Best Materials for Prototyping Robotics

Prototyping is an essential step in the design and development of robotic components, offering numerous benefits such as reducing design risk, gathering user feedback, and accelerating the product development schedule. This article will guide you through:

• The benefits of prototyping in robotics
• Common materials used for robotic prototypes and their advantages
• Tips on selecting a reliable prototyping manufacturer
• Practical tips to keep your development goals on track

Benefits of Robotics Prototyping

Developing a prototype can add expense and/or time to robotic designs. However there are many significant advantages that come with prototyping that can make it well worth the added efforts. 

Risk Mitigation

Any time a novel design is being developed, there is risk with the design not working as intended. Prototyping allows the designers to test the feasibility in many ways such; confirming that the required motion can be performed, identifying critical tolerances and clearances, as well as many other design flaws and details that are easily missed when looking at a computer screen. Another benefit allowing risk reduction is the interaction the robot has with existing infrastructure. If the prototype causes the facility to shake, collides with another piece of machinery, or overloads certain pre-existing systems that aren’t easily changed, then the next prototype or final design can be changed during the design phase much easier than a retrofit.

Iterative Design Improvement

The ability to make rapid changes without worrying about aesthetics, manufacturing efficiency, or weight efficiency can allow designers to focus on the performance of the robot to improve functionality. A prototype of the robot can allow this creative freedom to make low risk changes. Especially with the quick turn-around of technologies like 3D printing or rapid sheet metal services like what SendCutSend offers, many iterations can be made quickly, allowing an improved design to be achieved through efficient iterations.  

Accelerate Development

Sometimes a particular feature or problem in a design keeps coming up as problematic or high risk. When this happens, a prototype can help answer questions and steer design decisions with real world testing data rather than potentially long and drawn out theories or analysis. This data gathering can actually reduce the overall schedule of a project, thus reducing development costs. Often time is money, so weigh the costs of paying employees to discuss a design decision for a week when a simple mechanism demonstration prototype could be built in a matter of hours.

User Feedback

Often there is no substitute for getting feedback from the end users of a device. Showing and/or letting the users operate a prototype is a fantastic way to gather important feedback that can steer future iterations of the design. Perhaps a feature is inconvenient, or an additional function or range of motion is required from a robot that wasn’t captured in the initial design requirements. Adding in a user evaluation of an early prototype can save a lot of time and effort, and will ultimately lead to a more successful product. 

Considerations For Choosing a Prototyping Manufacturer

Many factors go into selecting a manufacturer for prototype parts. Here are some things to consider.

• Intellectual Property Protection
  • Ensure the manufacturer protects your design and keeps the intellectual property secure.
• Supply Chain Reliability
  • Verify that the manufacturer has a reliable supply chain to avoid missed deadlines and project delays.
• Quality of Communication
  • Assess the communication quality with the manufacturer to ensure clear understanding and synchronized work schedules.
• Avoiding Inferior Suppliers
  • Be cautious of suppliers that might be cheaper but struggle in protecting intellectual property, maintaining reliable supply chains, and providing clear communication.

Fortunately, here at SendCutSend, we are proud to say your designs are securely stored and never shared outside the company, our supply chains are strong and reliable, and we pride ourselves on communicating clearly and on your schedule. Additionally, our turnaround times, which were already very fast, have recently been improved in most cases by multiple days. Our already low costs have been dropped by up to 20% while also further securing our supply chains by more than doubling our raw material inventory. SendCutSend is also cost effective, even for the small quantities often used in robotic prototyping, with minimum orders at just less than $39 (with free shipping included!)

What Materials Are Used to Make Robots? 

Metal

• Aluminum
  • Benefits: High strength to weight ratio, corrosion resistant, easy to machine
• Mild Steel
  • Benefits: Cost effective, multiple finishes available, moderate strength, easy to machine
• Stainless Steel
  • Benefits: Corrosion resistant, food and/or medical product safe
• Titanium
  • Benefits: Corrosion resistant, ultra high strength to weight ratio
• AR400 and AR500
  • Benefits: Abrasion resistant, highly durable, impact resistant 

Composite Materials

• Carbon Fiber
  • Benefits: Very high strength to weight ratio, corrosion resistant, very stiff material, good aesthetics. 
• MDF
  • Benefits: Cost effective, easy to machine, easy to make modifications to. 
• Hardboard
  • Benefits: Lightweight, good strength to weight ratio, warp resistant. 
• Chipboard
  • Benefits: Environmentally friendly, easily formed, durable. 
• Micarta
  • Benefits: Impact resistant, easy to machine, moisture resistant, electrical insulator. 
• G10/FR-4
  • Benefits: Electrical insulator, water resistant, fire retardant, rigid. 

