certain risk in complex precision parts, because if there is any problem in the processing technology, the dimensional tolerance of precision parts will be unqualified. At present, many precision parts are directly processed by CNC lathe or CNC, which can ensure the processing accuracy, save labor and improve the production and processing efficiency. Now many machining manufacturers have added CNC machine tools, let’s see how to calculate CNC processing fee

CNC processing, also known as computer gong processing, is mainly controlled by computer programming code. The main feature is high processing precision, small batch processing parts can improve production efficiency, but also save labor operation. CNC processing fee is generally calculated according to 60-70 yuan / hour. For high-precision parts, the processing fee is determined according to different processing technology.

When CNC processes small batch parts, the processing fee will be quite low. Because the batch parts can be repeatedly clamped, it can reduce a lot of programming time and improve the production efficiency. Machining manufacturers hope to have small batch processing, repeated clamping processing is OK. CNC processing fee how to calculate, generally calculated by the hour price. Precision parts with different requirements can be calculated comprehensively according to the processing technology.

ken. tang@chengcg.com

CNC precision hardware processing technology

Precision hardware processing technology processes include turning, milling, planing, grinding, clamping, stamping, forging and other methods.

Stamping: the pre made die is used for cold stamping, and the first step is sheet metal processing, that is, most of the processing materials are sheet metal, so the processing efficiency is relatively high and suitable for mass production.

The process of fine hardware processing technology is divided into engineering die and connecting die. Engineering die is also called single punch die. Some more complex parts need several sets of dies, and the connecting die splits the shape of the commodity into several parts in the cavity of the die. In this way, a punch processing stroke is a finished product. High speed continuous punch can process 300 or 400 products per minute.

Lathe: lathe belongs to precision machining machinery, which is divided into general lathe, active lathe, instrument lathe and computer lathe. After holding the material clip, it reverses and processes radially or axially by the turning tool.

Nowadays, active lathe and computer lathe are more and more widely used. Because both of them are fully active processing, the accuracy error caused by human operation is reduced to the lowest point, and the processing speed is fast, which is used for mass production. Most of today’s computer lathes are equipped with side reverse cutter and reverse reverse cutter, that is to say, milling can also be carried out on the lathe. The surface roughness of lathe is about ra0.4-1.6;

ken. tang@chengcg.com

CNC typical parts processing technology

Shaft part is one of the most common typical parts. According to the different structural methods of shaft parts, they can be generally divided into three categories: optical axis, stepped axis and special-shaped axis; Or divided into solid shaft, hollow shaft, etc. They are used to support gear, pulley and other transmission parts in the machine to transfer torque or motion.

The machining technology of stepped shaft is typical, which reflects most of the contents and basic rules of shaft parts machining. Next, take the transmission shaft in the gearbox as an example to introduce the processing technology of general step shaft.

The part is the transmission shaft in the reducer. It belongs to stepped shaft parts, which is composed of cylindrical surface, shaft shoulder, thread, thread tail undercut, grinding wheel overtravel and keyway. The shoulder is generally used to determine the axial orientation of the parts on the shaft. The effect of each ring groove is to make the parts have an accurate orientation when they are used in the equipment, and to make it convenient to withdraw the tool when grinding the outer circle or turning the thread; Keyway is used for equipment key to transfer torque; Thread is used for all kinds of lock nuts and adjusting nuts.

According to the working performance and conditions, the typical parts processing technology, the transmission shaft drawing rules the primary journal m, N, excircle P, Q and shaft shoulder g, h, I, has higher standard, orientation accuracy and smaller surface roughness value, and has the need of heat treatment. These technologies need to be guaranteed in processing. Therefore, the key process of the transmission shaft is the processing of journal m, N and outer circle P, Q. The material of the transmission shaft is 45 steel, because it belongs to the general transmission shaft, so the selection of 45 steel can meet its needs. The transmission shaft of typical parts processing technology belongs to medium and small transmission shaft, and there is little difference in the outer circle diameter standard, so ¢ 60mm hot rolled round steel is selected as the blank.

