ball screw with caged ball technology

2

Caged Technology

TechnicalReference

Smooth Silent Ecological

®

CATALOG No.268-5E

For details, visit THK at www.thk.com＊Product information is updated regularly on the THK website.

1

Caged TechnologyIntroduction

Since ball bearings in the initial stage of development were not provided with a cage, they produced highlevels of noise, had a short service life and were unable to be used at high rotating speeds.

Later, caged ball bearings were developed that exhibited low noise levels even at high rotating speeds.In addition, these caged ball bearings were able to demonstrate long service life despite the number of

balls being fewer than full ball types, and evolved significantly so that they were able to be used in a widerange of applications.

THK, the first manufacturer in the world to develop the LM Guide, has developed its LM Guide with CagedBall Technology that is able to achieve a dramatic improvement in performance over conventional products.The LM Guide with Caged Ball Technology delivers a long service life and excellent high-speed performance inthe same manner as roller bearings, while also eliminating maintenance for a long period of time.

Initial Stage of Development (Full Ball Type)

• Metal contact between balls caused a shortage of grease life.• Short service life

Current Bearings (Caged Ball Type)• Grease is held by the cage for excellent lubrication.• No metal contact between balls for extended service life.• No metal contact between balls suppresses generation of heat.• No metal contact between balls eliminates ball collision noise.• Balls exhibit orderly movement for smooth operation.

Rotary Bearings

Case of the LM Guide

Balls

Friction occurs between balls resulting in the generation of collision noise

Oil film contact

Absence of friction between balls eliminates the generation of collision noise for quiet operation

Without caged ball

With caged ball

2

Structure of the LM Guide with Ball Cage

LM block

LM rail

End plate

End seal

Ball

Ball cage

3

Collision noise

Collision noiseDirection of travel

Mutual friction

Absence of collision noise between balls

Generation of collision noise between balls

Since metal contact occurs only at the load zone, metal noise is held to a minimum.

Conventional type (without

ball cage) circulating path

In the case of the full ball type, the balls demonstrate skewing and move randomly.

Ball cage type circulating path

Ball cage

Balls are guided by the ball cage so as to be uniformly aligned in the direction of circulation for smooth operation.

1 Quiet Operation that Minimizes Metal ContactCollision noise between balls is eliminated by the ball cageresulting in quiet operation.

Advantageof Caged Ball

2 Orderly Ball MovementSince the balls are held by the ball cage in the form of a belt, theyare aligned uniformly and move in a circulating manner. There isno skewing of the balls, while sudden variations in friction are alsoeliminated, allowing for stable movement.


4

3 Original Cage Structure Exhibiting ExcellentHigh-Speed PerformanceThe use of ball cages eliminates generation of heat caused byfriction between balls result ing in excellent high-speedperformance.


4 Grease Holding Structure (Consecutive Grease Pockets)for Long-Term, Maintenance-Free Operation, LongService LifeGrease pockets are provided consecutively over the entire ballcirculation path to constantly lubricate the balls enabling long-term,maintenance-free operation, Long Service Life.


Contact state between balls and ball cage State at turning sections

Ball cage

Grease retention status after travel (SHS45LV: load endurance test)

Grease pockets are provided throughout the ball cage.

5

The Caged Ball not only allows the LM guide to be run for a long time period free ofmaintenance, but also significantly improves the service life of the system. As described below,a performed service life test has offered data about this improvement.

Data on LM Guide with Caged Ball

Service life test for LM Guide1. Testing instrumentation

2. Testing parametersModel : SHS25V1SS+580LP / HSR25A1UU+580LPNumber of pieces : 32Load : 11.1 kN per LM block (0.35 C of SHS25V)Lubricant : Lithium soap base grease No. 2, Only initial lubrication

Load P

Load cell

Table Stroke

LM railLM block

Spring

Plate

Acceleration: 1 G

Cycle

Time (seconds)

Spe

ed (

m/m

in)

Stroke=350mm

0.250.1

60

0.40.1

Improved Service Life

6

3. Test results

Comparison in terms of dynamic durability values (C)and service life (L)

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The results of the performed test indicate that the dynamic durability values of the LM guideimplemented by Caged Technology are higher than of the conventional LM guide.

2-2. Status of Remaining Grease after the Durability Test

Ball cage before running

Remaining grease is observed in the ball cage.

