Chain length should be selected such that [no comma!] ...

Ohne Artikel, da es um die Länge mehrerer Kettensegmente geht.

Oder:

The length of the individual chains should be chosen such that they are angled at no more than 60° toward each other.

(a) One chain: The length of the chain... / The chain length...

(b) Multiple chains, all of the same length: The length of the chains... / The chain length...

(c) Multiple chains of various lengths: The lengths of the chains... / The chain lengths...

Note that the second form doesn't distinguish between the first two cases, so I'd prefer the first form. I suppose one could use

(a) The chain's length...

(b) The chains' length...

(c) The chains' lengths...

but I find (b) a bit dubious.

As others have said, there should be no comma before that, and note codero's suggestion to use the more elegant formulation such that rather than in such a way that. I'd use the verb chosen rather than selected.

As for the original question, article or no article, I can't follow the reasoning behind codero's Ohne Artikel, da es um die Länge mehrerer Kettensegmente geht. Just because it's one of my cases (b) or (c) doesn't mean it shouldn't have a The at the beginning, though I agree in a way with HappyWarrior - it doesn't really matter. It just makes it more of a telegraphic style without the The - it doesn't change the meaning. Personally I prefer it with the The, but it should be consistent with the style used in the rest of the document.

Finally, I do not really understand what is meant by the last part of the sentence. Why is it a slope angle and not just an angle? How can chains be said to have a slope? Codero's formulation of this part of the sentence is an improvement over the OP, but simply the angle between the chains does not exceed 60° is how I'd phrase it (IIUC).

Concerning my rash dictum in #1, I tried to rationalize that a bit more in #4, but maybe I just like the "without article" version better because brevity seems to fit a technical context.

@ #6: Cordero's Vorschlag aus #1 mag sprachlich schöner sein, entfernt sich jedoch relativ stark vom Original.

Trotzdem danke!

you might want to use "the" if it preceded an adjective but would still be intelligible without it.

"...The overall / total / combined chain length..."

"...Overall / total / combined chain length..."

I believe in the endangered conceptional/abstract form (even if it sounds singular) where it can be used. So, I would write, "Chain length should be selected..." when the discussion refers to how the matter should generally be handled. No article. See #1.

If, OTOH, you are interested only in a particular case, then analysis like #6 is called for.

I'm not sure there's universal agreement with that distinction. See, e.g., https://english.stackexchange.com/questions/1...

In any case, depending on the type of chain, lengths may indeed come in discrete steps, depending on the number of chain links.