When you first enter a workshop for management, the first thing you should do is to investigate the current management situation and existing problems. Well, what you feel now is that the workshop management is chaotic, so let's see how chaotic it is. Well, you said there were many quality problems, and this is the first breakthrough you are looking for.
To improve the quality problem, we should find the reasons that affect the quality, not only by ourselves, but also by mobilizing everyone to find it together. First of all, you should prepare the relevant quality report materials, sort out the main quality problems, and then call the relevant personnel to a meeting, using brainstorming methods, as well as people, machines, materials, methods, environment (4M 1E)+ fishbone diagram and other methods. Let everyone express their opinions on the main quality problems together, find out the reasons, then seek targeted solutions, formulate measures, and then ask everyone to resolutely implement them according to the corresponding measures.
Because these measures are formulated by everyone, not by you alone behind closed doors in the office, it is easy for everyone to accept and ensure their implementation.
Other aspects can refer to this method, such as production failure, waste, safety accidents, etc. Step by step, don't rush, as the saying goes, haste makes waste. The first thing to manage people is to manage their own hearts and ask everyone to obey you, not just rely on the so-called system to manage, block and pressure. Be good at using the strength of groups or teams.