Determine the processing method of the primary surface:

Most of the transmission shafts are rotary surfaces, which are mainly formed by turning and cylindrical grinding. Because the primary surface M, N, P, Q of the transmission shaft has higher service level (IT6) and smaller surface roughness Ra (RA = 0.8 UM), it needs grinding after turning. The processing plan of cylindrical surface (see table A-3) can be as follows: rough turning → semi finish turning → grinding.

Determine positioning datum:

Reasonable selection of positioning datum has a decisive effect on ensuring the standard and orientation accuracy of parts. As several primary cooperative surfaces (Q, P, N, m) and shoulder surfaces (h, g) of the transmission shaft need radial circular runout and end circular runout for the reference axis A-B, and it is also a solid shaft, the center hole at both ends should be selected as the reference, and the double tip clamping method should be selected to ensure the technical requirements of the parts.

The rough datum of typical parts processing technology is the blank outer circle of hot rolled round steel. Three jaw self centering chuck is used to clamp the outer circle of hot rolled round steel blank, turn the end face and drill the center hole. However, it is necessary to pay attention to the fact that it is generally not possible to drill the center hole at both ends by clamping the outer circle of the blank twice. Instead, it is necessary to take the outer circle of the blank as the rough datum, first process an end face, drill the center hole, and turn out the outer circle at one end; Then, take the turned outer circle as the benchmark, clamp it with the three jaw self centering chuck (sometimes set up the center frame at the turned outer circle in the previous step), turn the other end face and drill the center hole. Only in this way can the two center holes be coaxial.

ken. tang@chengcg.com

Accuracy of CNC non standard parts

1、 CNC non-standard parts processing Occupation:

Automation equipment: such as bank equipment, UAV, robot, intelligent equipment, etc;

Medical equipment: X-ray machine, hemodialysis instrument, monitor, foot health care box, etc;

Industrial equipment: wind turbine, pipeline inspection equipment, meter automatic verification equipment, intelligent equipment

Be able to work with robots, etc;

Household appliances: such as color TV, air conditioner, monitor, water cooker, coffee pot, rice cooker, juicer

Etc;

Digital communication: such as mobile phone, telephone, fax machine, video doorbell, camera, etc;

Car Occupation: car, motorcycle parts, car dashboard, lampshade and other parts;

Stationery dolls: such as pen, stationery box, pen holder, work furniture parts, doll model, etc

2、 CNC non-standard parts machining accuracy:

Precision range: Hardware: ± 0.01mm plastic parts: ± 0.05mm

Note: the machining personnel of 0.01mm is commonly known as “silk”, also known as “Tao”.

ken. tang@chengcg.com

CNC machining part guidelines

In the field of CNC processing industry, CNC processing is also known as CNC machine tools. It mainly refers to the path of feed processing. It refers to the path through which the turning tool starts to move from the tool setting point (or the fixed origin of the machine tool) until it comes back to this point and completes the processing program, including the path of cutting processing and the path of non cutting empty stroke such as cutting in and cutting out of the tool. These are NC commands to complete the operation automatically.

In the process of finishing, the feeding path is basically carried out along the order of parts generalization. Therefore, the key point of determining the feeding path is to determine the feeding path of rough machining and empty stroke.

In the process of NC machine tool machining, the machining process should follow the following rules.

  1. It should be able to ensure the accuracy and surface roughness of the workpiece to be processed.
  2. Make the processing path shortest, reduce the empty travel time and improve the processing power.
  3. Simplify the amount of numerical calculation and the processing procedure as much as possible.
  4. Subprogram should be used to save processing time for some repeated programs.

ken. tang@chengcg.com

Clamping method of CNC machining parts

In the mechanical processing industry, there is such a processing machine, the operation process is completely ordered by the technician with computer programming code, which belongs to precision processing equipment, which is often referred to as CNC processing. Today to a simple understanding of CNC machining parts in the clamping method which

Before CNC machining parts, the size of parts need to choose different clamping methods. What kinds of clamping methods are there in the process of parts processing? The first is to clamp the parts with the jaw, which is suitable for processing the parts with small appearance and not exceeding the scope of the jaw; The third is directly fixed to the platform for processing, which is generally large and complex parts processing, because fixed on the platform can also improve the processing quality; Finally, the use of fixture fixture to clamp parts processing, this for some batch parts or mass parts processing, the main advantage is accurate positioning processing, improve production and processing efficiency!

