Another case I received during my interviews. Again, I was told that this was a real case performed to perfection by real consultants 🙂
Interviewer: Okay, so there is this company in New South Wales in Australia. It makes wheels for railway carriages. Our client just bought this company and they feel that its performance can be improved. We have been called in to help.
Interviewee: (In this case, its me) Is it the production performance they are concerned about, or is the performance related to the revenues and costs?
Interviewer: Its a production issue.
Interviewee: What’s the issue?
Interviewer: Not many wheels are being manufactured.
Interviewee: Not many wheels compared to the competitors, I assume.
Interviewer: Yes.
Interviewee: Okay, how many wheels are we currently making? And how many are our competitors making?
Interviewer: We don’t have much information about our competitors except that they are making more wheels than we are. We currently make around 63,000 wheels per year.
Interviewee: Okay so 63,000 wheels per year is approximately 5250 wheels per month or 175 wheels per day. (I divided the monthly number by 30 to ease up my calculations). We need to make more than 175 wheels per day, right?
Interviewer: Yea, how do we do that?
Interviewee: How are the wheels made currently? Like what is the wheel making process?
Interviewer: We buy 1m x 10m bars of steel which are cut into 30cm slices called cheese. This cheese is melted and put into a milling furnace. While the hot cheese is spinning, heavy rollers squash it out into a wheel shape. This is then taken to a finishing area where it takes 2 days to cool down.
Interviewee: So each wheel takes 2 days to cool down?
Interviewer: That is correct.
Interviewee: Is there something that can be done differently in this process? Like quicker cooling?
Interviewer: No.
Interviewee: Could there be some process inefficiencies? Such as the steel bars not being the optimal shape for cutting, or steel impurities so that the cheese doesn’t melt as fast? Do we buy enough steel to produce more than 175 wheels/day? Could there any wastage of raw material?
Interviewer: Those are interesting observations. To your point, there aren’t any process inefficiencies that could be the cause of our low output. But we do buy enough steel to produce more than 175 wheels/day.
Interviewee: That is interesting. So we do have enough raw material, but somehow aren’t producing enough wheels. Could it be that some of the wheels being produced aren’t usable?
Interviewer: Good point! 5% of all wheels produced get rejected due to operational error. The wheel punching machine isn’t calibrated well. Another 5% get rejected during testing due to structural problems in the wheels.
Interviewee: So only 90% of the wheels we produce are usable?
Interviewer: That is correct.
Interviewee: Is the calibration issue due to human error? How can we improve the rejection rate?
Interviewer: Yes. The calibration issue is due to human error. Some of the factory workers are not well trained to operate the machines. The structural problems we cannot address. So, why don’t you tell me how we can improve the rejection rate?
Interviewee: Well, we can reduce the rejection rate from 10% to 5% if we can address the operational errors. As these errors are caused by poorly trained workers, we can implement training programs and quality control measures to ensure that lesser wheels get rejected.
Interviewer: Okay, very good. How will this improve my monthly output?
Interviewee: So let’s say we currently make x wheels/day out of which 10% are rejected. So 90% of x = 175. So x = 175/90%. As the rejection rate has gone down to 5% due to our improvements, our output increases to 95%. So the total number of wheels we will make after these improvements is: 95% of x = 184.7 (or 184 as we cannot have fractional wheels). The number of wheels we can make monthly would be 184 * 30 = 5520.
Interviewer: Very good. Now let’s stick to our 175 number. We did a little more digging, and we found out that even with this 5% improvement, we were still behind our competitors in the number of wheels produced.
Interviewee: Why? Is the factory running under capacity? How many wheels can the factory produce in a day?
Interviewer: We don’t know how many wheels the factory can produce in a day, but it is definitely running under capacity.
Interviewee: Okay, so we know that we buy enough steel to produce more wheels. Could it be that the factory is not running 24/7?
Interviewer: Excellent point. We asked around, and realized that each day, the factory experienced 8 hours of downtime:
- 30 minutes due to MRO
- 190 minutes of unplanned maintenance due to machine breakdowns
- 260 minutes due to production run changeovers where the operators change the wheel measurements
Interviewee: Which of these can we affect? Can we improve unplanned maintenance by buying new machines?
Interviewer: We don’t have the money to buy new machines.
Interviewee: What are production run changeovers? Why are wheel measurements changed? Can we shorten this?
Interviewer: Well – we make wheels in 2 sizes. During a production run changeover, we recalibrate the punching machine to change the size of the wheel being produced.
Interviewee: Are there inefficiencies in this process? Let me elaborate with an example – Let’s say we produce a big wheel and a small wheel. Suppose for the first quarter of the day, we make small wheels. Then we switch to making big wheels. In the third quarter of the day, we switch back to making small wheels – and so on. Each of these switches is contributing to wasted time during changeovers. If such inefficiencies exist, we can improve by only having 1 changeover. Lets make small wheels in the morning and big wheels in the evening. Hopefully, you get my drift =)
Interviewer: Great point. We actually did end up facing a similar issue. Let’s say, by improving the process , we can now reduce the time spent in production run changeovers to 80 minutes. How many more wheels will we make in a year?
Interviewee: Alright, let me have a couple of minutes to do some quick math.
Before: 24 – 8 (downtime) = 16 hours makes 175 wheels. In one hour – we make 175/16 wheels
After: Downtime is now 30 + 190 + 80 = 300 minutes or 5 hours. (Means we have 3 more hours each day to produce wheels) So each year, we would make 3 * 365 * 175/16 = 11,976 (roughly 12,000) more wheels
Interviewer: I think that sounds about right. Now do you have any questions for me?