Hand Doh Extruder

Using clay or derivatives there may be a requirement for lengths of a particular shape, say for decoration.

If this is simply a cylinder it could be rolled by hand.

However, for other elongated shapes hand forming is more variable, although if uniformity or consistency is what you seek than a mechanical option may be more efficient.

To this end a small extruder was created using readily available materials that are repurposed for a different task to that which they were originally intended.

M6 x 100 mm coach bolt with ~19 mm head.

M6 plain nut - Qty 3

M6 capped nut

M4 bolt 15 mm - Qty 2

M4 plain nut

Metal washer ~20 mm x M6 hole.

O ring 24 mm * 3.1 mm to fit tap connector.

O ring 26 mm * 3.1 mm to fit nut to hold shape plate.

Drawer or Cupboard Knob

Brass threaded blanking cap 15 mm dia.

Brass Compression reducer coupling 22 mm to 15 mm.

Brass Straight tap connector 15 mm.

Hole saw ~47 mm diameter.

Ruler

Fine tipped marker.

Spanners M4 & M6

Screwdrivers with ends appropriate for the bolts.

4 mm drill bit

Aluminium, PCB board or equivalent ~1.5 mm thick for shape plate(s), 25 x 25 mm square per design.

Selection of small drills and needle files to create shape plate designs.

Optional 3D printer to print custom or example shape plate designs.

The plumbing materials should be available from a hardware or plumbing merchants in brass or chrome compression fittings.

The extruder will require a handle for operation which is made primarily of perspex.

A hole saw is used to cut a 47 mm disc.

On the disc midway between the outer edge and the centre hole is made a 4 mm hole.

A rectangle is cut 73 mm long x 18 mm wide and three holes drilled 2 x 4 mm holes for the M4 bolts, one close to the edge for finger hold, one inline with the 4 mm hole on the disc. The other hole at 6 mm diameter aligns with the centre hole of the disc.

The 6 mm hole in the rectangle is aligned with the 6 mm hole in the disc and the 4 mm hole aligned and secured with an M4 nut and bolt passing through the hole in the rectangle and disc.

This two part option for the main part of the handle was chosen for addition strength and stability, a single part handle of similar strength could be substituted if required.

The knob (finger hold), is attached at the extreme end of the rectangle with an M4 bolt passing through the 4mm hole.

The handle is now complete.

The piston is made from a M6 coach bolt as this has a rounded top which fits into the 22 mm cavity of the reducer.

The coach bolt head and the retaining washer need to be <22 mm so as not to rub or scratch the inside of the reservoir.

The small gap around the perimeter needs to be filled with a flexible washer and this is held in place with a plain metal washer and M6 nut.

The flexible washer can be cut from a rubber inner tube, cushion flooring or a cork with ~22 mm diameter and a 6 mm hole in the centre. The washer should fit rubbing the sides of the cavity thereby reducing the likelyhood of material collecting behind the piston.

Pass the washer over the bolt followed by the plain metal washer and secure with a plain nut.

The blanking cap has to be modified to enable the piston to pass through it and hold the piston in place.

A 6mm hole is drilled in the centre of the cap and a M6 nut is fitted to align with the hole.

In this case the nut is soldered in place, alternatively it could be brazed or glued.

Brass fixings make soldering or brazing easier due to the abscence of chrome plating.

In order to align the nut with the end cap a bolt is partially screwed into the nut through the cap to hold it in place during soldering or gluing.

This dictates the pattern applied to the extruded length of clay.

Cut a blank disc to fit behind the large nut from aluminimum, pcb board or plastic etc. with 25 mm diameter.

Simply cut the required shape into the centre of the disc.

The larger the hole the shorter the extrusion.

As a variant to the single shape plate design a multi shape extrusion plate was also designed.

In this case a 22 mm blanking cap holds the shape plate via a nut in the centre enabling different shape patterns to be rotated in front of the extrusion aperture.

As an alternative the shape plate design could be produced by milling, laser cutting or 3D printing

CAD files for a couple of examples are included as a starting point.

Assembly and disassembly of the main body should only require hand adjustment.

If tools are required it may be worthwhile checking for burrs or damage to the threads in conjunction with a little lubrication. Plus assembling and disassembly a few times to smooth the threads.

First remove the 15 mm compatible nut from the reducer.

The straight tap connector is attached to the reducer at the matching 15 mm end with the screw on nut.

The end of the tap connector which will sit in the reducer may or may not come with a washer.

If a washer is required attach a 23 mm x 3.1 mm O ring to stablise the fitting and reduce the requirement to over tighten the nut enabling it to be secured by hand.

Next slide the piston into the reducer from the 22 mm fitting end as far as possible.

Screw the end cap containing the nut on to the end of the piston and tighten onto the tap connector.

Screw an M6 plain nut approximately 20 mm onto the piston.

Pass the 6 mm hole of the handle onto the threaded end of the piston up to the nut.

Tighten the handle in place with the M6 capped nut.

Adjust both M6 nuts to tighten the handle in place.

An Oring or washer (26 x 3.1 mm), is first placed in the 22 mm compatible fixing nut followed by the 25 mm shape plate and screwed to the reducer. This helps to prevent extrusion from the sides by creating a firm seal.

At this point assembly is complete.

Remove the nut containing the shape plate from the reduced and ensuring the piston is wound fully back.

Proceed to fill the cavity of the reduced with the material to be extruded (i.e. Clay).

Replace the large nut containing the shape plate.

Hold the extruder assembly in one hand and turn the handle with the other so that the piston moves forward forcing the material through the opening in the shape plate.

An alternative extruder was made using wholly 15 mm compatible compression fixings.

Same design considerations but on a slightly smaller scale.

A M6 X 100 mm bolt was used but the head requires reducing in diameter by grinding to fit.

The blanking cap was drilled with a 3 mm hole for a cylindrical extrusion.

Although designed as a hand extruder a support to enable bench mounting could be created but that's for another project.

Hope you found it of interest just to read or maybe even to construct.