Learn Hardcore Finnish: Hän aikoo valmistua insinööriksi ensi keväänä. - She/He plans to graduate as an engineer next spring.

In Hän aikoo valmistua insinööriksi ensi keväänä, the word ensi (next) and keväänä (in spring) already show that this is in the future, so present tense is enough.

So:

Hän aikoo… = He/She intends / is going to…
The future meaning comes from context, not from a special tense.

What exactly does aikoa mean? Is it the same as English will or going to?

Aikoa means “to intend, to plan (to do something)”. It expresses a deliberate intention, not just a future event.

Rough English equivalents:

Hän aikoo valmistua…
= He/She intends to graduate…
= He/She is planning to graduate…
= He/She is going to graduate… (with a strong sense of intention)

Unlike English will, aikoa always carries an idea of plan/intention, not just neutral future time.

Some examples:

Aion opiskella tänä iltana. – I intend to study tonight.
Aiotko tulla mukaan? – Are you planning to come along?

Could we just say Hän valmistuu insinööriksi ensi keväänä without aikoo? What is the difference?

Yes, Hän valmistuu insinööriksi ensi keväänä is grammatically correct and natural.

Difference in nuance:

Hän valmistuu insinööriksi ensi keväänä.
= He/She will graduate as an engineer next spring.
→ Neutral statement about a scheduled/expected fact.
Hän aikoo valmistua insinööriksi ensi keväänä.
= He/She is planning to graduate as an engineer next spring.
→ Emphasises his/her intention or plan, not just the fact.

So aikoa + infinitive highlights the person’s own decision/goal.

What does valmistua mean, and how is it different from valmistaa?

These two look similar but are different verbs:

valmistua (intransitive)
1. to graduate / qualify (from a school, in a profession)
2. to be finished / to be completed (as a process finishes)
valmistaa (transitive)
1. to prepare, make (something)
2. to manufacture, produce

Examples:

Hän valmistuu insinööriksi. – He/She graduates as an engineer.
Kakku valmistuu pian. – The cake will be ready soon.

vs.

Hän valmistaa kakun. – He/She bakes/makes a cake.
Tehdas valmistaa autoja. – The factory manufactures cars.

In your sentence, valmistua is about finishing studies and qualifying in a profession.

Why is insinööriksi in the translative case (-ksi) instead of just insinööri?

The ending -ksi is the translative case, and one of its main uses is to show a change of state or role – what something becomes.

Here it marks the resulting profession after graduating:

valmistua insinööriksi
literally: to graduate into an engineer
meaning: to qualify as an engineer

Other examples of translative for professions/roles:

Valmistuin lääkäriksi. – I graduated as a doctor.
Hän valittiin puheenjohtajaksi. – He/She was chosen as chairperson.
Kasvoin aikuiseksi. – I grew up to be an adult.

So insinööriksi tells us what he/she will be after graduating.

Could we say insinöörinä instead of insinööriksi? What would be the difference?

Insinöörinä is the essive case (-na/-nä), which often expresses being in a temporary role or state: as, in the capacity of.

Hän työskentelee insinöörinä. – He/She works as an engineer.
Puhun sinulle ystävänä. – I’m talking to you as a friend.

In your sentence we are not talking about working as something, but becoming something as a result of graduation. That’s why the translative (insinööriksi) is correct:

valmistua insinööriksi – to graduate/qualify as an engineer (become)
työskennellä insinöörinä – to work as an engineer (already be)

So insinööriksi is the natural and idiomatic choice here.

What cases does valmistua normally take? How do you say “graduate from X as Y”?

With valmistua in the sense to graduate, there are two very common patterns:

From where / in what field → usually elative (-sta/-stä)
As what / into what profession → translative (-ksi)

Examples:

valmistua yliopistosta – to graduate from university
valmistua ammattikoulusta – to graduate from vocational school
valmistua insinööriksi – to graduate as an engineer
valmistua opettajaksi – to graduate as a teacher

You can also combine them:

Hän aikoo valmistua insinööriksi yliopistosta ensi keväänä.
He/She intends to graduate as an engineer from (the) university next spring.

Does hän mean he or she? How do you know the gender?

Hän is a gender‑neutral third person singular pronoun. It covers both:

he
she

Finnish does not mark grammatical gender in pronouns (or nouns or adjectives). So:

Hän aikoo valmistua insinööriksi ensi keväänä.
Could mean either
→ He is going to graduate as an engineer next spring.
→ She is going to graduate as an engineer next spring.

If you need to know the gender, you rely on context, not on the pronoun itself.

What is going on in ensi keväänä? Why this form, and what case is keväänä?

Ensi keväänä = “next spring”.

Breakdown:

ensi = next (used specifically with time words, like ensi viikolla – next week)
kevät = spring (basic form)
keväänä = in (the) spring in the essive case (-na/-nä)

So keväänä is essive singular. In time expressions, the essive case often means “at that time / during that period”:

Ensi kesänä – next summer
Viime vuonna – last year
Tänä iltana – this evening

You might also see keväällä (adessive case -lla), e.g. keväällä = in (the) spring (during springtime), but ensi keväänä is the standard way to say next spring.

Can the word order change? For example, can we say Ensi keväänä hän aikoo valmistua insinööriksi?

Yes, Finnish word order is relatively flexible, and all of these are possible:

Hän aikoo valmistua insinööriksi ensi keväänä.
Ensi keväänä hän aikoo valmistua insinööriksi.
Hän aikoo ensi keväänä valmistua insinööriksi.

The basic information doesn’t change. What changes slightly is the emphasis:

Starting with Ensi keväänä… puts more focus on the time.
Keeping Hän first feels like a more neutral, default order.

All of them are acceptable and natural in the right context.

Why is it aikoo and not aikoa in the sentence? How is aikoa conjugated?

Aikoa is the dictionary (infinitive) form. In the sentence we need 3rd person singular present, which is aikoo.

Conjugation of aikoa (present tense):

minä aion – I intend
sinä aiot – you intend (sg)
hän aikoo – he/she intends
me aiomme – we intend
te aiotte – you intend (pl)
he aikovat – they intend

So in your sentence:

Hän (he/she) → aikoo (3rd person singular)
valmistua stays in the infinitive, because it’s the verb that aikoo governs:
aikoa + infinitive = to intend to do X

Is valmistua insinööriksi the usual way to say “become an engineer”? How is it different from tulla insinööriksi?

For graduating into a profession, valmistua insinööriksi is the most natural and idiomatic expression:

Hän aikoo valmistua insinööriksi.
→ He/She intends to complete a formal course of study and qualify as an engineer.

You can say tulla insinööriksi (to become an engineer), but:

tulla insinööriksi is more general: becoming an engineer by any path.
valmistua insinööriksi specifically refers to graduating / qualifying through education.

So in the context of education and graduation, valmistua insinööriksi is the natural choice.