Plastic

• ABS
  • Benefits: Good strength to weight ratio, impact resistant, electrical insulator. 
• Acrylic
  • Benefits: Light weight, weather resistant, versatile uses, cost effective. 
• Delrin
  • Benefits: Easy to machine, electrical insulator, good middle ground between plastic and metal. 
• Polycarbonate
  • Benefits: Optically clear, impact resistant, strong, electrical insulator. 
• HDPE
  • Benefits: Impact resistant, moisture resistant, non-toxic, great strength to weight ratio. 
• UHMW
  • Benefits: Impact resistant, easy to machine, lightweight, good abrasion resistance.

Other Materials

• Lego
• Wood
• Ceramics
• Silicon
• 3D printed components (e.g. PLA, ABS, PETG, Nylon)
• Rubber
• Kevlar
• Foamcore
• Cardboard
• Electrical components (e.g. arduino, circuit boards, sensors, motors)
• Biodegradable ‘smart’ materials
• Graphene

Tips for Prototyping Robots

Organization

The most important thing in prototyping is a clear design concept, and established objectives. Consistently keeping these front and center during the design and testing phases will help drive success in gathering the required data from a prototype.

• Focus on the highest risk objectives first, such as a complex/precise motion, or moving a payload when at the limit of range of motion.
• Break down each of these objectives into smaller simpler tasks to make them more approachable.
• Document updates, design decisions, fabrication details, problems encountered, prototype modifications, and testing outcomes to ensure that the final design can avoid mistakes discovered during the earlier phases of prototyping. 

Design

All robotics have to support some level of a structural load, sometimes that is simply the weight of the robot itself, other times, there is an additional payload such as a cargo being moved, wind loading, guest abuse loading, potential collisions, etc. Structural integrity of the robotic prototype is critical to making sure it survives long enough to achieve the prototype testing objectives. However, the cost of the prototype is often driven up by the durability and longevity of it, so durability and cost should be balanced as appropriate for the specific prototype. For example laser cut plastics would be very affordable for a sub-scale or short term prototype, whereas mild steel might be a better option for a full scale, longer term prototype. More broadly, the cost vs capability in general should be kept in mind to make sure the prototype doesn’t cost more than necessary to achieve the defined objectives. 

If considering all this seems daunting, consider collaborating with experts and/or mentors to gain insights and troubleshoot challenges. Even if the details of a design are confidential and can’t be shared, careful discussion can yield a lot of results on general recommendations. Ask questions on common mistakes and oversights made in robotics design.

• What are the common failure points?
• Where do current designs struggle the most?

The answers to questions like this can help avoid common pitfalls early on. If the project is more collaborative in nature, consider modern online platforms and communities that can help brainstorm and iterate designs quickly. These agile methods help to make rapid processes, though design decisions will still need to be vetted and examined before being implemented. 

Some final design considerations:

• Implement modularity when possible
  • The ability to swap out different length arms, or end effectors can cut costs and schedule with a modular design. However this isn’t limited to just the final pieces of the robot, consider how a piece could be made easily swappable anywhere within the robot. This will make prototyping and maintenance on the future final design much easier.
• Consider environment and use cases
  • Environmental conditions can make a huge impact on the material and component selection of a prototype. For example, a simple mechanism motion model can be made of cardboard and fasteners to see how a 2D design moves. However if that proof of movement requires submersion in water, a different material should be selected.
• Focus on functionality over aesthetics
  • In robotics, function should be over form, i.e. an ugly functional robot is more useful than an aesthetically pleasing broken robot. Get it working first, then make it pretty.
• Consider simulations like finite element analysis (FEA) or motion analysis
  • Finally, with the cost of computing getting lower with each passing month, consider simulations to supplement prototyping and inform design decisions. FEA can determine the strength of a design when subjected to a particular loading condition before a single bolt is turned. Similarly, motion analysis can determine if a model can physically move the way it is intended, and can inform the designer of the forces expected from a prescribed motion. These tools can be big time savers, though often can’t completely replace the need for getting hands dirty. 

Fabrication

Building out the prototype can inform a lot that can feed back into the iterations of the design. Consider the scalability and manufacturability during the fabrication. Can each step be done precisely, or efficiently at the level of production required? I.e. a robot that is only made once is allowed to be more difficult to manufacture than a design that will be mass produced. The specific fabrication technique can also make a large impact on the strength, convenience, and manufacturability of the design. Welding for example can locally weaken the joint in heat treated metal, whereas a bolted joint can introduce a maintenance inspection task to check proper torque. Even how the same part is produced should be considered. Thin metal parts can be laser cut, waterjet, or CNC milled; each with pros and cons such as tolerances, lead time, and cost. Finally, it is important to note any difficulties or adjustments made during the manufacturing process so that future iterations can either match, or change those specific features. 

