What to check, and when

The G1 has no service schedule, and no part is replaced on a timer. You replace something when it stops doing its job, and the machine is fairly loud about when that is. A checklist of parts to swap by date would cost you working parts and find nothing.

What follows is the short list of things that genuinely are routine, and then the much longer list of things to act on only when they happen.

Genuinely routine

Three moving systems and one filter. Everything else waits for a symptom.

What	How often	Why this one is on a clock
Linear rails — oil the carriages	Every 3–6 months, or when motion feels rough	Pellet dust works into the carriages. Lubricating early wastes nothing, so the interval is a reminder rather than a rule — see Lubricating linear rails
Z lead screws — solid grease	Every ~4 months, or as soon as they get noisy	Different lubricant from the rails: grease, not oil — see Z lead screws
Belts — tension and condition	Every 6–12 months	Tension by feel, and look at the cords rather than the teeth: fraying is the failure mode — see Belts and pulleys
Feeding filter — clean it	More often with recycled or stringy material	It is the one part in the feed path that reliably clogs — see Vacuum pump

Do the lubrication by feel, not by date

Turn the printer off and move the head by hand along each axis. It should be smooth, with only the even drag of the motor. Roughness, a sticking point or a grinding sound means it needs oil now, whatever the calendar says — and a machine that passes the test does not need it yet.

Before every print

Seconds, not minutes, and each one prevents a specific failure.

• The bed is clean — no debris, no residue where the part goes
• Nothing hanging off the nozzle. A hardened blob under the tip stops the probe reaching the bed, and the Z axis keeps driving down looking for contact — see Z lead screws
• The guillotine on the dryer is open. Closed, it looks exactly like a feeding failure: the vacuum cycles, nothing arrives — see Starting the dryer
• The feed line has no dip in it — pellets settle in any descending section until it plugs — see Corrugated tube
• Enough material in the dryer for the job, and the dryer still running

After something happens

This is where most of the machine lives. Nothing here is scheduled.

When	What to do
You changed the nozzle	Re-level and redo the Z offset. A different nozzle sits at a different height. Check Rotation Volume too if the diameter changed
You moved the machine	Run BED_LEVEL again. Check every connector — vibration loosens plugs — and see Transporting the G1
You changed material or colour	Purge properly, and empty the whole feed path, not just the hopper — see Material change and purge
The material was contaminated by the last one	Clean the hopper out. That is the one case that needs it — see Hopper cleaning
You ran powder or liquid masterbatch	The auger needs cleaning; otherwise it does not
Motion got noisy or rough	Oil the rails, grease the screws, look at the belt cords
Extrusion went black-flecked at low flow	Carbonised residue is coming out of the nozzle. Change it and purge — but there is no kilogram interval at which to do this pre-emptively, see Black splashes
The first layer stopped being right	Z offset first, then the bed surface

What never needs doing

Worth stating, because each of these gets done anyway and costs something.

• PID tuning. Never, on any zone or the bed. The bed is watermark control and the zones are factory set. A zone that will not hold temperature has a physical fault — see Heater band
• Replacing a nozzle on a schedule. There is no interval. Symptoms only
• Replacing a thermistor because a zone reads wrong. It is the wiring, essentially always — see Temperature sensor disconnected
• Replacing the E0 stepper. It has never failed in the field. If the screw will not turn, the fault is upstream — see Extruder driver and 55V step-up
• Throwing away clumped pellets. Drying does not degrade the polymer. Break the clumps apart and use them — see Starting the dryer

Check the kit before ordering

A new machine ships spare thermistors and a spare Z probe switch in the tools and screws box, under Spare Parts. Those are the two parts the troubleshooting notes send people to support for. Look there first — see Frame.

Printed parts you can make yourself: Printed spare parts.

Related notes

• Lubricating linear rails
• Hopper cleaning
• Nozzle replacement
• Material change and purge
• Transporting the G1
• Error messages — when the machine tells you instead