Ball cage after running 8,000 km(Test stop)

LM guide with caged ball …………………Model SHS25V　C＝31.7 kNLM guide without caged ball………………Model HSR25A　C＝19.9 kNUnder an applied load of P=11.1 kN

LM guide with caged ballModel SHS25VLM guide without caged ballModel HSR25A

L＝　　 ×50＝　　　×50＝1160kmCP（）

3 31.711.1（）

3

L＝　　 ×50＝　　　×50＝280kmCP（）

3 19.911.1

31.719.9

（）3

●　　　　　　　　　　　　　　　　　　＝1.6 1160280

●　　　　　　　　　　　＝4.0＊ Comparison in terms ofdynamic durability values Service life

＊For details, see General catalog

CalculationExample

■Rolling Resistance DataThe use of a ball cage enables the balls to be uniformly aligned, eliminatingcrowding of the balls that occurs when they enter the block. As a result, smoothand stable movement can be obtained in all forms of installation, and fluctuationsin rolling resistance are reduced for the realization of high accuracy.

00

50 100 150 200 250 300 350 400

2

4

6

8

10

12

14

16

18

20

Stroke (mm)

Rol

ling

resi

stan

ce v

alue

(N

)

Results of Measuring Fluctuations in Rolling Resistance of SHS25LV (with ball cage)

(feeding speed: 10 mm/sec)

00

50 100 150 200 250 300 350 400

2

4

6

8

10

12

14

16

18

20

Stroke (mm)

Rol

ling

resi

stan

ce v

alue

(N

)

Results of Measuring Fluctuations in Rolling Resistance of HSR25LR (without ball cage)

(feeding speed: 10 mm/sec)

7

■Noise Level DataThe use of a ball cage eliminates interference between balls resulting in lownoise levels.

LM Guide with Caged Ball Technology

Comparison of Noise LevelsBetween the SHS35LV and HSR35LR

(speed: 50 m/min)

Frequency (Hz)

0

10

20

30

40

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Noi

se le

vel (

dBA

)

HSR35LR

SHS35LV

(without ball cage)

(with ball cage)

50

30

40

50

60

70

90

80

0 25 50 75 100 125

Noi

se le

vel (

dBA

)

Comparison of Noise LevelsBetween the SHS35LV and HSR35LR

speed (m/min)

HSR35LR

9.6dBA

SHS35LV

(without ball cage)

(with ball cage)

8

■Low Generation of DustThe use of a ball cage eliminates friction between balls resulting in acorresponding decrease in the generation of metal wear fragments foroutstanding effects against prevention of the generation of dust.

00

100

200

300

5 10 15 20

Am

ount

of d

ust g

ener

ated

(par

ticle

s/2

min

-lite

r)

Time (hours)

SSR20 (with ball cage)

00

100

2 00

300

5 10 15 20

Am

ount

of d

ust g

ener

ated

(par

ticle

s/2

min

-lite

r)

Time (hours)

Conventional products (without ball cage)

0.3 – 0.50.5 – 1.01.0 – 2.0

2.0 – 5.05.0 –

Particle size (μm)

■High-Speed Durability Test ResultsSince the use of a ball cage eliminates friction between balls, there is lessgeneration of heat making it possible to demonstrate excellent high-speedoperation.

Grease was stillpresent and therewere no abnormalitiesobserved in the ballsor grease.

Detailed drawing of ball cage

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Sample : SHS65LVSSSpeed : 200 m/minStroke : 2500 mmLubrication : Initial injection of

grease onlyLoad : 34.5 kNAcceleration : 1.5 G

9

Structure of the typeSRG/SRN/SRW

LM rail

LM block

End plate

End seal

Roller cage

Roller

Rollercage

Standard Part Block Diagram

Roller cage (roller)retaining parts

Type SRG Type SRN Type SRW4545°°

4545°°4545°°

4545°°

Caged Roller Technology

SRG/SRN/SRW

Cross-sectional view

Enlarged view of circulating paths

10

Features of the typeSRG/SRN/SRW

Prevents roller skewing

The use of a roller cage allows the rollers to circulatewhile uniformly aligned, preventing skewing whenentering block load area, and reducing variation inroll ing resistance to obtain stable and smoothmovement.