The above is about the clamping method in CNC machining parts.

ken. tang@chengcg.com

Positioning error of CNC process

Precision machinery parts processing first station (engaged in precision parts processing, professional CNC processing manufacturers)! In the machining circuit, the parts with high precision are often encountered. Now let’s understand the analysis of the positioning error in the processing technology

In terms of machining process, positioning error can be divided into various situations. The following should be paid attention to during operation:

  1. Positioning error is the positioning error of a processing precision parameter in the processing of a part. It is a part of the machining error of the machining accuracy parameter.
  2. A process and positioning scheme can produce different positioning errors for several machining accuracy parameters of the process. Therefore, the positioning errors of these machining accuracy parameters should be calculated respectively.
  3. The premise of analyzing and calculating the positioning error is to ensure the accuracy of processing requirements by using fixture clamping and processing a batch of parts with adjustment method.
  4. The positioning error obtained by analysis and calculation refers to the maximum range of positioning error that may occur when processing a batch of workpieces. It is a limit value, not a specific value of the positioning error of a workpiece.
  5. The most important position change of the design datum of machining a batch of parts relative to the fixture tool adjustment datum is the cause of the positioning error, not necessarily the positioning error.

These simple understanding of the positioning error analysis and calculation, in the process of precision CNC machining parts, mechanical parts processing, there are many reasons affecting the size of the error.

ken. tang@chengcg.com

The difference between slow silk and fast silk

In the hardware processing and manufacturing industry, slow wire cutting and fast wire cutting both refer to WEDM, so what’s the difference between these two processing technologies? Let’s take a look at the following:

  1. Development status of low speed wire processing technology

Multiple cutting technology is the fundamental means to improve the machining accuracy and surface quality of slow wire. Generally, it is formed by one cutting, the accuracy is improved by two cutting, and the surface quality is improved by more than three cutting.

Because of the lag of the electrode wire when cutting the corner, the corner will collapse. In order to improve the corner cutting accuracy, more dynamic corner processing strategies are adopted. Such as: automatic change of processing speed, automatic adjustment of water pressure, control of processing energy, etc.

The high precision finishing circuit adopted by the advanced slow moving machine tool is an effective technology to improve the flatness of the workpiece, which significantly improves the accuracy of thick workpiece processing; In order to carry out micro finish machining of small fillet, narrow slot, narrow groove and micro parts, the NC low speed WEDM machine tool can use 0.02 ~ 0.03 mm electrode wire for cutting.

In order to ensure high-precision machining, the mechanical accuracy, pulse power supply accuracy and servo control accuracy of the machine tool (including the control of mechanical motion, pulse parameters, wire feeding system and working fluid system) have reached a very high level. Using water temperature cooling device, the internal temperature of the machine tool is the same as the water temperature, which reduces the thermal deformation of the machine tool; The closed-loop digital AC (DC) servo control system ensures excellent dynamic performance and high positioning accuracy. The machining accuracy can be controlled within several microns, and the precision positioning can achieve 0.1 μ The control of m equivalent; Immersion machining is used to reduce the thermal deformation of the workpiece; Motor servo, closed loop electrode wire tension control; Using voltage modulation tool setting power supply to achieve high-precision tool setting, tool setting accuracy can reach 0.002 mm, no damage to the workpiece, no matter dry or wet.

