Linear guides: an in-depth look at selection and applications

I. Introduction to Linear Guides

Linear guides, also known as slide rails, linear rails or linear sliders, support and guide moving components in reciprocating linear motion along a predetermined direction.

Given the same size of the moving components, they have a higher load rating and movement accuracy than linear bearings, while being able to withstand a certain amount of torque load.

As shown in Figures 1 and 2, linear guides can be used for transporting heavy loads in horizontal spaces, precise positioning movement, and precise guiding movement in vertical spaces. They ensure reliable movement in small spaces and have wide applications in the machine tool, electronics, medical and robotics industries.

As shown in Figure 3, the linear guide is composed of slide rails, glides, ball bearings, ball retainers, and recirculation grooves. The main principle is to make the steel balls circulate through the structure of the recirculation grooves and ball retainers, thus achieving a low-friction linear movement of the slider on the slide rail.

Linear Guide Basic Features :

This structure determines the following basic characteristics of the linear guide:

• Due to point-to-surface contact, frictional resistance is small, which allows fine movements and high-precision positioning of control devices.
• Since ball bearings have their own bearing grooves, the force on the rotating surface will be dispersed, therefore it has a large allowable load.
• The linear guide is unlikely to generate frictional heat during operation and is resistant to thermal deformation, making it suitable for high-speed movement.
• The contact angle of each row of ball bearings is generally 45 degrees, so the four action directions (radial, reverse radial and lateral) in the slider have the same rated load.

II. Classification of Linear Guides

Depending on different load applications, they can be mainly divided into miniature, medium and heavy types.

Since linear guides transfer loads mainly through ball bearings, the difference between miniature, medium and heavy types lies mainly in the number of rows of balls.

As shown in Figures 4 and 5, miniature linear guides generally have 2 rows of steel balls, with 4 points of contact with the rail surface, providing a compact structure.

Medium and heavy linear guides generally have 4 rows of steel balls, increasing their load capacity. The basic dynamic rated load of miniature linear guides is generally less than 10KN, while that of medium and heavy guides can reach up to 80KN.

Linear guides are classified according to different track widths and sliding widths and lengths, as follows:

Linear guide rails are classified as follows based on rail width and slider width and length:

III. Usage scenarios for wide tabs

The total height to track width ratio of standard guides is about 1.1, while that of wide guides is about 0.65. The total height of the wide track is 40% lower than that of the standard track. Therefore, in situations where height is limited, wide sashes are more suitable; on the other hand, use standard tracks where the width is restricted.

On the other hand, with a lower height-to-width ratio, the allowable static torque of wide belts is more than double that of standard belts. Their rigidity increases significantly, making them ideal for structures with displaced centers of gravity.

Usage scenarios for wide sliders:

Wide sliders and standard sliders have similar basic load ratings and allowable static torque. However, the fixing screws on the wide slider are larger than those on the standard slider, increasing the strength of the fixation.

Usage scenarios for sliders of various lengths:

After selecting the track, the decision to use sliders of what length is primarily based on the fact that the longer the slider, the greater the base rating and allowable static torque.

