March 2020 – Page 6 – CNC Machining & Turning, Milling, Metal parts

What is the effect of CNC rough machining on parts?

With the continuous development of the processing industry, what we use can only be completed after processing, and the processing must use machines to reduce product defects. Dongguan CNC parts processing is one of them, so what kind of consequences will be caused by rough CNC processing on parts?

1. Impact on wear resistance: the rougher the surface of CNC machining, the smaller the effective contact area between mating surfaces, the greater the pressure, the greater the friction resistance and the faster the wear.

2. Affect the stability of fit: for gap fit, the rougher the surface is, the easier it is to wear, so that the middle gap in the working process gradually increases; for interference fit, because the micro convex peak is squeezed flat during assembly, the practical effective interference is reduced, and the joint strength is reduced.

3. Influence on fatigue strength: there are large grooves on the surface of rough parts. Like sharp corner notches and cracks, they are sensitive to stress concentration, thus affecting the fatigue strength of parts.

4. Impact on corrosion resistance: the rough surface of parts is easy to make corrosive gas or liquid penetrate into the inner metal layer through the micro concave Valley on the surface, forming external corrosion.

5. Influence on sealing: rough surfaces cannot fit tightly, and gas or liquid leaks through the gap between contact surfaces.

6. Influence on contact stiffness: contact stiffness is the ability to resist contact deformation of the separation surface of the part under the action of external force. The stiffness of the machine depends on the contact stiffness between the parts to a great extent.

7. Affect the measurement accuracy: the surface roughness of the measured surface of the part and the measuring surface of the measuring tool will directly affect the measurement accuracy, which is in the fine measurement.

Which parts are suitable for precision machining?

We know that precision machining requires high precision. Precision machining has good rigidity, high manufacturing precision and accurate tool setting, so it can process parts with high precision. Which parts are suitable for precision machining? Here’s the introduction:

First of all, compared with the general lathe, CNC lathe has the function of constant linear speed cutting. No matter for the end face or the outer circle with different diameters, it can be processed with the same linear speed, which guarantees the surface roughness value and is relatively small. The general lathe is a constant speed, different diameter cutting speed is different. In the case of workpiece and tool material, finishing allowance and tool angle, surface roughness depends on cutting speed and feed speed.

When machining surfaces with different surface roughness, small feed speed is selected for surfaces with small roughness, and larger feed speed is selected for surfaces with large roughness, which has good variability, which is difficult to achieve in general lathe. Parts with complex contour. Any plane curve can be approximated by a straight line or an arc. CNC precision machining has the function of arc interpolation, which can process various parts with complex contour. The use of CNC precision machining needs the careful use of the operator.

CNC precision machining mainly includes finishing turning, boring, milling, grinding and other processes:

(1) Fine turning and fine boring: most of the precision light alloy (aluminum or magnesium alloy, etc.) parts of the aircraft are processed in this way. Generally, natural single crystal diamond cutting tools are used, and the arc radius of the cutting edge is less than 0.1 μ M. The surface roughness of 1 μ m and average height difference less than 0.2 μ M can be obtained by machining on high-precision lathe, and the coordinate accuracy can reach ± 2 μ M.

(2) Finish milling: used for machining aluminum or beryllium alloy structural parts with complex shape. Depending on the precision of machine tool’s guide rail and spindle, we can get high precision of mutual position. The precise mirror surface can be obtained by high-speed milling with a carefully ground diamond cutter head.

(3) Fine grinding: used for machining shaft or hole parts. Most of these parts are made of hardened steel with high hardness. Most high-precision grinding machine spindles adopt hydrostatic or hydrodynamic liquid bearings to ensure high stability. The grinding accuracy is not only affected by the rigidity of machine tool spindle and bed, but also related to the selection and balance of grinding wheel, the machining accuracy of workpiece center hole and other factors. The size accuracy of 1 μ m and the out of roundness of 0.5 μ M can be obtained by fine grinding.

(4) Grinding: select and process the irregular convex parts on the surface to be processed by the principle of mutual grinding of mating parts. Abrasive diameter, cutting force and cutting heat can be precisely controlled, so it is a high-precision machining method in precision machining technology. The hydraulic or pneumatic mating parts of the precise servo components of the aircraft and the bearing parts of the dynamic pressure gyro motor are processed by this method to achieve the accuracy of 0.1 or even 0.01 μ m and the micro unevenness of 0.005 μ M.

