July 2019 – Page 18 – CNC Machining & Turning, Milling, Metal parts

Attention should be paid to leakage protector when used

Speaking of leakage protector should be familiar to everyone, but asked about the principle of leakage protector is not very clear, in fact, the principle of leakage protector is not complicated, is the use of overload or short-circuit power at home when the protection device, remind everyone to check the current power consumption and stop unsafe behavior of the relay Continue. Now there will be leakage protectors in the home, because more and more household appliances are used, and the use of electricity is a certain danger, we need to leakage protectors to protect us to a certain extent, then what is the principle of leakage protectors, in the use of what should be noted.

1. What is leakage protector?

Leakage protector, referred to as leakage switch, also known as leakage circuit breaker, is mainly used in equipment leakage fault and fatal personal contact protection, overload and short circuit protection functions, can be used to protect the line or motor overload and short circuit, but also under normal circumstances as a line of infrequent switching. Switch to boot.

Two. Principle of leakage protector:
The leakage protector mainly consists of three parts: the detection element, the intermediate amplification link and the operation execution mechanism. Its working principle is:

The leakage protector is installed in the line, and the primary coil is connected with the line of the grid, and the secondary coil is connected with the tripper of the leakage protector.

When the electrical equipment is in normal operation, the current in the circuit is in balance state, and the sum of the current vectors in the transformer is zero (the current is a directional vector, such as “+” in the direction of outflow and “-“, and the current in the transformer is equal in magnitude, opposite in direction, and the positive and negative are offset each other). Since there is no residual current in the primary coil, the secondary coil will not be induced, and the switching device of the leakage protector is in a closed state.

When a leakage occurs in the shell of the equipment and someone touches it in time, a shunt will occur at the fault point. The leakage current will return to the neutral point of the transformer (not through the current transformer) through the human body-earth-work grounding, resulting in the imbalance of the current (the sum of the current vectors is not zero), and a coil will be left. Residual current. Therefore, the secondary coil will be induced, when this current value reaches the limit of the leakage protector action current value, automatic switch tripping, cut off the power supply.

Three. Points for attention in leakage protector:

1. Leakage protector is suitable for low-voltage distribution system where neutral point of power supply is directly grounded or grounded by resistance or reactance. For power source neutral grounding system, leakage protector is not suitable. Because the latter can not constitute a leakage electrical circuit, even if a grounding fault occurs, resulting in greater than or equal to the rated action current of the leakage protector, the protector can not act in time to cut off the power supply circuit; or rely on the human body to connect the fault point to constitute a leakage electrical circuit, to promote the leakage protector action, cut off the power supply back. The road. But this is not safe for the human body. Obviously, it is necessary to have the condition of grounding device. When the leakage current of electrical equipment occurs, and when the leakage current reaches the action current, it can immediately trip within 0.1 seconds, cutting off the main circuit of power supply.

2. The neutral line N of the leakage protector to protect the line must pass through the zero sequence current transformer. Otherwise, when it is connected, there will be an unbalanced current which makes the leakage protector malfunction.

3, zero protection line (PE) is not allowed to pass zero sequence current transformer. When the protection line (PE) passes through the zero-sequence current transformer, the leakage current passes through the PE protection line and then passes back through the zero-sequence current transformer, resulting in the current cancellation, and the leakage current value can not be detected on the transformer. When a fault occurs, the leakage protector will not act and will not protect.

4. The working neutral line of the control loop can not be repeatedly grounded. On the one hand, when grounded repeatedly, part of the working current will return to the neutral point of the power supply through repeated grounding under normal working conditions, and unbalanced current will appear in the current transformer. When the unbalanced current reaches a certain value, the leakage protector will produce misoperation; on the other hand, the leakage current on the protection line may pass through the individual line of the current transformer and return to the neutral point of the power supply, which cancels the leakage current of the transformer and makes the protector refuse to operate.

5. The neutral line N and the protective line (PE) behind the leakage protector can not be integrated into one. If the two are combined together, when leakage fault or electric shock occurs, the leakage current flows back through the current transformer, and the result is similar to case 3, causing the leakage protector to refuse to operate.

6, the lines between the protected electrical equipment and the leakage protector can not touch each other. If there is a line collision or zero-line intersection, it will immediately destroy the zero-sequence balanced current value, resulting in leakage protector maloperation; in addition, the protected electrical equipment can only be installed in parallel after the leakage protector, the connection is guaranteed to be correct, and the electrical equipment is not allowed to connect to the connection of the test button.

What is the principle of leakage protector, I believe that we all know now, leakage protector can be in the event of leakage fault automatically tripped off power, our safety has a great protective effect, so we must not be less in the home decoration leakage protector installation and use.

