Nuts & Volts - July 2004

Personal Robotics

Plastruct Bondene

Squadron putty: This is useful for filling gaps if you want to paint your creation. Do not build up huge volumes. Fill large gaps with thin, styrene pieces and then use the putty in a thin veneer. Thick sections of putty will crack and they take a long time to dry. The green is for use on military miniatures, while the white is a neutral color.

Epoxy: Five minute epoxy is good if you need a quick joint, but,

Squadron Putty

for ultimate strength, I like JB Weld or one hour cure epoxy. Be warned that epoxy will flow and JB Weld is attracted to magnetic fields. You can strengthen joints with other materials, like thread or even cotton. Cotton also helps keep epoxy contained.

Thick and thin Cyanoacrylate adhesive and accelerator: Special care must be taken with Cyanoacrylates. Urban legend has it that they were developed by the military as a chemical warfare

agent, to be squirted all over soldiers and chemically formulated to bond to flesh. What I do know is that they are used in surgery and, this being the case, gluing stuff to yourself qualifies as a major bummer. I can only imagine the horror of gluing your eyes.

That being said, they are very convenient and remarkably strong. Thin formulations allow you to use capillary action to bond large areas together and thick formulations have gap-filling properties. The accelerator will cause instant bonding.

Despite its convenience, I rarely use it for construction, saving it for repairs. The one exception is gluing servo horns to flat surfaces. When I use accelerator, I do not spray it everywhere, but, instead, dip a thin stick into it and touch that to the joint.

Styrene adhesive and needle applicator: Plastruct Bondene for Styrene and ABS is my preferred method of bonding Styrene plastics. I like to use a needle applicator and allow capillary action to carry the adhesive through the joint. Care must be taken not to touch your needle applicator to the glued joint, thereby clogging your applicator with melted Styrene.

F o r

E l e c t r o n i c s

NUTS & VOLTS E v e r y t h i n g

Basic gluing wisdom: Make sure your components are clean. Contamination can foul or weaken bonded joints. Epoxies work by making a molecular intermediary between materials, while Styrene adhesives actually melt the materials with solvents, creating a sort of “weld.”

Some plastics are cast with mold release or other lubricants in them or exhibit other “slippery” properties; you will likely have to resort to mechanical fasteners to join to them. This is often the case with the gearboxes and mechanical linkages of toys and no amount of surface preparation can help you.