LaundryMaster, as the name suggests, was a business that specialised in laundry appliances – washing machines, dryers, garment steamers, and so on. Even though the business was doing OK, there was always pressure from cheaper imported goods, and as operations manager Ben was one of the people who had to find ways of dealing with it. One afternoon, Ben saw the sales manager, Alex, walking through the office and called them over.
“Hey Alex,” he began. “I was wondering… those due dates you put on the jobs. How firm are they? Like, could I shuffle a few jobs around?”
Alex grimaced. “I’d rather you didn’t,” he said. “Getting things out on time is pretty important. Those customers hate being told their order is going to be late, and I don’t like telling them that either. Why do you want to change the sequence anyway?”
“It’s all because of testing,” Ben explained. “Everything we make has to go through the testing rig, right? And every product line needs a different setup on the rig. If we do jobs strictly in due date order, we often end up spending more time reconfiguring the rig than we do actually testing products, and that slows down output as a whole. I’m sure we could get more orders completed if we could just shuffle the sequence around a bit so that we’re testing more each testing run and spending less time resetting the testing rig.”
Alex shook his head. “Please don’t,” he said. “If you do that, we’ll end up with some jobs completed earlier than necessary. Last time that happened, some of them got damaged while they were waiting to be shipped, and I don’t want that happening again, and ‘No’ because sometimes I find that jobs are getting started later than necessary, which means we don’t hit our due dates. I know it might not be the most efficient way to do things, but I reckon due date performance is more important than setup time on the testing rig. Can’t we just get another one if that’s what’s slowing things down?”
“Not really, we just spent nearly three hundred thousand dollars on this one! The board was pretty resistant too, they aren’t going to approve funding for a second one.” Ben exclaimed. “And even if they did, we would have to train people to configure it and operate it, too. We wouldn’t even need another one if we could just shuffle around the sequence a bit…” Alex was shaking his head again, and Ben’s voice trailed off in frustration.
“Sorry,” Alex said, although he didn’t actually sound all that sorry in Ben’s opinion. “I’ll not risk missing our due dates. That’s a hard ‘no’.” He walked away again, leaving Ben with an unresolved problem. Ben knew they could get more products through the testing rig if only they weren’t reconfiguring it all the damn time.
At the same time, though, Alex had a point… it didn’t matter if they got more products tested if they were products that didn’t need to be tested yet, or if the tests happened too late for the products to hit their due date.
It was like his kid’s shape-sorting toy, there was a constant procession of shapes falling into a box. All the shapes – jobs, really – had to be passed through the matching shape hole in one side of the box, but Ben wasn’t allowed to feed in all of one shape at a time because the due dates said some jobs had to be done before others… he stopped. Actually, that wasn’t a bad analogy, was it? There were always more jobs coming in, so it wasn’t realistic to do all of one type of job, then all of another, because the various jobs arrived, seemingly at random and had to be processed, ‘sorted’ to use the analogy, within a limited window of time.
So, Ben realised he had to deal with whatever was in the to-be-sorted bin at the time… But he could tweak the sequence he sorted in, as long as they were all sorted in time… and therein lay the challenge.
OK, everything had to go through the testing rig. Anything that was at risk of missing its due date would have to get priority at the testing rig. After all those jobs were taken care of, though, it would be fine to change the sequence of what was left to minimise the number of reconfigurations. Now, surely, if he could minimise the reconfigurations then the testing rig would clear its queue of jobs faster. Could he actually pull ahead enough to lock in a window of time we could use to keep on feeding in jobs in a more efficient mix?
Ben would have to reassess the sequence every day – maybe more often, maybe less, he wasn’t sure yet – based on what jobs were ‘in the box,’ so to speak, but it would still be an improvement on doing everything strictly in due date order. Remembering Alex’s complaint about resequencing jobs meant that the size of this ‘mix’ window had to be carefully chosen, or else it might make some jobs late. As long as it didn’t make anything miss its due date, Ben was willing to bet that he could do it.
Ben grinned. It was time to see if this would work!
A few weeks later, Ben was clearing some of his email backlog when Alex came into his office.
“Hi Ben,” Alex said. “I just wanted to say thanks. Due dates have been a bit more reliable since we talked, and I’ve seen how busy your team is. I know that you’re under pressure to increase output, but I think sequencing by due date was the right call. I’m glad you’re sticking with it.”
Ben laughed awkwardly. “Ah… well, I’m glad you’re pleased with the results. To be totally honest, though, we’re not sequencing by due date. Well, not entirely, anyway.” He explained his new system for scheduling, and at the end of the explanation, Alex nodded thoughtfully. But then, a little perturbed, Alex said, “So you increased my lead times?”
Ben was ready for this one. “No, we pulled ahead just a little by clearing a few jobs quicker and then resisted immediately filling the gap with the next job. Our internal processing time sped up a little and we chose not to tell you.”
“Why?” snapped Alex, “We could have sold that shorter lead time!”
“No, you couldn’t,” replied Ben evenly. “That time window was too short for you to clear the jobs in time. Admit it, the change did you no harm, and as you reported, due date performance is more reliable now. This is better!”
“I see what you mean. You’re right, by the way – as long as we don’t miss due dates, I’m not too bothered by how you sequence the jobs. I was just worried that shuffling things around would cause us to miss due dates. It always has in the past. But it sounds like your idea solves that problem.”
“It does,” Ben agreed, “And I’ve actually discovered some other good points. Because we’re not constantly reconfiguring the test rig, it’s much easier to get jobs flowing consistently. The people operating it are happy that we don’t change the schedules as much too!”
Alex nodded and got up to leave. “Well, in any case, it seems to be working for you. Don’t go back to how it was before! Did I see Maria walking out as I came over?”
“Yes, you did,” Ben said. “She’s been looking at some of our products in terms of throughput. Since the test rig is sort of the main bottleneck for all of our products, she’s been comparing how long each product takes to test with how much margin we make on it. Even products with high margins don’t look so good if they tie up the rig for ages.”
Alex nodded again. “Well, if we need to change what we’re selling, we can do that. It sounds like getting the mixture of products right is going to be pretty important. Maybe you’ll be the mix master at LaundryMaster!”
Ben groaned as Alex walked out. Was he really going to be known as ‘the mixologist’ from now on?
