When we prototype nylon parts, we CNC machine them. Just recently, we have been prototyping a number of plastic hooks made from nylon for use with bungee cords. The customer project is called “the better bungee” and we continue to work with our client to improve it over time. We are presently finishing up version five. To develop the parts we start with a 3D printed ABS prototype to confirm size, shape, aesthetics and function. Then we CNC machine the hook in Nylon in order to test its strength. The final step is injection molding the production parts. Here’s a little bit more on the project:

Product (prototype) design and development:

Like I mentioned, we start the project by designing the specimen in Solidworks CAD and then printing an initial prototype with ABS plastic. We have a fully integrated software/hardware interface and a 3D printed part can be printed in as little as an hour or two once we’re happy with the design files. This 3D printed ABS plastic prototype provides us (and more importantly, our client) with something to hold in their hands. A lot of times your creative juices start flowing once you can touch a real part because it gives you a better idea of exactly what you’re dealing and a baseline to improve upon. A lot of designers have a great vision but they need to see a real product to take the next step. When we’re ready for the final prototype we use the CNC machine to produce it in the final production material. Then it’s available for testing and ultimately, for a decision about whether or not to progress forward with the project. This is a real product currently in development and hopefully coming to a store near you rather in the not so distant future. Here’s Mr. Jeff Dershem, Co-Owner and Technical Director at The Better Bungee, discussing the process and his experience in making the better bungee a reality:

“[the better bungee incorporates] a unique friction engagement system which was totally designed here [at Creative Mechanisms]. Working with Creative Mechanisms you have everything from the CAD drawings, which they developed, and you can go back and forth and tweak things … and they can show you different diagrams. That then moves to a 3D printing process and now you’re actually getting a model that you can hold in your hand. It may not be totally functional just because of the nature of the material [ABS] that is in the 3D printer but at least it gives you an idea and you can get a three-dimensional model of what you had conceptually in your mind now in your hand. From that Creative Mechanisms has the ability to go to a more robust model where they can carve [CNC machine] that piece out of a solid piece of plastic so that you can actually have a working model … Now we can test this [the “better bungee” cord], we can put this on the back of a trailer, we can pull this twice its length, and [now] we know how it’s going to respond. So therefore, we get an idea prior to going to full production [because] a four to eight cavity mold to make these is anywhere from perhaps $30,000 to $50,000. And the last thing you want to do is to expend those dollars if you don’t know if your product is going to work. So Creative Mechanisms has the ability to do that for designers like myself that want to be able to test something before we expend those dollars to go to full production. And it may end here. It may never get there because we say ‘it wasn’t what I thought it was going to be’ so I don’t have to spend $40,000 or $50,000 in the making of a tool to find that out. And it’s a very unique process where you can go from A to Z with Creative Mechanisms.”

Some of the key reasons for prototyping a part include costs savings, risk mitigation, and the ability to test the product to iron out all of the issues before production.

Prototype strength testing:

Pretty much all materials come from the manufacturer with known specifications (i.e. they have already been tested for strength, ductility, and other properties like melting point). But it’s important to realize that tests (such as the common tensile test) are typically done on “dogbone” specimens that may or may not exactly match the profile of your particular part. Most engineers and developers like to test the actual object in its expected environment when and if it’s at all possible. That takes a little bit of the guesswork out of the equation and helps you accurately produce a margin of safety (vice over-engineering that can waste both time and money).

When we engineer a part with a unique geometry (such as a plastic bungee hook) we like to do our own failure tests to ascertain just how strong the actual product really is. For this kind of project we’ll do both tensile testing with an actual specimen as well as practical “real-world” testing in different environments where the device is expected to be used (e.g. on the back of a truck or trailer). This kind of thing is really important mostly as a risk mitigation measure. It’s important to make sure things work so you don’t invest a significant amount of money in a faulty product.

Summary: Bringing a new product to market is a lengthy process. It helps to have expert assistance, particularly with regard to creative engineering and prototype development. That said, developing a functional product is only the beginning. For more advice on getting your product to market we suggest you read here. If Creative Mechanisms can be of service to you please feel free to call us at 215.788.4566 or contact us online.

To learn more about the manufacturing process click here