The restrictions can be external or internal. External restrictions occur when the system can produce more than the market requires. In such a case, the organization must create demand for the product in the market. A constraint limits the production that an entity can produce.
When analyzing these restrictions, the key question is whether an expansion of the restriction could generate more sales. If so, properly managing the constraint can generate more benefits. Given the importance of the concept of restraint, it is of utmost importance to understand the types of restrictions a company may be subject to. For example, a machine that can only produce a certain quantity of a crucial part will limit sales of final products that incorporate that part.
A typical configuration of the lines is that, under normal operating conditions, the conveyors located at the top of the constriction machine are always full to avoid starvation when they reach the constriction, and the conveyors that are in the downstream direction operate empty to prevent them from accumulating in the constriction. The limiting factor is now some other part of the system or it may be external to the system (an external constraint). The buffers used in this way protect the restriction from variations in the rest of the system and should allow normal variation in processing time and occasional (Murphy) alterations before and after the restriction. A machine that has a large amount of work ahead of it is obviously out of stock and could therefore be a limitation.
In a TOC system, the only situation where work is in danger is when the constraint can't process (either because of a malfunction, illness, or a hole in the buffer; if something goes wrong, the temporary buffer can't protect it). Whether it's the objective or a necessary condition, understanding how to make sound financial decisions based on performance, inventory, and operating expenses is a fundamental requirement. Depending on their design and construction, these machines operate at different speeds and capacities and therefore have different levels of efficiency. The concept of constraint in the Theory of Constraints is analogous to, but differs from, the constraint that appears in mathematical optimization.
Restrictions can appear in many ways, but a fundamental principle of OCD is that there are no dozens or hundreds of restrictions. An example of this limitation is the belief that the only good workstation is one that operates at 100% capacity, even if there is not enough demand to justify so much work. Ultimately, buffers save time, as happens before work reaches the limitation, and are often verbalized as time buffers. A prerequisite of the theory is that, with a constraint on the system, all other parts of the system must have sufficient capacity to keep up with the work at hand and to catch up in the event of wasted time.
Drum-Buffer-Rope (DBR) is the process of synchronizing operations with the constraint and, at the same time, minimizing work in progress. In the event of a stop on a machine other than the restriction machine, the conveyor can cushion the product so that the restriction machine continues to operate. An internal constraint becomes apparent when the market demands more from the system than it can offer.
Leave Message