Gearhead Characteristics

What is a Gearhead

• The gearhead is an instrumental device that not only reduces the revolution speed of the motor but also makes a torque change according to the gear ratio.

Characteristics of Gearhead

• Low noise type with big delivery capability
• Precise revolution speed according to the reduction ratio
• Good durability within the permissible torque
• Wide spectrum of reduction ratio according to necessary speed

Gearhead Ratio

• The ratio of spin speed between the driving shaft, and the driven shaft, in the reduction gear is called the reduction gear ratio.
• We have gone through precision process for the motor shaft and the helical gear, and as a result, we could make a remarkable reduction in noise level to 10dB. There are various types of exclusive gearheads that can be connected to the motor simply including 1/3~1/200 (1/3~1/250 in case of K6 and K8).
• If you need a ratio greater than 1/200, you can use inter-decimal gearhead (1/10).

Types of Gearhead

• Our gearheads are grossly divided into ㅁ60mm, ㅁ70mm, ㅁ80mm, and ㅁ90mm depending on the flange size.

GENERAL TYPE OF GEARHEAD

① means that the flange size is ㅁ80mm.
② is the shape of cutting.
③ is a ratio. There are 24 ratios from 1/3 to 1/200.
④ means a bearing type.
B : ALL BEARING TYPE
C : BALL BEARING + METAL BEARING,
M : ALL METAL BEARING TYPE
* If you need a ratio greater than 1/200, you can use an inter-decimal gearhead K8G10BX(1/10).
* K8G is adapted to 25W motor.

STRONG & SUPER-STRONG TYPES OF GEARHEAD

① means that the flange size is ㅁ90mm.
② is the shape of cutting.
③ is a ratio. There are 20 ratios from 1/3 to 1/180.
④ means a bearing type.
Strong types and super-strong types of gearheads are only in ball bearing types.
⑤ is a sign of strong type and super-strong type
No-Sign : Strong rectangle box type
F : Strong flange type
U : Super-strong type
UF : Super-strong flange type
* If you need a ratio greater than 1/180, you can use a decimal gearhead K9P10BX.
* K9P is adapted to 60W or 90W motor.

Combination Method Of Motor and Gearhead

FOR EXAMPLE, REFER TO (BELOW FIG.)

* Care should be taken when doing assembly because only if the size of combing side and the shape of cutting are the same, they can be combined.

WHEN USING A DECIMAL GEARHEAD TOGETHER, REFER TO (BELOW FIG.)

If you need bigger gear ratio which can not be got by gearhead itself, you can use the decimal gearhead. The number of rotations are reduced by 1/10 but the ambient torque would not be increased because the ambient torque already fixed on gearhead.

Number & Direction

Number of Rotation

• For the directly assembled gearhead, the number of rotations is expressed by the following equation.

NG : Revolutions of a gearhead (rpm)
NM : Revolutions of a motor (rpm)
i : gear ratio of a gearhead

Direction of Rotaions

• Rotating direction of the output shaft in the gearhead is either identical or opposite to the motor's rotating direction depending on the gear ratio. Refer to (Table 1).
• In case of using a decimal gearhead (1/10), the rotating direction is as same as the gearhead's direction.

(TABLE 1) THE ROTATING DIRECTION OF THE OUTPUT SHAFT IN THE GEARHEAD

Calculation Of Output Torque When Head Is Combined

The output torque when the gearhead is combined is calculated as follows. Refer to (Table 2) Transfer efficiency of gearhead

TG : Torque of a gearhead's output shaft
TM : Torque of a motor
i : Reduction ratio of a gearhead
η : Delivery efficiency of a gearhead.

(TABLE 2) DELIVERY EFFICIENCY OF GEARHEAD

Maximum Permissible Torque Of Gearhead

• Although the output torque of the gearhead is proportional to the ratio, the torque allowable to the gearhead has a limitation depending on what materials are used and the other conditions. This is called a maximum permissible torque and determined based on the size of the gearhead and the gear ratio.
• For example, when a 40W induction motor and a gear ratio of 1/180 is combined, the rated torque is 2.6kg·cm, which leads to TG = TM × i × η = 2.6 × 180 × 0.66 = 308.8kg·㎝Although the calculation turns out to be 308.8kg·cm, the maximum permissible torque for K9G180B is prescribed as 100kg·cm a shown in (Fig. 1) below.

Gearhead Lifetime And Service Factor

The lifetime of the gearhead is usually determined by how the shaft is supported. However, since the load varies in general, the lifetime of the gearhead is determined by the service factor based on the load. Refer to (Table 3).

Rated Lifetime

If the gearhead is used within the permissible torque, the rated lifetime of the gearhead is 5,000Hr for the ball bearing type and 2,000Hr for the metal type.
In case the gearhead operates as following conditions, the rated lifetime of the gearhead is the hours that it is impossible for the motor torque from the output shaft of the gearhead to convey and the gearhead has to stopped.

1. Torque : within the permissible torque
2. Load : Operating load in a constant direction without any load change
3. Operating hours: 8 hours a day
4. Temperature of the bearing : Metal type - 50℃ / Ball bearing type - 80℃
Temperature of the bearing : Metal type - 50℃ / Ball bearing type - 80℃

If a ball bearing type of gearhead is operating for 24 hours a day, the service factor should be taken into account. Therefore, a motor and a gearhead which have biggest permissible torque should be selected.

