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How to choose the right type of linear guide rail?

November 11,2022

In the design of industrial machinery, linear guide rails are always used, which involves the selection of linear guide rails.

Here’s a brief description of how to select the linear guide rail:

1. Determine the width of linear guide rail.
The width of guide rail is the key to determine the load of guide rail. Generally, the product widths of linear guide rail are 15, 20, 25 (23), 30 (28), 35 (35), 45, 55 (53) and 65 (63). Some brands can only achieve the specification of 45 at the maximum. There are also mini linear guide rails with specifications of 3, 5 and 7.
2. Determine the length of linear guide rail.
Determine the total length of the guide rail. The total length of the guide rail = effective stroke+slider length+slider spacing (more than 2 sliders) multiplied by the number of sliders+safe stroke at both ends. If additional protective covers are designed, it is necessary to calculate the compressed length of the protective covers at both ends. Generally, the whole rail of a linear guide rail is 4m, and some of them exceed 4m, which needs to be confirmed with the brand merchant. If the length of the selected guide rail exceeds the existing length, it needs to be butted. It is best to provide the interface drawing if the user wants to process the installation holes on the machine in advance. Another point, please pay special attention to the fact that the installation hole spacing on the guide rail is fixed. Users should pay attention to the position when determining the rail length, for example, the rail with a length of 15 is 600. If you don’t tell the supplier about the required end size, generally, there are 10 installation holes in the state of arrival. The distance between the two end faces of the guide rail and the center of the nearest installation hole is 30 or 30, but other sizes are possible. Each brand has slightly different shipping regulations for the end size, and most of them are equal at both ends by default. One more thing, the length error of the guide rail is 1 ~ 2mm below 2000 and 2 ~ 3mm below 2000~4000 by default in general brands. If the user’s requirements are more accurate, it is best to indicate the error value or provide drawings when ordering.
3. Determine the type and number of sliders.
There are two kinds of commonly used sliders, flange type and square type. The flange type is lower in height, the slider is wider in width, and the mounting holes are through threaded holes. The square type is higher in height, the slider is narrower, and the mounting holes are blind threaded holes. The two types of sliders are short, standard and extended, respectively. The main difference is that the metal lengths of sliders are different. At the same time, the mounting holes will be different. Generally, the short type is two mounting holes. The recommended basic principle is: as few as possible.
4. Determine the accuracy level.
Each manufacturer’s linear guide rail will be marked with the accuracy grade. Generally, the first letter of the accuracy name is adopted, namely, ordinary grade (N), advanced grade (H) precision grade (P), super precision (SP) and top precision (UP). Accuracy is a comprehensive concept, which is generally composed of the walking linear error of the slider reference face to the guide rail reference side, combined height error, side width error of slider reference on the lead side, paired height error and paired width error. Ordinary precision can meet the requirements, and the higher precision is required, the H grade is selected, and the NC machine tools are selected as P grade. The latter two grades need harsh installation and conditions to show their performance.
5. Determine other parameters.
The bearing satisfaction, coordination, preloading grade, fittings and processing technology of linear guide rail and slide block, etc.