Common faults and solutions for CNC machine tool spindles IV

Problem five:The spindle stops immediately after starts.

The cause of the failure and the solution:

1. System output pulse time is not enough: adjust the system's M code output time.

2. The inverter is in jog state: Refer to the instruction manual of the inverter and set the parameters.

3. The control components of the spindle line are damaged: check whether the contacts on the circuit are in good contact, check whether the DC relay is damaged which caused the contact can not self-lock. 

4. The spindle motor is short-circuited, causing thermal relay protection: find the cause of the short circuit and reset the thermal relay.

5. The spindle control loop does not have self-locking circuit, and the parameter is set to pulse signal output, so that the spindle can not operate normally: change the start and stop parameters of the system control spindle to the level control mode.

Problem six: the spindle rotation can not stop

The cause of the failure and the solution:

1. AC contactor or DC relay is damaged and uncontrollable: replace AC contactor or DC relay.

Common faults and solutions for CNC machine tool spindles III

Problem three: the rotating speed of the spindle without frequency conversion (shift spindle) is not controlled

The cause of the failure and the solution:

1. System has no S01-S04 control signal output: Check whether the system has shift control signal output. If no, it is system failure, replace the IC or send the factory for repair.

2. Connection line failure: If the system hasshift control signal output, check whether there is any open circuit or poor contact on each connection line, and check whether the DC relay or AC contactor is damaged.

3. The spindle motor is damaged or open circut : Check the spindle motor.

4. Machine is not linked: hang up the gear.

Problem four: the spindle has no brake

The cause of the failure and the solution:

1. Abnormal brake circuit or strong electrical components damage: Check whethr bridge stack, fuse or AC contactor is damaged; check if the high-voltage circuit is open.

2. Braking time is not long enough: adjust the braking time parameter of the system or inverter.

3. System has no brake signal output: replace internal components or send to the factory for repair.

4. The inverter control parameters are not adjusted: Check the inverter manual and set the inverter parameters correctly.

Common faults and solutions for CNC machine tool spindles II

Problem two: the spindle with the inverter does not turn​

The cause of the failure and the solution:

1. Mechanical transmission failure: Check whether the driving belt is broken or whether the machine tool is in neutral.

2. Three-phase power supply to the spindle is missing: Check the power supply and exchange any two power lines.

3. The inverter control parameters of the CNC system are not open: see the system manual to understand the inverter parameters and change them.

4. Line connection error between the system and the inverter: Check the connection manual of the system and the inverter to ensure the connection is correct.

5. The analog voltage output is not normal: Check whether the analog voltage output by the system is normal with a multimeter; check whether the analog voltage signal line connection is correct or the contact is good, and the analog voltage received by the inverter matches.

6. High-voltage control part is disconnected or component is damaged: Check whether the connection of each contact of the spindle power supply is reliable and whether the DC relay is damaged or the fuse is burnt out.

7. Inverter parameters are not adjusted: The inverter contains control mode selection, which is divided into inverter panel control spindle mode, NC system control spindle mode, etc. If NC system control mode is not selected, we can not control spindle with system; check if the relevant parameter settings are reasonable or change them if necessary. 

Common faults and solutions for CNC machine tool spindles I

Problem one: the spindle without frequency conversion does not turn

The cause of the failure and the solution:

1 Mechanical transmission failure: Check whether the driving belt is broken or whether the machine tool is in neutral.

2 Three-phase power supply to the spindle is missing or inverting: Check the power supply and exchange any two power lines.

3 Wrong circuit connection: Carefully refer to the circuit connection manual to ensure that the connection is correct.

4 The system has no corresponding spindle control signal output: use the multimeter to measure the system signal output terminal. If there is no spindle control signal output, you need to replace the relevant IC components or send it to the factory for maintenance.

5 The system has the corresponding spindle control signal output, but there is an open circuit or component damage in the power supply line and the control signal output line: use the multimeter to check the power supply circuit between the system and the spindle motor, and whether there is an open circuit in the signal control circuit; whether contact between the wires is not good; whether AC contactor or DC relay is damaged; check if the thermal relay is overcurrent; check if the fuse is burnt.

