El preformado termina antes del formado.

Because del is the mandatory contraction of de + el.

• antes de el formado → incorrect
• antes del formado → correct

This contraction happens whenever de is followed by the masculine singular article el.

Compare:

• del formado = de + el formado
• de la pieza = no contraction, because la does not contract

Because antes normally needs de before a noun.

So the pattern is:

• antes de + noun
• antes de + infinitive
• antes de que + clause

In this sentence, formado is being used like a noun, so you need de:

• antes del formado = before the forming/forming stage

Without de, the sentence would be ungrammatical.

Here they are being used as nouns, even though they come from participle forms.

In technical or industrial Spanish, it is very common to turn process names into nouns like this:

• el preformado
• el formado
• el sellado
• el laminado

So in this sentence, preformado and formado do not mean preformed and formed as adjectives describing something. They mean the preforming process and the forming process.

Because they are treated as specific named processes or stages, and in Spanish those often take the definite article.

So:

• el preformado = the preforming stage/process
• el formado = the forming stage/process

Spanish uses the definite article more often than English with abstract nouns, process names, and stage names.

Termina is the third-person singular present indicative of terminar.

Here it agrees with el preformado, which is singular:

• El preformado termina...

It can often be translated as:

• ends
• finishes

In technical writing, the Spanish present tense is often used for general facts or process descriptions.

Because the subject is singular: el preformado.

The verb must agree with the subject:

• El preformado termina = singular
• Los preformados terminan = plural

Even though two process names appear in the sentence, only el preformado is the subject of the verb. del formado is just part of the time expression after antes de.

Not in this sentence as it stands.

Use antes de when what follows is a noun or an infinitive:

• antes del formado
• antes de formar

Use antes de que when what follows is a conjugated verb clause:

• antes de que empiece el formado
• antes de que termine el formado

So antes del formado is correct because formado here is a noun.

In isolation, formado can be an adjective or participle, but in this sentence it is most naturally read as a noun, because it follows the article el and appears after antes de as the name of a process.

If it were adjectival, you would normally expect it to describe another noun:

• el material formado
• la pieza formada

But here we just have el formado, which strongly suggests a nominalized technical term: the forming process/stage.

It is normal in technical or industrial contexts. It is built from:

• prefix pre- = before
• formado = forming / formed

So preformado refers to a preliminary forming stage or preforming process.

A native speaker may not use it often in everyday conversation, but in manufacturing, engineering, or process documentation it sounds perfectly natural.

Often yes, especially if you mean finishes/ends in a general sense:

• El preformado acaba antes del formado.

That said, termina usually sounds a bit more neutral and standard in technical descriptions. Acaba can sometimes feel slightly more conversational, depending on context.

So in a process description, termina is a very natural choice.

Because this is a straightforward Spanish sentence with the usual order:

• Subject: El preformado
• Verb: termina
• Time relation / complement: antes del formado

Spanish often allows more flexible word order than English, but in technical statements the most neutral pattern is usually this simple subject + verb + complement structure.

No. Del only comes from de + el.

If the noun were feminine, you would use de la:

• antes de la fase final
• antes de la formación

So:

• del = de + el
• de la = no contraction