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The difference of machining center, engraving and milling machine and engraving machine

Carving and milling machine, carving machine and machining center (computer gong) are very similar in appearance and structure. The following is a comparative analysis of the three

Conceptually

Machining center: Hong Kong, Taiwan and Guangdong are called computer gongs. They are highly automatic multi-functional CNC machine tools with tool magazine and automatic tool changing device. The first machining center appeared in the United States in 1958. It can realize the centralized processing of milling, drilling, boring, reaming, tapping and other processes after the workpiece is clamped once, with special emphasis on “milling”.

Engraving machine: its spindle speed is high, suitable for small tool processing, torque is relatively small, focusing on the “engraving” function, such as wood (special processing of wood called wood engraving machine), two-color board, acrylic board and other low hardness plate, not suitable for strong cutting of large workpieces. At present, most of the products on the market under the banner of engraving machine are mainly for processing handicrafts with low cost. Due to the low precision, they are not suitable for mold development; but there are exceptions, such as wafer engraving machine.

Carving and milling machine: as the name suggests. It can be carved or milled. On the basis of engraving machine, the power of main shaft and servo motor is increased, and the bearing force of bed is increased. At the same time, the high speed of main shaft is maintained, and more importantly, the precision is very high. Engraving and milling machine is also developing at a high speed, commonly known as high-speed machine. It has stronger cutting ability and very high machining accuracy. It can also directly process materials with hardness above HRC60 for one-time forming.

In terms of appearance and volume

The volume of machining center is the largest, the volume of large 1690 machine is 4m * 3M, and that of small 850 machine is 2.5m * 2.5m; carving and milling machine is the second, and that of large 750 machine is 2.2m * 2m; carving machine is the smallest.

In terms of mechanical structure

Machining centers generally use cantilever type, carving and milling machines and carving machines generally use gantry type structure, gantry type is divided into pillar type and fixed beam type, at present, carving and milling machines are mostly fixed beam type.

In terms of index data

Spindle maximum speed (R / min): 8000 machining center; carving and milling machine is the most common 240000, high-speed machine is the lowest 30000; engraving machine is generally the same as carving and milling machine, engraving machine for high gloss processing can reach 80000, but it is not ordinary motorized spindle, but air floating spindle.

Spindle power: machining center is the largest, from thousands of watts to tens of kilowatts; carving and milling machine is the second, generally within ten kilowatts; carving machine is the smallest.

Cutting capacity: machining center is the largest, especially suitable for heavy cutting, roughing; carving and milling machine is the second, suitable for finishing; carving machine is the smallest.

Speed: because the engraving and milling machine and engraving machine are relatively light, their moving speed and feed speed are faster than the machining center, especially the high-speed machine equipped with linear motor, the maximum moving speed can reach 120m / min

Accuracy: the accuracy of the three is almost the same.

From the processing dimension: the area of the worktable can better reflect this. The smallest worktable area (unit mm, the same below) of domestic machining center (computer gong) is 830 * 500 (850 machines); the largest worktable area of engraving and milling machine is 700 * 620 (750 machines), and the smallest is 450 * 450 (400 machines); engraving machine generally does not exceed 450 * 450, the common is 45 * 270 (250 machines).

In terms of application objects: machining center is used to complete the processing equipment of large amount of milling work pieces, large molds and materials with relatively high hardness, which is also suitable for roughening of ordinary molds; engraving and milling machine is used to complete the finishing of small amount of milling work pieces and small molds, which is suitable for copper and graphite processing; low-end engraving machine is inclined to wood, two-color board, acrylic board and other materials with low hardness Plate processing, high-end suitable for wafer, metal shell polishing.

people say that

Machining center, engraving and milling machine can do both products and molds, engraving machine can only do products.

Tool magazine: Machining Center, there is a tool magazine is the machining center, no tool magazine is called computer gong or CNC milling; carving and milling machine generally does not equipped with tool magazine, even if the optional tool magazine is 12 knife umbrella tool magazine, or 6 knife in-line tool magazine; carving without tool magazine.

supplement

There is no CNC engraving and milling machine in foreign countries. Strictly speaking, engraving is a part of milling, so there is only the concept of machining center in foreign countries, and the concept of small machining center is derived to replace engraving and milling machine. Purchase engraving machine or purchase CNC milling machining center is often to ask their own questions, to see the actual production needs. In addition, there is the popular high-speed cutting machine (hscmachine), which is called high-speed machine in China.

