When should I start crafting?
As soon as you are rolling Refined and Epic objects faster than your placement limit can use them.
Mid-game
Rolling has a ceiling. Crafting is how you get past it, and it is the only realistic route to a Galaxy object.
Updated

The tier-up recipe consumes ten Refined and twenty Epic objects and returns one Legendary. It hands back a Wooden Tesla 52% of the time — an object that is a tiny fraction of a percent from the roll table.
Once you are producing surplus Refined and Epic objects faster than you can place them, every one you do not craft with is wasted.
| Result | Chance |
|---|---|
| Wooden Tesla | 52% |
| Rusty Mortar | 26% |
| Metal Spear Barrel | 6% |
| Rusty Trap | 6% |
| Slime Cannon | 5% |
| Metal Block | 5% |
Beyond the tier-up recipe, the machine holds recipes that consume a relic — Crooked Skull, Burger, Barbell, Wizard Hat and Soda. Each produces a specific object rather than a random one, and each rolls a mutation on top.
Heavy Harpoon is the odd one out on mutation odds: 88% plain, 11% Shiny, 1% Galaxy. The others observed so far use 92/7/1.

Every relic recipe rolls a mutation: usually 92% plain, 7% Shiny and 1% Galaxy. A flat 1% on a craft you were making anyway is far better than hunting a Galaxy through the roll table.
Given a Galaxy object was measured at 10.5x the health of its plain version and reads a full tier higher, that 1% is the most valuable percentage in the game.

Reinforced Cannon wants five Shiny Basic Cannons, not five random Shiny objects. Wizard Tower wants fifteen Witch Brew. Those recipes force you to unlock Shiny rolls and to keep specific objects in inventory instead of selling or placing them.

Stop placing every Refined and Epic object you roll. The recipes want them in stacks of ten and twenty, and a Mythic recipe wants twenty Mythics. Storage is what turns rolls into progress at this stage.
Also bank Witch Brew and Shiny Basic Cannon once you see those recipes on the machine — they are bottlenecks even when you are swimming in generic rarities.
The machine counts 21 recipes and six are confirmed with full tables on the crafting page. Wave gates exist at wave 75 and wave 225 for recipes whose names were not readable. This guide does not invent those recipes.
FAQ
As soon as you are rolling Refined and Epic objects faster than your placement limit can use them.
We do not know. They are consumed by recipes, but no relic drop appeared in roughly two hours of recordings from ten players, so we are not going to state a source.
On the Crafting page of this site — each verified recipe includes the percentages the game prints and a screenshot when we have one.