Cutting Tools Weekly – Meetyou Carbide Fri, 26 Feb 2021 02:13:16 +0000 en-US hourly 1 Cutting Tools Weekly – Meetyou Carbide 32 32 Few Useful Processing Methods of Grooving and Cutting Tools Fri, 26 Feb 2021 02:13:15 +0000

This article mainly introduces the installation and processing methods of cutting tools.

Grooving cutter has CNC grooving cutter, which is a tool used for cutting in mechanical manufacturing, also known as cutting tool.

The material of the knife has the following properties:

First, it has high hardness, and its normal temperature hardness is above HRC60.

Secondly, it has enough strength and toughness, enough bending strength and enough toughness to resist impact and vibration.

Third, high wear resistance. It has very high resistance to wear and can keep the blade sharp.

Fourth, high thermal hardness, which can maintain high hardness at high temperature.

Fifthly, good technology, easy to tool manufacturing and heat treatment.

According to the different equipment, the size of grooving cutter is also different. The function of slotting cutter is the same as that of many cutting tools, which is an essential cutting tool in mechanical manufacturing. Generally, it is used in some CNC lathe or CNC equipment. Of course, the use method of each slotting cutter is different. Let’s take an example.

For example, in CNC lathe slotting tool, it can not be lower than the center, the tool tip and the center of the workpiece the same height. In addition, when clamping the slotting tool, first of all, it should meet the general requirements of cylindrical turning tool clamping. The protruding part of the tool clamping on the tool holder should be as short as possible to enhance its rigidity. The number of gaskets should be as few as possible, and should be aligned with the edge of the tool holder. At least two screws should be used to compress them to prevent their vibration and produce bad use effect.

Of course, the size of slotting cutter should be consistent with the model of lathe. When the tip of the turning tool is higher than the axis of the workpiece, the actual back angle of the turning tool will be reduced, and there will be a very large friction between the back of the turning tool and the workpiece, which will shorten the tool life. If the tool tip is lower than the axis of the workpiece, the actual rake angle of the turning tool will decrease and the cutting resistance will increase. If the tool tip is not in the center, there will be a convex head when turning to the center of the end face. When using cemented carbide, if this point is ignored, turning to the center will cause the tool tip to break, so we must pay attention to it.

In addition, it is also necessary to pay special attention to that when clamping, the knife must not extend too long, and the center line of the knife must be perpendicular to the axis of the workpiece to ensure that the two secondary deflection angles are symmetrical, and the main cutting edge must be parallel to the axis of the workpiece; the bottom plane of the knife should be flat to ensure that the two secondary back angles are symmetrical. Therefore, it is very important to choose the size of slotting cutter.

Installation of external groove cutter

1. When the cutting tool can meet the processing requirements, the slotting tool should not extend too long during installation.

2. The height of the main cutting edge should be controlled within the range of 0 ± 0.2mm for the center of the workpiece when the groove is turned and the cross feed is carried out, and the height of the blade and the center of the workpiece should be as high as possible.

3. The blade shall be perpendicular to the center as far as possible, and the two secondary deflection angles shall be symmetrical to ensure that the main blade is parallel to the axis of the workpiece.

Installation of cutting tool

1. During installation, the cutter should not extend too long, and the center line of the cutter must be perpendicular to the center line of the workpiece, so as to ensure the symmetry of the two secondary deflection angles.

2. When cutting a solid workpiece, the main cutting edge of the cutter must be set at the same height as the center of the workpiece, otherwise it cannot be turned to the center, and it is easy to break the cutting edge or even break the turning tool

3. The bottom plane of the cutter should be flat to ensure the turning quality.

Processing method of straight groove outside car

1. When turning low and narrow grooves, the groove turning tool with the width equal to the groove width can be used, and the one-time straight forward method can be used.

2. For the groove with accuracy requirements, the two-step straight forward method is generally adopted.

Cut off method

1. Cut off the workpiece by straight forward method. The so-called straight forward method refers to cutting perpendicular to the axis of the workpiece. This method has high cutting efficiency, but it has high requirements for the grinding and installation of lathe and cutter, otherwise it is easy to break the cutter head.

2. Cut off the workpiece by the left and right knife method. In the case of insufficient cutting rigidity, the left and right tool borrowing method can be used to cut. Left and right borrowing method means that the cutter moves back and forth repeatedly in the axial direction, and then both sides feed radially until the workpiece is cut off.

3. Cut off the workpiece by reverse cutting. Reverse cutting method refers to the workpiece reverse, turning tool reverse clamping, this cutting method is suitable for larger diameter workpiece cutting.

A Cutting Tool Scheme for Automobile Engine Parts Processing Sat, 20 Feb 2021 09:02:30 +0000

The engine is responsible for generating the power required for the movement of the vehicle. Nowadays, with the demand of reducing emissions and improving power efficiency, the development of engine is more and more intense.

New materials, regulations and other drivers have brought a lot of investment into R & D. The main trend is miniaturization of internal combustion engines to minimize environmental impacts. Another development trend is power train electrification.

TESA precision’s solutions and tools for engine parts are backed by in-depth application of professional technology. With a professional engineering team supporting the automotive industry through a variety of high-quality solutions, we also have a place in the international market. Here, we will share selected high productivity solutions for some of the challenging features of engine parts production.