2、 Analysis from the angle of numerical control

  1. — the CNC milling center requires a general speed for the CNC system, and the spindle speed is about 0 ~ 8000rpm
  2. — the engraving and milling machine requires a high-speed numerical control system, and the spindle speed is about 3000 ~ 30000 rpm
  3. High speed cutting machine tools require high-speed CNC system and excellent servo motor characteristics. The spindle speed is about 1500 ~ 30000 rpm
About CNC Turniing

ken.tang @ chengcg.com

Installation of gantry milling machine

What points should be paid attention to when machining and installing workpieces with gantry milling machine

When machining and installing workpieces with gantry milling machine, if it is necessary to use pad iron, a certain thickness of copper plate (about 5mm) should be padded between the pad iron and the worktable, and a thin copper sheet should be padded between the pad iron and the worktable to prevent the surface of the worktable and workpieces from producing marks. When using pad iron, pay attention to the pad iron and the fixing screw as low as possible, And the iron pad should be placed outside a certain area of the workpiece processing range, in order to avoid the damage caused by the impact of the iron pad on the tool head and tool chuck. When loading and unloading workpieces, it is necessary to handle them with care to reduce the friction and movement of workpieces on the worktable as far as possible. It is forbidden to drag workpieces on the worktable of the machine tool by using the edges and corners of many workpieces as support points (this will seriously scratch the worktable of the machine tool and affect the flatness of the worktable). It is forbidden to place tools such as socket, screw wrench, screw, rubber hammer, oilstone, file, etc. on the worktable of the machine tool to prevent damage Damage the working table of the machine tool. Operation method of gantry milling: before starting the machine, first check whether the lubricating oil is appropriate and whether the machine is in normal state, then turn on the machine power (turn the knob from “off” to “on” when turning on the machine power), then turn on the power switch of the control panel and turn out the emergency stop key.

After the machine is started, the origin of the machine tool will return and the tool magazine will return to zero. Before the origin return, check whether the position of the tool relative to the workpiece is safe, and then determine how to return the origin (the machine tool can return to the zero position according to the sequence of axes). Select zero return (machine tool origin return); select arc manual → press Magazing zero return (tool magazine return). Check the shift record to make clear today’s tasks and precautions. For each workpiece, check in advance whether the processing program is complete, whether the tools are complete and in good condition, number the tools, and write the tool number on the tool with a marker pen. Easy to check. According to the programmer’s requirements, prepare the workpiece and fixture, and determine the method of clamping the workpiece (the bottom of the work should be polished with an oilstone).

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ken.tang @ chengcg.com

Structure of gantry machining center

1 worktable

The worktable of gantry machining center is basically rectangular. Large castings such as worktable, bed, column, crossbeam and RAM are made of mihanna cast iron. The inner cavity of the castings is honeycomb composite arrangement structure. The design is advanced. All of them are treated by aging and secondary tempering to eliminate residual internal stress, stabilize the material, ensure the stability of workpiece processing accuracy and machine life.

2 Longmen

The gantry consists of a beam and two columns. It can be divided into three types: fixed beam, locking sectional lifting beam by positioning block and arbitrary lifting beam.

3 RAM

The structure of RAM can be divided into open type and closed type. The ram with open structure is clamped on the spindle box by pressing plate, and the cross-sectional area of ram is large; the ram with closed structure is clamped in the spindle box, and the cross-sectional area of ram is small.

4 tool magazine

There are three basic types of tool magazine: turret type, drum type and chain length type.

Attachment 5

The processing of large and complex parts usually needs a lot of accessories. The accessory head is specially designed according to the processing requirements of the workpiece, which is generally divided into right angle head, extended head, special angle head and universal head.

6 CNC system

The CNC system generally adopts SINUMERIK 840C and 840D of Siemens company of Germany or 31I series of FANUC company of Japan, and the CNC axis adopts full closed-loop control.

7 accuracy

The accuracy of machine tool refers to the original accuracy of machine tool without external load. The accuracy is usually expressed by the deviation between its opposite side and ideal state (error for short). The smaller the error is, the higher the accuracy is.

About CNC Turniing

ken.tang @ chengcg.com

Four conditions of CNC machining center

CNC machining center must meet the following four conditions

1、 Environmental requirements for machining center location

The machining center should be located far away from the vibration source, avoid the influence of direct sunlight and thermal radiation, and avoid the influence of humidity and airflow. If there is a vibration source near the CNC machine tool, the anti vibration groove should be set around the machining center. Otherwise, it will directly affect the machining accuracy and stability of CNC machine tools, make the electronic components in poor contact, cause failure, and affect the reliability of the machining center.

