Most line managers believe that when there’s a bottleneck it’s because a machine isn’t fast enough. Well, it’s not the machine, it’s usually everything happening between machines. Slow material flow, clumping, and inconsistent input are the culprits of low throughput, and none of them imply the need for new machines.
Where material flow breaks down
The first step is eliminating what engineers call “surge points” – moments where material arrives at a station in bursts rather than a steady stream. It sounds like a small problem, but in many operations, surge points account for the lion’s share of quality and uptime issues. That sudden sluice of parts tips off sensors that something’s gone haywire, meaning they automatically stop the line, start passing product through un-inspected, or much worse.
Then, the solutions part. The most common is also the simplest. If the material’s bulk-fed and someone’s just dumping boxes into a hopper by hand, you’re always going to have some clumping or shingling. That’s not just a vision or image analysis problem – it’s a pure mechanical issue. Bulk material needs to be separated into a single, evenly spaced stream of parts.
Automated metered feeding vs. manual loading
When bulk density seems to be the culprit, the solution is to fine-tune the feeder – usually in combination with changing the hopper and track design to optimize the part’s orientation as it moves. Vibratory feeders deliver a controlled, adjustable flow of parts by varying vibration amplitude and frequency – which means you can dial in the exact feed rate a downstream sorter or packaging machine expects. Bulk density isn’t a flaw or an obstacle. It’s just another factor that needs to be taken into account from the outset of the design process, so that you can size a feeder and a hopper that will play nicely with the materials you need to feed.
The accumulation gap problem
Well, even the smoothest-run lines have short stoppages at the sorting stage. One label runs out, a jam clears itself, a sensor was a tad out of adjustment. The issue is whether a short stoppage at one stage automatically halts the entire line.
In most lines, it does. There’s no accumulation between sorting and final packaging, so the packager goes dry as soon as sorting stops. This isn’t an operator issue, it’s a bad design.
Solution? Put a physical accumulation conveyor between the two stages – a section of the line that can hold a 30 to 90 second supply of sorted product – and the packager will continue to run through short interruptions. This is very low tech to implement and has a direct, measurable %OEE impact. If your line is scheduled to run for 8 hours and has 4, 2-minute sort stoppages at the packager that cascade through the line, and that time the packager isn’t running but you could be producing rolls off the sorter, there’s 8 minutes (or roughly 1%) of packaging output needlessly lost per mechanical reason.
Matching conveyor mechanics to product type
Many people believe that faster is always better when it comes to in-feed systems. But that’s not actually the case, especially when you’re working with fragile or irregularly shaped parts. If vibration amplitude is too high, for example, the parts bounce and rub against each other, damaging the surfaces. In some cases, the parts can even chip, creating a reject rate that adds cost and time to the process.
Damage and defects are bad enough. But one of the less intuitive problems with overspeeding feeders is “nesting.” When parts are especially irregular in shape, they often nest as they come off a fast tray feeder onto a conveyor, essentially becoming interlocked with one another. This defeats the purpose of the feeder, which is designed to meter parts in a single file at a consistent rate onto the conveyor. In the end, those clumps of parts may end up on the floor or back in a bin, causing further difficulty for the sorters downstream.
The key to effective part outflow isn’t simply to run the feeder as fast as possible but as fast as necessary. That means setting appropriate frequency and stroke rates to optimize the feed rate for the part in question. For optimal control, a PLC-driven conveyor manages part outflow by referencing part-specific frequency and stroke rate settings. Coordinating these conveyor adjustments with a robotic vision system can further help in maintaining proper part orientation and spacing as the parts leave the feed tray and move onto the conveyor.
Rhythm over raw speed
You’re not trying to run things as fast as you can all the time, you’re just trying to run systems unsupervised for as long as you can. Proper feed rates, singulation, and a gap between workstations do not make your machines faster, they allow the ones you already have to run unattended at the speed they were designed for. Most times, this is plenty fast enough.