Long-Term,Maintenance-Free Operation

The use of a roller cage eliminates friction betweenrollers, and retains lubricant in the grease pocketsbetween adjacent rollers, ensuring the required amountof lubricating oil is supplied to the curved contactsurfaces of the spacers and rollers of the circulatingpath to realize long-term maintenance-free operation.

Ultra-HighRigidity

Ultra-high rigidity is achieved by using rollers having alow degree of elastic deformation for the roll ingelements and an optimized roller diameter and length.Also, each row of rollers is arranged at a 45° contactangle so that an equal load rating is applied in fourdirections (radial, reverse radial, and lateral directions).

Global StandardDimensions

The dimensional design complies with the Type HSRdeveloped by THK as the pioneer of linear motionsystems and has become the global standard.

11

LM Guide with Caged Roller Technology

0

10

20

30

40

50

60

0 100 200 300 400 500

Stroke (mm)

SRG45LC2.26N

Full-roller type roller guide# 45

10.63N

Rol

ling

resi

stan

ce (

N)

Sample) : SRG45LCC0

Conditions) : Pre-loading : C0 clearanceSpeed : 180 m/minAcceleration : 1.5 GStroke : 2300 mmLubricant : Initial injection of

grease only

• Intermediate results:No abnormalities during 15,000 km oftravel

flaking or insufficientgrease was not observed( )

Nodiscolorationof grease isobserved.

Detailed drawing of roller cage

Adequate greaseremains

Roller

Rollers

Roller Cage

■Rolling Resistance Value DataThe use of a roller cage eliminates friction between rollers while also enabling therollers to circulate while uniformly aligned. As a result, there is reducedoccurrence of skewing allowing stable movement.

■Durability DataThe use of a roller cage enables grease to be retained in the space betweenadjacent rollers, realizing long-term, maintenance-free operation by inhibiting theescape of grease from the circulating path.

12

■Rigidity valuesRadial clearance SRG : Clearance C0

Conventional roller guide : Equivalent to C0

0

2

4

6

8

10

12

0 5 10 15 20 25 30

Conventional roller guide#45

SRG45LC (with roller cage)

Radial load (kN)

Dis

plac

emen

t (μm

)

0

5

10

15

20

0 5 10 15 20 25 30



Reverse Radial load (kN)

Dis

plac

emen

t (μ

m)

Lateral load (kN)

0

10

20

30

40

0 5 10 15 20 25 30



Dis

plac

emen

t (μm

)

Fixed table bolt Unfixed bolt (free movement)

Radial rigidity

Reverse radial rigidity

Lateral rigidity

Radial clearance

Structure of the typeSBK

High-Speed Ball Screw with Ball Cage

SBK

Ball cage

End cap

Two-raceway,large-leadscrew shaft

BallsBall screw nut

13

14

Features of the typeSBK

Low Noise, Acceptable Running SoundUse of a ball cage allows balls to be evenly spaced and

eliminates collision noise between balls. In addition, ballsare picked up in the tangential direction, which alsocontributes to eliminating collision noise. As a result, lownoise and acceptable running sound are achieved.

Long-term Maintenance-free OperationThe formation of grease pockets increases grease retention

and achieves long-term maintenance-free operation. Inaddition, even in adverse environments (e.g., coolant, foreignmatter), this model ensures long-term maintenance-freeoperation when attached with an optional wiper ring or a QZLubricator*.(*: For wiper ring and QZ Lubricator, contact THK.)

Excellent Sliding PropertiesBall cages arranged between balls eliminate mutual friction of

the balls and significantly improve torque characteristics. Pre-load dynamic torque fluctuations are also reduced allowing theobtaining of excellent sliding properties.

High-speed OperationBecause of its circulation structure where the end caps enable the balls to be picked up in the

tangential direction and the lead angle direction, this model is capable of high-speed operation ata DN value of 160,000, achieving high-speed feed 2.2 times faster than the conventional model.

Point (metal) contact

Oil film contactGrease pockets

Ball cage structure

Conventional structure

Locations of grease pockets

Balls circulate in the tangential direction Balls circulate in the lead angle direction

15

Improved Service Life

■Service life testService life test under a high speed (free of maintenance)

Testing instrumentation for a long-period high-speed test was used to test model SBK withlubrication system QZ. The operating cycles were run under a DN value of 160,000 andwith only initial lubrication carried out.