What should we pay attention to when processing precision hardware parts?

We have introduced the process flow of precision hardware parts to you before, so today’s chief engineer of hardware will share the following precautions for precision hardware parts processing:

1. Check whether the moving part is filled with lubricating oil before the operation of precision hardware parts processing machinery, then start and check whether the clutch and brake are normal, and run the machine tool for 1-3 minutes by air. It is forbidden to operate when the precision hardware parts processing machinery is in fault.

2. Keep correct posture at work, and have enough spirit to deal with the work. If you find physical discomfort, you should leave the post immediately and report to the leader. During the operation, the operator shall be concentrated, no chatting and cooperating with each other. The operator shall not operate in the state of fidgety and tired to avoid

In case of accident, ensure operation safety. Before entering the work position, all employees shall check whether their clothes meet the work requirements. It is not allowed to wear slippers, high-heeled shoes and clothes that affect safety. Those with long hair shall wear safety helmet.

3、 When the die is replaced, the power supply shall be turned off first, and the die can be installed and debugged only after the movement Department of the press stops running. After installation and adjustment, move the flywheel by hand twice for trial punching, and check whether the upper and lower dies are symmetrical and reasonable, whether the screws are firm, and whether the blank holder is in a reasonable position.

4. After other personnel leave the mechanical working area and take away the sundries on the workbench, the power supply can be started to start the machine.

5. When the precision hardware parts processing machinery works, it is forbidden to extend your hand into the sliding block working area, and it is forbidden to take and place the workpiece by hand. Use standard tools when taking and placing workpieces in the die. In case of abnormal sound or failure of the machine, turn off the power switch immediately for inspection.

After the machine is started, one person shall transport materials and operate the machine. Other people shall not press the electric building or step on the foot switch board, nor put the hand into the mechanical working area or touch the moving part of the machine by hand.

6. When leaving work, turn off the power supply and tidy up the finished products, leftovers and sundries on the post to ensure the working environment is clean and safe.

What should be paid attention to in CNC machining?

Nowadays, with the continuous improvement of science and technology, our industry needs to use a variety of processing, in the process of processing, we will inevitably have a variety of problems, or we need to comply with the problem, Dongguan CNC parts processing is one of them, so what should be paid attention to CNC parts processing?

1. Observe the operation regulations of machining center.

2. Before work, wear protective equipment and cuff as required. Scarf, gloves, tie and apron are not allowed. Women’s hair braid shall be tied in the hat.

3. Check whether the tool compensation, machine zero point, workpiece zero point, etc. are correct before starting the machine.

4. The relative position of each button shall meet the operation requirements. Carefully compile and input numerical control program.

5. Check the operation conditions of the protection, safety, signal, position, mechanical transmission part, electrical, hydraulic digital display and other systems on the equipment, and carry out cutting under all normal conditions.

6. Before the CNC parts are processed, the test run of the machine tool shall be carried out to check the operation conditions of the lubrication, mechanical, electrical, hydraulic, digital display and other systems, and the machining can be carried out under normal conditions.

7. After the machine tool enters the processing operation according to the program, the operator is not allowed to contact the moving workpiece, cutter and transmission part, and is not allowed to transfer or take tools and other items across the transmission part of the machine tool.

8. When adjusting the machine tool, clamping workpiece and cutter, and wiping the machine tool, stop the machine.

9. Tools or other articles shall not be placed on electrical appliances, operation cabinets and protective covers.

10. It is not allowed to remove iron chips directly by hand, and special tools shall be used for cleaning.

11. In case of abnormal condition and alarm signal, stop the vehicle and ask relevant personnel to check. CNC machining center.

12. It is not allowed to leave the work position when the machine tool is running. If you want to leave for some reason, put the workbench in the middle position, return the cutter bar, stop the machine, and cut off the power supply of the main machine.

What are the technical requirements in machining?

Machining is mainly precision machining, because precision machining can highlight the importance of machining products at work. Now machining is important for every project and technology. Now machining is getting better and better, and technology is also better. Now, there are more purchases of machining raw materials. With the development of society, we are With continuous development, many machining industries are expanding at a fast speed.

(1) Remove oxide skin from parts.

(2) There shall be no scratch, scratch and other defects on the machined surface of parts.

