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What is the usual speed of CNC machine tools

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.

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ken. tang@chengcg.com

How to select hard rail processing and wire rail processing for iron parts?

In the machining industry, iron parts belong to common processing workpieces. When using machining centers to process iron parts, should we choose hard rail machining centers or wire rail machining centers?

When selecting hard rail machining center and wire rail machining center, machining manufacturers need to understand the size of iron parts processed by themselves, whether they are finish machining or rough machining,

Only by understanding these details can a manufacturer specializing in the production of CNC machining centers give an accurate answer.

Generally, large-size iron parts have high quality and large cutting amount. In this case, it is more appropriate to select the hard rail machining center. The hard rail machining center has strong rigidity, earthquake resistance and load-bearing capacity, which is more suitable for heavy-load cutting.

In this case, if the wire rail machining center is used for processing for a long time, the guide rail may be damaged. Customers are generally advised to use hard rail CNC machining centers, such as table group finishing machines T-8, T-10, T-12, T-13 and T-15, which are hard rail machining centers, compared with 850, 1060 and 1270 in the market. These hard rail CNC machining centers are generally suitable for heavy-duty cutting.

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ken. tang@chengcg.com

How to ensure the accuracy of CNC machining

For many non-standard parts processing customers, when selecting suppliers, they are most concerned about the machining accuracy of mechanical precision parts. In the precision machining industry, it is easy to find suppliers, but it is difficult to find CNC machining center suppliers with appropriate accuracy, so we must be cautious. In short, precision is risky and processing needs to be cautious.

Machining of mechanical precision parts

In the machining center of non-standard parts, more cutting tools are generally used in the machining process. In order to ensure the machining accuracy of precision parts, the replacement sequence of cutting tools must be arranged reasonably. The corresponding replacement of machining tools is the machining sequence. The general process principle is to make the datum first, then punch holes, and then divide the primary and secondary rough and then fine.

In the machining process of mechanical precision parts, the machining of datum surface is the best, which provides positioning reference for the machining of other surfaces. The benchmark of this process positioning is the benchmark of the next process positioning. Therefore, when the positioning datum of all processes of machining a non-standard part is determined, the sequence arrangement of the whole machining process can be pushed forward.

When arranging the processing sequence of mechanical precision parts, it must be clear whether non-standard parts need to be processed and processed. Pre machining is also usually done by CNC lathes. If the workpiece has high rough accuracy, the positioning is guaranteed, or the processing volume is sufficient, it can be processed directly in the machining center without pretreatment. This needs to consider the difference between the accuracy of the rough datum and the process of the machining center, which can be completed by several processes or one process.

Similarly, if the pretreatment surface has different standard requirements from the operation surface of the machining center, sufficient machining allowance must be reserved during pretreatment. At the end of one-time clamping in the machining center of non-standard mechanical precision parts, all machining contents including the pre machined surface must also be included to ensure the final machining accuracy of precision parts.

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ken. tang@chengcg.com

Influence of spindle speed on large CNC machining center

Since the development of large CNC machining centers, the total output value has gradually increased, and the domestic machine tool industry is becoming more and more prosperous. According to the appearance design of most machining centers in the market, the slicing conveyor can be adjusted to the back of the production line, which is suitable for customizing the arrangement of the production line, which is also one of the reasons why customers like it. The machine adopts high torque motor. The output of the motor can fully reflect the characteristics of the main shaft. The indexing disc has high efficiency and high precision, including 8 oil circuit joints. One air pressure is tightly confirmed and has high mobility. It can be used with oil pressure fixture.

The main shaft of the large NC machining center is a vertical machining center, the structural form is a fixed column, the worktable is rectangular and has no indexing rotation function. It is suitable for machining disc, sleeve and plate parts. It has three linear motion coordinate axes, and it can be installed on a rotary table rotating along the horizontal axis on the worktable to process spiral parts. The replacement of the machine tool adopts pneumatic mode, which is fast and convenient. The machine adopts automatic lubrication to ensure the good operation of all parts of the machine tool.

The structure of the machine tool adopts the form of horizontal carriage, and the layout is reasonable. The three-axis feed adopts precision ball screw connected with servo motor to improve the transmission accuracy. The X and y-axis guide rails of the machine adopt precision rolling linear guide rails with high feed sensitivity; The z-axis adopts rectangular hardened cast iron plastic sliding guide rail pair, which has good vibration absorption; The machine control system adopts AC servo system, which is suitable for the processing of complex parts, especially complex molds.

