Monthly Archive September 10, 2020

1. Three basic requirements for selecting datum: (1) the selected datum should be able to ensure accurate positioning of workpiece, convenient and reliable loading and unloading. (2) The size calculation of the selected datum and each processing part is simple. (3) Ensure the machining accuracy.

(2) the positioning accuracy of the workpiece should be controlled strictly when the fixture is installed; (2) the positioning accuracy of all parts should be controlled strictly when the fixture is installed; (4) the positioning accuracy of all parts should be controlled strictly when the fixture is installed The selected datum should ensure the completion of as many processing contents as possible; (5) during batch processing, the part positioning datum should coincide with the tool setting datum of workpiece coordinate system as much as possible; (6) when multiple clamping is needed, the datum should be unified before and after.

Determination of fixture for machining center:

1. The basic requirements of the fixture: (1) the clamping mechanism shall not affect the feed, and the processing part shall be open; (2) the fixture can be installed in the machine tool in a directional way; (3) the rigidity and stability of the fixture shall be good.
2. Types of commonly used fixtures: (1) general fixture: such as vise, dividing head, chuck, etc.; (2) modular fixture: modular fixture is composed of a set of universal components with standardized structure and dimension; (3) special fixture: fixture specially designed and manufactured for one or several similar processing items; (4) modular fixture Adjustable fixture: the combination of modular fixture and special fixture can not only ensure the accuracy of processing, but also make clamping more flexible; (5) multi position fixture: the fixture that can clamp multiple workpieces at the same time; (6) Group Fixture: it is specially used for clamping workpieces with similar shape, size and positioning, clamping and processing methods.

The selection principle of machining center: 3

(1) On the premise of ensuring the machining accuracy and production efficiency, the general fixture is preferred;

(2) Simple special fixture can be considered for batch processing;

(3) Multi position fixture and high efficiency special fixture such as air pressure and hydraulic pressure can be considered for mass processing;

(4) Group fixture should be used when group process is adopted;

1. The best clamping position of the workpiece on the machine tool table: the clamping position of the workpiece should ensure that the workpiece is within the processing stroke range of each axis of the machine tool, and make the length of the tool as short as possible, so as to improve the processing rigidity of the tool.

1、 Pause instruction

G04X（U）_ /P_ It refers to the tool pause time (feed stop, spindle does not stop), the value after address P or X is the pause time. The value after X should have a decimal point. Otherwise, it should be calculated by one thousandth of this value in seconds (s). The value after P cannot have a decimal point (i.e., an integer), and the unit is Ms.

For example, G04 x2.0; or G04 X2000; pause for 2 seconds

G04 P2000；

However, in some hole series processing instructions (such as g82, G88 and g89), in order to ensure the roughness of the hole bottom, when the tool is machined to the hole bottom, there should be a pause time. At this time, it can only be expressed by the address P. if the address x is used, the control system thinks that x is the x-axis coordinate value for execution.

For example, g82x100.0y100.0z-20.0r5.0f200p2000; drilling (100.0100.0) to the bottom of the hole for 2 seconds

G82x100.0y100.0z-20.0r5.0f200x2.0; drilling (2.0100.0) to the bottom of the hole will not be suspended.

2、 The difference and relation of M00, M01, M02 and M30

M00 is the program unconditional pause instruction. When the program is executed, the feed stops and the spindle stops. To restart the program, you must first return to the og state, press CW (spindle forward rotation) to start the spindle, and then return to the auto state and press the start key to start the program.

M01 is the program selective pause instruction. The op stop key on the control panel must be opened before the program is executed. The effect after execution is the same as that of M00. Restart the program as above.

M00 and M01 are often used in the inspection or chip removal of workpiece size in the process of machining.

M02 is the end instruction of main program. Execute this command, feed stop, spindle stop, coolant off. But the program cursor stops at the end of the program.

M30 is the main program end instruction. The function is the same as that of M02, except that the cursor returns to the program head position, regardless of whether there are other program segments after M30.

