This paper describes 13 steps for safe, accurate weighing in safety cabinets or other enclosures. more
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The management concept “Lean Laboratory” is increasingly being implemented in the laboratory environment, with the aim of optimizing efficiency. An essential approach here is the “First-Defect-Stop”, which is based on the Jidoka principle and refers to the earliest possible identification of problems in production machines, but also in manual assembly lines. But how might a laboratory benefit from Lean Management principles? If properly implemented, the results can be impressive: easier workflows and processes, reduced lead times and above all increased efficiency.
The Japanese term Jidoka goes back to the founder of Toyota Motor Company, Toyoda Sakichi (1867–1930), and the Toyota engineer Ōno Taiichi (1912–1990). The latter is considered to be the inventor of the Toyota Production System (TPS), on which lean management is based. Taiichi combined the Jidoka principle with the just-in-time concept and the continuous improvement process. Jidoka is known as the ability of a system to automatically detect errors or malfunctions in the process and to switch itself off.
The strict implementation of Jidoka is a prerequisite for successful implementation of the Right-First-Time (RFT) principle. This means optimizing the process to achieve correct results right from the start. As an aid, the use of First-Defect-Stop is ideal. The RFT approach entails the obligation to the customer not to make any mistakes. It requires all laboratory technicians to be responsible for process quality and inefficiency. If a problem arises, they must find and eliminate the error within a specified time (e.g. max. 9 min 59 s). If the problem cannot be resolved easily, the lab technician has to follow an escalation procedure. This usually means calling the supervisor. The ultimate challenge is, of course, not only to solve the problem once, but to eliminate it once and for all, so that the error no longer occurs. To ignore the root cause of the error again and again, no matter how insignificant it seems, is a waste of resources, or “Muda” in Japanese. This principle can also be applied to the laboratory. Inaccurate results, poor reproducibility and long analyses times can be eliminated.
Let`s take sample preparation for HPLC measurements as an example of a typical lab workflow using a lab balance: this classic workflow is illustrated in Figure 1:
The weighing workflow steps also include:
Where is the potential for errors in this workflow? In order to reduce errors, it is essential that the lab technician closely follows Standard Operating Procedures (SOPs). However while weighing, it is more than possible that systematic and/or random weighing errors arise. Systematic errors occur when the balance has not been configured correctly or has not been tested appropriately. The balance might have an unduly long settling time of 12 seconds or more. For the lab technician, the problem might go undetected and be considered “normal”, because the balance “always behaves in this way”. Another cause of error might be a consequence of winter, when room heaters are switched on and humidity drops below 45%. When weighing powders, this low humidity can easily lead to electrostatic charges, which adversely affect weighing results, leading to incorrect HPLC analyses. A First-Defect-Stop system prevents these types of errors, since the laboratory technician can immediately stop weighing, correctly identify the source of the problem and eliminate it.
A key principle of the lean management approach based on the Toyota Production System is “Go and See” (Japanese: Genchi Genbutsu). This means that in order to truly understand a situation one needs to go to the “real place” - where work is done (Japanese: Gemba).
With a so-called Gemba walk to Genchi Genbutsu, literally translated as “management by wandering around (MBWA)”, clarity can be gained on the cause of a problem. With the support of external experts, in our case from the balance manufacturer, problems can be identified quickly and appropriate solutions proposed. Unfortunately an expert is not always on hand for every instrument or piece of equipment in the lab. In this case the Jidoka problem-solving cycle methodology can be deployed by the lab technician, as shown in Figure 2.
Metter-Toledo has created a First-Defect-Stop guide in order to help identify specific laboratory balance problems and to analyze their causes. The guide is designed to make it easier for the process manager to find the right measures for solving the problem.
Andon is a Japanese quality method which is designed to indicate a production problem, immediately alerting staff of an issue in the production process who then trigger a so-called "First-Defect-Stop" procedure. In a production environment equipped with an Andon system, the issue is indicated by "traffic light" signals, using the colors red-orange-green. The colors visualize the current operating status. Some Andon systems also signal the problem with an acoustic sound. Ideally, Andon alerts should be collected centrally and displayed prominently in real time on an Andon display board, so that remedial action can be implemented immediately and production staff are aware of the situation at all times.
This visualization support can also be implemented in a laboratory process. With this intention Metter-Toledo has followed the Andon principles in the development of its modern balances. The balances of the XPE and XPR series include a Status Light function. This color-coded alert is located on the display at the front of the balance and is always visible to the user. Operational readiness is confirmed by a green LED light constantly illuminated on the display. If the balance has a technical or calibration error, the Status Light will change to red. In this way the lab technician is immediately made aware that something on the balance is wrong, and that weighing on this balance should be stopped. The balance display also proposes remedial action with clear guidance on the menu screen.
The latest generation, the XPR series of balances, goes a unique step further and comes extremely close to the Andon principle with a new, extended StatusLight function - "GWP Approved".
The GWP® Approved label is the highest quality label in weighing, which confirms that the balance has undergone a risk based assessment (GWP Verification), in which the safe weighing range has been defined and confirmed according to the customer’s tolerances and specifications. The GWP Approved function of the new XPR Microbalance closes the gap between the consulting service GWP Verification and the instrument itself. It actively monitors that all quality relevant functions and settings are active and running correctly. The on-screen icon is your reassurance of accurate results (see Fig. 3).
Benefits for the process manager:
Jidoka Japanese for autonomic Automation or Autonomation or automation with a human touch
Muda Japanese for “wastage”
Gemba Japanese for the “real place” - where work is done
Genchi Genbutsu Japanese for “going to the source” or “Go and See”
Andon: Japanese, describes the visualization of the Jidoka principle
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