Glossary¶

The words this site uses in a particular way, and the acronyms it does not spell out every time. Acronyms expand on hover wherever they appear.

The machine¶

Bench reference: The one machine every measurement on this site was taken on, unless the page says otherwise: a Glowforge Basic built in late 2017. A measurement is never a specification (The bench reference).
Head: The print head: the lens and its carriage, the air assist, the beam detector, the accelerometer, and a small microcontroller that answers over I²C. Its presence is that microcontroller answering, never the head-attention line.
Lid switches, interlock, button: The three physical inputs the hardware safing chain reads. Both lid switches in series are the lid term; the interlock is the remote lockout loop, brought out on a Pro; the button is the operator's consent (The safing chain).
OK_2_FIRE: The hardware chain's verdict that the machine may emit. FIRE ∧ OK_2_FIRE is LASER_ON, and LASER_ON is never a bare processor pin.
The 40 V rail: The motor rail that feeds the stepper drivers. It stays up while the machine is on, because the drivers can latch into an unserviceable state on a glitch (Motion hardware).

Pulse file: A precomputed byte stream, one byte per machine tick, that the factory service sends and the machine plays. It opens with a header of 4-character tags (Factory firmware).
Machine tick: The fixed rate at which the hardware timer consumes pulse bytes. Speed is the density of step bits across bytes, never a change of tick.
Ring: The pulse buffer in reserved memory that the playback engine reads from. GRBL mode streams into a small window of it; cloud mode preloads (The step engine).
Underrun: The ring ran dry while a program was playing. Motion stops instantly and the position is no longer trusted.
Backtrack: Replaying the ring backward from a controlled stop, with the beam off, so a resume can lead back in over ground already cut. Bounded by the retained history the writer leaves behind the play head.
Anchor: The reference that turns the kernel's step counters into machine coordinates, written at a completed homing. Anything that invalidates position drops it.
Envelope: The operating limits a job carries in its pulse header: fan duties, temperature ceilings, tach floors, accelerometer thresholds. A header can tighten a local limit for its job and never loosen one.

Armed window: The per-job period in which the beam may fire. It opens only on the operator's physical button press and closes at program end, on a sender change, after the disarm grace, or on any fault (The armed window).
The latch: The kernel's laser lockout. Locked by default, and every close of the pulse device locks it again. It puts the fire line beyond the reach of the playback engine.
Fire gate: A condition that blocks emission without stopping the machine: a coolant fault, an over-temperature, a fan below its floor, a flame or crash reading.
Density: The dose model. Every pulse fires at full power and the commanded level sets how many ticks of each period fire, so no level lands in the tube's dead band (The laser).
Verdict: The cooling engine's published answer to "may the laser fire right now", which the running controller reads and enforces. A missing or stale verdict is a bad verdict (The verdict file).
Hunt: The lens focus sequence the Glowforge service drives. It references Z against the hall sensor in the head.

Broker: The daemon's single, exclusive hold on the pulse device. Controllers inherit the file descriptor, so a handover never closes the device or cycles the motor rail (Pulse-device ownership).
Dead man: A hold that safes the machine when its holder disappears. The kernel's fires on the final close of the pulse device; the supervisor covers a controller's death; the cooling engine covers a controller's hang.
Slot: One of the two 200 MiB root filesystem partitions on the internal storage. ForgeFIRM installs into the one that is not running, and a boot selection chooses between them (Boot and storage).
Pin: The exact source revision at which a recipe fetches a component. A commit changes nothing on a machine until its pin moves (Release flow).
Campaign: One run of the release acceptance catalog against one image. A release is signed only when a campaign authorizes the rootfs it was built from (Acceptance).
Fingerprint: The hash that decides whether a recorded test result still applies to a new build: the files the test covers, the platform identity, and the test's own implementation.
Drill: A bench procedure run against a real machine, usually with the operator present.
Null sink: The driver built without a pulse device, so the real core, planner and stream code run on a workstation and the laser path can be tested without hardware (Test).