Machining center (MC) is a kind of automatic tool changing CNC machine tool, which adapts to the requirements of labor-saving, time-saving and energy-saving. It integrates mechanical technology, electronic technology, computer software technology, pneumatic technology, etc It is a high-tech product of drag technology, modern control theory, measurement and sensing technology, communication diagnosis, tool and programming technology. It integrates the functions of milling machine, drilling machine and boring machine. It is an efficient and highly automatic machine tool controlled by computer. Because the machining center has a variety of tool change or tool selection functions and automatic workbench exchange device (APC), after one clamping, it can automatically carry out drilling, reaming, reaming, boring, tapping, milling and other processes of the workpiece automatically, and automatically complete or nearly complete more than sequence processing of multiple planes or angles of the workpiece, so as to greatly improve the production efficiency and white degree.

Because the machining center can greatly reduce the workpiece clamping, measuring and machine tool adjustment time, reduce the turnover, handling and storage time of the parts, the cutting time utilization rate of the machine tool is 3-4 times higher than that of the ordinary machine tool; moreover, the machining center has better additive consistency, and can eliminate the human interference in the process flow compared with the single machine and the personnel operation mode, and has higher production Production and stable quality, especially the processing shape is more complex, high precision requirements, varieties change frequently, more economic.

With the rapid development of electronic technology, the appearance and application of various sensors with good performance make the function of machining center more and more perfect. These functions include: tool life monitoring function, tool wear and damage monitoring function, cutting state monitoring function, cutting abnormal monitoring, alarm and automatic stop function, automatic detection and self diagnosis function and adaptive control Control function, etc. The machining center is also connected with the automatic pallet carrying the accompanying fixture, and can cut the eyebrow automatically, which makes the machining center become the key equipment and basic unit of flexible manufacturing system, computer integrated remanufacturing system and automatic chemical plant

The process requirements of typical parts are mainly the structural size, processing range and precision requirements of the parts. According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Reliability is the guarantee to improve product quality and production efficiency. The reliability of CNC machine tool means that the machine tool can run stably for a long time without failure when it performs its functions under specified conditions. That is, the average time between failures is long, even if there is a fault, it can be recovered in a short time and put into use again. Select the machine tools with reasonable structure, excellent manufacturing and mass production. Shenzhen CNC lathe processing is general, the more users, the better the evaluation after use, the higher the reliability of CNC system

Computer gong is a kind of artificial intelligence, which is controlled by computer to complete complex processing.

Computer gongs processing is also known as CNC milling machine processing, CNC milling machine is developed on the basis of general milling machine, the processing technology of the two is basically the same, the structure is also somewhat similar, CNC milling machine is in the ordinary milling machine integrated digital control system, under the control of program code more accurate milling processing machine tool.

1、 Inspection standard of computer gongs before processing

1. Divide the center and read the number. After each time, copy the number of working coordinates. After clearing, check again whether the distance from the center to both sides is consistent, so as to ensure that the center and reading are correct.
2. Tool selection, tool loading, tool setting and z-axis coordinate reading. Select the appropriate tool according to the programming list. Clean the cutter head and nozzle thoroughly before installing the tool. After installing the tool, use the calibration table to check whether the tool has deflection. It is necessary to check again after the tool is set and the number is read, so as to avoid the wrong knife, which will bring great loss to the company.
3. transmit program, start processing: use the single section execution before the knife, transfer the speed and feed speed to the slowest, slow down the knife, watch the machine tool showing the Z axis margin, check whether there is any abnormal, if abnormal, press the pause button immediately, find out the reason to solve the anomaly, confirm that everything is adjusted to the right speed to start processing.
4. In the process of processing, always pay attention to observe whether the processing is abnormal and whether the tool is worn. If the tool wear is serious, the grinding shall be suspended to ensure the normal processing.

Milling cutter is used on CNC machining center or ordinary milling machine.

Material and hardness of milling cutter.

Specifications of milling cutter, such as: length of cutting edge, total length, diameter of cutting edge, diameter of shank, etc.

