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Home > EP Plastic self-lubricating bearings

Product Size

EPT
EPG
EPH
EPX
EPJ
EPS
EPF
EPW
EP Plastic self-lubricating bearings

EP series of high-performance engineering plastic polymer bearings as the base material, through modification of polymer materials technology into high-strength fibers and specialty solid improvement in its internal grease integrated wear resistance; high strength fiber reinforced network structure strength of the material, the composite solid special grease allows EP series plastic bearings with excellent self-lubricating properties and wear resistance. Whether it is a high durability requirements the automotive industry.

Material property sheet
Common Capability Unit EPT EPG EPH EPX EPJ EPS
Density g/cm³ 1.46 1.46 1.65   1.49 1.24
Color   Black gray Dark grey Grey Black Yellow Beige
Max.water absorption,23℃/ 50% [% weight] 0.2 0.7 0.1   0.3 2.02
Max.water absorption [% weight] <1.2 <4 <0.3 <0.5 <1.3 <0.1
Dynamic friction /steel μ 0.05-0.15 0.08-0.18 0.07-0.20 0.09-0.27 0.06-0.18 0.05-0.15
Max.PV(dry) MPa•m/s 0.4 0.5 1.37 1.32 0.34 0.4
Mechanical behavior
E-module MPa 2,300 7,800 12,500 8,100 2,400 830
Tensile strength,20℃ MPa 80 200 175 170 73 18
Compressive strength MPa 65 80 90 150 35 10
Max.static pressure of the surface,20℃ MPa 35 80 150 90 20 10
Shore D hardness   70 112 87 85 74 73
Physical and thermal properties
Continuous work tempreature +80 +130 +200 +250 +90 +260
short-time work tempreature +120 +220 +240 +315 +120 +310
Minimum operating temperature -40 -40 -40 -100 -50 -200
Thermal conductivity W/m•K 0.2 0.25 0.60 0.60 0.25 0.24
Max.water absorption,23℃ K-1•10-5 7 9 4 5 10 12
Conductivity
Volume resisticity Ωcm >1012 >1013 <104 <105 >1013 >1015
Surface resisticity Ω >1015 >1011 <105 <103 >1012 >1015
EP Material structural characteristics

EP series of materials has excellent self-lubricating and wear resistance is mainly engineers take full advantage of the self-lubricating material modification technology, high-performance engineering plastics used in high-strength fiber to improve the material load and special grease reduced The friction coefficient of the material (Figure 1), thereby enhancing the comprehensive wear resistance of the material to extend the service life of the bearing.    High-performance engineering plastics as the base material mainly as wear-resistant carrier;    Reinforced fiber to improve the bearing in the bearing and impact resistance;    Special grease reduces the coefficient of friction of the bearing from the role of lubrication.

Chart 1 EP series material internal structure sketch map

Boby material Fibre Lubricant
EP plastic bearings and traditional oil bearing

As EP series bearing greases are included in the bulk material, none On how long the working time of the bearing grease will continue to play from the friction surface seepage Long-term lubrication, while the traditional powder metallurgy oil-bearing in the use of the process benefits The lubricating oil in the micropores acts as a self-lubricating effect when these lubricants are depleted or After the end of volatile bearing wear will rapidly intensify, at this time to declare the effective bearing With the end of life (Figure 2).

Chart 2 plastic bearings and traditional composite bearing wear


Plastic bearing has longer service life

Lubricating oil is easy to be failed
EP series friction coefficient

EP series of self-lubricating properties of plastic bearings by modifying technology in the base material to add solid grease and functional fibers to achieve, the coefficient of friction through the solid grease reduced, while the friction coefficient is also subject to working load, speed and axis surface roughness . Coefficient of friction generally decreases with increasing working load and increases with increasing operating speed (see Figure 3). The relationship between friction coefficient and shaft surface roughness is shown in Fig.

Chart 3: Coefficient of friction - load - speed
Bearing wear

Any self-lubricating bearing as long as a load in the work, the bearing will produce subtle wear. The same is true for the EP series bearings, where the grease gradually leaches out and gradually fills the friction surface and transfers to the counter shaft surface during the start-up phase (Figure 4). When the working area is filled with grease The formation of a thin layer of lubricating isolation film, this time the initial bearing wear is almost over, in the latter part of the long work of the bearing wear rate greatly reduced and more stable (Figure 5).

Chart 4: Lubricating film formation after operation

Chart 5: Bearing wear versus operating time

Bearing load noun construct
■ Load calculation method

◇ straight sets, flanging products
P= F / d×L (N/mm²)
F=Bearing capacity (N)
d=Shaft diameter (mm²)
L=Shaft diameter length(mm²)
◇ Thrust washer
P= 4F / π(D2-d2) (N/mm²)
F=Gasket bearing capacityd (N)
D=Outside diameter of gasket OD(mm²)
d=Gasket inner diameter ID(mm²)
The actual bearing surface pressure (Pact) of the bearing is larger than the theoretical value (Pmean) due to the influence of the clearance, the material strength, the internal oil groove,。

■ Maximum surface static load

Bearing the actual work dynamic load is often slightly smaller than the data sheet in the recommended maximum surface static load, the axis and the bearing with the gap is always there, so the actual bearing bearing area is not the projection area of the bearing, the size of the size of the axis with the tolerance Decision. This value is suitable for shaft standstill or operating speed less than 0.01m / s, higher load in the running time is very short (short time refers to within 3 minutes).