Cylinder block

The cylinder block is the main structure of the engine, which is the shell of many different moving parts to generate the power required by the vehicle movement.

The cylinder block is a part of the main structure of the engine. It is the shell of many different moving parts that generate the power required by the vehicle movement together.

For many years, the engine cylinder block is made of cast iron alloy because of its high strength, low cost and good wear resistance. However, as the engine becomes more and more complex, in order to reduce the weight of the engine and improve the strength and wear resistance, new materials are also put into use. Nowadays, the most commonly used material of passenger car engine is aluminum alloy, which is due to its lighter weight and excellent casting performance. Commercial vehicles will continue to use cast iron, but more high strength alloys.

The manufacturing process of cylinder block involves the most machine tools in the production of automobile parts, as well as several complex processes and strict tolerances. The high quality of cylinder block is very important to the performance of vehicle. For these types of parts, high economy manufacturing is very important.

The cylinder cover

The cylinder head delivers air and fuel to the combustion chamber and covers the cylinder. It is also the shell of many different parts.

The cylinder head is used to deliver air and fuel to the combustion chamber. Because it is located on the top of the cylinder block, it can cover the cylinder. It is also the housing of many different parts such as valves, spark plugs and fuel injectors.

In addition to the cylinder block, the manufacturing process of the cylinder head also involves the machine tool with the largest number of automobile parts. In addition, several complicated processes and tight tolerances are involved, especially when machining valve seat, valve guide and top surface. As the cylinder head is an important part of the engine, its quality is very important for the performance of the vehicle. For these types of parts, high economy manufacturing is also very important.


This part is used to convert linear motion and power into rotary motion, so as to make the shaft rotate, so as to make the vehicle move.

Asymmetric and relatively slender crankshafts form the heart of all vehicle internal combustion engines, from motorcycles to heavy trucks. It is also one of the most challenging parts to process. Considering the structure of crankshaft, high tolerance requirements and machining challenging materials (forged steel or nodular cast iron), only the truly optimized tools and methods can be used to process successfully.


The camshaft is used to control the valve operation so that the combustion cycle is synchronized.

In internal combustion engines, camshaft is used to control valve movement and synchronization. It consists of a shaft with multiple lobes and a camshaft for each valve. When the cam blade rotates, it exerts pressure on the valve (or some intermediate mechanism) to force the valve to open.

connecting rod

The connecting rod is used to transmit linear motion from the piston to rotate the crankshaft.

The connecting rod is used to transmit linear motion from the piston to rotate the crankshaft. It is under the huge stress produced by the reciprocating load, and it will be stretched and compressed every time it rotates. The reciprocating load increases squarely with the increase of engine speed. Different from the early methods of cutting with milling cutter, the big end is usually processed by pyrolysis. When cracking the big end, it may be necessary to pre process a laser crack, which will put forward high requirements for the subsequent boring process.

The manufacturing process of connecting rod must be precise in terms of important tolerance and high economy at the same time.

Do You Know the Commonplace 6 Mistakes in Machanical engineering Tue, 26 Jan 2021 01:10:07 +0000

1、 Double nut locking

Double screw thread is used to prevent loosing. The structure shown in Fig. (a) is not allowed. The structure shown in Fig. (b) should be adopted. Flat nut is used at the bottom and thick nut is used at the top. However, considering that flat nut wrench can not be used at the bottom and can not be tightened, only two thick nuts can be used, as shown in Fig. (c).

2、 The two dowels should be of different lengths

The assembly of large box often needs to set several locating pins. It is forbidden to make all locating pins the same height, as shown in figure a, because it is difficult to align several locating pins at the same time. The locating pins should be made into different lengths, as shown in Figure B. It is easier to align one locating pin first when closing the box.

3、 In gear transmission, the correct configuration of big and small gears

In order to facilitate the installation and avoid step wear during the running of the gear, the width of the pinion should be 5 ~ 10 mm wider than that of the large gear, as shown in Fig. C. However, if the pinion is made of plastic, the tooth width of the pinion should be smaller than that of the large gear, as shown in Fig. D, so as to avoid grinding dents on the gear.

4、 Screw connection often disassembled and assembled

The screw connection is shown in Figure a. the characteristic of this connection is that the screw is directly screwed into the threaded hole to be connected without nut. The structure is simple and compact. It is suitable for those structures that cannot be connected by bolts. The screw connection should not be used in the occasions with large mining force or frequent disassembly. If it is disassembled frequently, the thread will be easily worn and the connected parts may be scrapped, If the screw hole is made of steel or surface steel, H ≈ D; if the screw hole is made of cast iron, H = (1.25 ~ 1.5) d; if the screw hole is made of aluminum alloy, H = (1.5 ~ 2.5) d, threaded hole H1 = H + (2 ~ 2.5) P (P is thread pitch), and drilling depth h2 = H1 + (0.5 ~ 1) d.

5、 Intermediate coupling bearing of high speed shaft

When the coupling is installed on the shaft end suspension with high rotation, the structure shown in Fig. A is forbidden. The length of the cantilever should be reduced. The larger the cantilever is, the greater the deformation and unbalanced weight will be. Therefore, when the coupling is installed on the cantilever end, in addition to the stress of the ruler to reduce the weight of the coupling, the ruler should also be close to the bearing.