(3) The tolerance of undeclared shape shall meet the requirements of gb1184-80, and the allowable deviation of undeclared length dimension shall be ± 0.5mm.

(4) The tolerance zone of casting is symmetrical to the basic dimension configuration of rough casting.

(5) It is allowed to heat the assembled rolling bearing with engine oil, and the temperature of the oil shall not exceed 100 ℃.

(6) When assembling the hydraulic system, it is allowed to use sealing filler or sealant, but it shall be prevented from entering the system.

(7) The parts and components to be assembled can be assembled only after they have the certificate of inspection department.

(8) Parts must be cleaned and cleaned before assembly, without burr, flash, oxide skin, rust, chip, oil stain, colorant and dust, etc.

(9) Before assembly, the main fitting dimensions of parts and components, including interference fit dimensions and relevant accuracy, shall be rechecked.

(10) Parts shall not be knocked, bumped, scratched or rusted during assembly.

(11) When screws, bolts and nuts are tightened, it is strictly prohibited to strike or use improper screwdrivers and wrenches. After fastening, the screw slot, nut, screw and bolt head shall not be damaged.

(12) The fasteners with specified tightening torque shall be tightened with torque wrench according to the specified tightening torque.

(13) Excess adhesive shall be removed after bonding.

(14) The semicircle holes of the bearing outer ring, the open bearing seat and the bearing cover shall not be stuck; the semicircle holes of the bearing outer ring, the open bearing seat and the bearing cover shall be in good contact. During the color coating inspection, they shall be in uniform contact within the range of 120 ° symmetrical to the center line and 90 ° symmetrical to the center line.

(15) After the bearing outer ring is assembled, it shall be in even contact with the end face of the bearing cover at the locating end.

(16) After the rolling bearing is installed, it shall rotate flexibly and stably by hand.

(17) The joint surface of the upper and lower bearing shells shall be closely pasted and cannot be checked with a 0.05mm feeler gauge.

(18) When fixing the bearing bush with the locating pin, the reaming and pin distribution shall be conducted under the condition that the opening and closing surfaces and the end face of the bearing bush mouth and the end face are flush with the opening and closing surfaces of the relevant bearing holes and the end face package. The pin shall not be loose after driving.

(19) When the surface of the alloy bearing liner is yellow, it is not allowed to use it, and there is no phenomenon of nucleation within the specified contact angle. The area of nucleation outside the contact angle shall not be greater than 10% of the total area of the non-contact area.

(20) The reference end face of gear (worm gear) and the end face of shaft shoulder (or locating sleeve) shall fit, and the 0.05mm feeler gauge shall be used to check whether they can not enter. The perpendicularity of the gear reference end face and the axis shall be ensured.

General principles of precision parts processing

Today I would like to add the general principle of precision parts processing, that is, the general principle of precision parts processing process, which is mainly elaborated from the following four points:

1. Benchmark first

That is to say, the datum plane should be processed first. In the process of machining, the surface as the positioning datum should be processed first, so as to provide the precision datum for the subsequent processing as soon as possible.

2. Division of processing stages

The appearance with high machining quality request can be divided into three stages: rough machining, semi finish machining and finish machining. The main purpose is to ensure the processing quality; to facilitate the scientific application of equipment; to facilitate the arrangement of heat treatment process; and to facilitate the detection of blank defects.

3. Face before hole

For the box, bracket, connecting rod and other parts, the plane shall be machined before the hole is machined. In this way, the hole can be machined by plane positioning, ensuring the position accuracy of plane and hole, and bringing convenience to the machining of hole on plane.

4. Finishing

Finishing of main surfaces, such as grinding, honing, finishing, rolling, etc., shall be placed at the end of the process route. The general principle of drawing up the processing route of precision parts and the formulation of the processing procedure of precision parts can be roughly divided into two parts. First of all, it is to draw up the process route of parts processing, and then determine the process size of each process, used equipment and process equipment, cutting specifications, working hours quota, etc.

Processing requirements for precision parts

Mechanical parts processing industry is the pillar industry of the national economy, with a very considerable prospect. In the processing of precision mechanical parts, the processing factory will have many requirements and regulations on the processing technology to ensure the qualified rate of the parts. So do you know the requirements of precision machining technology? Let’s take a look at it!