Chart 6: EP series of plastic bearings maximum static load distribution
■ load and temperature, speed relationship

The bearing load will increase with the bearing operating temperature gradually reduced, when transported The load carrying capacity of the bearing will drastically decrease after the line temperature exceeds the maximum service temperature (Exhibit 7). Bearing load will be with the speed of bearing speed up and gradually reduce, when transported Line speed will lead to the friction bearing temperature gradually increased, while the load will be With the bearing temperature rising gradually decreased.

Chart 7: Load versus temperature plot

For sliding bearings, the running speed is a key parameter, due to sliding Bearings work with the shaft occurs between the relative sliding friction rather than rolling friction Rub, so the maximum running speed sliding bearings to be much lower than the rolling bearing. Here The speed refers to the relative line speed between the shaft and the bearing, not the revolution speed.

■ Line speed calculation formula

V=π×d×n / 1000×60 (m/s)
d=Shaft (mm²)
n=Rpm
◇ Oscillationg motion
V= π×d×C×θ / 1000×360×60
d=Shaft (mm²)
C=Frequency
θ=Oscillating angle
◇ Reciprocating motion
V=π×d×n / 1000×60 (m/s)
S=Stoke distance (m)
C=Frequency

Bearing speed

The maximum permissible speed for the EP series bearings is shown in Fig. These values Is the limit load achieved when the bearing load is very small, the actual use of these speeds Degree is very difficult to achieve, because the bearing in the work inevitably bear labor As the load, when the bearing load increases when the allowable speed will be reduced. As the bearing speed and bearing operating temperature is inversely proportional to the relationship, so the bearings The maximum speed allowed by the different operating modes is also different.

Chart 8: Maximum bearing speed
Material Rotate Swing Straight line
EPT 0.1 0.7 3.0
EPG 1.0 0.7 4.0
EPH 1.0 0.7 3.0
EPX 1.5 1.1 5.0
EPJ 1.5 1.1 8.0
EPS 2.0 1.4 5.0
Bearing temperature

EP series bearings are limited to the minimum and maximum operating temperature. Minimum Temperature refers to the critical temperature at which the bearing material will become brittle (Figure 10), the highest temperature used Temperature is the bearing wear resistance will not change the critical temperature, short-term operation of the most High temperature is the critical temperature at which the bearing material becomes soft (Figure 9). Such as bearings Often alternating in high temperature and low temperature, the bearing may be shedding phenomenon, So at this time must rely on the auxiliary device to ensure the normal operation of the bearing.

Chart 9: Maximum operating temperature of bearings

Chart 10: Minimum operating temperature of bearings
Material Lowest temperature
EPT -40
EPG -40
EPH -40
EPX -100
EPJ -50
EPS -200
Chart 11: Provide the starting thermometer for the positioning mechanism
Material Starting temperature
EPT -40
EPG -40
EPH -40
EPX -100
EPJ -50
EPS -200
Bearing the PV value

PV value is the bearing in a certain load and linear velocity of the product value, bearing Of the PV value is to evaluate the sliding bearing performance is an important indicator. Actual PV value And the service life of the bearing is inversely proportional to the relationship (Figure 12), so the proposed design as possible A relatively low PV value can be used to ensure a longer service life of the bearing.
PVPerm.=(K1×π×λk×△T / μ×s) + (K2×π×λs×△T / μ×b1×2) ×y1×y2×10-3
Here:
K1, K2 = heat dissipation factor (K1 = 0.5, K2 = 0.042)
S = wall thickness of the bearing (unit: mm)
B1 = length of bearing (unit: mm)
Μ = coefficient of friction
Λs = thermal conductivity of the axis
Λk = thermal conductivity of the bearing
△ T = (Ta - Tu)
Tu = ambient temperature
Ta = maximum operating temperature
Y1 = correction factor for intermittent operation
Y2 = lubrication operation correction factor

Chart 12: Bearing PV
Intermittent operation correction coefficient y1

In many cases the bearing is not running continuously, because the bearing short-term work (running time of 10 minutes or less) and never reach the maximum allowable temperature, then the bearing The permissible PV value is increased because the friction heat generated by the friction is dissipated sufficiently during the stoppage time. Figure 13 illustrates the bearing stop time Bearing time of different ratios of bearing PV correction factor y1;

Chart 13: Correction factor for PV value
under intermittent operation
Lubrication operation correction coefficient y2

