4.6 Accuracy

4.6.1 Accuracy Classes

SCHNEEBERGER offers four different accuracy classes for its MONORAIL guideways. They allow users to make precise and application-specific guideway selections based on design requirements.

Ultra-high precision, Super precision, High precision, Standard precision

The accuracy class determines the tolerance of the reference dimensions of the carriage relative to the guide rail, see figure below and section 4.6.2 - Accuracy - Dimensional tolerances, as well as the running accuracy of the carriage on the guide rail, see section 4.6.3 - Accuracy - Running accuracy.

Reference measurement tolerance of carriage relative to guide rail

Fields of Application

4.6.2 Dimensional Tolerances

System Dimensions A and B₂

MONORAIL carriages and guide rails are manufactured independently with extremely high precision and are therefore completely interchangeable. This means that any carriage can be used on any guide rail of the same size without affecting the preload class, as the preload is determined by the rolling elements of the carriage. For dimensional differences of any carriage on any guide rail, the values in the "A/B₂" column of the table below apply.

Dimensional Tolerance for Any Carriage on Any Guide Rail – A/B₂

Maximum Dimensional Difference Between Carriages on a Guide Rail – ΔA/ΔB₂

Maximum Dimensional Difference of Carriages on Two or More Parallel Guide Rails, Standard – ΔA Standard

Matched Carriages

All carriages in a set are matched to the production measurement standard and reground on their top and side locating surfaces. The main dimensions A and B₂ are then measured on the master guide rail so that the carriages are matched to each other. Carriage matching can be provided in two qualities.

Matched Guide Rails

For "matched guide rails", suitable guide rails with similar running characteristics are sought from existing data. The criterion for the selection process is the maximum difference during running over the guide rail length, the so-called matching tolerance.

All boundaries of the running protocols are within this tolerance of the matched guide rails. Guide rail matching can be provided in four qualities.

Limited Tolerance of ΔA

For carriages assembled close together on the same guide rail or adjacent guide rails, limited tolerance of ΔA applies. When using a very rigid connecting structure to prevent reduced service life, the following conditions apply:

Dimensions of Guide Rails and Carriages

Guide Rail Width B₁

Dimensions of Guide Rails and Carriages

Guide Rail Height J₁

Carriage Width B

4.6.3 Running Accuracy

Running accuracy describes the vertical and horizontal parallelism deviation of the carriage as it moves along the guide rail. It can exhibit a linear or undulating curve within the tolerance range (vertical XTZ and horizontal XTY). The tolerance class relative to the carriage center can be determined according to the following diagram, based on guide rail length and accuracy class.

SCHNEEBERGER accuracy classes G0-G3: Relationship between guide rail length l (mm) and maximum permissible deviation Δ (μm)

Reading example: For a guide rail length L3 = 2000 mm, the permissible tolerance for accuracy class G2 is 0.015 mm.