2、 Power requirements

The general machining center installed in the machining workshop, not only the environmental temperature changes greatly, the use of poor conditions, and a variety of mechanical and electrical equipment, resulting in large fluctuations in the power grid. Therefore, the installation position of machining center needs strict control of power supply voltage. The fluctuation of power supply voltage must be within the allowable range and keep relatively stable. Otherwise, it will affect the normal work of CNC system of machining center.

3、 Temperature conditions

The environment temperature of NC machining center is less than 30 degree, and the relative temperature is less than 80%. Generally speaking, there are exhaust fans or air coolers in the CNC electric control box to keep the working temperature of electronic components, especially the CPU constant or the temperature difference changes little. Too high temperature and humidity will reduce the life of control system components and increase the number of faults. With the increase of temperature and humidity, more dust will bond on the integrated circuit board and lead to short circuit.

4、 Use the machining center according to the instruction

Users are not allowed to arbitrarily change the parameters set by the manufacturer in the control system when using the machining center. The setting of these machining center parameters is directly related to the dynamic characteristics of machining center components. Only the gap compensation parameters can be adjusted according to the actual situation.

About CNC Turniing

ken.tang @ chengcg.com

Selection of cutting tools for CNC machine tools

1、 Selection of blade (cutter)

The following aspects should be considered when selecting a blade or cutter

  1. The workpiece materials are steel materials (carbon steel, low alloy steel, tool steel, stainless steel). And other complex materials, such as copper, iron and non-metallic materials.
  2. The material properties of machined parts include properties, toughness, microstructure, etc.
  3. The categories of cutting technology include turning, milling, boring, drilling; machining, superfinishing; inner hole, outer circle, plane, groove; cutting flow state, tool displacement time interval, etc.
  4. The geometric shape of the workpiece affects the continuous cutting or intermittent cutting, the cutting in or out angle of the tool. Part accuracy (dimensional tolerance, geometric tolerance, surface roughness) and machining allowance.
  5. Cutting parameters of blade (tool) (back feed, cutting speed)
  6. Production site conditions (operation interruption time, feed rate, cutting speed)
  7. Processing of workpieces and production batch. Economic life of blade (cutter)

2、 Selection of boring tools:

In the selection of boring tools, the main problem is the rigidity of the tool bar, and the vibration should be prevented or eliminated as far as possible. The main points for consideration are as follows;

  1. The diameter of the reverse bar should be as large as possible, close to the boring diameter.
  2. Select the short arm (working length) as far as possible. When the working length is less than 4 times the diameter of the tool bar, steel tool bar can be used. When machining holes with high requirements, cemented carbide tool bar is best used. When the working length is 7-10 times the diameter of the arbor, the small hole is made of cemented carbide arbor, and the drilling is made of shock absorber arbor. When the working length is 7-10 times the diameter of the cutter bar, the damping cutter bar should be used.
  3. The main deflection angle is more than 75 ° and close to 90 °
  4. Select the blade without coating to reduce the radius of cutting arc and tool tip.
  5. The positive cutting edge (positive rake angle) blade and tool are used for finish machining, and the negative cutting edge (negative rake angle) blade and tool are used for rough machining.
  6. When boring deep through holes, cooling measures should be taken. Compressed air (air cooling) or cutting fluid (chip removal and cooling) can be used.
  7. Choose the right and fast boring tool holder.

3、 Selection of milling cutter:

  1. Indexable carbide milling cutter should be used when milling plane on CNC machine tool. It can be divided into two steps. One rough milling and one finish milling. When continuous cutting. The diameter of rough milling cutter should be reduced. The diameter of the finishing cutter should be larger, and it is better to contain the whole width of the surface to be machined. When the machining allowance is large and the machined surface is uneven, the tool diameter should be selected smaller. Otherwise, when rough machining, it will affect the machining quality due to the deep tool mark.
  2. High speed steel end mills are mostly used to process boss and groove, so it is better not to use them to process blank, because there are hardening layer and cracks in the blank. It will accelerate the tool wear.
  3. The machining allowance is small and the surface roughness is required to be low, so the CBN end mill or ceramic end mill should be used.

The end milling cutter with carbide insert can be used for machining groove, concave surface, convex surface and blank surface.