1. Parts shall be free of oxide skin, scratches, scratches and other defects that may damage the surface of parts, and burr and flash shall be removed;

2. After quenching and tempering, the parts are quenched at high frequency, tempered at 350-370 ℃, hrc40-45, carburized at a depth of 0.3mm, and aged at high temperature.

3. The tolerance of undeclared shape shall meet the requirements of gb1184-80, the allowable deviation of undeclared length dimension shall be ± 0.5mm, and the tolerance zone of casting shall be symmetrical to the basic dimension configuration of rough casting;

4. The radius of undeclared fillet R5, undeclared chamfer are 2 × 45 °, sharp angle is blunt;

5. The temperature shall not exceed 100 ℃, after the gear is assembled, the contact spot and side clearance of the gear surface shall meet the provisions of GB10095 and gb11365;

6. When assembling the hydraulic system, it is allowed to use sealing filler or sealant, but it shall be prevented from entering into the system. The parts and components (including purchased parts and outsourced parts) that enter into the assembly must have the qualification certificate of the inspection department before assembling.

How to inspect precision machining parts?

Precision machine parts require precision. In the actual production process, we must reach the relevant standards for precision and try to improve it. At present, how to improve the precision of precision mechanical parts has become a key issue for related enterprises. The problems of deburring and polishing in the process of machining will directly affect the accuracy of parts, and it is also a difficult problem to solve in the current production automation. What I want to explain to you today is how to inspect precision machining parts?

One、 Basic requirements for inspectors:

1. To have professional knowledge and practical work experience, but also need to meet the requirements of the first product inspection work.

2. The measuring instruments used shall be verified by the measuring department and within the specified verification period.

3. Before product acceptance, it is necessary to be familiar with relevant drawings and technical documents, and understand the key dimensions of parts and key points of assembly.

4. The parts shall be determined in strict accordance with the requirements of drawings and technical documents.

5. Mark the products in process in the workshop according to the regulations.

Two、 Inspection system:

1. First inspection system: for the first part processed by each operator, it is necessary to conduct all-round inspection and keep it.

2. Inspection system: ensure that key parts will be able to obtain the whole process of controlled state.

3. Sequence transfer inspection system: for parts to be transferred to the next process, inspection shall be carried out to avoid unqualified products flowing into the next process.

4. Completion inspection system: the completion inspection shall be carried out for the products to be warehoused after the completion of production, including size and shape, whether there is missing processing procedure, etc.

Knowledge of CNC turning and milling machining

Composite machining is one of the processing technologies in the field of machining. It is an advanced manufacturing technology. Compound machining is to realize several different machining processes on one machine tool. Compound machining is the most widely used and most difficult, which is turning milling compound machining. Turning milling compound machining center is equivalent to the compound of a CNC lathe and a machining center.

brief introduction

Turning and milling compound machine tool is the fastest developing and most widely used numerical control equipment in compound machine tool. Machine tool compounding is one of the important directions of machine tool development. The compound machine tool also includes turning milling compound, turning milling compound, milling compound, cutting and 3D printing compound, cutting and ultrasonic vibration compound, laser and stamping compound and other various forms. The compound purpose is to make a machine tool have multi-function, can complete multi tasks at a time, improve processing efficiency and processing accuracy

advantage

Compared with the conventional NC machining process, the outstanding advantages of composite machining are mainly shown in the following aspects.

(1) Shorten product manufacturing process chain and improve production efficiency. Turning milling compound machining can complete all or most of the processing procedures by one-time loading, thus greatly shortening the product manufacturing process chain. On the one hand, it can reduce the auxiliary production time caused by the change of fixture, and reduce the manufacturing cycle and waiting time of fixture, which can significantly improve the production efficiency.

(3) Reduce floor space and production cost. Although the price of a single turning milling complex processing equipment is relatively high, due to the shortening of manufacturing process chain and the reduction of equipment required for products, as well as the reduction of the number of tooling and fixtures, the floor area of workshop and equipment maintenance costs, it can effectively reduce the investment, production operation and management costs of the overall fixed assets.