(TABLE 3) EXAMPLE OF LOAD AND SERVICE FACTOR

Type of Load	Example of Load	SERVICE FACTORY
		5 hours a day	8 hours a day	24 hours a day
General Load	Belt Conveyor, Continuous operation in one direction	0.8	1.0	1.5
Medium Load	Frequent starting/operating, Frequent CAM driving	1.2	1.5	2.0
Medium Load	Instantaneous reversal operation, Instantaneous stopping	1.5	2.0	2.5
Heavy Impact Load	Very frequent occurrence of medium impact load operation	2.0 ~ 2.5	2.5 ~ 3.0	3.0 ~ 3.5

(TABLE 4) STANDARD LIFETIME

BALL BEARING TYPE	5,000 hour
METAL TYPE	2,000 hour

Overhung Load And Thrust Load

The overhung load is loaded where the places between more than two supporting mechanisms are not on the shaft.

• When a chain, a gear, or a belt is employed as an output delivery mechanism for the output shaft of a gearhead, the overhung load is loaded upon the shaft. (Fig. 4)
• Since the overhung load exerts a load directly on the gearhead, it affects the life span of the gear.
• The overhung load can be calculated from the following equation.

• W : Overhung load [Kg]
• K : Weight coefficient by driving method (Refer to Table 5)
• T : Delivery force [Kg ¡¤cm] of a gearhead output shaft
• f : Service factor (Refer to Table 3)
• r : Effective radius of gear, pulley, etc. [cm]

(TABLE 5) LOAD COEFFICIENT BY DRIVING METHOD

Driving Method	K
CHAIN,SPROCHET	1
Gear	1.25
V-BELT	1.5
PLATE-BELT	2.5

• If the motor operates with the calculated overhung load greater than the maximum allowable value in (Table 6), then care should be taken, because the damage of the bearing may result in shortening of the lifetime, the output shaft may bend, the fatigue deformation may occur due to the repeated load.
• In such a case, please set up the structure of the motor as depicted in (Fig. 5) to withstand the overhung load.
• Also, if a load should be directly imposed on the output shaft, please place the load as near to the gearhead as possible to avoid the one-sided load.
• If a helical gear or a worm gear is employed as an output delivery mechanism, make sure not to exceed both the overhung load and the thrust load simultaneously.

(TABLE 6 ) PERMISSIBLE OVERHUNG LOAD AND PERMISSIBLE THRUST LOAD

MODEL	GEAR RATIO	Maximum Ambient Torque (kgf,㎝)	Permissible Overhung Load (kg)	Permissible Thrust Load (kg)
K6G□B(C)	3 ~ 18	30	5	3
	20 ~ 250		12
K7G□B(C)	3 ~ 18	50	8	4
	20 ~ 200		45
K8G□B(C)	3 ~ 18	80	10	5
	20 ~ 250		20
K9G□B(C)	3 ~ 18	100	25	10
	20 ~ 200		30
K9P□B K9P□BF	3 ~ 10	200	40	15
	12.5 ~ 20		45
	25 ~ 200		50
K9P□BU K9P□BUF	3 ~ 10	300	40	15
	12.5 ~ 20
	25 ~ 200
K10H□B	3 ~ 36	400	55	20
	40 ~ 200		65

*Note

• The maximum permissible torque varies depending on the ratio. Use an range of permissible torque each for ratio.

Assembly Method OF Motor And Gearhead

• To assemble the motor and the gearhead, adjust the assembling faces together in such a way as shown in (Fig. 4) and turn slowly to complete the assembly. When doing the assembly, special care should be taken neither to exert excessive force on the motor shaft nor to hit inside of the gearhead. Otherwise, the gear will get damaged, resulting in a abnormal noise and a shortened lifetime of the motor.
  When assembling the motor's gearhead, use a specified bolt of that motor to avoid a gap between the assembling faces.
  For a motor equipped with a cooling fan, leave a space at least 10cm from the fan cover to prevent the motor's intake hole from being clogged.(See Figure5)

Table of Gearhead Type

GEAR HEAD SIZE	MOTOR	Heat Treatment (Yes/No)	BEARING TYPE			Remark
			ALL BALL BEARING	BALL BEARING+ METAL BEARING	METAL BEARING
□60mm	6W	No	K6G□B	K6G□C	K6G□M
□70mm	15W	No	K7G□B	K7G□C	K7G□M
□80mm	25W	No	K8G□B	K8G□C	K8G□M
□90mm	40W	Yes,No	K9G□B	K9G□C	K9G□M
	60W~200W	Yes	K9P□B			BOX TYPE
			K9P□BF			FLANGE TYPE
	60W~200W	Yes	K9P□BU			BOX TYPE
			K9P□BUF			FLANGE TYPE
□104mm	200W	Yes	K10H□B

How to Fix the Load

To facilitate fastening a load to the gearhead output shaft, there is a groove in the key and D-cut in the smaller gearhead. Refer to (Fig.6)

• In case of D-cut processing, use a clamping bolt to the D-cut processing area in order to prevent the load from making racing. Refer to (Fig. 7)

• In case of key groove processing, make a key groove in a delivery device such a chain, a pulley, or sprocket and use a key (Fig. 8), a part, to the key groove in order to fasten the load.
• It should not give impact when the gearhead shaft fasten on delivery device otherwise. It is caused a damage and shortening the lifetime.