The machine tool spindle adopts servo spindle motor, and the spindle box is equipped with counterweight device to ensure the smooth operation of z-axis. As we all know, the spindle speed of large CNC machining center is generally high, but with the continuous improvement of spindle speed, especially the rapid and various random vibrations, the instability of rotating shaft will increase. When the anti fatigue strength of spindle is exceeded, the spindle rotation error will increase reversibly, and finally affect the machining accuracy of machine tool. Therefore, the selection of spindle speed is very important.

About CNC Turniing

ken. tang@chengcg.com

Skills of avoiding Tool Collision in CNC machining center

What are the tips for avoiding knife collision in CNC machining center? With the development of computer technology and the continuous expansion of CNC machining teaching, there are more and more NC machining simulation systems, and their functions are becoming more and more perfect. Therefore, it can be used in the preliminary inspection program to observe the movement of the tool to determine whether a collision may occur.

1、 Using the simulation display function of CNC machining center

Generally, advanced CNC machining centers have graphic display function. When inputting the program, you can call the graphic simulation display function to observe the tool path in detail, so as to check whether there is possible collision between the tool and the workpiece or fixture.

2、 Using the empty running function of CNC machining center

The idling function of CNC machining center can be used to check the correctness of tool path. When the program is in the NC machining center, you can install it on the tool or workpiece, and then press the empty operation button. At this time, the axis does not rotate, and the automatic operation is tracked according to the planned worksheet. At this time, you can find out whether the tool may contact the workpiece or fixture. However, in this case, it must be ensured that the tool cannot be installed when the workpiece is installed; When the tool is installed, the workpiece cannot be installed, otherwise collision will occur.

3、 Using the locking function of CNC machining center

General CNC machining center has locking function (full lock or single shaft lock). After entering the program, lock the z-axis, and you can use the coordinate value of the z-axis to judge whether there will be a collision. When applying this function, avoid tool change and other operations, otherwise the program cannot pass.

4、 Improve programming skills

Programming is the most important part of large CNC machining center. Improving programming skills can avoid some unnecessary collisions to a great extent.

About CNC Turniing

ken. tang@chengcg.com

Problems in high speed machining

In the machining and manufacturing industry, high-speed machining is often used to process the automobile transmission housing. Although high-speed cutting technology has the advantages of high machining efficiency, small cutting force, reduced influence of cutting heat on workpiece, high machining accuracy and intensive process, the following problems are encountered at present:

  1. Lack of reasonable processing parameter selection scheme

As a new cutting method, high-speed cutting has no complete machining parameter table to choose from, and there are not many machining examples for reference. In high-speed cutting, most of them still rely on previous experience or carry out a large number of trial cuts to select parameters to achieve the best cutting effect. Finding reasonable machining parameters is a primary problem in the application of high-speed cutting.

  1. Lack of proper tool selection method

Cutting tool is a key problem in the popularization and application of high speed cutting. Because the cutting mechanism of high-speed cutting is completely different from traditional cutting, the wear mechanism and failure form of machining, the stress state of cutting tool and the cutting shape are different. In traditional milling, the main failure form of tools is flank wear, while in high-speed cutting, its failure form is completely different according to the processing conditions and workpiece materials, such as tool tip breakage, flank wear, tool rod fracture and other forms, and the effects of different combinations of tools and different workpiece materials are also different. How to choose a reasonable high-speed cutting tool, prolong the service life of the tool as much as possible and give full play to the performance of the tool is a very key technology for high-speed cutting technology.

Tempering treatment of steel in CNC processing

In the machining of machinery industry, steel generally needs heat treatment, and the allowance will be indicated in the process drawing for grinding and finishing. In the process of steel heat treatment, tempering is required to harden the steel parts, then heat them to a temperature below AC1, hold them for a certain time, and then cool them to room temperature. Common tempering processes include low temperature tempering, medium temperature tempering, high temperature tempering and multiple tempering. The purpose of tempering: it is mainly to eliminate the stress generated by steel parts during quenching, so that the steel parts have high hardness and wear resistance, as well as the required plasticity and toughness.

