Self watering seed propagator / tray

This design has a capacity of 21 std industry 28x28mm plugs

Update(Feb23): design updated. Water bed increased to 6mm (from 5mm) and outer water ports increased to 7mm (from 5mm) to achieve more even water supply to central plugs.

The main aim of this propagator tray is to create a seedling tray that is self-watering and could be left for a good few days without attention, but that would not drown the developing root system. This is achieved by an inverted water reservoir (an old 65mm dia mineral water bottle will do). The base steps allow for a constant 4mm of water in the base of the tray, partial pressures deal with control of the inverted water bottle supply. A clear water bottle would allow you to check on reserves. The central spike gives stability and reduces spillage as the bottle is inverted. A 30mm int dia base is provided to further increase a recycled water bottle's stability (see vid and pictures - you don't need or want a threaded seal). The tray prints right way up and does not require supports.

< Demo video here: https://youtu.be/5ildijI4YXI >

There is only one water reservoir because there is an aqueduct system running around the edge of the seed tray (in the outer wall). All outer plugs are linked to this water course. When soil is in the plugs this further reduces surface tension and improves water distribution from the aqueduct.

There is a simple living-hinge basket insert to move seedlings when grown. It takes away minimal plug volume and is held to shape by the plug cavity. This basket allows good soil contact with the water and maintains irrigation.

In summary, partial pressures look after the water supply, gravity and capillary action look after the watering, all you need do is look after the printing (& eat the crop).

Printing notes: Walls optimised for a 0.4 noz. Use PETG at 40% hex fill (10% off-set) on a 0.15 layer. PETG is UV resistant & waterproof (improved further by setting perimeters=5), perfect for greenhouse use.