Advantages of 2-wire processing technology

Medium speed wire cut electrical discharge machining (ms-wedm) belongs to the category of reciprocating high-speed WEDM, which realizes multiple cutting function on high-speed reciprocating WEDM, and is commonly known as “medium speed wire cut”. The so-called middle wire cutting does not mean that the wire cutting speed is between high speed and low speed, but the compound wire cutting machine. That is to say, the wire cutting principle is to adopt high speed (8-12m / s) wire cutting in rough machining and low speed (1-3m / s) wire cutting in finish machining. In this way, the work is relatively stable and the jitter is small, and the error caused by material deformation and molybdenum wire loss can be reduced through multiple cutting, The processing quality can be between high speed wire feeder and low speed wire feeder. Therefore, the user’s “medium wire” is actually a reciprocating WEDM, which uses the processing technology of some low-speed wire cutting machines for reference, and realizes the stripless cutting and multiple cutting.

As for the second cutting, low speed wire feeding and speed limited feeding are adopted. In the process of machining, the deformation treatment should be paid attention to for many times of cutting, because when the workpiece is online cutting, with the effect of the original internal stress and the influence of the processing thermal stress produced by spark discharge, the non directional and irregular deformation will be produced, which makes the cutting depth uneven and affects the processing quality and accuracy. Therefore, it is necessary to reserve different machining allowance according to different materials, so as to fully release the internal stress and complete torsion deformation of the workpiece. In the subsequent multiple cutting, there is enough allowance for finishing machining, so that the later size of the workpiece can be guaranteed.

▌ advantages of fast wire processing technology

As the name suggests, fast wire processing is named for the high speed wire running of electrode wire in the cutting process. Fast moving machine tool is an electric machine tool created by Du in China. After decades of continuous improvement and development, it has become an important processing means in the manufacturing industry. It can meet the requirements of medium and low-grade mold processing and other complex parts manufacturing, and occupies a considerable proportion in the medium and low-grade market.

At present, the technical index of fast cutting machine tool: the efficiency of one cutting is 180 mm ²/ The surface roughness is RA ≤ 1.0 μ m. The average efficiency is 50 mm ²/ The machining precision is 0.01mm, and the loss of electrode wire is less than or equal to 0.01mm/200000 mm ² 。 These performance indicators seem to be quite good, but it should be noted that to obtain these indicators, we need to ensure all aspects. Once there are differences, such as the concentration of working fluid and the loss of electrode wire, the stability of processing quality will be affected.

Due to the stronger social demand for product diversification, the proportion of multi variety, medium and small batch production has increased significantly, and the traditional ordinary processing equipment used in middle walking processing has been difficult to adapt to the requirements of high efficiency, high quality and diversification. However, middle walking processing has the characteristics of simple structure, low cost and low consumption, so it also has its living space. Compared with fast-moving machine tool, slow-moving machine tool has obvious advantages in processing efficiency, precision and surface quality. Although the price of the machine tool is more expensive, with the rapid development of the manufacturing industry, it will be more and more used in various processing fields.

ken. tang@chengcg.com

Advantages of thread milling cutter and tap tapping

Nowadays, manufacturers have more and more strict requirements on cutting tools. Maybe a small tool determines the quality of this product. Introduce some advantages of cutting tools

The thread milling cutter has many advantages, which is much better than the wire tapping. The thread milling cutter is more than ten times faster than the wire tapping, and has high precision and good surface roughness. The same pitch can get large and small holes, which can be processed with one cutter. The drilling and milling thread chamfering can be formed at one time, and it will not be taken out like the wire tapping after it is broken, and the resistance of the machine tool is also small.

Thread milling cutter introduction:

The traditional thread processing methods are mainly turning thread with thread turning tool or manual tapping with tap and die. With the development of NC machining technology, especially the appearance of three-axis NC machining system, a more advanced thread machining method, NC milling of thread, has been realized. Compared with traditional thread processing, thread milling has great advantages in processing accuracy and efficiency, and is not limited by thread structure and thread direction. For example, a thread milling cutter can process a variety of internal and external threads in different directions. It is very difficult to machine the thread with transition thread or undercut structure by traditional turning method or tap and die, but it is very easy to realize by NC milling. In addition, the durability of thread milling cutter is more than ten times or even tens of times that of tap, and in the process of NC milling thread, it is very convenient to adjust the diameter of thread, which is difficult to do with tap and die.