6、 Deep hole machining of small diameter

It is difficult to process the small diameter deep hole with high cost and low efficiency. It is forbidden to design deep and small diameter lubrication holes on the rotating shaft, as shown in Figure A. if possible, open larger holes as far as possible. If necessary, make different diameters as shown in Figure B.

Crucial Calculation Formulas of Cutting Speed, Cutting Depth and Feed Speed Mon, 18 Jan 2021 05:49:13 +0000

selection principle of cutting parameters

In rough machining, productivity is generally improved, but economy and processing cost should also be considered; in semi finish machining and finish machining, cutting efficiency, economy and processing cost should be considered on the premise of ensuring processing quality. The specific value should be determined according to the machine tool manual, cutting data manual and experience.

Starting from the tool life, the selection order of cutting parameters is: first determine the back feed, then determine the feed, and finally determine the cutting speed.

determination of back knife amount

The back feed is determined by the rigidity of the machine tool, workpiece and cutter. If the rigidity is allowed, the back feed should be equal to the machining allowance of the workpiece as far as possible, so as to reduce the number of tool feed and improve the production efficiency.

The principle of determining the amount of back knife:

(1) When the surface roughness of the workpiece is required to be Ra12.5 μ m ~ 25 μ m, if the machining allowance of NC machining is less than 5 mm ~ 6 mm, one feed of rough machining can meet the requirements. However, when the allowance is large, the rigidity of the process system is poor or the power of the machine tool is insufficient, the feeding can be completed by several times.

(2) When the surface roughness of the workpiece is required to be between 3.2 μ m and 12.5 μ m, it can be divided into rough machining and semi finish machining. The amount of back cutting in rough machining is the same as before. The allowance of 0.5mm ~ 1.0mm shall be left after rough machining and cut off during semi finish machining.

(3) When the surface roughness of the workpiece is required to be Ra0.8 μ m ~ 3.2 μ m, it can be divided into three steps: rough machining, semi finish machining and finish machining. 5 mm ~ 2 mm for semi finishing. When finishing, the back knife is 0.3mm ~ 0.5mm.

determination of feed rate

The feed rate is mainly based on the machining accuracy and surface roughness requirements of parts, as well as the material selection of tools and workpieces. The maximum feed speed is limited by the stiffness of the machine tool and the performance of the feed system.

The principle of determining the feed speed is as follows:

1) When the quality requirements of the workpiece can be guaranteed, in order to improve the production efficiency, a higher feed speed can be selected. It is generally selected in the range of 100-200m / min.

2) When cutting, machining deep hole or machining with high speed steel tool, it is better to choose a lower feed speed, generally in the range of 20 ~ 50M / min.

3) When the requirements of machining accuracy and surface roughness are high, the feed speed should be smaller, generally in the range of 20 ~ 50M / min.

4) When the tool has no stroke, especially when it returns to zero in a long distance, the maximum feed speed set by the NC system of the machine tool can be selected.

determination of spindle speed

Spindle speed should be selected according to the allowable cutting speed and workpiece (or tool) diameter. The calculation formula is as follows:


V — cutting speed, M / min, determined by tool life;

N — spindle speed, unit: R / min;

D — diameter of workpiece or cutter, unit: mm.

Finally, according to the instructions of the machine tool, the speed n of the spindle should be selected.

In a word, the specific value of cutting parameters should be determined by analogy according to the machine performance, relevant manuals and practical experience. At the same time, the spindle speed, cutting depth and feed speed can be adapted to each other to form the best cutting parameters.

reference formula

1) Depth of cut

The vertical distance between the machined surface and the surface to be machined is called back feed. Back draft is measured through the cutting edge base point and perpendicular to the direction of the work plane. It is the depth of the turning tool cutting into the workpiece during each feed, so it is also called cutting depth. According to this definition, if it is in the longitudinal outer circle, the back cutting amount can be calculated according to the following formula:

ap =(dw-dm)/2

Where, AP — the amount of back cutting (mm);

DW — diameter of workpiece surface to be machined (mm);

DM — diameter of machined surface of workpiece (mm).

Example 1: it is known that the diameter of the workpiece surface to be machined is Φ 95mm; now the diameter of the workpiece is Φ 90mm, and the back feed is calculated.

Solution: AP = (DW DM) / 2 = (95-90) / 2 = 2.5mm

2) Feed rate ﹥ f

The relative displacement between the tool and the workpiece in the direction of feed motion when the workpiece or cutter rotates one cycle. According to the different feed direction, it is divided into longitudinal feed and transverse feed. Longitudinal feed refers to the feed along the lathe bed guide direction, and transverse feed refers to the feed perpendicular to the lathe bed guide direction.

The feed speed VF refers to the instantaneous speed of the selected point on the cutting edge relative to the workpiece feed motion.


Where VF — feed speed (mm / s);

N — spindle speed (R / s);

F — feed rate (mm / s).

3) Cutting speed ﹣ VC

The instantaneous velocity of the selected point on the cutting edge relative to the main motion of the workpiece.

vc=( π*dw*n)/1000

Where VC — cutting speed (M / min);

DW — diameter of workpiece surface to be machined (mm);

N — workpiece speed (R / min).