What is a sheet metal laser cutting machine

The so-called laser (LASER) is composed of the first letter of each word in English using the “magnification of stimulated radiation”. Pass this sentence
It can be known that the laser is a kind of light.
Light Amplifications by Stimulated Emissions of Radiation High-output lasers for processing materials are mainly divided into: gas lasers, solid lasers. 1 carbon dioxide laser
High power is relatively easy, high reliability, and low cost. It is a representative laser for processing. kW level
The high output power laser is used for sheet metal cutting?
The carbon dioxide laser shines on the metal (depending on the type of material). 90% of the metal material for laser processing is reflected. But this reflectivity is
The value of the metal solid is easily absorbed by the molten metal. Therefore, when cutting metal, the metal must first be melted a little. The method of melting the metal is to use a lens to collect light on the metal surface to maximize the energy density.
The laser can be continuously absorbed after the start of melting, and even a metal with a high reflectance can be easily cut. In fact, only the focused laser is cut from metal. The laser is irradiated with an auxiliary gas such as oxygen to blow the molten metal.

Mechanical maintenance

Regardless of whether the manufacturer maintains and maintains the machinery after-sales, whether it is new or old customers, they must pay attention to the maintenance and maintenance of the equipment. No matter how good the equipment does not know how to maintain and repair, the life of the equipment will never be large.

This is the first stage of troubleshooting and is a very critical stage. The main tasks should be as follows:

1 Inquiring into the investigation When receiving the information on the machine site where the fault is required to be eliminated, the operator should first be required to maintain the on-site fault state as much as possible, without any treatment, which is beneficial to quickly and accurately analyze the cause of the fault. At the same time, carefully inquire about the fault indication situation, the fault appearance and the background of the fault, and make a preliminary judgment in order to determine the tools, instruments, drawings and materials, spare parts, etc. that should be carried on the site to reduce the round-trip time.

2 On-site inspection After arriving at the scene, first verify the accuracy and completeness of the various conditions provided by the operator to verify the accuracy of the preliminary judgment. Due to the level of the operator, there are many cases where the fault condition is unclear or even completely inaccurate. Therefore, after going to the scene, do not rush to handle it, and re-examine the situation carefully to avoid damage to the scene and increase the difficulty of troubleshooting.

3 Fault Analysis According to the known fault conditions, the fault classification is analyzed according to the fault classification method described in the previous section to determine the troubleshooting principle. Since most faults are indicated, in general, the CNC machining system diagnostic manual and instruction manual for the machine tool can be used to list the various possible causes of the fault.

4 Determining the cause Check the various possible causes to find out the real cause of the fault. At this time, the maintenance personnel is a comprehensive test of the familiarity, knowledge level, practical experience and analytical judgment of the machine.

5 troubleshooting methods for troubleshooting may be very simple, some faults are often complicated, and a series of preparations are needed, such as preparation of tools and meters, partial disassembly, repair of components, procurement of components, and even platooning. Therefore, the formulation of the planning steps and so on.

Influence of punching clearance of metal mold on stamping quality

First, the concept of punching gap

The blanking gap refers to the gap between the punch edge and the die edge.

Z normal: the upper and lower micro-cracks coincide.

There are unilateral gaps and bilateral gaps.

Second, the impact of punching clearance on stamping

1. Influence of clearance on section quality

Normal: the upper and lower cracks coincide, the bright band is large, the sag angle, burr, taper is small, and the surface is flat;

Too large: the upper and lower cracks do not coincide, the tear is broken, the section is thick, the light band is small, the sag angle is large, and the thorn angle is large;

Too small: the upper and lower cracks do not coincide, secondary shear occurs, forming a second bright band, and the burr is large;

Unevenness: Small mass section features appear on the side with small gap, and large gap section quality characteristics appear on the side with large gap.

2. The effect of gap on dimensional accuracy

Due to the existence of elastic deformation, the elastic recovery occurs after the blanking, so that the size and the size of the edge of the convex and concave die are deviated, and the elastic deformation has a direct relationship with the blanking clearance.

3, the impact of clearance on the cutting force

The influence of the punching clearance on the punching force is that the smaller the gap is, the larger the compressive stress component in the deformation zone is, the smaller the tensile stress component is, the more the material deformation resistance increases, and the punching force is larger. On the contrary, the larger the gap, the larger the tensile stress component in the deformation zone, the lower the deformation resistance, and the smaller the punching force. When the gap reaches 5%-20% of the material thickness, the punching force decreases not significantly.

When the one-side gap Z is increased to 15%-20% of the material thickness, the discharge force is zero.

4, the impact of the gap on the life of the mold

Due to the friction between the workpiece and the side walls of the convex and concave molds, the gap is small, the friction is large, and the mold life is short. During the blanking process, the punch and the punched hole, the die and the valve of the blanking member have friction, and the smaller the sound gap, the more severe the friction. Therefore, the too small gap is extremely unfavorable for the life of the mold, and the larger gap can reduce the friction between the side of the punch and the die and the material, and the well can reduce the influence of the unevenness of the gap, thereby improving the life of the mold.

