What are the key factors to consider when choosing materials for your robot?

In my experience related to industrial robotics, weight balance is by sure one of the choice factor, even if often is a matter of compromises. Weight reduction of the arm structures is important expecialy for the ones far from the robot base (forearm and wrist), but motors and gearboxes are quite heavy too ... so just adopting light structure could be a very partial solution to the problem. Trying to put the components that can't be weight reduced very often forces to use complex / expensive trasmission in between the motors / gearboxes and the end of the robot axis. Using very light materials (i.e. composites) will increase dramatically the costs. That's why cast iron and aluminum castings are still the most used solutions.

In order to satisfy the structural needs, is fundamental to define the worst cases to be considered for the sizing of the components. The focus is on arm structures; motors and gearboxes are usually commercial specialized componentes. All the sizing must consider fatigue and shocks that could happen (we are not talking about a tank ... some common sense, please). Structural analysis is key: topological approach and/or the generative design can be a great help ... if only the load cases are defined in the proper way. Stifness is an important factor! Gearboxes are the main fonts of non-stifness, but a flappy structure could be a problen in obtainig good motion performances ... not always easy to reach with a clever motion control-loop.

In my experience related to industrial robotics thermal management is important only in a very limited application cases. By sure robots operating in foundry or inside a refrigerator will have specific needs, not only in the choiche of the arm material, but also in terms of cabling, lubricants, ... On board eletronics is a real problem only in few cases with high temperatures and/or high stressing working cycles. Adopting a cooling fan is usaually an effective approach. Operating temperature range must be specified in the technical info. Considering also some geographical factor is important not only for heat but for humidity as well. Robot arm could be (or not) far from the robot controller; this is another aspect to take in consideration.

There are plenty of norms about how to approach the design of machines with electronics on board; please consider they can vary according different Country. Electromagnetic compatibility is another important factor to be taken in consideration when approaching the design choiche in terms of cabling (isolation, shields, ...), connectors, on board electronics, motor transducers. It's not only a matter of safety and/or conductivity. Fatigue resistance of all the cabling and hoses is another important factor to design and test in order to give a product with the proper reliability ... that is absolutely key to reach the incredible MTBF in the magnitude of several thousand hours.

"Design to cost" is fundamental in all the fields, in robotics too. Avoid to use materials that are not really necessary for the application the robot is designed for. Exothic materials are cool, but usually not cheap and/or easy to produce anywhere. Take in account geographical constrains for the production ("design for manufacturing") because some materials could be a valid choice only in specific areas. Avoid to make choices that could mean heavy constrains in the purchasing, taking in consideration that putting multiple suppliers in competition is always useful.