What is a Soil Blocker, its a device that takes loose compost and turns it in to a self supporting block for seed sowing. This eliminates the need for sowing trays and pots.

In addition to creating a soil block the device creates a small pit in the top of the block into which the seed it to be placed.

Once the seedlings are growing they can be, complete with the soil block transferred to pots or garden all without disturbing the root system.

The process of designing and using a soil blocker will be the demonstrated within this project.

Supplies

BlocksCAD

3D Printer

Filament

Cura

Sanding paper/file

Modelling blade

Compost

Water

Step 1: Design

This particular design of soil blocker was created using BlocksCAD.

The first step was to decide on a shape for the container for simplicity of holding in the hand and 3d printing, as a result a cylinder was chosen.

Next was the compactor which needed to be comfortable in the hand and easy to hold.

This would be cylindrical as it needs to fit in to the container with the addition of 5 elongated cylinders formed in to the shape of a four leaf clover (the fifth cylinder fills the centre to add strength). The recesses allow the fingers to sit inside and improve the grip on top of this sits a spherical pommel which fits in to the palm of the hand.

In to the end of the compactor is fitted a pointed peg to make the pit in the soil block to accommodate the seed(s).

Dimensions:

Cylinder

Outer Diameter = 50 mm

Inside Diameter = 40 mm

Height = 50 mm

Compactor

Height = 75 mm

Width = 39 mm

Peg

Depth = 1 cm

Width maximum = 1 cm

Once the rendering process is complete an OBJ file is created which will be used in the slicer to create the Gcode file for 3D printing.

The 3d Printing files may also be found at YouMagine

soil_blocker.stl
Download

Step 2: Slicing

Using in this case Cura (or your preferred application), we load the previously created OBJ file.

At this stage the settings are adjusted to suit the printing requirements.

Printing settings used:

Layer Height = 0.15 mm

Infill Density = 25 %

Infill Pattern = Tri-Hexagon

Base Adhesion = Brim.

Size = 99.5 x 50.1 x 75.0 mm

Filament weight = 57 g

Filament length = 19 m

Print time 6 hr 27 min

Save the resulting Gcode file.

Step 3: 3D Printing

Load the Gcode file generated by your slicer into your 3D printer and initiate the printing process.

When printing is complete remove the brim this should peel off but may leave some material behind which can be remove with a knife, file or sanding paper to smooth.

The inner lip of the cylinder can act as an end stop for the compactor and helps to keep them together in storage. However, the absence of an inner lip either removed by choice or absent as a result of the printing process just means the compactor passes all the way through and allows the soil block to be ejected a little easier.

The edges of the peg hole and the part of the peg that sits in the hole will required some sanding to enable them to fit together. it's designed for snug fit so should not require any glue but a little can be applied to hold it in place if required

Step 4: Preparation

Now you have a completed soil blocker, so how do you make use of it.

You will need some suitable compost (a finer texture is preferred as it holds its form better and suitable nutrient composition for the type of plants to propagate), to create the soil blocks.

Apply water to the compost until it is very soggy.

Step 5: Filling

Fill the container to the top with the compost, it does not have to be perfectly flat a small hump is not a problem.

Step 6: Compacting

Place the compactor over the inner cylinder and align.

The bottom of the cylinder should be in contact with a flat surface during the compacting process to prevent it coming out.

Once aligned apply firm downward pressure to the compactor to compress the compost whilst holding the cylinder in place, you should see plenty of wafer being expelled. If there is little water ejected then the compost is too dry.

When the main 20 mm section of the compactor is just below the top level of the cylinder this is sufficient for a suitable soil block. With the bottom of the peg around the middle of the soil block.

If there is insufficient compost in the cylinder the bottom of the peg will sit at the very bottom of the block which is too low.

Step 7: Removal

Having compacted the compost, raise the bottom of the cylinder off the flat surface and continue to push the soil block out of the bottom of the cylinder. There should be a pit in the centre the of the block the depth of the peg in which seed(s) may be placed.

There is no need to pot the soil block until the seed(s) germinate, until then they can simply be kept on a tray.

Keep the soil blocks moist and do not over water or allow to dry out