5. Determination of reasonable gap value

The clearance is selected to achieve better cross-section quality, higher dimensional accuracy, smaller punching force, and higher die life.

Reasonable gap refers to a range of values, the maximum reasonable gap, and the minimum reasonable gap. The gap is determined by considering the influence of each of the above factors, and selecting an appropriate gap range as a reasonable gap. The upper limit is the maximum reasonable sound gap, and the lower limit is the minimum reasonable gap, that is, the reasonable gap refers to a range value. When designing the mold in its body, it can be selected according to the following principles according to the specific requirements of the workpiece and production:

(l) When the cross-section quality of the workpiece is not strictly required, in order to improve the life of the mold and reduce the punching force, a larger gap value can be selected.

(2) When the workpiece section quality and manufacturing tolerance requirements are high, a smaller gap value should be selected.

(3) When calculating the daily size of the blanking die, taking into account the wear of the mold during use will increase the edge clearance, which should be calculated according to the Zmin value.

The role of the winder before the cloth is cut into bundles

The winder is a part of the whole set of stripping machine, its main function is to take up the fabric. So what is the role of this machine in the whole process? What effect does it have on subsequent cuts? This is the topic we are going to discuss today.

China is a big garment manufacturer and uses a lot of fabric every year. Therefore, the demand on the finishing machine of the fabric is very large, and the winder is a machine for taking up the fabric. It can make the fabric easy to store, and it can also be applied to other aspects, such as the winding of the fabric at different angles in the packaging, or the winding of the fabric for subsequent cutting, etc. . Today we mainly talk about the application of the winder to take up the fabric.

The main function of the rolling machine in cutting the bundle is that the winding machine can roll the cloth neatly, so that the cloth can reduce the cutting distance when cutting the strip, and can make the cutting without deviation, which is beneficial to the cutting. Moreover, the fully automatic winder is equipped with a coder that records the length of the take-up fabric and the speed of the take-up.

Therefore, the winder is very important when cutting the bundle of cloth, which makes the cloth automatic and convenient in cutting the bundle. Therefore, the winder is a very important equipment in the clothing industry and is a must-have device.

Precision CNC machining of those things

CNC precision machining refers to the high precision marked on the production and processing drawings, which requires the completion of precision machining equipment.

The ultra-precision processing equipment of mechanical processing manufacturers mainly include: CNC machining center, precision grinding machine and CNC lathe; CNC machining center has high precision, high precision, complex type, small batch parts processing has unique advantages; precision grinding machine belongs to precision processing equipment One is mainly the finishing, mainly for the processing of quenched parts; the CNC lathe is also an automatic processing equipment, and the general shaft, rod and round type parts are processed, which has advantages for special precision requirements or small batch parts processing.

A, CNC processing technology and working principle

1. Division of process and work steps; determination of tool points and tool change points;

2. Determination of processing route; selection of processing method and determination of processing plan.

3, the reasonable selection of machine tools, the choice of different parts of the accuracy of the workpiece;

4. Installation of parts and selection of fixtures;

5. The selection of the tool and the determination of the cutting amount;

6. Process analysis of CNC machining parts and reasonable processing technology.

B, the correct operation method of CNC precision machining

First, the geometric information and process information on the CNC machined part drawing are digitized, that is, the relative movement path of the tool and the workpiece, the change of the spindle speed and the feed speed during the CNC machining, the switch of the coolant, the transformation of the workpiece and the tool, etc. And the operation, the machining program is programmed according to the specified code and format, and then the program is input into the numerical control system.

The numerical control system first performs corresponding calculations and processing according to the requirements of the program, and then issues control commands to coordinate the coordinate axes, the main shafts and the auxiliary actions to realize the relative movement of the tool and the workpiece, and automatically complete the machining of the parts.

C, the accuracy of CNC machine tools choose to consider those factors

The precision of CNC machine tools and the precision of machining process are different. They represent the two different concepts of CNC machine tools. One is the machine’s own precision and the other is the process precision it processes. These two reasons seem to be irrelevant, but they are also related.

It is wrong to regard the positional accuracy on the manufacturer’s sample or on the product certificate as the machining accuracy of the machine tool. The positional accuracy indicated on the sample or certificate is the accuracy of the machine itself, and the machining accuracy is the sum of the errors produced by various factors of the entire process system, including the tolerances allowed by the machine itself. When selecting the type, the evaluation method of the process capability kp can be referred to as the basis for selecting the accuracy.

CNC accuracy has a significant impact on the quality of the process. It is important to note that machining accuracy and machine accuracy are two different concepts. The rigidity of the machine tool directly affects the productivity and machining accuracy. The machining speed of the machining center is much higher than that of the ordinary machine tool, and the motor power is also higher than that of the ordinary machine tool of the same specification. Therefore, the rigidity of the structural design is much higher than that of the ordinary machine tool. When ordering, the process requirements, allowable torque, power, axial force and maximum feed force can be checked according to the values provided by the manufacturer.