Classification of thread milling

Clip on type:

Single tooth machine clamp: mechanical structure is similar to thread turning tool. The blade is connected with the turning tool, and there is only one thread processing tooth. The cutter can only process one tooth per spiral movement cycle, and the corresponding pitch is reduced by one in the z-axis direction. The efficiency is lower than that of the thread milling cutter with multi tooth machine clamp. Multi tooth machine clamp: there are multiple thread processing teeth on the blade. When the cutter rotates for one cycle, multiple thread teeth can be processed by reducing the corresponding pitch in the z-axis, The processing effect is high

Integral type:

Integral type: there are many thread processing teeth on the blade, which is a kind of fixed pitch thread milling cutter. The cutter is made of integral cemented carbide, with good rigidity, high cutting speed and feed speed, wide processing range, compact structure, and can process small and medium diameter internal threads. But its price is more expensive

Characteristics of thread milling

1 stability

When machining difficult to machine materials such as titanium alloy, superalloy and high hardness materials, the tap will often twist or even break in the parts due to too much cutting force. In the process of long chip material, once the chip removal is not smooth, the chip will wind the tap or block the hole, which often leads to the tap crack or broken in the parts. Taking out the broken tap is not only time-consuming and laborious, but also may damage the parts. To solve this problem, we can use thread milling cutter. Because the thread milling cutter cuts into the material gradually, it produces less cutting force and seldom breaks. Even in case of tool breakage, because the diameter of the milling cutter is much smaller than that of the threaded hole, the broken part can be easily removed from the part without damaging the part;

  1. High precision

Because the thread milling is through the tool high-speed rotation, spindle interpolation way to finish processing internal thread, chip removal is convenient. Milling thread belongs to chip breaking cutting, and the chip is short. In addition, the diameter of machining tool is smaller than that of machining thread, which can avoid the turning line formed by tap reversal (it is not allowed in the case of high sealing requirements). Because there is no turning line in the original milling cutter, and the tap can not be avoided. It is not easy to form sticky chips. For soft materials, chip sticking is easy to occur in the process of processing, but the screw thread requires low machine power. Because thread milling is chip breaking cutting, tool contact is local, cutting force is small, and tap tool damage is easy to deal with;

  1. High efficiency

Processing efficiency we know that in the mass thread processing, due to the low cutting speed limit of the tap and the reverse tool withdrawal after processing the thread, it is very difficult to improve the processing efficiency. However, if we use thread milling cutter, not only its own milling speed is very high, but also its multi groove design increases the number of cutting edges, which can easily improve the feed speed, which can greatly improve the processing efficiency. In the processing of long thread, we can also choose the blade with longer blade to reduce the axial feed distance (equivalent to making the thread shorter) to further improve the processing efficiency;

  1. Good finish

Due to the influence of low cutting speed and difficult chip breaking, it is very difficult to obtain good surface finish and thread precision when machining with tap. However, for thread milling, everything is not a problem! High cutting speed and small cutting force make the cutting surface smooth; The fine chips can be easily washed out by the coolant, and the workpiece will not scratch the machined surface. For the workpiece with high thread accuracy requirements, because the thread milling cutter relies on spiral interpolation to ensure the accuracy, only need to adjust the program to easily obtain the required high-precision thread. This feature has a great advantage in precision thread processing.

