# Poka Yoke in Smart Production Systems with Pick-to-Light Implementation to Increase Efficiency
## 3 Materials and Methods
### Pick-to-Light System  
Poka Yoke minimizes unintentional errors or errors due to inattention to almost 100%. The group of solution systems also includes other methods, such as Pick by Voice, Pick and Work, Pick by Vision and so on. Even though these systems are mostly implemented in logistics, they are increasingly finding their place in assembly as well [27]. Devices using the principles of the Pick-to-Light system are adapted so that a given assembly or storage cannot be carried out in more than one way. The main means of these devices are optical signalling elements that gradually light up, placed above each warehouse position, respectively (cell). When a component is removed from any situation, the worker's hand will interrupt the light beam, causing the corresponding signalling to go out and another signalling to be lit in another position. The system is capable of notifying the worker of a possible error with a light or sound warning [28]. In this way, the presence of paper expenses, assembly sheets, etc., is unnecessary. The flawless worker workflow is monitored by a sophisticated system that navigates him during assembly and warns him if he has made a mistake. From the point of view of increasing the production process quality, the Pick-to-Light systems represent the philosophy of \"zero error rate\". Visual control of the production process is used in several industrial areas (electrical and automotive industries, logistics, storage, etc.) [29]. The main benefits of Pick-to-Light systems are:  
* Increasing work productivity;
* Improving quality;
* Reducing the occurrence of errors to zero;
* Continuous inventory;
* Connection to ERP and warehouse systems;
* Increasing flexibility;
* Speed of new personnel training. The Pick-to-Light system is used in the order-picking environment. It allows the employee (male or female) to quickly and easily find the right position using lights or LED displays. Each tag represents an item in the storage location. In addition to guiding the employee to the exact location, the light shows the same amount of items in the rack's bins. The system requires confirmation before the item is selected. As Figure 3 shows, the architecture of the PTL system consists of the following components. * A rack consisting of multiple Pick-to-Light units;
* A bar code reader for scanning items inserted and removed from the rack;
* A control unit/controller (network or wireless) connected to the Pick-to-Light system;
* A router or network hub;
* A remote PC installed with real-time material inventory management software. The PTL system works as follows. In the rack of several rows, an optical sensor and a control unit are mounted on each controlled cell. Each row has several cells connected to a control unit that ensures sensing and informing the employee. Subsequently, several units are connected to a central router, which sends all information to the inventory management software (IMS). The unloading and storage of individual components in the cell is recorded using a barcode reader [28; 30]. This information is sent to IMS, which informs the operators in the warehouse about the box preparation with the exact number of parts. After it is inserted into the IMS cell, it keeps inventory records and loads the program for the specified assembly. According to the requirements, the individual cells are explained in the exact order, and the number of pieces is displayed on the LED display. When selecting a component, the employee's hand is read using an optical sensor and the operation is completed. Subsequently, another cell is illuminated, and the employee repeats the process [30]. The individual steps are entered into the control units connected to the router. Linking the Poka Yoke and Pick-to-Light methods in the intelligent manufacturing system can be achieved by integrating and cooperating with these systems.