D, how to maintain the high strength of parts in precision parts processing

The principle measures for improving the strength of parts are: using high-strength materials, heat-treating materials to improve strength and reducing internal stress, controlling the processing to reduce or eliminate micro-defects, etc.; trying to reduce the load on the parts; increasing the dangerous section of the parts The size of the section is reasonably designed to increase the moment of inertia of the section; the structure of the part is properly involved to reduce the concentration of stress.

CNC precision parts processing can be multi-coordinate linkage, can process parts with complex shapes; high processing precision and stable processing quality; mass production, product quality is easy to control; when machining parts change, generally only need to change the NC program, Save production preparation time; the machine itself has high precision and rigidity, can choose favorable processing quantity, high productivity (usually 3~5 times of ordinary machine tools); high degree of machine automation, can reduce labor intensity; professional for operators The quality requirements are lower, and the technical requirements for maintenance personnel are higher.

Gear pump test plan

The reliability test includes two methods, the test room and the site. The test can be carried out according to the specific conditions.

Complete sample test—test is carried out until each test pump reaches the service life.
Incomplete sample test:
(1) Timing censoring test—-The test is stopped when the test is carried out until the test time T* specified before the test.
When the sample size is large, especially in laboratory tests, a timing censor test protocol can be used.
(2) Fixed-end censoring test—-test The test is carried out when the number of failures specified before the test is stopped.
When the user limits the number of pump failures, a fixed censoring test scheme can be used.

cnc machining for gear

Trolley caster installation tips

The trolley is a common handling tool for our daily production and life. It is divided into a wheelbarrow, a two-wheeled trolley, a three-wheeled trolley and a four-wheeled trolley according to the number of casters. Among them, the four-wheel plastic flat trolley has a wide range of use and is relatively simple to operate.

How do we properly install the cart casters when installing or replacing such four-wheel plastic flat cart casters?

First, according to the approved load of the trolley, the load of the plastic flatbed trolley is less than 300 kg, so the single wheel load of the caster can be about 100 kg. It is recommended to use a 4 inch or more caster, because the larger the wheel, the easier it is to push.

Second, according to the use of the trolley, if it is a quiet place in the floor paint workshop, electronic workshop or hotel, it is recommended to use a caster with a mute effect such as TPR or polyurethane.

Third, in the case of satisfying the above two conditions, it is necessary to confirm whether the mounting hole distance of the caster is the same as the mounting hole distance on the plastic flatbed. Because the installation pitch of conventional medium-sized casters on the market is 74mm*45mm, the mounting pitch of such plastic flatbeds is generally 84mm*71mm. If the medium-sized casters do not find a suitable mounting hole, they can also be replaced directly with heavy-duty casters, because the mounting pitch of heavy-duty casters is the same as the mounting hole of this plastic flatbed, but the price of heavy-duty casters is more expensive than that of medium-sized casters. Some, but the quality is much better.

Fourth, when installing such a caster caster, it is recommended to use two directional wheels with two universal wheels, and the universal wheel should be installed on the side close to the handle. This method of installation is better at controlling the direction of the cart.

Which is better for sliding door pulleys

Which is better for sliding door pulleys?
Sliding doors, we all know that it is more decorative than traditional doors, and many people will use them in small spaces such as kitchens or bathrooms, not occupying an inch of space.
However, many people have forgotten the importance of the pulley when they installed it, only to care about the beauty of the door. So is the pulley made of stainless steel or plastic? The master thinks that the sliding door pulley is still not good for buying plastic. It is actually a display.
Sliding doors are not only the decorative nature of the door, but also the quality of its hardware, including the important pulleys. At present, the pulleys on the market are roughly classified into three kinds of materials: plastic, metal, and glass fiber, and many of them are stainless steel machining.

Hardware application

Auxiliary, accessory finished products used in daily life and industrial production. In the early days, it was made of metal materials such as gold, silver, copper, iron and tin, hence the name.
Hardware
In addition to the use of various metal materials, it is also widely used in non-metallic materials such as plastics and glass fibers. Hardware products have played an important role in the survival and development of human beings. With the development of social economy and the refinement of social division of labor, hardware products are gradually enriched and improved, and more and more varieties. Modern hardware products can be divided into three categories according to their purposes: daily hardware for daily life, hand tools for production and living aids, construction of joints, fasteners and supporting facilities in buildings and structures. Hardware. Metal materials are generally made by forging blanks, cnc machining, surface treatment and other processes. The purpose of surface treatment is to prevent corrosion and aesthetics. Non-metallic materials are mostly molded or pressure molded, which is light and convenient.