  1. The end milling cutter with cemented carbide can be used for powerful cutting. Milling the surface of the blank and rough machining the hole.
  2. When machining the groove with high accuracy requirements, the end milling cutter with diameter smaller than the groove width can be used. Firstly, the middle part of the groove is milled, and then the two sides of the groove are milled by using the radius compensation function of the cutter until the accuracy requirements are met.
  3. When drilling on CNC milling machine, the drill die is generally not used. When the depth of the hole is about 5 times of the diameter, it is easy to break the drill bit. Fixed cycle program can be used to advance and retreat automatically for many times to facilitate cooling and drainage. Before drilling, it is better to drill a central hole with a central drill or to drill the bottom hole with a section drill with good rigidity for positioning

When drilling on the milling machine, the drilling die is not generally used. When the depth of the hole is about 5 times of the diameter, it is easy to break the drill bit, and fixed circulation can be used

About CNC Turniing

ken.tang @ chengcg.com

Key operation points of CNC machining center

As a skilled operator, you must understand the requirements of processing parts, process route, machine characteristics before you can operate the machine to complete the processing tasks. Operation points:

1) In order to simplify the positioning and installation, each positioning surface of the fixture should have accurate coordinate dimensions relative to the machining origin of the machining center.

2) In order to ensure that the orientation of the parts is consistent with the orientation of the workpiece coordinate system and the machine coordinate system selected in the programming, and the directional installation.

3) After a short time of disassembly, it can be changed into a fixture suitable for new workpiece. As the auxiliary time of machining center has been compressed very short, the loading and unloading of supporting fixture can not take up too much time.

4) The fixture should have as few components as possible and high stiffness.

5) The fixture should be open as far as possible, the space position of the clamping element can be low as possible, and the installation fixture should not interfere with the tool path of the working step.

6) Ensure that the processing content of the workpiece is completed within the stroke range of the spindle.

7) For the machining center with interactive worktable, due to the movement, up support, down support and rotation of worktable, the fixture design must prevent the space interference between fixture and machine tool.

8) Try to finish all the processing contents in one clamping. When it is not necessary to replace the clamping point, special attention should be paid not to damage the positioning accuracy due to replacing the clamping point. If necessary, it should be explained in the process documents.

9) For the contact between the bottom surface of the fixture and the worktable, the flatness of the bottom surface of the fixture must be within 0.01-0.02MM, and the surface roughness shall not be greater than ra3.2um.

About CNC Turniing

ken.tang@chengcg.com

The importance of CNC machine tool spindle

Machine tool spindle refers to the machine tool to drive the workpiece or tool rotation axis. It is usually composed of spindle, bearing and transmission parts (gear or pulley). In addition to planer, broaching machine and other machine tools whose main motion is linear motion, most machine tools have spindle components. The motion accuracy and structural stiffness of spindle components are important factors to determine the machining quality and cutting efficiency. The main indexes to measure the performance of spindle components are rotation accuracy, stiffness and speed adaptability.

For the modular design of CNC machine tools, simplify the structure of machine tools, improve the performance of machine tools

a. Simplify the structure and promote the modularization of machine tool structure

Motorized spindle can form standardized and serial products according to the use, structure, performance parameters and other characteristics, which can be selected by the host machine, so as to promote the modular structure of the machine tool.

b. Reduce the cost of machine tools and shorten the development cycle of machine tools

The development of motorized spindle is changeable and easy to form a series of standardized products.

c. Improve machine performance and reliability

The reliability of CNC machine tools with motorized spindle structure is improved due to its simplified structure and reduced transmission and connection links; the motorized spindle functional parts with mature technology, perfect function, excellent performance and reliable quality make the performance of the machine tools more perfect and the reliability further improved.

d. Realize the special requirements of some high-grade CNC machine tools

Some high-end CNC machine tools, such as parallel motion machine tools, pentahedral machining centers, small hole and super small hole machining machines, must use motorized spindle to meet the perfect functional requirements.

About CNC Turniing

ken.tang @ chengcg.com

Safe operation of CNC machining

No matter what products we process or what operations we carry out, the most important thing is our safety. We can’t underestimate this aspect. Its influence is very big, and so is CNC processing. So how should we do the safe operation of CNC processing?

1) Try to install the material first and then the cutter, so as to prevent the hand from touching the cutter when installing the material. If the cutter has been installed, when loading the material, the worktable should be moved to the outside to ensure that the material will not interfere with the cutter, so as to avoid injury or breaking the cutter.

2) When disassembling the tool in CNC machining, we must first observe whether the spindle stops rotating.

3) Don’t hold or pinch the edge of the tool when unloading the tool to avoid the blade scratch.