  1. Low cost

The thread milling cutter is flexible and can be used in various working conditions. For example, we can use the same thread milling cutter to process left-hand thread or right-hand thread; It can process both external thread and internal thread. All this just needs to be done by adjusting the interpolation program. If there are multiple threaded holes with different diameters but same pitch on the part, taps with different diameters are needed. This not only requires a lot of taps, but also takes a lot of time to change the tool. If the thread milling cutter is used, because it uses spiral interpolation to process, it only needs to change the processing program to complete the processing of all diameter threads, which greatly saves the cost of the cutter and the time of tool change. In order to ensure the thread accuracy, different types of taps are needed when machining different materials with taps. However, the use of thread milling cutter has no such limitation. The same thread milling cutter can process most materials and obtain high precision thread. This can also greatly reduce the cost of cutting tools. When the processing thread is close to the bottom of the blind hole, it is difficult to obtain the complete thread at the bottom if tapping with tap. And it is possible that the tool will continue to move forward a little distance (floating tapping) during the time when the tap stops at the bottom and is ready to reverse back, which is easy to cause the tap to break. This problem can be avoided by using the thread milling cutter – the thread milling cutter is smaller than the hole, there is no need to reverse the tool, and the thread shape is still complete at the tool tip. In this way, we can get complete and precise thread depth! In some processing, thread milling can help us solve many problems. For example: in large, non-circular parts of the thread processing, if processing on the lathe, it needs complex clamping and balancing to avoid vibration. At this time can be used in the machining center processing, parts do not move, thread milling cutter rotation, to avoid balance problems. For example, when machining intermittent threads, the vibration impact has a great impact on the blade, which is easy to produce cracks. When thread milling cutter is used, because the cutter cuts into the intermittent part of the material gradually, the big impact is avoided and the tool life is prolonged.

ken. tang@chengcg.com

Functions of lathes, milling machines and grinders

At present, numerical control equipment is more and more common, there are many kinds of ordinary machine tools.

Lathe

It is mainly used for machining various rotating surfaces and end faces of rotating body. For example, turning inner and outer cylindrical surface, conical surface, ring groove and forming rotating surface, turning end face and various common threads, processing equipment can also process various special shapes. Drilling, reaming, reaming and knurling can also be carried out on the lathe.

Milling machine

The utility model relates to a multifunctional machine tool, which can process plane (horizontal and vertical), groove (keyway, T-groove, dovetail groove, etc.) and surface (thread, spiral groove) of split parts (gear, spline shaft, sprocket, screw) and various curved surfaces. In addition, it can also be used for machining and cutting the surface of the rotating body. When the milling machine is working, the workpiece is installed on the worktable or dividing head and other accessories. The tool rotates as the main motion, supplemented by the feed motion of the worktable or milling head, the workpiece can obtain the required machining surface. The productivity of milling machine is very high because of multi cutter intermittent cutting.

Planer

It is mainly used for processing all kinds of plane (such as horizontal, vertical and inclined surfaces, and all kinds of grooves, such as T-shaped groove, dovetail groove, V-shaped groove, etc.) and linear forming surface. If equipped with contour processing device, it can also process space surface, such as turbine wheel, spiral groove, etc. This type of machine tool has a simple tool structure, and will not cut when returning, so the productivity is low, and is usually used for single piece small batch production.

Trampoline

It is suitable for plane milling and hole machining of single batch or small batch parts in machining workshop. The end of the headstock is designed with a flat rotating disc tool holder, which is used to drill large holes and planes. In addition, it can also drill, ream and thread.

Grinding machine

A kind of machine tool, which uses grinding abrasive (grinding wheel, abrasive belt, oilstone, abrasive, etc.) as a tool to cut the surface of workpiece, is collectively referred to as grinder. Grinding machine can process all kinds of surface, such as inner and outer cylinder and cone surface, plane, gear tooth surface, spiral surface and all kinds of forming surface, as well as grinding tools and cutting, etc. Because grinding is easy to obtain high machining accuracy and good surface quality, grinding machine is mainly used for finishing parts, especially hardened steel parts and high hardness special materials.

Drilling machine

Multifunctional machine tool, suitable for drilling, reaming, reaming, boring and tapping and other applications. When the radial drilling machine is equipped with process equipment, it can also be used for drilling; The drilling rig can be equipped with a universal worktable (mdt-180 type) or milling keyway.

Gear machine

Gears are the most commonly used transmissions, including cylindrical gears with straight, spiral and herringbone teeth, bevel gears with straight and spiral teeth, worm gears and non-circular gears. The processing gear tooth surface machine tool is called gear processing machine tool.

The machine tools mentioned above are the most common

ken. tang@chengcg.com