4. Dimensions overview of linear guide rails

Category	Types of Sliders	Characteristics	Product number	Rail length (mm)	Rated dynamic load (KN)	W slider width (mm)	Slider Length L (L1) (mm)	Slider height K (mm)	Price
Microtype	Standard type	The most basic type in industry standard specifications, with a wide range of sizes and high cost-performance ratio.	Misumi Micro Linear Guide Standard Slider Type (Recommended)	25~700	0.3~5.2	12~40	17.4~50	4.5~15	￥176+
			THK micro, sliding variant type SRS M	50~630	2.69~6.66	20~32	30.8~43	8.5~13.3	￥289+
	Short type	Compared to the standard type of slider, its volume can be reduced by 20%.	Misumi short sliding type micro linear guide	35~670	0.79~3.08	17~32	19.6~32.7	65~12	￥1788+
	Enlarged type	Compared with standard products, the screw size increases and the fastening strength improves.	Misumi Micro Linear Guide Slider, Enlarged Standard Type	35~700	0.9~5.2	24~54	23.6~50	6.5~15	￥203+
	Extended type	Compared to the standard slider type, it has higher rated load and allowable torque.	Misumi Micro Linear Guide Slider, Extended Type	40~700	0.6~7.2	12~40	21~67.7	4.5~15	￥172+
	Enlarged and extended type	The size of the screw increases, improving the strength of the fixation. It also has a higher rated load and allowable torque compared to the standard sliding type.	Misumi Micro Linear Guide Slider, Enlarged and Extended Type	40~700	1.6~7.2	24~54	32~67.7	6.5~15	￥265+
	With location hole type	Effectively reduces equipment assembly time and allows for easier repetitive positioning.	Misumi Micro Linear Guide with Locating Hole, Short Slider Type	35~670	0.79~3.08	17~32	19.6~32.7	6.5~12	￥234+
			Misumi Micro Linear Guide with Locating Hole, Standard Sliding Type	35~700	0.9~5.2	17~40	23.6~50	6.5~15	￥244+
	Widened type of rail	Compared to standard products, the screw size increases, resulting in greater fastening strength.	Misumi Micro Linear Guide Rail, Flared Type, Flared Sliding Type	50~670	1.4~5.8	36~74	31.1~55	7~13	￥246+
			THK micro, sliding variant type SRS WM	50~630	3.29~9.12	30~60	39~55.5	9.1~13.3	￥327+
	High temperature resistant	It can be used in environments with a maximum temperature of 150℃.	Misumi micro linear guide, heat resistant type	35~670	0.79~5.8	17~32	19.6~58.3	6.5~12	￥268+
Tough type	Standard type	Used for high-precision positioning, high load and high-frequency driving.	Misumi ultra-heavy linear guide with resin retainer	220~1960	16.3~35.5	44~90	69.8~98.6	25~33	￥1021+
		This THK product is a global standard size and has automatic self-alignment capability, providing excellent durability.	THK, R variant of HSR type slider	64 ~ 1960	8.33~50.2	34~70	56.6~134.8	23.3~47.5	￥370+
		This THK product is a worldwide standard size and has automatic self-alignment capability. It has a low center of gravity and high rigidity.	THK, SHS type slider V variant	71 ~ 1960	14.2~72.9	34~70	64.4~152	21~40.5	￥373+
		It has a steel ball contact structure with strong bearing capacity in the radial direction, making it suitable for horizontal installation.	THK, slider variant type SSR XW	64 ~ 1960	14.7~31.5	34~48	56.9~83	19.5~26.2	￥379+
		It has an integrated lubrication-free system, offering high precision, low coefficient of friction and low maintenance costs.	ABBA, BR R0 series slider variant	80~2200	8.5~48	34~70	66~134.8	28~55	￥167+
			ABBA, BR series (with threaded flange type)	80~2200	8.5~48	47~100	66~134.8	24~48	￥172+
			ABBA, BR series (without threaded flange type)	80~2200	8.5~48	34~70	66~134.8	28~55	￥167+
	Short type	Compared to the standard slider type, its volume can be reduced by 20%.	THK, sliding variant type SSR XV	47 ~ 1960	9.1~21.7	34~48	40.3~60	19.5~26.2	￥328+
			ABBA, BR SU series slider variant (short type without threaded flange)	80~2200	5.2~12.5	34~48	47.6~62.5	24~33	￥151+
	Enlarged type	The screw size increases, resulting in greater clamping strength. It also has a higher rated load and allowable torque compared to the standard slider type.	THK, slider type HSR variant A	64 ~ 1960	8.33~50.2	47~100	56.6~134.8	19.3~40.5	￥334+
			THK, slider type HSR variant B	64 ~ 1960	8.33~50.2	47~100	56.6~134.8	19.3~40.5	￥335+
		This THK product is a worldwide standard size and has automatic self-alignment capability. It has a low center of gravity and high rigidity.	THK, slider type SHS variant C	71 ~ 1960	14.2~72.9	47~100	64.4~152	21~40.5	￥155+
	Extended type	Compared to the standard slider type, it has a higher rated load and allowable torque.	ABBA, BR LR series slider variant (without threaded flange type)	80~2200	8.5~48	34~70	66~134.8	28~55	￥235+
	Enlarged and extended type	The size of the screw increases, improving the strength of the fixation. It also has a higher rated load and allowable torque compared to the standard sliding type.	THK, sliding variant type HSR LB	64 ~ 1960	8.33~50.2	47~100	56.6~134.8	19.3~40.5	￥421+
	With location hole type	Effectively reduces equipment assembly time and allows for easier repetitive positioning.	Misumi Medium Duty Linear Guide	100~1960	5~11.7	34~48	41~92.6	20~26.5	￥484+