Dongguan CNC processing

4) The spanner should be placed in the tool storage area after use, and it is not allowed to be placed on the y-axis shield or crossbeam.

5) In the process of machining, the operator is not allowed to observe the cutting position closely to prevent chips from crashing into the eyes.

6) Before the start of processing, check the position of the oil nozzle before opening the oil pump switch to avoid spraying oil to other positions.

7) When pausing to observe the gap of CNC machining, the worktable must be moved away from the cutting position.

About CNC Turniing

ken.tang @ chengcg.com

CNC machining center spindle does not rotate solution

Many CNC machining center friends do not know much about mechanical equipment, so in the work will encounter some problems, if you encounter CNC machining center spindle computer gongs do not turn, how to deal with it? In addition, the machine has not prompted any alarm information. What should you do at this time?

CNC machining center of computer gongs, in use, the spindle of CNC machining center of computer gongs does not rotate, which is a knife arm type tool magazine. When processing, the spindle does not rotate suddenly, and there is no alarm signal. And all the three axes can move normally. After giving a speed command in MDI mode, the spindle will not move a bit. At first, it was suspected that the shift signal was incorrect. After disassembling the z-axis gearbox, it was found that the shift of the spindle gear was normal and in place, and the in place signal was correct. But the spindle doesn’t rotate. In principle, if the spindle encoder or spindle is not powered on, it will cause an alarm. Therefore, the above two suspicions are eliminated, and the solutions to such problems are as follows:

Solution 1: first of all, you need to know whether you can see the parameters after 9000, and if you can, whether the parameters have been changed. I have encountered such a situation, is 0i-MC system, each axis is normal, that is, the spindle does not rotate. Later, the parameters after 9000 were changed.

Solution 2: there was an oi-m in the company before. It was found that the pneumatic valve of the knife arm was stuck. After the tool change, the knife arm should be ready for the next knife, but the knife arm was not put down, and there was no alarm. After the valve change, it was ready. And whether there is a hydraulic fixture, the fixture is not tightened, or the clamping signal is disconnected.

Solution 3: first take a look at the spindle monitoring, and turn the spindle manually to see if there are any values? Is the value right? The main shaft doesn’t rotate. There is no monitoring value, adjust the distance, or replace it with a new speed detection.

About CNC Turniing

ken.tang @ chengcg.com

Influence of CNC machining tool material on quality

Over the years, users in accordance with the standard, interchange the use of a variety of tool manufacturers produced by the milling cutter and blade. However, these standards make various restrictions on milling cutters and inserts, including the shape and thickness of the inserts, the inscribed circle of the cutting inserts, the size of the holder and wedge clamping parts, and the size of the cutter body. Due to the limited design range of blade material, edge and chip breaking groove, the tool suppliers and users who abide by the standard are limited by the machining function.

However, today, the concept of milling cutter tends to be flexible, which provides tool developers with the freedom to adopt new tools and blade design. These designs can be optimized, and the use of new tool concept can better solve the problems of machining safety, accuracy, appearance quality, metal removal rate, tool overhang, high-speed cutting, and the ability of different cutting paths.

Today’s milling tools are constantly optimized to meet the needs of modern production, machine tools and data, and are widely accepted by all industries. The new tool can remove metal several times faster, with smaller cutting force and better orientation. Its typical runout is only a fraction of the old standard tool. Therefore, the machining tolerance can always be controlled in a smaller range, and the loss of cutting edge is also smaller and more ideal. The axial and radial runout are very small, which means that the accuracy of the cutting edge is improved, so the appearance quality of the workpiece is better, the tolerance is smaller, the tool life is longer, and the cutting load is more uniform, so as to improve the cutting speed and reduce the noise, vibration and loss.

The use of tools also helps to increase spindle speed, high-speed feed and hard part milling, and expands the opportunities for dry cutting. The design of these cutting tools is more concise, and the workload and time required for adjustment and maintenance are very small. The cutter body is rigid and accurate in size. It is made of pre hardened steel, which ensures that the blade is accurately and firmly installed on the milling cutter body, and the appropriate pitch can be selected according to different applications.

The new milling tools use the blade material and groove type developed for specific data or process. The functions and achievements of the new milling tools with these blades are far better than those of ISO or ans standard tools and blades. Compared with most standard inserts, modern new inserts and tools can provide larger rake angle and more complex groove, thus reducing the cutting force and forming the synergistic effect of faster and more stable metal removal.

About CNC Turniing

ken.tang @ chengcg.com

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