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[utunnels]

For some reason, magma crabs always find a way to get into my fortress.

I built some magma forges by channeling out some floor tiles, could it be the cause?
.........
..xxx...
..xxx...
..xxx...
.........

. = warm floor
x = forge
x = magma channel

[Tacomagic]

For some reason, magma crabs always find a way to get into my fortress.

I built some magma forges by channeling out some floor tiles, could it be the cause?
.........
..xxx...
..xxx...
..xxx...
.........

. = warm floor
x = forge
x = magma channel

Typically you want the channeled tile under a solid (dark green) portion of the forge, otherwise stuff can path up through the building.

For magma forge it's one of these two:

.........
..xxx...
..xxx...
..xxx...
.........

For Magma smelter/kiln/glass furnace it's this one:

.........
..xxx...
..xxx...
..xxx...
.........

[utunnels]

Oh thank you.

[utunnels]

Wait, I checked the wiki, it says:

"Placing an impassable tile of the workshop over the magma will prevent dwarves from getting knocked in but will not prevent magma creatures from crawling out."

[Tacomagic]

Wait, I checked the wiki, it says:

"Placing an impassable tile of the workshop over the magma will prevent dwarves from getting knocked in but will not prevent magma creatures from crawling out."

Huh. I've always done it with impassible tiles and never had a problem, but maybe I'm just super lucky.  As I've always said, better to be lucky than good.

I just checked and it looks to be linked to a single incident involving a magma man by a single user.   So it might have something to do with building destroyers being able to destroy a building above them when they have a different open path.  In this case magma men are level 2 building destroyers.  The guy who made the change did it unilaterally and I do not think the information is 100% accurate, nor well tested.  If you look at previous versions, the text is that it DOES block creatures.

I've had magma crabs wander around under my forges many times, and they've never pathed up into the fort.

[Tacomagic]

If I had to guess, what happened is that the user in question had one of the cavern layers connected to the surface (or to his fort somewhere) with only trap barriers.  The level connected had a magma-pipe somewhere that created a fully pathable rout to the magma forge.  Since the magma man had a routable path, he destroyed the forge and walked up into the fort.

Either way it certainly appears related to building destroyers.  Reason enough to move the magma somewhere else, really.

[StagnantSoul]

I've not once had a magma creature come up in all my playing.

[TBeholder]

It needs only a tile of magma under it, not a connection to magma sea.
So you can just cut off the magma channel with a floodgate or bridge. Or build a whole sluice on it.
If you don't want to use a minor exploit, that is (if not too shallow, even in 1x1 pit magma will remain hot and full forever).

[utunnels]

Huh. I've always done it with impassible tiles and never had a problem, but maybe I'm just super lucky.  As I've always said, better to be lucky than good.

I'll try that anyway to see if it changes anything. But you are right this kind of event is luck based, my fortress had been crab free for years after the forge was constructed.

It needs only a tile of magma under it, not a connection to magma sea.
So you can just cut off the magma channel with a floodgate or bridge. Or build a whole sluice on it.
If you don't want to use a minor exploit, that is (if not too shallow, even in 1x1 pit magma will remain hot and full forever).

Thank you.
Maybe I need to do some investigation, never used a floodgate on magma before.

[danmanthedog]

Your lucky it was just magma crabs I have an invasion of little red frogs. About 20 of them in a corner of the cavern... and they are breeding more. Haa

[Paaaad]

Wait, I checked the wiki, it says:

"Placing an impassable tile of the workshop over the magma will prevent dwarves from getting knocked in but will not prevent magma creatures from crawling out."

Huh. I've always done it with impassible tiles and never had a problem, but maybe I'm just super lucky.  As I've always said, better to be lucky than good.

I just checked and it looks to be linked to a single incident involving a magma man by a single user.   So it might have something to do with building destroyers being able to destroy a building above them when they have a different open path.  In this case magma men are level 2 building destroyers.  The guy who made the change did it unilaterally and I do not think the information is 100% accurate, nor well tested.  If you look at previous versions, the text is that it DOES block creatures.

I've had magma crabs wander around under my forges many times, and they've never pathed up into the fort.

I've just edited the page for the Magma Smelter to reflect the information in this thread, and practically Tacomagic's post below.

If I had to guess, what happened is that the user in question had one of the cavern layers connected to the surface (or to his fort somewhere) with only trap barriers.  The level connected had a magma-pipe somewhere that created a fully pathable rout to the magma forge.  Since the magma man had a routable path, he destroyed the forge and walked up into the fort.

Either way it certainly appears related to building destroyers.  Reason enough to move the magma somewhere else, really.

[Max™]

Huh, thought that was more commonly known.

Smelter/Kiln/Furnace:
Dig Channel Dig
Dig -- Dig -- Dig
Dig -- Dig -- Dig

Forge:
Dig -- Dig -- Dig
Dig -- Dig -- Channel
Dig -- Dig -- Dig

Then smooth it all and run a link under it, include bridges raising to the inside made of magma-safe materials if you're worried about building destroyers, but I've never had this happen once, and didn't even know magma men were building destroyers until this thread.

I'm just wondering how the AI can get so close to the safe layout but screw it up every time, with smelters on a pattern that would be safe with forges and forges on a layout that would be safe with smelters... baffling.

[utunnels]

Now I see the problem, I have a whole natural magma sea beneath my floor.
So basically I need to move my smelters/forges upstairs then food the previous room with magma?

[BoogieMan]

I've yet to had this happen to me, although I always install a floodgate which I close once my forges become active, and further down a magmasafe wall grate. And a fortification if there is time before the magma reaches the area.

[Max™]

Fortification won't help sadly once liquids get to 7/7 stuff goes through them like they aren't there, but you could smooth the wall near where you breach and just carve a fortification in it.