Method of Judging Grease Metamorphism

In order to provide better performance, the bearings are lubricated by lubricating grease, which can reduce the friction and temperature of the bearings, if the grease is bad. Not only does not play a related role, but is more adverse to the use of bearings, so we must learn how to buy grease to tell whether the grease has deteriorated.

  

Method of judging grease metamorphism

1. Oil flow observation method

    Take two measuring cups , one of the lubricating oil to be inspected , the other empty on the desktop , lift the measuring cup full of lubricating oil away from the table top 30 - 40 cm and tilt , let the lubricating oil slowly flow into the empty cup , observe the flowing condition , the quality good lubricating oil oil flow should be slender , uniform and continuous , if the oil flow is lost or slow , and there is large flow of oil , the lubricating oil has deteriorated .

2. Hand twisting

    Twisting lubricating oil between thumb and index finger repeatedly grinding, a better lubricating oil hand feel lubricity, less debris, no friction, if feel the sand between fingers such as a greater sense of friction, it shows that there are many impurities in the lubricating oil. New lubricating oil should be replaced if it cannot be used again.

3.Illumination method

     On sunny days, use a screwdriver to lift the lubricating oil at an angle of 45 degrees to the horizontal level. Compare the sunlight and observe the oil droplets. Under light, you can clearly see that the lubricating oil is good without debris and can continue to function. If there is too much debris, replace the lubricating oil.

4. Oil drop trace method

    Take a clean white filter paper, drop a few drops on the filter paper, after oil leakage, if the surface of black powder, with the hand touch has a sense of resistance, then the lubricating oil has a lot of impurities. Good lubricating oil without powder, touch dry and smooth with hands, and yellow marks.

General information of ZYS needle bearing

The needle bearing is roller bearing with a cylindrical roller, which is both thin and long with respect to its diameter. In spite of the smaller cross-section, the bearing still has a high load bearing capacity. The needle bearing is equipped with thin and long rollers (roller diameter D ≤ 5mm, L/D ≥ 2.5, L means the length of the roller), therefore its radial structure is compact. When the inner diameter size and load capacity are the same as those of other types, the outer diameter is the smallest, which is particularly suitable for a support structure in which the radial installation size is limited.

Structure type
This type of bearing has a radial needle and thrust full of ball, or with a thrust ball, or with a thrust cylindrical roller, or with the angular contact ball into one, can withstand unidirectional or two-way axial load. Can also be designed according to the user's specific structural requirements.
Materials
Needle roller material for the GCr15 bearing steel, hardened HRC60-65.
Inside and outside the ring material for the GCr15 bearing steel, hardened HRC61-65.
The cage material is made of high quality mild steel or reinforced nylon.
Application
It is widely used in machine tools, metallurgical machinery, textile machinery and printing machinery and other machinery and equipment, and mechanical design can be more compact and smart.

http://www.zys-bearings.com/bearing/the-needle-bearing.html

High temperature adaptability of bearings

The high temperature adaptability of the bearing and the heat treatment process of the bearing within an outer diameter of  240 mm ensure that it is dimensionally stable below 150 degrees. Special heat treatments are required if the operating temperature is above 150 degrees. These bearings are marked with the suffixes S1 to S4 (DIN 623).

S1: Maximum operating temperature 200 degrees

S2: Maximum operating temperature 250 degrees

S3: Maximum working temperature 300 degrees

S4: Maximum operating temperature 350 degrees

Bearings with an outer diameter＞240 mm are generally stable at temperatures below 200 degrees. The bearings use the cages made of glass fiber reinforced nylon 66 and can be stably operated at working temperatures below 120 degrees. When this kind of bearing is lubricated with oil, if the oil contains additives, the life of the cage may be shortened. When the temperature exceeds 120 degrees, the aged lubricant will also shorten the life of the cage. Therefore, you should pay attention to observe and replace the lubricant as scheduled.

