INTRO

The assembly of the neck was shown in the previous page (>> Page 11). This page shows the attachment of the head and jaw components.

These parts will complete the assembly of the 3D printed parts of the Techno-saurus, besides the controller which will be the subject of the next page.

When completed it will look like this (new parts coloured blue):

PARTS

List of components presented in this page:

• Short neck-rod (60)
• Lower jaw (61)
• Teeth (x2) (62)
• Lower fang, RHS (63)
• Lower fang, LHS (64)
• Upper jaw (65)
• Upper fang, RHS (66)
• Upper fang, LHS (67)
• Jaw lever (68)
• Eye (x2) (69)
• LDPE tubing 6mm OD, 4mm ID, (75mm)
• M4 Socket screw x 20mm (x1)
• M4 washers (x2)
• M3 Socket screws x 16mm (x2)
• M2.5 socket screws x 20mm (x2)
• M2.5 socket screws x 12mm (x2)
• M2.5 socket screws x 8mm (x2)
• M4 locknut (x1)
• M3 nut (x2)
• M2.5 nuts (x6)
• Self-tapping screws (x2)

Exploded views (new parts coloured blue).

ASSEMBLY

The parts are shown below as they are assembled:

The first part to attach is the lower jaw (61).

This is attached to the end of the front horizontal neck section (58) using two M3 socket screws x 16mm long and two captive M3 nuts, (orange arrows below)….

Next is to add the lower teeth (62).

The lower and upper teeth are the same. For best effect use a red filament for the base and then switch to white for the teeth. That is, monitor the 3D print until the red base has been completed and just as the printer starts on the teeth, switch to white.

For strength the seven teeth are all joined together.

As can be seen above some fine wisps of PLA will need to be removed with a sharp modelling knife / scalpel.

Two M2.5 x 12mm socket screws are used along with M2.5 nuts.

It is a good idea to run a 2.5mm drill bit through the holes to aid assembly. Once the teeth are in place in the recess and the screws are pushed through, the M2.5 nuts can be added as shown below:

The next thing to do is print off the lower fangs and attach these.

The right and left fangs (of both the upper and lower jaws) are mirror images of each other. The lower fangs differ from the upper ones slightly due to the different shapes of the upper and lower jaws.

These have an internal shape to slide over the teeth and the M2.5 fixing screws used to hold the teeth in place.

A simple push fit should hold them on but a small amount of silicone sealant can be used as a weak bonding agent to keep them seated (and this should still enable them to be removed in the event that they break).

The next step is to attach the short neck rod (60).

Nb due to the shape there is not much surface area to bond to the printer bed, so a strip of material has been added (shown in wireframe view above). Once printed out, just break it off as you would support material and sand / trim as required.

This attaches to the long neck rod (attached page 11) using a piece of OD 6mm polyethylene tubing 35mm long (red arrow below).

Next is the upper jaw (65):

To this is attached the jaw lever (68):

The jaw lever is attached with two M2.5 x 8mm socket screws and captive nuts. The jaw lever fits inside a recess in the upper jaw.

The teeth are the same design for the upper and lower jaws but the upper fangs have a slightly different shape.

The teeth and fangs are attached in the same way as for the lower jaw except 2 x 20mm, M2.5 screws are used.

(Nb in the image above the jaw lever (#68) has not yet been attached.

As with the lower jaw fangs the upper jaw fangs simply press onto the screws with a little silicone sealant.

Next join the upper jaw assembly to the lugs on the front horizontal neck section (#58) and lower jaw (#61) using an M4 x 20mm socket screw, two washers and an M4 locknut.

The M4 locknut is held captive in a recess:

Tighten the locknut to draw it into the recess and then release it a half turn or so to allow the top jaw to rotate

It should now be attached and should move freely.

Join the short and long neck rods with 40mm of 6mm OD polyethylene tubing. This is a friction-fit. The tubing acts as a kind of ‘live hinge’. Some adjustment is possible (with both lengths of flexible tubing) by modifying how far the plastic rods are pushed in at each end.

The device should now work. Test to make sure the jaws clamp shut correctly.

The eyes (#69) are the same and are on short stalks. They are printed together and are then snapped off.

As can be seen above some wisps of PLA need to be cleaned off.

The eyes are pressed into place with a dab of superglue.

The completed head / jaws assembly is shown below:

It should now look like this*…

(*See note below about the spring on the top jaw)

This completes the assembly of the Techno-saurus, except for the controller and final wiring up. The image below is an exploded view of all the 3D printed parts and fasteners that have so far been used.

Additional part….

On the early prototypes that were cut from sheet material the upper jaw opened when the head/neck parts were retracted but on this version it was found that a little help was needed with a spring as shown below

Extension spring.

To attach this, use two self-tapping screws. Drill a 2.5mm hole in the upper jaw and the horizontal neck section as shown above and attach the spring. This should be done when the mouth is open. Ideally the spring should be under slight tension when the jaws are fully open, that is not slack. Tip: drill and attach one end first to the jaw and then mark where the second hole should be on the neck.

The next page is the assembly of the controller and the final wiring up