Spaghetti diagram and transport load: measuring the current path

Why it matters

A spaghetti diagram is a drawing that shows the path that a product, a transport container or a worker follows in the current layout. The number of lines or the complexity of the drawing does not by itself tell the size of the loss. Two lines that look the same may carry different quantities of product; a short path can create a significant load because it is used very often. For this reason the drawing is read together with the start and end points, direction, quantity moved and measured distance. First it is chosen what is being tracked. When tracking the path of a part, writing the worker's empty return as if the same quantity of material were being carried is wrong. If the worker's total movement needs to be examined, a separate record is opened for it. When the tracked entity changes, the meaning of the measure changes too.

In this lesson, transport load is defined as the product of units and distance and is shown with the unit·m unit. It summarizes how many products travelled how far within the same family in a given period. This quantity is not physical force or energy; it does not explain strain without knowing the masses of the parts. Two transports with the same unit·m value can create different risks because of different grip, height and crossing conditions. Calculating the load does not replace a safe manual handling assessment. For this reason the numerical result is interpreted together with the safe use of the path and the handling conditions. Moving an unsuitable load over a shorter distance cannot be accepted merely because the distance decreased.

A straight line between two points on the diagram may not be the real path. Racks, guards, doors, the crossing direction and the working area determine the route to be followed. Measurement is made along the path that can actually be used; a shortcut through an obstacle is not a distance gain. A closed crossing, a blind corner or a dangerous pedestrian crossing is recorded separately. If a shorter proposal breaks the safe crossing, it is eliminated even if its numerical load is lower. This decision is not reversed by adding a caution warning afterward. Safety is not balanced against distance gain like a scoring item. First the usable paths are determined, then the load and time results of these paths are compared. While measuring, the observer must also not block the path of workers or of the transport.

The scope of this lesson is to record the current path, to calculate the transport load and to separate the safe options. The design of the cell layout is covered in the later layout module, and the need for vehicles and drivers in the internal logistics module. A vehicle count cannot be derived directly from the unit·m total here. For a vehicle calculation, other data such as the transport cycle, output interval, container limit and driver capacity are required. Likewise, deleting a line does not prove that the operations can be placed side by side safely. The current measurement becomes input to the later design. A well-prepared record should show, in a comparable way, which movement has really disappeared and which has only been moved to another resource or another time.

Formula