Parallelism refers to the degree of parallelism maintenance, which indicates the condition that the actual measured element of the part maintains an equidistant state with respect to the benchmark.
The parallelism tolerance is the maximum allowable deviation between the actual direction of the measured element and the ideal direction parallel to the benchmark.
Example of parallelism: //0.03A
Parallelism tolerance with illustrations
1. Tolerance to parallelism between lines
The tolerance zone is the area between two parallel planes located at a distance of tolerance value t from the reference line and in the given direction.
The axis being measured must be located between two parallel planes that are at a distance of 0.1 tolerance value and are parallel to the reference axis in the given direction.
The axis to be measured must be located between two parallel planes that are at a distance of 0.2 from the tolerance value and are parallel to the reference line in the given direction.
The tolerance zone is the area between two pairs of parallel planes, perpendicular to each other and located at a distance of tolerance values t1 and t2, respectively, from the reference line.
The axis to be measured must be located between two sets of parallel planes, perpendicular to each other and parallel to the reference axis, at distances of tolerance values 0.2 and 0.1 respectively.
If Φ is added before the tolerance value, the tolerance zone is the area within a cylindrical surface with a diameter of tolerance value t and parallel to the reference line.
The axis to be measured must be located within a cylindrical surface with a diameter of tolerance value 0.03 and parallel to the reference axis.
2. Parallelism tolerance between line and surface
The tolerance zone is the area between two parallel planes located at a distance of tolerance value t from the reference plane and parallel to it.
The axis to be measured must be located between two parallel planes that are at a distance of 0.01 tolerance value from the reference surface B (reference plane) and are parallel to it.
3. Parallelism tolerance between surface and line
The tolerance zone is the area between two parallel planes that are at a distance of the tolerance value t from the reference line and are parallel to it.
The surface to be measured must be located between two parallel planes that are at a distance of 0.01 tolerance value from the reference axis C (reference line) and are parallel to it.
4. Parallelism tolerance between surfaces
The tolerance zone is the area between two parallel planes located at a distance of tolerance value t from the reference surface and are parallel to it.
The surface to be measured must be located between two parallel planes that are at a distance of 0.01 tolerance value from the reference surface D (reference plane) and are parallel to it.
5. Schematic diagram of parallelism measurement using CMM
The. Measured surface characteristic.
B. Reference plane.
The CMM probe can change angles and positions to measure surface features, acquire real coordinate data of measured elements through sensors, and evaluate the parallelism value using software.
Issue:
When the actual measured element belongs to non-rigid components such as soft resin products and rubber, the measuring force of the probe may cause deformation of the measured surface, making accurate measurements difficult.
Furthermore, for shapes that cannot be smoothly fixed to the reference plate with the reference plane of the target object, accurate measurements are also difficult to perform.
Parallelism measurement diagram using drag indicator.
Explanation:
- Parallelism requires a reference plane.
- Parallelism controls direction, not position.
- When parallelism controls the surface, it also controls the shape error (flatness).