The allowable temperature of sealed bearing also depends on the filled grease and the requirements of the contact seal. Sealed bearings are lubricated with specially tested high quality lithium grease. This grease can withstand high temperatures of 120 degrees in a short time. If the stable operating temperature reaches 70 degrees or higher, the life of standard lithium grease will be shortened.

ZYS has special technical team to develop the lubricant to meet the different kinds of bearing. If you want to know more, please check http://www.zys-bearings.com/bearing-materials/lubricant/antirust-oil-for-bearing.html.

The importance of lubricant on bearing torque

Rolling element bearings, such as ball bearing and roller bearings, support the load required to carry out a machine’s function at a much lower friction than a fluid bearing alternative. This reduces the power required to drive the equipment, lowering the cost of moving the load and the energy required to operate the equipment.
Bearing torque is the force required to overcome internal friction to start or maintain rotation of the bearing. This frictional torque is generally increased with a larger bearing, increased load or increased lubricant drag.

How can we get the right bearing torque?
Many applications require the bearing to spin easily with extremely low frictional torque, without generating excess heat. Dry lubricant is one way of meeting these low torque requirements. Despite being solid, dry lubricants can reduce friction between two surfaces without the need for oil or grease.
Instrument oils are another option for low torque requirements. They will often produce very low torque levels especially at very low speeds.

There are many oils and greases to choose from, and there are other factors to consider aside from torque, such as contamination, speed or corrosion resistance. With the right lubrication type, correct fill level and consideration of load, you’ll be able to source bearings with the correct frictional torque for the specific application.

Bearing components

1. Bearing part

One of the parts that make up the rolling bearing, but does not include all the accessories.

2. Bearing ring

Including the annular part of radial rolling bearing with one or several raceways.

3. Bearing washer

Including the annular part of thrust rolling bearing with one or several raceways.

4. Flat ring

A detachable flat washer with its inner or outer portion as a rib for the outer or inner ring of a radial cylindrical roller bearing.

5. Oblique ring (separable)

A separable ring with "L" shaped cross section with its outer portion as a rib of the inner ring of radial cylindrical roller bearing.

6. Middle retaining ring

A separable ring in a roller bearing with two or more rows of rollers for isolating the two rows of rollers and guiding the rollers.

7. Stop ring

A single port ring with constant cross-section, mounted in an annular groove, axially positions the rolling bearing within the housing or on the shaft.

8. Lock ring

A single-mouth ring with a constant cross-section, mounted in the annular groove as a retaining ring to hold the roller or cage in the bearing.

9. Spacer

It is a toroidal part used between two bearing rings or bearing washers or between two half bearing rings or between two half bearing washers to maintain a defined axial distance between them.

10. Sealing ring

An annular cover consisting of one or several parts, fixed to a ferrule or washer of the bearing and in contact with another ferrule or gasket or forming a narrow labyrinth gap to prevent leakage of lubricating oil and invasion of foreign objects.

11. Dust cover

It is an annular cover, usually stamped from a thin metal plate, fixed to a ferrule or washer of the bearing and extending toward the other ring or gasket to cover the inner space of the bearing, but not in contact with another ferrule or gasket. .

12. Guard ring

A part attached to the inner ring or shaft ring that utilizes centrifugal force to enhance the ability of the rolling bearing to prevent foreign objects from entering.

13. Rolling body

A ball or roller that rolls between the raceways.

14. Cage

A bearing component that partially wraps around and moves with all of the rolling elements to isolate the rolling elements and also generally guides the rolling elements and retains them within the bearings.

The working principle of Induction heaters

Induction heaters use the principle of power frequency short circuit current heating bearing, and adopt advanced electronic temperature control circuit, then the temperature can be settled automatically according to the input values in the range of 0-200℃. Set up the highest upper limited temperature in the process of heating, once the temperature reach the highest value, the induction heater can cut the heating circuit automatically and give overtemperature alarm. The heaters use the intelligent dual digital display mode to set up, control and display the temperature. Set time and actual time can be displayed in dual digital display mode. Therefore, user can know the temperature and heating time of the heated inner ring anytime and anywhere. In the heating process, only bearing is hot while the temperature of heater itself keeps normal.

