Plasteel is a rare material that exists in a form of mountain veins, and it is quite difficult to be found on a map - you may get one such vein on a large map, though.
But often, when you find such a vein it should have a large deposit of the material; the same with deep drilling. Once you discover a large deposit, it can cover almost all your needs (turrets, space ship).
8 Ways to get Plasteel in Rimworld
1. Smelt the Starting Knife
The first choice of getting some plasteel is to smelt the starting knife - you won’t get much out of it, but it is something anyway.
2. Buld a Long Range Scanner
Building this thing allows your scientists to search for some plasteel chunk. The chunk will probably be guarded, but since it is very light, you will be able to bring the whole thing to your base.
So once you discover it, send a mining party - a single deposit can have around 1000-2000 of plasteel.
Long range scanner is one of the most efficient ways to get plasteel. It usually takes around 8-9 days to find a plasteel meteorite that will give you around 300-500 of the material.
To set up a mining camp will take another 3 days, so it all takes around 11 days, and in the end you will be getting 27-45 plasteel per day.
3. Deep Drilling
You can try finding a plasteel vein with deep drilling, but the downside is that deep drills can spawn mini-infestations. Of course, the drilling in the open shouldn’t give you much headache, but if done inside the base, it may not be very pleasant. If you happen to discover a deposit near your turrets, that may relieve your from some pain.
The benefit of deep drilling is that it is a consistent way of getting plasteel: you will be getting about 7 plasteel per “cycle” (depending on mining skill), and there are around 4 cycles per day. So with this method you will have about 14 units of this material per day. And deep drilling is easier to manage than the long range scanner.
4. Mechanoid Raid
If you have a disassemble table, you can wait for a mechanoid raid or provoke it, and then disassemble them to get some plasteel. While provoking mechanoids in ancient dangers is probably not the most efficient way to achieve your goal, it this quite funny nonetheless.
Yet another way is to make a caravan to a friendly colony for trading (but not a tribal one). Actually, this can be quite effective - not only for plasteel, but for uranium and gold as well.
To give you an example, with a month’s caravan journey with enough pack beasts you can bring back over 1000 of each of these materials.
6. Mining Colony
You can establish a new colony dedicated solely for mining. For that you will need to enable multiple colonies in the options menu. But keep in mind that abandoning it afterwards will turn it into an obstacle.
Also sometimes there are trade ships that pass by your place, and they often have some plasteel for trade. Trading with a spaceship would be the best choice, but bulk good traders might also have some.
Trading can bring home a few hundreds of the material, but it might be expensive and your economy should be good enough for a successful trading, so probably, this method can become more useful later in the game.
For trading you can sell slaves, clothes, or even make some stuff solely for this purpose, like human leather dusters, various drugs, or even wooden grand sculptures. If you scale it nicely, you will get lots of the material and gold.
8. Rimworld Dev Mode
Ultimately, just try using a dev mode to spawn in some plasteel if you are desperate or think that your game has bugged out the whole thing.