Vacuum Fiber Molding (VFM) Machine for Creating Liquid Crystal Elastomer Actuators

Liquid Crystal Elastomers (LCEs) are a new type of shape-changing actuator for Soft Robotics which are programmable and reversible. When activated by heat or light, LCEs generate a molecular-level structural change, resulting in a shape-change. We introduce a novel rapid prototyping approach for thermo-responsive LCE fiber actuators based on vacuum molding extrusion.

This Instructables guides you through the steps of making a Vacuum Fiber Molding (VFM) machine, a tool for soft roboticists to design and iterate LCE actuators rapidly. The VFM machine allows fabricating these LCE actuators in different shapes using custom molds. The VFM machine is designed for easy use in a lab and can be made using widely accessible tools and materials.

Tools needed:

-Laser cutter

-3D printer

-Screwdriver

-Glass drill

-superglue

-hot glue

-wirestrippers

Parts needed:

-5mm perspex

-Glass pane +/- 10x15cm (max 2 mm thick)

-Fan guard +/- 9x9cm

-XH-W1209 thermostat

-Female DC Jack

-12V 3 amp powersupply

-Regular 3D printer heater block with M6 thread

-6mm heater cartridge

-1/2" xM24 air valve

-1/2" coupling

-1/2" hose connector

-Linear bearing SCS8UU

-8mm by 235mm metal rod

-8mm rail support

-Spring 10x15mm (4x)

-Tensionspring 5x15mm

-Neodymium magnet 10x2mm (5x)

-Heat sink +/- 1x1cm

-Breadboard +/- 10x30x2mm

-felt

-zipties

-Nylon Bolt M3x8 (4)

-Bolt M3x20 (28x)

-Bolt M3x60 (6x)

-Bolt M3x25 (4x)

-Bolt M3x8 (4x)

-Spacer M3x20 (4x)

-M3 nut (44x)

-M3x10 Nylon spacer (2)

-M3x20 metal spacer (4x)

-Bolt M5x20 (4x)

-M5 nut (4x)

-Coach bolt M6x60 (4x)

-Bolt M6x12

-M6 nut (4x)

-Silicone

Lasercut the 3 DXF files out of 5 mm perspex (or any other 5mm thick material of choice).

Use 15 M3x20 bolts and nuts to secure the two perspex base plates together (see pictures for reference of placement). Then glue a stack of 2 magnets in the two holes on top of the frame as shown in the last two pictures.

Use superglue to glue the parts of the thermostat box together as indicated on the schematic.

Use superglue to to attach the thermostat box in the base frame at an angle, make sure before glueing in place that the cover of the thermostat box can be easily put in place and removed.

Glue the parts of the heating element cover as indicated on the schematic.

First drill a 6mm hole in the centre of the heat sink. Then, cut a piece of breadboard to about 30 by 16 mm. in the bottom of the breadboard two 3 mm holes need to be drilled, use the holes in the heating element cover as a guide to drill the holes. Then drill another 6 mm hole on the top of the breadboard. Now use the nylon spacers and bolts to assemble the heating element, heat sink and breadboard to the perspex cover. Optionally another heatsink can be placed on top of the breadboard.

Glue the parts of the slider in place, then screw the SCS8UU in place using four M3x25 bolts and nuts. Glue a magnet to the bottom of the slider, also cut and glue four pieces of felt to the legs of the slider.

Connect the heating element to the slider using the 4 plexiglas arms and M3x60 and M3x20 nuts and bolts as seen on the images.

Slide the 8mm rod through the linear bearing and screw the rail support in place at the ends of the rod. Then attach the rail support to the corners of the plexiglass frame using 4 M5 nuts and bolts

Solder the DC Female jack to the contacts on the bottom side of the thermostat. Then bridge the K1 and 12v by soldering a wire between the terminals on the bottom of the thermostat. The wires of the heater cartridge can be screwed in the outer left and right screw terminals of the thermostat.

First use 4 M3x20 bolts and nuts to screw the thermostat in the perspex box. Then pull the cables of the heater cartridge and thermometer though the holes in the frame and insert the heater cartridge and thermometer in the heater block. When everything is in place use zipties to keep the cables in place. Make sure to keep enough cable length to allow the slider to move from left to right.

Attach the fan guard to shield the heating element using the M3x20 spacers and M3x8 bolts. The legs of the fan guard might need some bending to fit in place depending on the type of fan guard.

Assemble the air valve, connector and hose connector as seen on the picture, and glue the air valve flush with the back of the perspex frame. Then, drill a hole in the glass pane using a specialized glass drill bit. The hole needs to be marked at the top of the inside of the air valve while the glass pane covers both the air valve and the square hole of the the frame (see second picture). Afterwards the glass pane can be glued to the perspex frame, do this by adding a thick ring of glue on the perspex around the air valve. Make sure to use a sufficient amount of glue making the seal airtight.

Screw the two larger plates of the clamp together using 6 M3x20 bolts and nuts. Then glue the 2 smaller plates together and on the two back plates. The clamp can then be screwed in place using the coach bolts, springs and nuts (see second picture)

Now it is time to create your desired fibre shape mold. Since the molds are custom and cast in silicone, a negative needs to be 3d designed, 3D printed and then cast in silicone. SLA printing is recommended for higher resolution. However, regular FDM printing is already sufficient. Attached are three example STL's to experiment with or to base new designs on.

First image: SLA printed negative of curl/hook fiber

Second image: silicone fiber mold casted from said negative

Your Vacuum Fiber Molding machine is now ready for use!