About CNC Turniing

ken. tang@chengcg.com

ey points for safe operation of CNC machine tools

  1. Operators shall wear tight work clothes with tight cuffs; Female comrades should wear protective helmets; Wear protective glasses during high-speed milling; Wear masks when milling iron castings; During operation, it is strictly prohibited to wear gloves to prevent hands from being rolled between the rotating tool and the workpiece.
  2. Before operation, check whether all parts and safety devices of the milling machine are safe and reliable; Check whether the electrical part of the equipment is safe and reliable.
  3. When loading and unloading workpieces, the workbench shall be retracted to a safe position. When tightening workpieces with a wrench, the force direction shall avoid the milling cutter to prevent the wrench from hitting the cutter or fixture when it slips.
  4. When assembling and disassembling the milling cutter, it shall be padded with a special pad, and do not hold the milling cutter directly by hand.
  5. When the work piece is not evenly divided and the work piece is not evenly held by the vise, the special clamping fixture shall be placed in the middle of the work piece, and the special clamping fixture shall be avoided as much as possible.
  6. During rapid or automatic feed milling, it is not allowed to move the worktable to two extremes to avoid crushing the screw rod.
  7. When the machine tool is running, it is not allowed to adjust and measure the workpiece and change the lubrication mode, so as to prevent the hand from touching the tool and hurting the fingers.
  8. Do not brake by hand until the milling cutter rotation has stopped completely.
  9. During milling, do not remove chips by hand or blow with your mouth to prevent chips from damaging skin and eyes.
  10. In case of motorized rapid feed, the hand wheel clutch shall be opened to prevent injury caused by rapid rotation of the hand wheel.
  11. When reversing the workbench, stop the reversing handle at the middle position first, and then reverse. Direct reversing is not allowed.
  12. When milling keyway shafts or cutting thin workpieces, strictly prevent milling the dividing head or worktable.
  13. When milling the plane, the cutter head with more than four cutter heads must be used, and the appropriate cutting parameters must be selected to prevent the vibration of the machine tool in milling.
  14. After work, stop the worktable at the middle position and the lifting table falls to the lowest position.
  15. For CNC vertical milling machine, pre selection of relevant work procedures, spindle speed, tool feed, tool trajectory and continuous offside shall be carried out according to the process requirements before work. Put the electrical knob in the “adjustment” position for commissioning. After confirming that there is no problem, put the electrical knob in the automatic or semi-automatic position for operation.
About CNC Turniing

ken. tang@chengcg.com

Function of CNC processing equipment

Due to the increasing diversification of product demand, the acceleration of renewal and the shortening of product life cycle, multi-type mass production has become the mainstream of production shape in mechanical manufacturing industry. Therefore, the flexibility requirements for automatic processing equipment are higher and higher. For the automatic processing system used for small and medium-sized batch production, we should consider making it have the following functions.

  1. The function of actively changing the processing sequence is related to automatic processing equipment. One or a group of electronic accounting machines can be set, which can make the system have the demand for production according to different products. Under the condition of continuous machine, it is convenient to quickly and actively change the task sequence of various equipment and reduce the re adjustment time of the system.
  2. The function of actively completing the processing of multiple products or parts. The transportation system and processing system of workpiece and accompanying fixture set in the processing system have considerable universality and high initiative sequence, so that the whole system can actively complete the processing of multiple products or parts on the basis of group skills.
  3. A highly flexible processing system for the function of processing sequence and production rhythm according to local conditions shall have the function of random transformation of process sequence and production rhythm of various product parts.
  4. High efficiency active machining and active tool change technology. The CNC machine tool with tool magazine and active tool change installation can make the system have high efficiency active machining and active tool change function.
  5. The active monitoring and fault diagnosis function sets up the active inspection, monitoring and fault diagnosis installation of the production process, and then improves the task reliability of the equipment and reduces downtime and waste damage.
About CNC Turniing

ken. tang@chengcg.com

Difference between NC machining and machining

Difference between machining and NC machining

Numerical control machining is a kind of machining. Numerical control is a full-automatic machining method. If you input the instruction manually, the machine can run according to the instruction and process the required parts. It has the advantages of convenient programming, flexible use, high efficiency and labor saving.

There are many kinds of machining, including manual, semi-automatic and full-automatic. The first two have low work efficiency.

CNC machine tools are generally composed of the following parts:

  1. Host, which is the theme of CNC machine tools, including machine tool body, column, spindle, feed mechanism and other mechanical parts. It is a mechanical part used to complete various cutting processes.
  2. NC device is the core of NC machine tool, including hardware (printed circuit board, CRT display, key box, paper tape reader, etc.) and corresponding software. It is used to input digital part program, complete input information storage, data transformation, interpolation operation and realize various control functions. CNC machinery
  3. Driving device, which is the driving part of the actuator of NC machine tool, including spindle driving unit, feed unit, spindle motor and feed motor. He realizes spindle and feed drive through electrical or electro-hydraulic servo system under the control of NC device. When several feeds are linked, the machining of positioning, straight line, plane curve and space curve can be completed.
  4. Auxiliary device, some necessary supporting parts of index control machine tool, to ensure the operation of NC machine tool, such as cooling, chip removal, lubrication, lighting, monitoring, etc. It includes hydraulic and pneumatic devices, chip removal devices, exchange worktables, CNC turntables and CNC indexing heads, as well as cutting tools and monitoring and detection devices.
  5. Programming and other auxiliary equipment can be used to program and store parts outside the machine.
About CNC Turniing

ken. tang@chengcg.com

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