How does Assembly-Rig work? Can they summon a 3 token every turn?

How Assembly Rig Works

Assembly Rig is a Gear card with the following activated ability:

"[1] [C], Recycle a unit from your trash, [T]: Play a 3 [S] Mech unit token to your base."

To activate this ability, you must pay all three costs simultaneously:

1. [1] [C]: Pay 1 energy and 1 power of the card's domain (Fury).
2. Recycle a unit from your trash: You must choose one unit card from your trash and move it to the bottom of your Main Deck (Rule 403.1).
3. [T]: Exhaust the Assembly Rig.

Because this is an activated ability, it uses the chain (Rule 370.2). Once the costs are paid and the ability is on the chain, your opponent has an opportunity to respond. If it resolves, you play a 3 [S] Mech unit token into your base.

Can you summon a 3 [S] Mech unit token every turn?

Yes, provided you can consistently pay the costs. There is no "once per turn" restriction on the card's text. However, you are limited by the following factors:

• Resource Availability: You must have the required energy and a Fury power available each time you wish to activate it.
• Trash Availability: You must have at least one unit card in your trash to pay the "Recycle" cost. If your trash is empty, you cannot pay the cost, and therefore cannot activate the ability (Rule 403.3).
• Ready Status: Because the ability requires you to exhaust the Assembly Rig ([T]), you can only activate it once per turn unless you have a way to "ready" the Gear to activate it again.

Important Rules References:

• Rule 403 (Recycle): Recycling is the action of taking one or more cards from a specific zone (in this case, your trash) and putting them on the bottom of the corresponding deck (your Main Deck). When listed as a cost, the action must be able to be completed in full for the cost to be paid.
• Rule 370.2 (Activated Abilities): Activated abilities use the chain, meaning they can be responded to by your opponent.
• Rule 179.1.d (Tokens): The 3 [S] Mech unit token is a unit. It enters play exhausted (as is standard for units played from hand/effects unless otherwise specified) and follows all rules for units.

Note: I could not fully verify this ruling against the retrieved rules.