Breakdown of Они берут ткань с собой на фабрику.
они
they
на
on, at / by (transport) / to (a place) / to (in answer to)
с
with (also со)
брать
to take (imperfective)
Questions & Answers about Они берут ткань с собой на фабрику.
Why do we use с собой (with themselves) instead of с ними (with them)?
Собой is the instrumental case of the reflexive pronoun себя. We use it here because the action reflects back to the subject of the sentence, Они (They). If you said с ними, it would mean they are taking the fabric with a completely different group of people, not with themselves.
Why is the preposition на used in на фабрику instead of в?
The noun фабрика (factory) is one of those traditional Russian locations that specifically requires the preposition на rather than в. Because the sentence shows motion toward a destination, на is followed by the accusative case (фабрику).
What case is ткань in, and why doesn't its ending change?
Ткань (fabric) is the direct object being taken, so it is in the accusative case. It is a feminine noun ending in a soft sign (a 3rd declension noun). For inanimate nouns in this group, the accusative form looks exactly the same as the dictionary (nominative) form.
The verb берут looks quite different from its infinitive. What is the infinitive form?