Running distance (km)0 1,000 2,000 3,000 4,000 5,000

The test results on 3,000-km of running performance show that the lubricant film neither peels off nor is broken.

Sample tested

Number of samples

Maximum rotation speed

Stroke

Lubricant

Grease quantity

Applied load

Acceleration

SBK3620-7.6

3

4200 min-1(DN value : 160,000)

400 mm

Multemp HRL grease (initial lubrication only)

8 cm3

1.87 kN (preload only)

1G

Conditions

16

Ball Screw with Caged Ball Technology

0 500 1,000 1,500

Shaft rotational speed (min-1)

2,000 2,500 3,000 3,500

60

50

40

30

20

AFG greaseTHK general-purpose grease

Sat

urat

ion

tem

pera

ture

out

side

nut

(°C

)

ItemShaft diameter/lead

Shaft rotational speed

Stroke

Lubricant

Description32 / 10 mm

400-3000 min-1

400 mm AFG grease THK general-purpose grease

Shaft rotational speed (min-1)

Conventional type(without ball cage)

SBN type

80

70

60

50

0 1,000 2,000 3,000 4,000

Noi

se le

vel (

dBA

)


Lubricant

Measuring distance


AFG grease1 m


Speed

Shaft rotational speed

Stroke

Lubricant


10 mm/s60 min-1

700 mmMobil Vactra No. 2 oil

-1.0

-0.5

0.0

0.5

1.0

0 25 50 75 100 125 150

Conventional type(without ball cage)SBN TYPE

Time(s)

Tor

que(

N-m

)

■Torque Fluctuations and Sliding PropertiesThe ball cage reduces torque fluctuations enabling excellent constant speedcharacteristics to be obtained even at low speed for a high degree of positioning accuracy.

■Noise Level DataThe use of a ball cage reduces friction between balls to realize low noise levels.

■Heat Generation DataAlthough the use of a ball cage eliminates friction between balls making it possible todemonstrate low levels of heat generation and outstanding high-speed operation, the use ofTHK AFG grease (low heat-generation grease) suppresses heat generation even more.

Conditions

Conditions

Conditions

Global Standard

Model

Radial Type

ModelWide, Low Gravity Center Type

Model

Lightweight, Compact

Model

Ultra-heavy Load Type

Model

Conveyance systemNC latheMachining center

FPD manufacturing machineDrilling machine

Conveyance systemFPD manufacturing machineMedical equipment

Semiconductor manu-facturing machineChip mounter

Semiconductor manufacturing machineOptical stageMedical equipment

FPD manufacturing machinePrinterChip mounter

Machining centerNC lathe

Five-axis milling machineGrinding machine

Semiconductor manu-facturing machineConveyance system

FPD manufacturingmachineChip mounter

Caged Ball LM Guides

A Lineup of Caged Ball/Roller LM Systems

17

18

High Speed Ball Screw

Model

Super-ultra-high Rigidity, Low Gravity Center Type

ModelSRW

ModelSRN

ModelSRG

High-speed machining centerHigh-speed chip mounter

High-speed conveyance systemHigh-speed printed boarddrilling machine

Super-ultra-high Rigidity Type

Super-ultra-high Rigidity, Wide Type

High Speed Ball Screw

ModelSBK

High Load Ball Screw

ModelHBN

Caged Roller LM Guides High Speed Ball Screws with Ball Cage

with Superb Features S Series

Machining centerUltra precision latheHeavy cutting machine

Five-axis millingmachineDrilling machine

Machining centerUltra precision latheHeavy cutting machine

Five-axis millingmachineDrilling machine

Plano millerLarge pressingmachine

Large five-face millingmachineInjection molding machine

Injection moldingmachineDie-casting machine

Extrusion moldingmachinePressing machine

High-speed machining centerHigh-speed chip mounter

High-speed conveyance systemHigh-speed printed boarddrilling machine

1

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● The photo may differ slightly in appearance from the actual product. ● The appearance and specifications of the product are subject to change without notice. Contact THK before placing an order.● Although great care has been taken in the production of this catalog, THK will not take any responsibility for damage resulting from typographical errors or omissions.● For the export of our products or technologies and for the sale for exports, THK in principle complies with the foreign exchange law and the Foreign Exchange

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ball screw with caged ball technology

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