In the calculation, the maximum cutting speed should be taken as the criterion. For example, in turning, the value of the diameter of the surface to be machined should be taken as the basis, because the speed here is the highest and the tool wear is the fastest.

Example 2: when turning the outer circle of the workpiece with a diameter of Φ 60mm, the selected lathe spindle speed is 600r / min, and VC is calculated

Solution: V C = (π * D * w * n) / 1000 = 3.14x600x600/1000 = 113 M / min

In actual production, the diameter of the workpiece is often known. The cutting speed is selected according to the material of the workpiece, the material of the cutting tool and the processing requirements, and then the cutting speed is converted into the rotation speed of the lathe spindle, so as to adjust the lathe

n=( 1000*vc)/π*dw

Example 3: in CA6140 horizontal lathe, cut the outer circle of belt pulley with diameter of 260mm, select VC as 90m / min, and find n.

Solution: n = (1000 * VC) / π * DW = (1000×90) / (3.14×260) = 110R / min

After calculating the lathe spindle speed, the value close to the nameplate should be selected, that is, n = 100r / min should be selected as the actual speed of the lathe.


The three elements of cutting parameters refer to cutting speed VC, feed rate f (or feed rate VF) and back cutting amount AP.

1. The amount of back knife AP (mm)

ap=(dw-dm) / 2

2. Feed rate f (mm / R)


3. Cutting speed VC (M / min)

vc=( π*dw*n)/1000

Various Classification and Function of rack and pinion Wed, 09 Dec 2020 08:28:44 +0000

Gear is a kind of meshing mechanical parts with teeth. It is widely used in mechanical transmission and even in the whole machinery industry and daily life. The application of gear has a long history, and it is also an indispensable important part in the machinery industry.

The working principle of rack and pinion is objective

The working principle of the rack and pinion is to change the rotary motion of the gear into the reciprocating linear motion of the rack, or the reciprocating linear motion of the rack into the rotary motion of the gear.

Gear classification

Parallel shaft gear & Spur gear & rack 

Spur gear

A cylindrical gear whose tooth line is parallel to the axis line. Because it is easy to process, it is widely used in power transmission


A straight toothed strip gear meshed with a spur gear. It can be regarded as a special case when the pitch diameter of spur gear becomes infinite.

Internal gear & helical gear 

Internal gear

A gear that is meshed with a spur gear and has teeth machined on the inside of the ring. It is mainly used in planetary gear rotating mechanism and gear coupling

Helical gear

Cylindrical gear with helical tooth line. It is widely used because it is stronger than spur gear and runs smoothly. Axial thrust is generated during transmission.

Helical rack & herringbone gear

Helical rack

A strip gear that meshes with a helical gear. It is equivalent to the case when the pitch diameter of helical gear becomes infinite.

Herringbone gear

The tooth line is composed of two helical gears of left and right rotation. It has the advantage of not producing thrust in the axial direction.

Straight bevel gear

Straight bevel gear

A bevel gear in which the generatrix of the tooth line and pitch cone line are consistent. In bevel gear, it belongs to the type which is easy to manufacture

Spiral bevel gear & zero degree bevel gear

Spiral bevel gear

The tooth line is a curve bevel gear with spiral angle. Although compared with the straight bevel gear, it is more difficult to make, but it is also widely used as a gear with high strength and low noise.

Zero degree bevel gear

Curved bevel teeth with zero helix angle

Zero degree bevel gear

Spiral bevel gear with zero helix angle. Because it has the characteristics of both straight and curved bevel gears, the force on the tooth surface is the same as that of the straight bevel gear.

Staggered shaft gear

Cylindrical worm pair & staggered helical gear

Cylindrical worm pair

Other special gears

Drum worm pair & hypoid gear

Face gear

Face gear

It can be meshed with spur or helical gears. Drive between the straight axis and the staggered shaft.

pinion and rack

The rack and pinion mechanism is composed of gears and racks. We have a detailed explanation of gears in front of them. The rack is divided into straight rack and helical rack. The tooth profile of rack is straight line rather than involute, which is equivalent to cylindrical gear with infinite dividing circle radius.

Main features of rack

Because the rack tooth profile is straight line, each point on the tooth profile has the same pressure angle, which is equal to the inclination angle of the tooth profile. This angle is called the tooth profile angle, and the standard value is 20 °.

Any straight line parallel to the addendum has the same pitch and modulus.

The straight line parallel to the tooth top line and the tooth thickness equal to the width of the tooth space is called the dividing line (center line), which is the reference line for calculating the rack size.

Application range of rack and pinion drive

1. Suitable for fast and accurate positioning mechanism

2. It is suitable for CNC machine tools, machining centers, cutting machines and welding machines with heavy load, high precision, high rigidity, high speed and long stroke

3. It is suitable for fast transplanting machine of factory automation, industrial robot arm grabbing mechanism, etc

Scan Bearings from the Perspective of Shapes Fri, 04 Dec 2020 05:57:58 +0000

Self aligning ball bearing

The self-aligning roller bearing is equipped with drum roller between the inner ring with two raceways and the outer ring with spherical raceway. The curvature center of outer ring raceway surface is consistent with the bearing center, so it has the same self-aligning function as the self-aligning ball bearing. Wechat of metal processing has good content and deserves attention. When the shaft and shell are flexed, the load can be adjusted automatically and the axial load in two directions can be realized. Radial load capacity, suitable for heavy load, impact load. The inner diameter of inner ring is tapered hole bearing, which can be directly installed. Or install it on the cylindrical shaft with a set sleeve and a disassembly cylinder. The cages are made of steel sheet, polyamide and copper alloy.