Characteristic

1. The turning milling compound machining center uses high-precision internal spindle;

2. The free mobile operation panel improves the working efficiency;

3. The machine is mainly used for mass production of various small parts and complex parts with high-speed processing and diversified processing;

4. In particular, the long and thin complex process can be processed and formed at one time, and the automatic feeding device can be configured to improve the efficiency;

5. Material details: cutting, copper, iron, aluminum alloy, stainless steel, Teflon and other materials.

Development status

Most of the turning and milling complex machining is completed in the turning center, while the general turning center only changes the ordinary turret tool rest of the CNC lathe into the turret tool rest with the power tool, and the spindle adds the c-axis function. Due to the limitation of turret structure and dimension, the power of the power head is small, the rotating speed is not high, and the larger tool can not be installed. This kind of turning center is mainly for turning, milling and drilling functions are only for some auxiliary processing. Because of the high cost of power tool holder, the cost of turning center remains high. The price of domestic tool holder is generally more than 100000 yuan, and that of imported tool holder is more than 200000 yuan, which can not be afforded by general users. Most of the economical turn milling composites are XZC axis, that is, a rotating C axis is added to the chuck to realize the basic milling function.

There are many kinds of equipment in the market, such as WFL, DMG, Dalian machine tool, Taiwan Taiyu precision machine, Doosan (Doosan machine tool), all of which have high-end equipment; the well-known software of the market is Edgecam, UG NX, etc.

Machining of CNC turning and milling composite parts

In order to improve the machining efficiency and accuracy of complex special-shaped products, technologists have been seeking for efficient and precise machining methods. The appearance of turn milling compound machining equipment provides an effective solution for improving the machining accuracy and efficiency of aerospace parts.

Machining efficiency and precision is the eternal goal in the field of metal processing. With the continuous development of numerical control technology, computer technology, machine tool technology and processing technology, the traditional processing concept can not meet the requirements of processing speed, efficiency and accuracy. In this context, composite machining technology came into being. Generally speaking, composite processing refers to the general term of processing technology that can complete different processes or different process methods on a single processing equipment. There are two different types of compound processing technology, one is the combination of different processing methods based on energy or motion mode; the other is the combination based on the principle of process concentration and mechanical processing technology. Turning milling compound processing is one of the processing methods that have developed rapidly in recent years.

Aviation product parts are characterized by many varieties, small batch, complex process, and widely used as a whole thin-walled structure and difficult to process materials. Therefore, there are many bottlenecks in the manufacturing process, such as long manufacturing cycle, large amount of material removal, low processing efficiency and serious processing deformation. In order to improve the machining efficiency and accuracy of aviation complex products, technologists have been seeking more efficient and precise machining methods. The appearance of turn milling compound machining equipment provides an effective solution for improving the machining accuracy and efficiency of aviation parts.

Meaning

Turning and milling is an advanced cutting method which uses the combined movement of milling cutter rotation and workpiece rotation to realize the cutting of workpiece and make the workpiece meet the requirements in many aspects such as shape accuracy, position accuracy, machined surface integrity, etc. Turning milling compound machining is not only a combination of turning and milling methods into a machine tool, but also a new cutting theory and technology under the condition of great development of CNC technology.

advantage

Compared with the conventional NC machining process, the outstanding advantages of turning milling composite machining mainly lie in the following aspects:

(1) Shorten product manufacturing process chain and improve production efficiency. A variety of special cutters can be installed, new cutter arrangement can reduce tool change time, improve processing efficiency, turn milling compound processing can achieve one-time clamping to complete all or most of the processing procedures, thus greatly shortening the product manufacturing process chain. On the one hand, it can reduce the auxiliary production time caused by the change of fixture, and reduce the manufacturing cycle and waiting time of fixture, which can significantly improve the production efficiency.

(2) Reduce clamping times and improve machining accuracy. The reduction of the loading times avoids the error accumulation caused by the transformation of the positioning datum. At the same time, most of the turning milling complex processing equipment has the function of on-line detection, which can realize the on-site detection and precision control of key data in the manufacturing process, so as to improve the processing accuracy of products; the high-strength integrated bed design improves the gravity processing power of difficult cutting materials; the machine is equipped with an automatic feeding device, which can realize the automatic feeding for continuous, basically realized Assembly line operation of single machine tool.

(3) Reduce floor space and production cost. Compact and beautiful appearance design improves the way of space utilization, Maintenance and repair are more convenient for customers to get great satisfaction; although the price of single turning milling compound processing equipment is relatively high, due to the shortening of manufacturing process chain and the reduction of equipment required for products, as well as the reduction of fixture quantity, workshop floor area and equipment maintenance cost, it can effectively reduce the investment, production operation and management cost of total fixed assets.

Monthly Archive March 18, 2020