Get to know slewing bearing

Slewing bearing, that is turntable bearings, which can bear large radial load, axial load and tilting moment. For application field, slewing bearings are widely used in large-scale rotary device engineering, mining machinery, metallurgy, wind power, ship, port, petroleum, chemicals, light industry, medical equipment, food, vehicles, robotics, aerospace, radar and military industries. Generally speaking, slewing bearing has lubrication holes, mounting holes and sealing devices, to meet the various hosts under various working conditions. In addition, slewing bearing has some features, such as compact structure, easy to guide the rotation, easy to install and easy to maintain. 

Slewing bearing can be divided into crossed roller wheel bearing, double row different ball slewing bearing, four-point contact ball turntable bearing, roller and ball combination slewing bearing and other types bearings. According the different structure, they can also be divided into no gear type, external gear type and internal gear type.

Bearing failure cause analysis program

1. Determine the most complete operating condition information.

2. Related photos in the process.

3. Alignment of used and unused lubricant samples.

4. Mark the bearing and its location in the device.

5. Carefully disassemble the bearings to avoid unnecessary extra damage.

6. Inspect other machine components to determine incidental damage.

7. Confirm the bearing base and seat.

8. Confirm the condition and distribution of the lubricant in the bearing. Extract additional samples if possible.

9. Clean the bearings and components, if possible, record the logo, brand and full name.

10. Realize the analysis of bearings and corresponding parts. Take other photos.

11. Compare the failure mode standard photos provided by the International Standards Organization 15243 and/or the bearing manufacturer to determine the cause of the failure.

12. Determine the necessary corrective actions necessary to avoid the same failure again.

13. Protect and retain faulty bearings for future comparisons.

14. Example: Some of the above cases will be shown

15. Interactive exercises: Some interactions with bearing failures will be shown during the workshop

16. Conclusions and recommendations. http://www.zys-bearings.com/

The Role and Use of Tapered Roller Bearings

Tapered roller bearings are to bear radial primarily diameter, the axial joint load. Rolling bearing capacity depends on the angle of the outer ring, the bearing capacity of the larger angle. This kind of bearing is separable bearings, roller bearings according to the number of columns is divided into single row, double row and four row circular cone roller bearings separately. Tapered roller bearing clearance adjustment to users in the installation; double row and four row tapered roller bearing clearance has been in the factory according to user requirements given, the user does not have to adjust.

    Tapered roller bearings have conical inner ring and outer ring raceway. Tapered rollers are arranged in between. Projection lines on all conical surfaces converge at the same point in the bearing axis. This design makes tapered roller bearings particularly suitable for bearing composite (radial and axial). Load. The axial load capacity of the bearing is mostly determined by the contact angle α; The greater the α angle, the higher the axial load capacity. The greater the e value, the greater the contact angle, the greater the applicability of bearing to axial load.

    Tapered roller bearings are usually of separate type, i.e. conical inner ring assemblies consisting of inner rings with roller and cage assemblies can be mounted separately from conical outer rings (outer rings).

Tapered roller bearings are widely used in automobile, rolling mill, mining, metallurgy, plastic machinery and other industries.

    The main reason is that the emergence of tapered roller bearing device in the process are: bearing device, when assembling the emergence of the inner ring, the outer ring of skew; or perhaps the emergence of load device and assembling charge into the enemy ranks are in the process of the final formation. That is the emergence of the bearing device conical roller bearing should be in accordance with the job specification to stop, not many results, such as to form or not when the device, will emerge the scar formation of linear bearing raceway surface and rolling bearing surface. Device of deep groove ball bearing with bearing using the indirect reaction when precision, life and function.

    Although the quality of tapered roller bearings is good, the rolling bearings are precision parts, and their use should be carefully carried out accordingly. No matter how high performance bearings are used, if they are not used properly. The expected high performance will not be obtained. The following considerations are noted for the use of bearings:
(1)、Keep the tapered roller bearings and their surroundings clean. Even small dust that is invisible to the eyes can have a bad effect on the bearings. So keep the surroundings clean so that the dust does not intrude into the bearings.