Needle roller bearing

Solid needle roller bearing

The basic structure of bearing with inner ring is the same as that of Nu type cylindrical roller bearing. However, due to the use of needle roller, its volume can be reduced and it can bear large radial load. The mounting surface of shaft with appropriate accuracy and hardness should be used as raceway surface for bearings without inner ring.

Thrust needle roller bearing

The separated type bearing is composed of raceway ring, needle roller and cage assembly. It can be combined with thin raceway ring (W) processed by stamping or thick raceway ring (WS) machined by cutting. Non separable bearing is an integral bearing composed of raceway ring, needle roller and cage assembly. This kind of bearing can bear unidirectional axial load. The space occupied is small, which is conducive to the compact design of machinery. Most of them only use needle roller and cage components, and use the mounting surface of shaft and shell as raceway surface.

Tapered roller bearing

This kind of bearing is equipped with cone-shaped roller, which is guided by the large rib of inner ring. In design, the top points of the inner ring raceway surface, outer ring raceway surface and tapered surface of roller rolling surface intersect at a point on the bearing center line. Single row bearing can bear radial load and unidirectional axial load, double row bearing can bear radial load and bidirectional axial load, which is suitable for bearing heavy load and impact load.

Cylindrical roller bearing

According to the different number of columns of rolling elements, cylindrical roller bearings can be divided into single row, double row and multi row cylindrical roller bearings. The single row cylindrical roller bearing with cage is widely used. In addition, there are single row or double row full loaded roller and other structures of cylindrical roller bearings.

The single row cylindrical roller bearing can be divided into N type, nu type, NJ type, NF type and NUP type according to the different ring rib. Cylindrical roller bearing can bear large radial load, and can also bear certain unidirectional or bidirectional axial load according to the structure of ring flange. NN type and NNU type double row cylindrical roller bearings are compact in structure, strong in rigidity, large in bearing capacity and small in deformation after being loaded. They are mostly used to support machine tool spindles. FC, FCD and fcdp type four row cylindrical roller bearings can bear large radial load, and are mostly used in heavy machinery such as rolling mills.

Self aligning roller bearing

This kind of bearing is equipped with spherical roller between the outer ring of spherical raceway and the inner ring of double raceway. According to the internal structure, it can be divided into four types: R, Rh, RHA and Sr. Because the arc center of the outer ring raceway is consistent with the bearing center, it can automatically adjust the center misalignment caused by the deflection or non concentricity of the shaft or shell. It can bear radial load and bidirectional axial load. Especially the radial load capacity is large, which is suitable for bearing heavy load and impact load. Wechat of metal processing has good content and deserves attention. The tapered bore bearing can be assembled and disassembled on the shaft by using fasteners or stripping sleeve. The self-aligning roller bearing can bear large radial load and certain axial load at the same time. The raceway of the outer ring of this kind of bearing is spherical, so it has the function of centering. When the shaft is bent or tilted, the relative inclination between the center line of the inner ring and the center line of the outer ring is no more than 1 ° to 2.5 °.

Thrust roller bearing

Thrust roller bearings include thrust self-aligning roller bearings, thrust cylindrical roller bearings and thrust tapered roller bearings. The thrust self-aligning roller bearing can bear both axial and radial loads, but the radial load should not exceed 55% of the axial load. Another important feature of this kind of bearing is its self-aligning performance, which makes it insensitive to different centrality and shaft deflection. As long as the load P and P. Under 0.05c and the rotation of the shaft ring, the bearing is allowed a certain range of centering angle. Small values are suitable for large bearings, and the allowable centering angle will decrease when the load increases.

Outer spherical bearing

Spherical bearings are preferred for applications requiring simple equipment and parts, such as agricultural machinery, transportation systems or construction machinery.

It is mainly used to bear the combined radial and axial load, which is mainly radial load. Generally, it is not suitable to bear the axial load alone. This kind of bearing can be installed with inner ring (with full set of rollers and retainer) and outer ring respectively. This kind of bearing does not allow the shaft to tilt relative to the shell, which will produce additional axial force under radial load. The axial clearance of this kind of bearing has a great influence on whether the bearing can work normally. When the axial clearance is too small, the temperature rise is high; when the axial clearance is large, the bearing is easy to be damaged. Therefore, special attention should be paid to adjusting the axial clearance of the bearing during installation and operation. If necessary, pre interference installation can be used to increase the rigidity of the bearing.

Plain bearing

There are two types of plain bearings: lubricated and self-lubricating. Plain bearing is a kind of sliding bearing with special structure. Its structure is simpler than that of rolling bearing. It is mainly composed of one outer ring with inner spherical surface, which can bear larger load. According to the inner ring with outer spherical surface and its different types and structures, it can bear radial load, axial load or combined load with radial and axial simultaneously. It is generally used for swing motion with low speed (i.e. angular movement, or inclined movement within a certain angle range (i.e. centering movement). Since the sliding surface is spherical, it can still work normally when the supporting shaft and the shaft shell hole are not concentric.