If it is used on the CNC machining center, it should choose the whole cemented carbide, ordinary milling machine can choose white steel.

The hardness of white steel milling cutter is softer than that of carbide milling cutter. The high-speed steel cutter is cheap and has good toughness, but its strength is not high, so it is easy to let the cutter. Moreover, the wear resistance and thermal hardness of the high-speed steel cutter are relatively poor. The thermal hardness of the high-speed steel milling cutter is about 600 degrees, and the hardness is about 65hrc. Obviously, when milling harder materials with white steel, if the coolant is not in place, it is easy to burn the cutter, which is one of the reasons for the low thermal hardness.

Cemented carbide milling cutter has good thermal hardness, wear resistance, but poor impact resistance. The blade will be broken if it is dropped casually. Cemented carbide is made by powder metallurgy, with hardness of about 90hra and thermal property of 900-1000 degrees. Therefore, white steel is suitable for ordinary milling machine, alloy milling cutter for CNC machining center.

Selection of milling cutter diameter

The selection of milling cutter diameter depends on different products and production batches. The selection of cutter diameter mainly depends on the specification of equipment and the processing size of workpiece.

① Plane milling cutter. When selecting the diameter of the plane milling cutter, the power required by the cutter should be within the power range of the machine tool, and the diameter of the spindle of the machine tool can also be used as the basis for selection. The diameter of plane milling cutter can be selected as d = 1.5D (D is the diameter of spindle). In mass production, the tool diameter can also be selected according to 1.6 times of the cutting width of the workpiece.

② End mills. The selection of end mill diameter should mainly consider the requirements of workpiece processing size, and ensure that the power required by the cutter is within the rated power range of the machine tool. If it is a small diameter end mill, whether the highest speed of the machine tool can reach the minimum cutting speed (60m / min) should be mainly considered.

③ Groove milling cutter. The diameter and width of the groove milling cutter should be selected according to the size of the workpiece to be processed, and the cutting power should be within the allowable power range of the machine tool.

Selection of 2 milling cutter blade

For fine milling, it is better to select the grinding blade. This kind of blade has better dimensional accuracy, so the positioning accuracy of the blade in milling is higher, and better machining accuracy and surface roughness can be obtained. In addition, the development trend of milling insert used in finish machining is to grind out the chip groove to form a large cutting edge with positive rake angle, which allows the blade to cut in small feed and small cutting depth. The tool tip will rub the workpiece and the tool life will be short if the carbide blade without sharp rake angle is used for small feed and small depth cutting.

It is suitable to select the pressing blade in some processing occasions, and sometimes it is necessary to select the grinding blade. The best choice for rough machining is the pressed blade, which can reduce the processing cost. The dimension accuracy and edge sharpness of the pressing blade are worse than those of the grinding blade, but the edge strength of the pressing blade is better, and it can withstand impact and large cutting depth and feed rate in rough machining. Sometimes, there is a chip groove on the front face of the pressed blade, which can reduce the cutting force, reduce the friction with the workpiece and chip, and reduce the power demand.

In order to improve the company’s efficiency and ensure the delivery time of parts processing, it is necessary to standardize the operation methods.

2 scope of application

Applicable to the company computer gong operator.

3 responsibilities and authorities

Daily cleaning and maintenance work and training for users, correct operation and use of computer gongs.

Work content:

Clamping method and tool use standard before processing:

Press bar, vise, magnetic table, fixture, select the best clamping mode according to the applicability of the workpiece.

Laminating: pay attention to the cleaning of the burr and scrap iron on the plane of the machine and the adjustment of the height of the strip, so as to avoid the collision between the knife arm and the strip.

. vise: pay attention to the cleaning of the fixed surface and moving surface of the vice and the clamping force.

Magnetic table: when using the magnetic table, it is necessary to consider whether the bottom of the workpiece is flat, the adsorption surface should be large enough, and the processing cushion block of the workpiece edge should be blocked. In order to ensure that the process will not be loose.