Testing

Testing can be done in phases to help inform and make design changes throughout the prototyping process. A great first step is to use low-fidelity materials such as paper models, cardboard prototypes, or 3D printed components. These are typically very quickly generated and tested to rapidly iterate designs. 

Next would be to test components individually before integrating them into the system. In the example of a simple robotic arm; consider testing the end effector first, then the motion of the base, then the actuators. Next, build up the arm one sub-system at a time, testing each time a new subsystem is added. During this testing, try to keep the mindset that failures are learning opportunities, and a way to adjust the design to be more robust. Any failure found during prototyping is one less that an end user might face had the prototyping phase been skipped. If any problems or anomalies are found, note them and the solution so future iterations can avoid them and/or instructions materials can be generated to prevent future problems. 

Iteration

Developing a prototype is a design iteration, it gathers feedback from the testing, to loop through the design process again to improve the robot. It is important to gather feedback and data during the testing so that future decisions can be driven based on this newly gathered information. Sometimes that feedback is quantitative, such as how much a robot can move, other times it might be feedback from users which could be more general in nature and harder to capture in a simple numerical value. All of this data should be reviewed and compared against the objectives to see where improvements can be made. This is where the design process restarts, and alternative designs are developed, new materials are considered, a new mechanism might be created, even just switching the fabrication technique can significantly change a design. Just remember that iteration is a natural part of the process, and that the design improves with every iteration and makes forward progress towards the robot of your dreams. 

Prototypes are an important step in most industries, but often especially so when developing a robotic design. Robots have moving parts, and multiple complex mechanisms that are hard to execute perfectly on the first try. Even a subsystem prototype is of great help for the design team to ensure proper performance. Keep an open mind when developing a prototype, as many non-traditional robotics materials can be utilized to reduce costs and development time. Even paper and cardboard can be utilized for simple mechanism prototypes! Don’t forget the utility of rapid prototyping tools like 3D printers and your friendly neighborhood laser cutting service, SendCutSend. If you have any questions, feel free to reach out to us at support@sendcutsend.com. If you’re curious how else we can help, check out this brief article: What SCS can do for you. When you’re ready, upload your design and get an instant quote today! 

FAQs

• What role does CNC machining play in the robotics prototyping process?
  • Typically CNC machining is associated with traditional milling and turning operations. These can produce extremely tight tolerance designs, but usually at the tradeoff of longer lead times and/or expense. CNC machining can be used in prototyping, but other methods of manufacturing often work better for the shorter lifespan of a prototype robot. 
• What role do 3D printing technologies play in robotics manufacturing?
  • 3D printed or additively manufactured parts can produce simple proof of concept parts, full scale prototypes, or in some cases production quality parts. The ability to rapidly produce parts and iterate designs on the typical scale of minutes or hours allows for rapid prototyping, and can also produce geometries impossible with traditional fabrication methods. 
• Can injection molding be used for robotic prototyping?
  • Yes, injection molded parts can be used in robotic prototypes, and are often used to produce very intricate plastic designs. However the costs associated with developing the molds can be prohibitive. Typically the use of injection molding is for parts that are mature designs and that can be used in the prototype as well as in the full production robot. 
• Can vacuum casting be used to make robotics prototype parts?
  • Yes, vacuum casting produces very good quality plastic parts, and is efficient at low to medium scale production. This technology is often paired with 3D printing to produce the initial form used for the vacuum casting process. 
• Can sheet metal fabrication be used for producing robotics prototypes?
  • Yes, sheet metal fabrication is a great option for robotic prototypes. Sheet metal is both cost and weight efficient, plus the quick turnaround time and ease of modifications make it a perfect choice for prototyping. Here at SendCutSend we offer a large selection of materials, thicknesses, and services to help with your next project. 
• What are some tips for surface finishing in the manufacturing of robotic parts?
  • The main concerns for surface finish in robotics would be environmental concerns (corrosion, cleanliness requirements, etc), and abrasion.
    • Environmental: make sure parts subject to corrosion are properly protected with a finish like powder coating or plating. Cleanliness requirements might require a process like tin plating or passivation. 
    • Abrasion: abrasion can cause robots to lose critical tolerance or break altogether. Finishes such as anodizing, or powder coating are great options to increase abrasion resistance. 
• What are robot frames made of?
  • Robot frames are the main structural component of the design. Typically they are made of metallic components, but in weight critical or light duty applications, composite materials are often used.