Transcript for EO403 - How you apply FMEA.PDF

Graduate Apprenticeship - Engineering Design and Manufacture Class: EO403 - Design for X How you apply FMEA In this video, we'll be looking at the FMEA process and the steps you take in undertaking a Failure Mode Effect Analysis. The process starts with defining the system that's to be analysed. We...

Graduate Apprenticeship - Engineering Design and Manufacture Class: EO403 - Design for X How you apply FMEA In this video, we'll be looking at the FMEA process and the steps you take in undertaking a Failure Mode Effect Analysis. The process starts with defining the system that's to be analysed. We can construct a functional block diagram to show relationships between components or subsystems. We then want to list the components and subsystems, and identify potential failure modes. We then complete the FMEA worksheet, assessing the effect of each failure on the overall system performance. And we assign severity ratings and evaluate the criticality of each failure mode on system performance. We then identify critical components and suggest the overall design improvements. Let's take a look at this process in greater detail. So we start with the part. We list all the different parts in our overall product or system. We then look at the function. What function does each part provide? We list these in the table. We then list any potential failure modes, so this could have input from numerous different people in the design team. And we think, where could potential failure occur? What could be the potential failure modes associated with each part? Parts can have more than one potential failure mode. We just list everything down in the table. We then think about the potential effect of such a failure mode. So what is the overall outcome of that failure occurring? What could potentially happen? What would be the effect if that failure was to occur in the product while it's operating? We then think about severity and we assign a severity rating to each overall failure mode. We then think about the potential causes of the failure. So how could that have been caused in the first place? We then think about the occurrence. How likely is it to actually occur? And we provide a rating to the occurrence. We then look at current controls. What current controls do we have in place for prevention and detection? And we list these on our chart as well. And then we think about detection and we assign a rating for the detection. How likely is it that we or the customers are going to detect that that failure has occurred? We then calculate a risk priority number, which is simply severity multiplied by occurrence multiplied by detection. This then provides us with a list of RPNs for all the different parts and failure modes associated with that product. And we can then list any potential actions that we want to take into our design process or into future product development to minimise those risks from happening in the first place. Let's take a look at an example, so a ballpoint pen. To start off with, we would enter the part name and number of all the parts or subassemblies of the product. So let's just focus on one part. Let's just look at the ink. So we put the ink into our table. The second step is then to enter the function of each part. So use a verb noun combination. For example, provide writing medium. And this is relative to what the part is that you've put into the Page 1/3 table. So in the case of the ink, it's to provide writing medium. Step three, we then look at the potential failure modes for each of the functions listed in step two. So for example, a potential failure mode, the way in which the ink could fail would be to provide incorrect viscosity. So we put incorrect viscosity into our table. Step four is then to describe the effect of the failures for each failure mode identified. So if the ink, which provides the writing medium, was to provide the incorrect viscosity, what would be the effect? Well, it might be we have high ink flow or we have low ink flow, so we populate these into our table. And you can put down as many failure modes as you think are relevant to that associated function and part. We then look at severity. So use the severity rating table to rate the most serious effect due to the potential failure. And this is where we pull in our table-our FMEA rating table. So what you'll see here on screen is our failure mode effect rating table, which has severity, occurrence, and detection. And there's a scale of one to eight, with different criteria that describes what level is associated with each. So we are looking at the severity column to start off with. And we've got high ink flow and low ink flow. So we look at our table and we're looking at the severity aspect of this overall failure mode. And for high ink flow, we might decide that, well, it's a number four. The operator will be dissatisfied with the line and its function. And that would be the same for regardless of whether it's high ink flow or low flow. So this tells us the severity rating is a four. So we take this number over and we populate it into our chart. So the next step is then to enter the potential causes of the failure mode. So what is it that is causing us to have high ink flow or low flow? So in this case for high ink flow, it could be that there's too much solvent and for low flow, there's not enough solvent. So we write down what's the potential cause of failure. Step seven is then to enter the occurrence rating of each cause of the failure identified in the previous step. So again, we go back to our FMEA rating chart. And this time, we're looking at the occurrence column. So for high ink flow, we might think, well, it's only going to occur very occasionally, so in this case, it's a number two. And the same with low flow. It might only be occurring very occasionally, so we'll assign that number two as well. We then take these and populate these into the chart, so a two for each in occurrence. The next step is then to consider how the process that is currently in place can help to detect the potential failure mode. So in this case, we might already have quality control in the ink supply, so we write that down into our table. And that would apply to both failure modes. So quality control on the ink supply. The next step is then to look at the detection. So enter a detection rating that reflects the ability to detect the cause of failure identified in step eight. So back to our FMEA rating chart. And this time, we're looking at the last column, which is detection. So we've got high ink flow and low flow. And in this case, we're going to say that the high ink flow is a medium detection rating, so failure may be detected. So in this case, let's assign it a number four. With low flow, we're assigning that a number three. So if there's not enough flow of ink coming out of the pen, then it's going to be a high detection rating. The customer is going to be very aware that this is happening, so we'll assign that a three. We then take those numbers over and populate them into our chart, so a four and a three. This then let's us calculate a risk priority number associated with that failure mode. And that's calculated by multiplying severity by occurrence by detection. So in this case, we've got 4 multiplied by 2 multiplied by 4, which gives us a risk priority number of 32. We would do this for each of the Page 2/3 failure modes identified in the overall product that we're analysing. The last step would then be to complete the actions column. So this is where we would then look through all the potential risks that we've identified, prioritise the highest risk priority numbers, and think about what actions might we take to minimise those risks from happening in the first place. What we would hope to achieve is a completed table with all the different parts listed and all the different potential failure modes identified. We would then have a long list of risk priority numbers, which will let us prioritise what's the highest risk factors. When considering failure and their effect on function, it's important not to just give each the same level of importance. And the reason for that is the design team might only be able to address a few of the issues. If you have a table with, say, 200 risk priority numbers, you might only be able to address, let's say, the top 20 of those. So you want to make sure that there's enough variation that you can identify what's the highest risk failure modes. Prioritisation of failure modes and their effects is essential to failure mode effects analysis. Page 3/3