The prototype was intended to be an experiment for me to try and produce a professional chassis and outer shell for my future robot projects. I have had the shape of this robot in my head for a number of years and I have had it sketched and drawn in slightly different forms all throughout my various sketch books. The prototype is meant to look like an insect larva, which i hoped would be a fitting start to build a robot.
I have only completed the shell of the robot which turned out a lot better than I had hoped. I have added a large LED to the prototype to show the finished effect that I was hoping for. I had the idea to create this blog after I started this build so I do not have as many photos of the procedure as I would have preferred. Feel free to email me and ask any questions that you might have. Future robot builds that will use this method for the chassis will contain all photos that I have missed here.
The materials that I use in this build can get quite messy so I recommend that you perform them outside or in a workshop and also to wear gloves and a respirator. You could also build an Apartment Work Space Box to keep your workspace tidy.
Part 1: Foam Construction
- A block of dry grey florist foam (NOT the green wet type it is too soft and brittle)
- A knife or small hacksaw
- A Hand sized block of wood (your hand size)
- Very coarse sandpaper
- Paper printout or cut-out sketch of your lower robot chassis
- PVA glue
- Using the PVA glue, attach the outline of your chassis to the foam block (In the picture below I have sketched the robot outline onto the block to show where to attach).
- Using the knife or small hacksaw cut the outline of the chassis to remove the outside foam.
- Wrap your sandpaper around the wooden block to create a sanding block.
- Using the sanding block, carve out the shape of your robot (this will produce a lot of dust) by using back and forth gentle smooth strokes. You will need to know exactly how your robot looks like in your head while doing this.
- When getting into the finer details of your robot, use finer sandpaper. Fiberglass mat/cloth will not be able to enter small crevasses, cuts or sharp rounds so very fine details are not for this stage of the model.
- Continue to carve until you have your desired shape.
Part 2: Fiberglass coating
- Fiberglass mat or cloth
- Epoxy resin (Not Polyurethane Resin – this will melt the foam)
- Cheap brushes (throw away after use)
- Cardboard Toilet Roll
- Plastic mat (I used a large plastic bag)
- Gloves & respirator
- Mix the main epoxy resin to prepare for fiberglass mat/cloth
- Insert the cardboard toilet roll into the bottom of the model to keep it raised off the table surface.
- Lay down the plastic mat and secure the model on top using tape.
- Coat the foam model in epoxy to prime and strengthen the surface using a brush.
- Cut the fiberglass cloth into strips/squares.
- Wet the model surface with epoxy and begin to lay the fiberglass strips one at a time.
- Overlap the strips by half for each one laid.
- Apply epoxy in between strips and on the top of the strips.
- Allow epoxy to cure and dry.
- Once the fiberglass has completely cured, cut off the overhanging resin/fiberglass (I used a Dremel with the plastic rotary disc to cut the excess).
Part 3: Spray Coating
- A can of spray putty
- A spray can of High Gloss Black enamel paint
- Fine grit sand paper and wood block
- Working gloves and a respirator
- Epoxy resin
- Epoxy putty (Only if required)
- Using the fine grit sandpaper block rough over the whole shell to prime the fiberglass surface (Use strong working gloves so that you do not get any fiberglass in your fingers).
- Using a paper towel and some water, wipe away the dust and allow to dry completely.
- Using large back and forward sweeping motions spray the putty over the surface of the shell and allow to dry (check out you tube for how to spray paint to see how the technique should be done). You want the putty to fill the gaps in the cloth/weave of the fiberglass.
- Sand down the shell until smooth.
- Respray, sand and repeat until you have a smooth shell.
- Wipe down the shell with a paper towel and water and let dry.
- Using a spoon or something similar, carve out the inner foam and discard.
- Wash the inside of the shell with water to remove all loose foam and allow to dry thoroughly.
- Drill out any holes for sensors, actuators or lights.
- Sand down any rough or sharp edges.
- Mix epoxy resin and apply a coat to the inside of the shell and allow to cure.
- Begin spray coating your shell. You will need at least 5 coats in total. I sprayed, waited for 1 minute and sprayed again. I then let it dry for the night and repeated the next day, continue until you have at least 5 coats.
Once painting is complete your robot shell is ready.
To finish off the prototype I inserted a 20mm LED into the eye hole attached to a switch and battery. The prototype now functions as a small nightlight until I put something else inside.