Identifying Bottlenecks

The activities presented in the publication concern the shortening of the changeover time of the multitask bending machine. This is conditioned by the fact that the machine belongs to the bottleneck and significantly affects the much extended time of the entire retooling. In addition, reducing the changeover time of this machine is very important, because it is the most complex machine in the entire machine park, characterized by the largest number of parts for conversion and the largest number of retooling's.

After analysing the video, it was necessary to analyse the current state. First of all, the specification of all the activities performed during the conversion of the machine along with determining the responsibility and time of their execution - this division is presented in the table below (table 1), so that all aspects of the conversion can be analysed in a very clear and transparent way.

The data presented in the table shows a list of all activities performed by the setter during the conversion of a bending machine. Of all activities, all those that result from poor organization of the workplace, improper preparation for retooling or lack of appropriate conversion standards are bolded. As a result, the time wasted to perform unnecessary activities was 490 seconds, which out of a total re-set time of 8150 seconds, gives 6% of the time.

Table 1. A list of operations during the retooling of the bending machine before the implementation of SMED.

Another aspect requiring improvement concerned the time of screwing in and removing the screws. With this machine, the setter has 22 screws to screw in, where it uses a large heavy wrench, a rattle or other screwdrivers, sometimes also assisting with a hammer. The time needed to screw / unscrew the screws in this way was 40 seconds, which in total gives 440 seconds, which in turn makes up almost 11% of the total retooling time of the bending machine.

In this way, after a very preliminary analysis of the operations, it was possible to identify operations that generated as much as 17% of losses in the overall retooling time of the bending machine. It was very important to find a golden mean, so as to be able to reduce the losses to a minimum.

However, at this stage of the analysis it was very important to also retool the machine RZ. As mentioned earlier in the analyses, the time needed for the reconstruction of RZ was 2h 28min, therefore it was very important to analyse all the activities performed during this operation, so as to be able to identify those that we are able to change. In this case, the analysis of the activities showed that the situation looked very similar to the bending machine, so the issues related to poor organization of the workplace and improper work preparation resulted in the following results:

• 400 seconds of loss for consultations and documentation review, which is more than 4% of total reconstruction time of RZ,
• 2072 seconds of loss to go to the tool magazine for missing parts, results in over 23% of the total changeover time of the RZ.

Issues related to the organization of work resulted in losses in the form of 27% of total changeover time. However, in the case of the RZ machine, the issue of tightening / unscrewing the screws is also of key importance. As with the bending machine, the time needed to screw / unscrew 1 screw was 40 seconds, which with 36 screws gives a total of 1440 seconds, representing in turn more than 16% of the total retooling time RZ.