(2)、 Give taper roller bearing a strong impact in use, will produce scars and indentation, become the cause of the accident. In serious cases, will crack, fracture, so we must pay attention to.

(3)、Use the right operating tools. Avoid using existing tools. Use the right tools.

(4)、Attention should be paid to the corrosion of tapered roller bearings.

     When operating the bearing, the sweat on the hand can be the cause of rust. Use clean hands and wear gloves as far as possible. Tapered roller bearings use hearing to identify irregular movement is a very common method. For example, using an electronic stethoscope to detect a zero piece of abnormal noise is used by an experienced operator. Bearings in good working condition emit a low whine. A sharp hissing tapered roller bearing, squeak and other irregular sounds usually indicate that the bearing is in bad working condition.

1, tile surface corrosion: spectra of non-ferrous metal element concentration anomaly; there are many nonferrous metal components of sub micron particle wear ferrography; oil water exceed the standard, exceed the standard value.

2, the journal surface strain spectrum: iron iron line cutting abrasive or black metal oxide particles, temper the surface. 

3, shaft neck surface corrosion: spectral analysis of iron concentrations found abnormal, submicron particles have many iron components of iron in the spectrum of lubricating oil or water exceed the standard.

4 value exceed the standard, the surface strain: iron spectrum is found in cutting abrasive, abrasive composition for nonferrous metals. 

5, tile back fretting wear the spectral analysis showed that iron The concentration is abnormal, and there are many submicron wear particles of iron in the iron spectrum, and the water and acid value of the lubricating oil are abnormal. Under the condition of liquid lubrication , the sliding surface is separated from the lubricating oil without direct contact , the friction loss and the surface abrasion can be greatly reduced , and the oil film also has certain vibration absorption capacity

     A sharp creak noise may be due to inadequate lubrication caused. The bearing clearance can also cause inappropriate metallic sound. Dent taper roller bearings on the track will cause vibration, resulting in smooth crisp sound, if the installation of the percussion scars will produce noise, the noise will follow bearing speed vary. If intermittent noise, said rolling element may be damaged, tapered roller bearings, this sound is when the damage occurred in the surface is rolled out, bearing if hissing sound pollution often caused serious damage to the bearing will produce irregular and loud noise.

   Bearing damage can be detected by hearing, but usually the bearing must be replaced immediately by this time. Therefore, better methods such as using electronic condition monitoring instruments. The operation of tapered roller bearings is broken in advance.

http://www.zys-bearings.com/bearing/automotive-bearing/single-row-tapered-roller-bearings.html

Ensure the lubrication quantity

It is important to ensure the proper fill quantity of lubrication in order that all contact surfaces are provided with a suitable lubricating film over the operating life. Both over-lubrication and under-lubrication are very harmful. With over-lubrication, there is an increase in the internal friction of the component as excess lubricant is moved through the free space. This results in increased heat generation and then the shorter service life. With under-lubrication, not all contact surfaces are supplied with the proper quantity of lubricant. This may lead to wear and then shorten the bearing service life. 

The purpose of the lubricant is to provide the contact surfaces with a consistent lubricating film, thick enough to prevent metal-to-metal contact. The correct lubricant quantity is determined by the design, operating speeds, reservoir volume, and the extent of sealing or shielding found in the application. http://www.zys-bearings.com/

Online Automatic Packaging Machine

Technological Parameters

1、Processing range: 5mm-30mm; Angle 1°0’-4°30’

2、Processing Rate: Take the rollers, of which the diameter is 18mm as an example: 120 pieces/min;

3、Total Power of the Machine Tool: 3.5Kw.

4、External Dimension of the machine tool(Length*Width*Height): 3200X800X1100mm.

5、Total weight of the machine tool: About 1200Kg.

6、Maximum working pressure of pneumatic system: 0.6Mpa.

7、 Realizing the functions of automatic sorting, counting, automatic packing and so on.

8、 The equipment consists of the feeding area, the sorting area, the packing bag heating area, the operation area and discharge hole, etc.

