What are Positions or Ergonomic Constraints ?

    OptiLine supports both Workstation-level and Operator-level working positions. Each of the two levels of position constraint can be specified for both workstations and operations: the position constraints of an operation must be compatible with those of the workstation it is being assigned to - learn here exactly how.
    Fully customizable, the meaning of each constraint is defined in the Edit Position Structure dialog, while the choice of a set of constraints for a particular operation or workstation is made in the Edit Position dialog. Learn here how the various position constraints are represented in the graphical interface.

Workstation-level Positions

    In assemblies of large products, such as cars, buses, etc., the working position of the operator becomes an important issue. Indeed, consider the operation of fixing the exhaust system on a car: since the part must be fixed from below to the chassis, the operator would need to crawl if the car was just standing on the floor. The ergonomy of the operation would be extremely bad, resulting in long operation duration and increased fatigue of the operator. Clearly, to fix the exhaust system, the car must be elevated, i.e., the operation requires the elevation of the car. On the other hand, consider the operation of mounting the breaks: the car should be elevated so that the operator does not need to squat, but not to such an extent that the operator would have to jump to reach the axle - in short, the car should be at a medium elevation. Finally, in order to get inside the car for instance (say to fix the rear view mirror), the car should not be elevated at all, as illustrated in the following figure:

 

    Consider now a workstation where the exhaust system is being mounted. Since that operation requires the elevation of the car, the car will be elevated. Yet, it is typically counter-productive (and often impossible) to elevate and lower the car during its stay in the workstation, which means that any other operation carried out in that workstation will also be done with the car in the elevated position. Clearly, that excludes operations that need the car in other elevations, such as mounting the breaks or the rear view mirror.

    In some situations, the elevation of the car in a given workstation may be fixed in advance, for example by the conveyor system already in place. In many others however, the desired elevation is part of the optimization problem: which workstation(s) should elevate the car (and to what extent), so that the efficiency of the line is maximal?
    As of version 3.0, OptiLine fully supports these operator positions, or ergonomic constraints. It lets you specify for each operation and each workstation its operator position. However, OptiLine does not require you to fix any of these in advance: extreme flexibility is achieved by being able to specify "Any", both for an operation and a workstation.
    This feature is extremely powerful: it is for example possible to specify positions of some (possibly all) operations, yet not specify the positions of some (possibly any) of the workstations, by specifying "Any" for their positions. In that case, the automatic balancing algorithm finds itself the position of all workstations, such that the line is the most efficient.
    When "Any" is specified for the elevation of a workstation, then the elevation of the workstation will depend on the operations that are assigned to the workstation. Needless to say, all operations assigned to the workstation will be compatible with the resulting elevation of the car in that workstation. When "Any" is specified for the elevation of an operation, then it will be carried out with the car elevated as required by the other operations carried out in that workstation. Needless to say, when a defined (that is, not "Any") elevation is specified for the operation and the workstation, they will match each other.

    OptiLine currently supports three kinds of operator position, or ergonomic, constraints, each independent of the others. All are fully customizable thanks to a user-friendly graphical editor. By default (as shipped), OptiLine defines the following positional attributes:

  • Side: Back, Front, Left, Right, Center, or Any
  • Elevation: Low, Medium, High, or Any
  • Tilt: Tilted, Not tilted, or Any

    Any of these can be specified for an operation and/or a workstation. The positional constraints are taken into account in the following way: All operations assigned to a workstation will match each other's positions. In addition, they will match the one specified for the workstation, if one is given. In the matching, "Any" matches any of the other positions (as well as "Any").

    The above positions pertain to the whole workstation: if a workstation has several operators, all of them will work in the same position (e.g. on the left of the car, with high elevation of the car), learn here the exact rules. For positions relative to individual operators in a workstation, see the Operator Positions below.

Learn more on how the positions are represented in the graphical interface here. Learn here how the position constraints are defined.


Operator-level Positions

    In assemblies of large products, such as cars, buses, heavy equipment, etc., it is common to have several operators working in different positions around (or on) the product simultaneously. In those situations, forcing all of them to be, say, on the left of the product, would be too restrictive.
    To account for these situations, OptiLine also offers support for operator positions. In this case, a working position is specified for each operator in the workstation. For instance, a workstation with three operators may specify that there is one operator in front-left, one in front-center and one in front-right of the product. Likewise, a working position is specified for each operator required for an operation. For instance, an operation that requires the collaboration of two operators may specify that the first operator must be in the front-left and the other in the front-center of the product.
    The operator positions of operations are matched against the operator positions of workstations: an operation is assigned to a workstation only if all the operators required for the operation are available in the workstation. Thus for instance, given

  • Workstation Ws1 with three operators: front-left, front-center and front-right

and

  • Operation Op1 requiring one operator: front-center
  • Operation Op2 requiring two operators: front-left and front-center
  • Operation Op3 requiring two operators: front-left and center-left,

Op3 cannot be assigned to Ws1 because there is no operator in center-left. Learn here the complete rules.

    It also is possible not to specify a position for an operator in a workstation, which amounts to position "any" for that operator. Such an operator can execute operations taking place at any position. However, the algorithm makes sure that there is never more than one operator at any position at the same time. Thus for instance, if there are two operations taking place on the left that could start at the same time, and two operators who could perform those operators are available, one of the two operations will nevertheless be delayed until the end of the other operation, so that the two operators do not interfere with each other in the left position.
    It is equally possible not to specify a position for some, possibly any, of the operators carying out an operation, which again amounts to position "any" for that operator. The corresponding task of the operator is considered to be taking place "anywhere": it can be executed by an operator in any position, and at the same time as any other operation. In particular, there can be more than one such tasks being executed at the same time in the workstation.

Learn more on how the positions are represented in the graphical interface here. Learn here about how the position constraints are defined.