Linear bearing

Linear motion ball bearing is mainly used in the parts of mechanical equipment with linear reciprocating motion. It has the advantages of small friction, flexible movement and convenient maintenance and replacement. It is widely used in textile machinery, printing machinery, medical machinery, precision machine tools, electrical cutting machines and automatic recorders and other fields.

Angular contact bearing

Angular contact ball bearing can bear both radial load and axial load at the same time. It can also increase the limit speed with pure axial load. The axial load bearing capacity of this kind of bearing is determined by the contact angle. The contact angle is large and the bearing capacity is high.

When to Use Wet Milling or Dry Milling? Tue, 24 Nov 2020 06:07:39 +0000

Milling process is essentially a kind of intermittent processing process. This causes the temperature at the cutting edge to fluctuate between high temperature (about 1000 ℃) and low temperature.

Effect of cutting fluid

When the cutting edge cuts in and cuts out, the temperature change will increase. As a result, the cutting edge is subject to thermal shock and periodic stresses, which may result in cracks and, in the worst case, premature end of tool life.

The higher the temperature of the cutting area, the less suitable the cutting fluid is.

In the finishing process, the use of cutting fluid will not shorten the tool life as much as in rough machining due to the reduced heat generated.

Hot cracks on cutting edge

dry milling

Dry milling can prolong the life of cutting edge. The temperature does change, but it will remain within the design range of cemented carbide materials.

Rough milling should always be carried out without cutting fluid.

wet milling with cutting fluid

There are some exceptions to the use of cutting fluid:

1) Finish machining of stainless steel and aluminum alloys – used to prevent metal particles from sticking to the surface structure

2) Milling superalloys at low cutting speeds – for lubrication and cooling of parts

3) Cast iron milling, used to wet and remove dust to protect the environment and health and ensure the accuracy of parts

4) Milling of thin wall parts to prevent geometric deformation

5) When machining deep cavity, micro lubrication system (i.e. compressed air containing a small amount of special oil) can be used to assist chip removal

Use compressed air and oil mist

In the micro lubrication system, the “oil mist” is only a few milliliters of oil per hour, and is discharged through the ordinary filtering ventilation system.

Use a large flow of internal and external coolant

If wet milling must be carried out, a sufficient amount of cutting fluid should be used.

Speaking of the 9 Cognitive Misunderstandings on Machinery Lubrication… Sat, 21 Nov 2020 00:35:44 +0000

The correct lubrication method can improve the performance of the equipment and prolong its working life. Any equipment can not do without lubrication. But in actual production, there will be a misunderstanding of lubrication due to various reasons, such as thinking that oil can be lubricated, the viscosity of oil is greater, the effect is better and so on. In order to avoid damage to the machine caused by wrong operation, this paper introduces nine common mistakes for your reference.

01. The purpose of lubrication is to make the machine run faster

The contact surface of the relative moving parts in the machine will produce friction and wear. According to statistics, more than 1 / 3 of the world’s energy consumption is in friction loss. When the wear exceeds the allowable limit, it directly affects the normal operation and service life of the machine. Therefore, lubricant is added between the relative moving parts to form a lubricating oil film to reduce friction and reduce wear. At the same time, it can also play the role of cooling, buffering, vibration absorption and sealing.

The purpose of lubrication is not only to make the machine run faster, but also to ensure the normal operation and prolong the service life of the machine.

02. Mistakenly think that oil can lubricate

There are different kinds of lubricating oils and their working properties. In order to improve some properties of lubricating oils, the corresponding additives should be added.

In order to make the machine get reasonable lubrication, different types of lubricating oil and additives should be selected for different types, different working conditions and different oil supply methods.

Therefore, it can not be considered that any oil can be lubricated. What’s more, improper selection of lubricating oil will also cause lubrication accidents, which accounts for a large proportion of equipment failures.

03.The more lubricating oil, the better the lubrication effect

In case of grease lubrication, excessive resistance will increase, causing bearing heating, leading to grease leakage, especially for high-speed and heavy-duty machines.

Generally, oil level indicator can be used to show the height of oil level. For example, the immersion depth of the high-speed gear in the gearbox is 1-2 teeth high, so as to avoid poor lubrication of the high-speed gear, and reduce the movement resistance and oil temperature rise of the gear. Generally, the filling amount of grease for rolling bearing does not exceed 1 / 3-1 / 2 of bearing clearance.

04. The higher the viscosity of lubricating oil, the better the lubrication effect

Viscosity is the main index of lubricating oil, and its standard is usually determined at the temperature of 100 ℃. The higher the brand, the thicker the lubricating oil film formed. Although the friction force of friction surface is reduced, the resistance is increased, the power loss is increased, and the waste of energy is increased.

When the machine is just started, the temperature is low, and part of the lubricating oil on the friction surface will be lost due to the increase of temperature after working for a period of time. The lubrication can not form an effective lubricating oil film and the oil can not be quickly replenished to the friction surface of the machine. Due to the high viscosity and slow flow of the oil, the wear of the parts is large.

Some data show that 15% fuel can be saved by reducing the viscosity of lubricating oil by 1 mm 2 / s. The selection of viscosity should consider the working speed, working temperature and other factors. Low viscosity of lubricating oil is one of the measures to save oil.