9、The electrical program is controlled by PLC and is set and operated through a touch screen. The touch screen consists of four interfaces.When the power switch is started, it shows "welcome to use", namely the first interface, hinting to touch "operation interface" template to enter the second "user operating interfaces". According to all the hints of this interface, with safe operation only, it is easy to enter the third "basic setting interface" and the fourth "temperature control interface.   Each interface can be set voluntarily  according to the actual needs to realize automatic packaging. http://www.zys-bearings.com/

Load and failure of Rolling bearings

I. Load characteristics of Rolling bearings

1. The contact load and stress of the rotating ring and the rolling body passing through each point of the bearing zone are varied, and the contact load and stress at each contact point show the characteristic of pulsating cycle, and the contact load and stress are not loaded in the non-bearing area.

2. For the fixed ring, the load and stress at each point are different, but the contact load and stress at each bearing point show the same characteristics of pulsating cycle, but the amplitude is different.

The highest load value for deep groove ball bearings (six types) at the lowest end: F0=（4.37/Z）Fr.

II. Failure form of Rolling bearing

1. The fatigue pitting of the inner and outer ring and the rolling body for the normal running bearing is 10 r / min < n < nlim.

2. The plastic deformation of the inner ring, outer ring and rolling body for bearing of static or low rotational speed (n ≤ 10 r / min) or intermittent swing.

3. The inevitable friction and wear of inner and outer ring and rolling body.

III. Design criteria for rolling bearings

1. For the normal running bearing-to prevent fatigue pitting corrosion, basing on the calculation of fatigue strength, the life of bearing is calculated.

2. For low-speed bearing, or for bearing continuous load or discontinuous load without rotating bearing, it is necessary to control plastic deformation to calculate static strength.

3. For high-speed running bearings, apart from life calculation, it also needs to check the ultimate speed of bearings.

Bearing failure

We may find the following problems while identifying bearing failure:

1. Cage Damage – During use, the cage damage may occour, such as vibration, excessive speed, wear, & blockage.

2. Contamination – Contamination may be caused by the entrance of foreign objects into the bearing, such as scratches, pits, and lapping of the raceways.

3. Fatigue Failure – It is characterized by flaking or spalling of the raceway.  Fatigue failure is caused by granular weakening of the bearing steel which begins at the sub-surface and spreads to the raceway. 

4. Lubrication Failure – The original color of grease will usually turn to dark. If the grease is stiff or changed in color, it indicates lubrication failure. The grease will have an odor of burnt petroleum oil. If there is lack of oil, the lubricating oil will disappear. 

5. Misalignment – When one side of bearing is misaligned in relation to the other, the ball or roller path will run from one side of the race. This can result in high temperature and destroy of lubricant.

2018 National Bearing Industry Quality Conference

Thrust ball bearings, also known as thrust bearings, consist of a row of steel balls (with cage), a shaft ring (tightly fitted with the shaft) and a race (with a clearance from the shaft and tightly fitted with the housing bore). Steel ball is rotating between the shaft ring and the race. It can only withstand axial loads in one direction and cannot withstand radial loads. Since the axial load is evenly distributed on each steel ball, the load capacity is large; however, when working, the temperature rise is large, and the allowed limit speed is low.

Thrust ball bearings can not limit the radial movement of the shaft or casing, but can limit the axial movement of the shaft and casing in one direction. Therefore, such bearings are often used in conjunction with deep groove ball bearings.

When installing, the axis of the shaft and housing bore must be kept concentric, otherwise the bearing will be prematurely damaged due to stress concentration. In order to eliminate this phenomenon, a radial gap of 0.5 to 1 mm may be left between the outer diameter of the race and the hole of the outer casing. The shaft center line and the bearing support surface should be vertical, and the shaft should not be inclined or deflected. Otherwise, the bearing will be damaged prematurely due to uneven load distribution. In order to eliminate the inclination of the bearing axis, the support surface of the race can be padded with an elastic material such as an oil-resistant rubber, leather, or thrust ball bearing with a spherical seat.

Thrust ball bearings are mainly used in automobiles, machine tools, oil rigs, iron and steel machinery industries.