With restriction

With restriction refers to an assembly process in which obstructions may occur due to poor visibility or insufficient space.

With restriction sight:

Obstruction of the line of sight to the positioning location by the object to be positioned does not necessarily result in unfavorable body posture. With relatively small components, it can be expected that an obscured positioning location may lead to assembly delays due to corrective movements. But this does not generally result in unfavorable body posture. Unfavorable body posture such as bending, rotation of the trunk, or lateral bending may, however, occur due to an obstruction of the view when relatively large or heavy components are involved. An obstruction of the view is therefore taken into account when evaluating ergonomic risks.

With restriction space:

Restriction due to space generally means that access to the positioning location is more difficult for the positioning hand/fingers. To get access, unfavorable joint positions of the positioning arms (upper limbs) can be expected. From an ergonomic point of view, joint positions are considered unfavorable if the average joint mobility exceeds 50 %. This applies to the wrist, elbow joint, and shoulder joint. A restriction in terms of access is therefore taken into account when evaluating strains on the upper limbs.

Rule M-B1:

In the case of restriction due to space or visibility, a frequency of 1 is entered in the corresponding column.

Rule M-B2:

In the case of restriction due to space and visibility, both types of restriction are evaluated with a frequency of 1.

Rule M-B3:

If when positioning a component, the positioning locations are hidden by the component itself, restriction due to visibility is analyzed.

Without positioning aids

Without positioning aids refers to an assembly process in which neither the component or sub-assembly, nor the positioning location, is equipped with positioning aids, such as stops, guides, etc.

Without positioning aids:

Missing positioning aids inevitably result in assembly interferences.

w/o positioning aid

with positioning aid

With fixing of position

With fixing of position refers to an assembly process in which a component or sub-assembly is not in a stable (final) position after initial positioning.

With fixing of position:

Fixing of position comprises all measures necessary to keep a part in a specific position until it has reached a stable position through a subsequent assembly process.

Please note:

From an ergonomic perspective, fixing a component in position for the subsequent Assembly process (e.g. screwing, locking into place) can result in an actual static action. This means that the component must be controlled for a longer period (4 seconds or more). Depending on the weight of the component and the type of grip (e.g. thumb and index finger or fist closure), this may result in an increased ergonomic risk for the upper limbs. The assembly difficulty "With fixing of position" is therefore taken into account in the ergonomic evaluation.

Fault assembly

Fault assembly position possible refers to an assembly process in which it is possible to assemble a component or sub-assembly in more than one way. One or more of the possible positions may be wrong (Poka Yoke).

The design of the component or sub-assembly allows for fitting in more than one way. This may cause rework of individual components or sub-assemblies, or it may represent a risk of improper functioning. To avoid this, components or sub-assemblies should be designed in such a way that no fault assembly position is possible (see schematic diagram or e.g. nose on a plug with a defined pin).

The assembly difficulty "Fault assembly position possible" has no bearing on the ergonomic risk evaluation.