05. Unchanged oil selection according to the oil grade specified in the equipment manual

Most of the equipment managers believe that the oil specified by the equipment manufacturer is the law. In fact, the oil specified in the manual refers to the general working conditions, which may not be suitable for the actual working conditions, so it should be selected flexibly according to the actual conditions.

06. If the lubricating oil turns black, it means that the lubricating oil has deteriorated

If the lubricating oil turns black, it means that the lubricating oil has deteriorated and should be changed. This understanding is one-sided. For example, it is normal for machinery oil with detergent dispersant to turn black soon after use. It is not easy to think that the oil has deteriorated. The lubricating oil added with additives often produces a dark protective oil film on the bearing surface. It is normal to blacken the bearing surface in the process of use. It is not necessary to remove the blackened lubricant. Therefore, to determine whether the lubricating oil is deteriorated, comprehensive analysis should be carried out to change the oil according to its quality.

07. Used lubricating oil cannot be used and must be discarded

In fact, in addition to the rotten oil, there are more lubricating oil can be used.

The replaced oil, if only mixed with impurities, can be reused after precipitation and filtration;

After simple treatment, the oil with heavy pollution can be used as lubricant for rough processing equipment, antirust for outdoor equipment, or the waste oil can be collected and turned over for waste oil recycling

The oil that is difficult to be recycled can be burned as fuel oil after simple treatment.

08. All lubricating oils can be used interchangeably

The selection of lubricating oil depends on the working conditions, working environment, specific characteristics of friction surface and lubrication mode of the machine, and the type and brand of lubricating oil selected are also different, which cannot be replaced in general.

09. Do not replace or replenish lubricating oil for a long time

After using for a period of time, the performance of lubricating oil decreases or changes. With the decline of oil quality, if the lubricating oil is not replaced or supplemented in time, the lubricity is poor and high temperature is easy to occur.

In addition, many people lengthen the oil change cycle of air compressor in order to save money, but in fact, poor lubrication will cause large current, serious waste of power, and increase the operation cost, which is not worth the loss.

Is the Accuracy and Efficiency of Slow Wire Processing Abnormal? These Three Points are Worth Your Attention Wed, 04 Nov 2020 07:50:50 +0000

Slow wire machine is a kind of high-precision machining machine, which can achieve machining accuracy of several μ m, and the surface roughness Ra can reach < 0.2 μ M. However, some mold factories do not pay attention to the details when using the slow wire machine, thinking that a good machine tool can easily achieve high-efficiency and high-precision machining. In fact, precision machining must establish the concept of precision machining!

 process premise

Slow wire machine tools are equipped with process parameter library, and the process parameters are generally obtained by testing under specific conditions (such as workpiece material, electrode wire, temperature 20 ± 3 ℃, humidity 40-80%, etc.). If the following conditions change or fail to meet the requirements, the machining results may be deviated.

1. Flushing specification: when processing according to the standard parameters, the difference between the indicated value of the water pressure gauge and the theoretical value should be less than 0.5bar;

2. Clearance between workpiece and nozzle: 0.05 ~ 0.10 mm;

3. When the surface roughness is required to be RA ≥ 0.35 μ m, the efficiency oriented cutting wire can be selected (the same type of wire as the machine tool is recommended). When RA is less than 0.35 μ m, in order to obtain a good processing surface, the galvanized wire which pays attention to the surface should be selected for processing;

4. When finishing, please ensure that the water is less than 10, especially when finishing, please follow the process parameters. If necessary, replace the resin or purified water.

Influence of temperature on machining accuracy

In order to carry out high-precision and high-quality WEDM, the environment must be stable and meet the specified requirements. There should be no direct sunlight or air flow. The temperature change should be monitored. The temperature range to ensure the working accuracy of the machine tool is 20 ± 3 degrees. If the temperature difference is large, the machining accuracy and surface roughness will be affected.

The change of room temperature has a great influence on the machining accuracy, which is reflected in the size, position and shape. As shown in the figure below, the greater the temperature change and the larger the workpiece size, the more obvious the influence of temperature. For example, a 200 mm long workpiece with a temperature difference of 5 degrees will produce a dimension error of 0.01 mm. It is better to finish a larger part in one start-up. If it is put on for one night, the main cutting has little effect, but if it is stopped during trimming, it is difficult to ensure the machining accuracy.

Influence of room temperature change on machining accuracy

The thermal characteristics of CNC machine tools have an important impact on the machining accuracy, accounting for more than half of the machining accuracy. There is a big difference between the machining accuracy of the machine tool in the long-term stop state and the thermal balance state. The reason is that the temperature of the spindle and each moving axis of the CNC machine tool is relatively maintained at a fixed level after running for a period of time, and with the change of processing time, the thermal accuracy of CNC machine tools tends to be stable, which shows that even high-precision machine tools have only one Stable machining accuracy can be obtained only under stable temperature environment and thermal balance state. It is the most basic knowledge of precision machining to preheat the machine tool. However, the warm-up movement of machine tools is ignored or unknown by many factories.

