From quoting all the way through to loading trusses on to the truck, the whole thing is a production line.
If I were a betting man, I’d bet that every single day, at least one of those things would be holding up your production. One of these processes will be your bottleneck. It’s the part of the puzzle that you need to improve.
Detailers lagging behind? They need to detail more! Waiting on info from the builder? We need a new system that gets all the information when the job is booked in! (good luck). Finished jobs taking too long to load on the truck? Let’s get a loading consultant in (I made that up, but surely there is one somewhere in the world) to increase efficiencies.
Of course, all of this work to increase productivity seems like a good way to spend your time - And I definitely wouldn’t say that they are a bad way to make your shed more efficient. So what do you do first? How do you decide the priority? That’s the problem. You are always chasing the bottleneck, always trying to squeeze maximum productivity and efficiency out of every individual process. “No one should be standing around doing nothing, that’s unproductive!” That sounds bloody exhausting.
There is always going to be a step in the assembly line of your product that is slower than the rest. Even if the slowest one is relatively fast, it’s still the slowest one. That slowest step in the production line decides the throughput (the rate that the system - or production line in this case - generates money through sales) of finished product out of your shed.
It doesn’t matter how fast your press is if it’s waiting for pieces from the saw. It doesn’t matter how quickly your yardman can load the truck if he is waiting for the completed job to get strapped up. You get the gist. The ‘bottleneck’ is the slowest step. Nothing gets produced faster than the slowest link in the production chain. If there is always one bottleneck, why not manage that bottleneck.
Make your life as a production manager or business owner a whole lot less stressful. You get to stop chasing your tail and you get to start focusing on the things that will actually move the needle on your business.
Okay, so what’s the bottleneck in your plant? If you said anything other than the truss press, you’d be wrong dear reader. If the bottle neck in your production line is your saw, or your detailing, or even the orders coming in the door, you need to increase the available capacity of those processes. Your press always needs to be the bottleneck.
Having a predetermined bottleneck is a bonus of truss manufacturing compared to other manufacturing businesses. It’s predetermined in truss manufacturing because most fabricators incorporate all of the plant’s overheads into their Production Point/EQA and Lineal metre costs. Production points are based on assembly times of trusses on your press. The only way that you pay for your whole operation is by that press continuously jamming nail plates into timber. No squish, no money.
Once you have defined your bottleneck you can start systematically eliminating any bad processes in your shed that make the bottleneck stop working.
Let’s look at a hypothetical scenario based on things that have come up in a few different businesses.
Shed A loves when everybody is always busy. The saw operator has the saw running 8 hours a day cutting jobs for the truss line. He’s been able to cut heaps more since the boss got that new linear saw. Sometimes, with the old saw, the press would be waiting for him to finish a trolley so they could keep manufacturing, but not anymore. He has actually run out of trolleys to fill on some days and started stacking webs and chords on pallets until the press started catching up.
The guys on the press just can’t keep up. They are working flat out to make the trusses, stack the trusses, grab the brackets for girders to box up as they make them, return the empty trolley back to the saw, strap the finished job, push it out of the shed, grab another trolley of parts, replenish the nail plate stock….. the list goes on.
The owner is seeing a marginal increase in throughput out of the shed, but not as much as he thought. This new saw was supposed to cut twice the parts in half the time, shouldn’t we make twice as many trusses in half the time? The press was waiting for the material a lot of the time before, and they shouldn’t be waiting anymore!
So, what’s going on here?
Shed A upgrades to a linear saw
The press was previously unproductive some of the time waiting for the old saw to catch up
Because of this, press operators have taken on a lot of secondary work
The saw operator is creating a massive backlog of Work In Process materials
Total production has increased slightly, but not enough to justify the new saw purchase.
The owner was absolutely heading in the right direction with this. The press operators were being held up by a lagging saw which created down time on the press, so they upgraded the saw. The new saw had so much excess capacity that the operator was running out of space to store the WIP material he was producing. An unexpected side effect of this was that the press operators had no downtime to perform all of the secondary work (stacking and strapping trusses, returning trolleys, etc) that they had to do in order to produce a finished product.
The balance of excess capacity shifted from the press to the saw, which is the right goal, but the secondary work didn’t shift accordingly, leading to the downtime on the press only decreasing marginally. To see the full benefit of the saw, all of the secondary work that the press operators were performing, shifted from the press operators to the saw operators and the yard workers, which finally increased the capacity of the press to one that could justify the paurchase of the new machinery.
Once you get your focus back to the bottleneck and evaluating what the new change has done to it, the answer becomes obvious, and dare I say it, common sense (if there is such a thing).
Keeping your press pressing means every other one of the processes in the assembly line needs to have an excess capacity that accounts for the hiccups in day to day manufacturing. For the process immediately before the bottleneck, there should always be a buffer of work in process materials appropriately large enough to protect the press from any reasonable fluctuations in production upstream of the press.
When you make your press a bottleneck, every other process is subordinate to it, meaning every other process only needs to worry about meeting the needs of the press, not filling their individual capacity. It’s an incredible focusing mechanism. If the press is operating at absolute capacity, all you have to focus on is increasing that capacity through intelligent and data backed improvements. If the press is not operating at capacity, all you have to worry about is the process that is holding up the press.
See? Bottlenecks aren’t as scary as some make them out to be. They shouldn’t be eliminated as soon as they are found. Not every machine should be fully optimised, but it can be pretty scary to see a very expensive machine doing nothing! Before putting that machine back to work you should always consider if that machine doing more work is going to contribute to the throughput of trusses out of your shed, instead of just increasing material on the shop floor.
Protecting the bottleneck from stopping work matters much more than non bottleneck processes being idle for periods.
This whole article is a bit of a primer on the Theory of Constraints. You can read more about it in the book ‘the Goal’ by E.M. Goldratt. I definitely recommend it!
