Filling the Cooling Circuit

Required Tools & Equipment
  • Deionized¬†Water, 2L
  • A coin or large flathead driver
  • A small flathead screwdriver
  • Wire Cutters
  • Jug, pitcher, bottle, or otherwise similar container for coolant

1 Preparing the Coolant

Deionized water, commonly referred to as DI water, is required to fill the cooling circuit. AON3D does not provide DI water with each machine and it is up to the end user to purchase the water.


Deionized water and distilled water are not the same product, please ensure that only deionized water is used to mix the coolant.

Do not use regular tap water or any other coolant mixture not authorized by AON3D. With improper cooling fluid, potential failure mechanisms include: galvanic corrosion, algal growth, scale formation, and polymeric degradation. Any or all of these mechanisms will negatively affect the performance of the cooling system and can lead to catastrophic component failure.

AON3D recommends premixing the DI water and the entire bottle of coolant concentrate in a separate container (ideally a pitcher with a narrow lip for easy pouring). The ratio of DI water to coolant should be 9:1. The bottle of coolant provided with the AON-M2 is 100mm, so you should mix 1 bottle of coolant for every 1 L of DI water used.

1.1 Initial Gravity Fill

Start by opening the fill port of the pump reservoir with a coin or a large flathead driver. Using the included funnel, pour coolant into the circuit until the reservoir is almost filled to the top.


Pour the coolant at a slow and steady pace to ensure that the coolant mixture does not spill.

Pump Fill

Once filled, set the red speed controller dials, numbered from 1 to 5 and located on the rear face of the pump motors, to position 5 using a small flathead screwdriver. This allows the coolant to flow more quickly and more easily fills the coolant circuit.

Red dial indicators set to position 1.

1.2 Pump Fill

Let the pump run until the reservoir level goes down. Disconnect the power cord shown in the figure below to turn off the pumps. Proceed to fill the pump reservoir. The funnel should be removed from the fill port when not actively filling the pump to let the air easily escape from the system.

The pump power cord.


The coolant pumps are not intended to be run dry. Avoid having the pumps run when the reservoir level is low. The pumps will make a sound like ripping paper when the reservoir is too low. If this happens turn off the pump to let the air escape.

The pumps are most effective at driving air out of the system when the reservoir is near full before starting, so make sure to top up before you reconnect the pump power. If you find the pump is still unable to fill the circuit, cycling the pump power off and on a few times is effective at letting any air escape that is clogging the circuit.

1.3 Flush Out Remaining Bubbles

After about three cycles, there should be enough coolant in the circuit to achieve steady state flow. At this point, you no longer need to cycle the pump on and off - simply keep refilling the reservoir as necessary as the air continues to flush out of the circuit. 

Let the circuit run until no more bubbles are visible, top off the reservoir levels one last time, then replace the fill port cap, and return the red indicator dials to the 1 position before starting to print.

Air will continue to bleed from the system, so after the first ten (10) and fifty (50) hours of operation, remove the fill port cap and top up the reservoir with pure DI water or any remaining coolant.

1.4 Check the Coolant Reservoir

Checking the reservoir levels about once a month is recommended, as the coolant evaporates over time. If the coolant circuit lines at the back of the pump have bubbles running through them, please refill the resevoir at the back. The GIF below shows what it may look like when the coolant circuit is lacking coolant.

A coolant circuit that needs to be topped up.

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