If the machine tool has been shelved for more than several days, it is recommended to preheat the machine tool for more than 30 minutes before high-precision machining; if the machine tool is in a state of only a few hours, it is recommended to preheat for 5-10 minutes before high-precision machining. The process of preheating is to let the machine tool participate in the repeated movement of the machining axis. It is better to carry out multi axis linkage. For example, let XYZ axis move from the lower left corner of the coordinate system to the upper right corner position, and repeatedly walk the diagonal line. When executing, you can write a macro program on the machine tool to let the machine repeatedly perform the warm-up action.

Factors affecting processing efficiency

There are many factors that affect the efficiency of WEDM. In case of inefficiency in processing, the following two factors can be considered.

(1) Limited by the part structure and clamping, it can not effectively flush high-pressure water

At this time, we can see whether the cutting parts can be improved from the clamping. Some parts are affected by the support fixture, the bottom surface is raised, some parts are affected by the position of the pressure plate and clamping screw, so they have to lift the upper nozzle, and some parts are afraid that the operator may touch the nozzle and fail to lower the upper nozzle. If the lower surface is raised, it depends on whether the fixture supporting surface is on the same plane as the worktable, or clamp the workpiece directly on the worktable.

Affected by the screw pressure plate and parts, see whether the jaw clamp can be used for clamping; if the operator is worried that the upper nozzle does not fall to the lowest position, a 0.1 mm feeler gauge can be prepared as required. For the parts that can not be effectively flushed with high-pressure water due to the structure limitation, the cutting energy can only be reduced. At this time, a correct understanding of the cutting efficiency is required.

(2)Silk transport system related (related to maintenance)

1) Check whether the cooling water of the conductive block is normal. In particular, whether there is cooling water for the lower conductive block, because copper dust will drop during cutting, which may block the cooling water of the lower conductive block or even flush water for processing the lower nozzle after long-term use of the machine tool. It should be cleaned and dredged;

2) The lower guide wheel on the lower arm rotates flexibly. Check and clean;

3) Whether the reeling wheel is normal;

  • Check the tension and speed of the wire and readjust it if necessary;
  • Check and clean the wire guide nozzle and conductive block.

The Elixir of Machining Threads–Whirlwind Milling Tue, 27 Oct 2020 06:57:50 +0000

In the lathe for non turning processing, is the lack of equipment and other factors have to do it, but in this process, the intelligent working people found that after the transformation of the machine tool, can complete a lot of efficient and high-quality processing.

In the milling process on the lathe, there is a kind of whirlwind milling thread, which is one of them.

What is whirlwind milling

Because of its high milling speed (up to 400m / min) and high machining efficiency, compressed air is used for chip removal and cooling. In the process of machining, cutting spatter is named after whirlwind.

Whirlwind milling thread is a method that whirlwind milling head is used to process thread, which only needs one cutting.

1.Determination process of whirlwind milling tool

2.Determine part shape

3.Determine tool shape according to parts

4.Make the corresponding blade

There are several companies specialized in the production of thread milling inserts, such as Camex, NTK, haoen and Fengyi, which are commonly used in domestic cyclone milling equipment.

5.Install the blade on the cutter head

  • Five movements of whirlwind milling
  • After the whirlwind milling is matched with the lathe, five machining movements need to be completed in the processing process
  • The cutter head drives the carbide forming cutter to rotate at high speed (main motion)
  • Qualification
  • Express alarm about
  • The lathe spindle drives the workpiece to rotate slowly (auxiliary motion)
  • The whirlwind milling machine moves along the axial direction of the workpiece according to the pitch or lead of the workpiece (feed motion)
  • The whirlwind milling is driven by the carriage in the lathe to carry out radial movement (cutting movement)
  • The spiral milling angle can be adjusted within a certain range. (rotational motion)

Necessary equipment for whirlywind milling

Equipment structure of whirlwind mill:

  1. Medical industry (implants).

Medical industry, medical bone nail, etc

  • Automotive industry.

Automobile automatic transmission shaft, such as transmission shaft on automatic seat, etc

  • Machine tool industry and others.

Machine tool screw with whirlwind milling processing, will have a high efficiency

Whirlwind milling process

1. It is composed of whirlwind milling cutter head, workpiece and guide sleeve.

2. Adjust the installation deflection angle according to the screw angle of the thread.

The installation deflection angle determines the size of thread pitch, and large installation angle determines the processing of large pitch thread.

3. Down milling

The rotation direction of the whirlwind milling cutter head is opposite to that of the machine tool spindle (part), so it can process good surface quality. On the contrary, it is reverse milling, and the surface quality is poor.

Advantages of whirlwind milling

Advantages of whirlwind milling thread cutting:

1. High processing efficiency, higher than the traditional turning processing efficiency! Up to 10 times.

2. The product is formed by one knife, and the eccentric cutting does not need to withdraw the cutter.

3. Without changing the structure of lathe, the angle of helix can be adjusted, and the installation is convenient.

4. The surface roughness can reach Ra0.8 μ m or even higher, and the machining accuracy can be improved by 2 levels.

5. The programming method is simple and fast, forming blade, high positioning accuracy of blade and blade groove, reducing the technical requirements of workers.

Whirlywind milling can achieve dry cutting, heavy cutting, difficult to machine materials and ultra-high speed cutting, with low power consumption. The surface roughness can reach Ra0.8 μ M. Lathe spindle speed is slow, so the machine tool motion accuracy is high, dynamic stability is good, is an advanced thread processing method.