Although the EP series of plastic bearings is designed for dry friction applications, but its general grease and other lubricants are most of the good compatibility; in the bearing Start-up phase by adding lubricating media can improve the bearing's starting performance, thus shortening the bearing run-in period. And the bearing in the presence of a lubricating medium when the carrying capacity will be large Because of the external lubrication intervention in the case of a significant reduction in the friction coefficient of heat generated by the bearing temperature decreases, the bearing capacity will increase. Figure 14 says Out in a variety of lubrication medium under the PV correction factor y2;

Chart 14: Correction factor of PV value in different lubrication modes y2
Lubrication Correction factor
Dry 1
Grease 2
Water 4
Oil 5
Bearing wear

As the bearing wear resistance by many factors, it is difficult to accurately Describe the wear or life of the bearing. Through numerous tests that affect the bearing Wear resistance or life of the factors: load, speed, movement, shaft material And roughness, ambient temperature and dust, external lubrication media category and so on. Bearing wear resistance generally increases with the load, speed, temperature and gradually decreased Low, when there is external lubrication medium, the bearing wear resistance will be doubled. Hengxing recommended the use of the shaft roughness Ra0.2 - Ra0.8, the shaft is too rough or Too smooth will lead to increased wear and tear, the shaft is too rough as scraper scratch Bearing the friction surface, the shaft is too smooth in the friction surface and the bearing surface of the glue Leading to increased wear. The EP series bearings for the shaft material are not particularly limited, but are not limited Kind of shaft material on the impact of bearing wear is different, it is recommended to use more Hengxing For the universal surface hard chrome plated shaft material, the hardness of the shaft is also not limited, But Hengxing recommended the use of HRC35 or more shaft material, in order to avoid bearing the initial work For the wear of the stage shaft.

Chart 15: Thermal conductivity of the shaft or base material
Material Thermal conductivity[W/m x k]
Carbon steels 46
Hardened steel 46
Hard chrome shaft 46
Stainless steel 16
Hardened aluminum 204
Plastic 0.24
Bearing anti-UV performance

Sliding bearings for outdoor equipment will often be exposed to a variety of harsh environments. Anti-UV properties are an important factor in the resistance of various bearing materials to UV-ray breakage index. EP series of plastic bearing anti-UV performance control chart shown in Figure 16.

Bearing chemical resistance

EP series of plastic bearings are often used for chemical media contact occasions, at this time bearing anti-chemical corrosion performance is particularly important. As the chemical medium can be Can lead to changes in the composition of the bearing material, this change depends on the type of chemical medium, temperature, exposure time, and bearing load and movement Way, and sometimes the chemical medium as an effective lubricant which will extend the service life of the bearing. See Figure 16 for details.

Exhibit 16: Bearing UV resistance and chemical resistance
Bearing installation

■ Block hole: EP series plastic bearing with seat hole material None Particularly limited, but the hole at one end must be chamfered 25. To avoid bearing Scratch the outer diameter when pressing, pressing the ladder shaft should be used slowly Press, prohibit direct hit the end, so as not to affect the deformation of the bearing ruler Inch, EP series of internal diameter tolerance are pressed into the H7 standard Hole after the get.

■ The axis: EP series of plastic bearings with the axis of the material without special Do not limit, but Hengxing recommend the use of chrome-plated hard axis. To make the axis In the assembly process is more simple and does not damage the bearing friction surface, shaft The end face must be chamfered smooth transition. Another axis surface roughness The friction coefficient of the bearing has a greater impact, the shaft is too smooth friction surface Will produce crawling phenomenon or produce scream, the axis surface is too rough will Speed up the bearing wear. Hengxing recommended the use of shaft surface roughness Ra0.2-0.8. Bearing friction coefficient and surface roughness of the relationship shown in Figure Table 19.

Chart 17: Press-fit diagram

Chart 19: Relationship between friction coefficient u and shaft surface roughness Ra

EP series bearings with the tolerance in accordance with IS0 3547-1 standard design and manufacturing see Figure 18. Although the EP series of products designed for self-lubricating products, but in the equipment Timing on the friction surface coated with an appropriate amount of external lubricant (such as grease) will shorten the bearing of the run-in period and thus extend the service life of the bearing.

Chart 18: Tolerances for EP series bearings
Diametermm² Tolerance after press fitting E10 Mounting aperture H7 With the shaft diameter h9
>0~3 +0.014~+0.054 0~+0.010 0~-0.025
>3~6 +0.020~+0.068 0~+0.012 0~-0.030
>6~10 +0.025~+0.083 0~+0.015 0~-0.036
>10~18 +0.032~+0.102 0~+0.018 0~-0.043
>18~30 +0.040~+0.124 0~+0.021 0~-0.052
>30~50 +0.050~+0.150 0~+0.025 0~-0.062
>50~80 +0.060~+0.180 0~+0.030 0~-0.074
>80~120 +0.072~+0.212 0~+0.035 0~-0.087
>120~180 +0.085~+0.245 0~+0.040 0~-0.100

■ Adhesives : EP series plastic bearings generally do not need to use adhesive, High temperature adhesive, Hengxing suggested that the necessary testing of this situation.

EP Plastic self-lubricating bearings Classification

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