Full saturation of a gigabit LAN should let you transfer around 95 plots per day (a little more, but let’s go with that). Are you creating 95 plots per day?
A consumer grade switch such as the Netgear GS308 is advertised as having 16gbit switch bandwidth, but generally that rarely holds true on consumer gear, and it is usually X bits of data (gigabit in this case) per bank of (usually four) network ports.
So four ports will offer, technically, 8 gigabits of (full duplex) bandwidth, but what frequently happens is that a) those four ports are sharing two gigabits or four gigabits of bandwidth. You frequently need to pull the top off of the switch to figure out what the switching chipset is, and then track down the data sheet to see how much the manufacturer fudged the Atari math.
The other problem is that, sure, you have 16 gigabits of full duplex bandwidth, but the interconnect between each bank of four ports is limited to two gigabits full duplex. Or four. Or eight. It again, depends on the chipset, but frequently, each bank of four ports has full bandwidth switching to any other port on that bank of four. But between each bank of four, the interconnect is lousy.
Which is why the numbers on the box, much like NVMe SSD burst read/write speeds vs sustained read/write speeds aren’t quite so easy. It’s all Atari math - “Well you see,” said Jack Tramiel, “we add up the clock speed of all the chips in the computer, and that’s how fast it is.” Surely aprocryphal as to its source, but that’s pretty much what you’re staring at.
If your plotters are moved to multiple farms, you can hook up plotters to separate switches, and then a common interconnect between those switches. Or you can try moving the plugs around between plotters and farms in the switch to see if that gets what you need. If your machines are Linux you have a decent network card, you can shotgun together multiple gigabit connections to get a speed up which is how I originally had my 40gbit QFSP+ card configured, then I switched to 20gbit ethernet but also do the same. You could have the plotters running at gigabit, and the farm running at dual gigabit.
I have a friend shifting five NUCs of plots per day to a single farm node over gigabit and he is around 80% of network load.
For reference, my NAS is connected to dual 10gig on the switch, but prior to that setup I used all four gigabit ports on the back of the NAS going to four separate bank of four ports on a 16-port mid-tier “enterprise” (haha! not!) switch before I eventually upgraded. Those four separate gigabit connections to four separate banks of ports ensured I wasn’t saturing the internal switching capability of the switch itself.