To Prototype or not to Prototype?

Previously we spoke about 3D printers, their promise or lack thereof! I will admit I have been a bit cynical of their reliability, accuracy and actual usefulness. There is absolutely no doubt that 3D printers are here to stay and promise great things for our future. Sadly, for most of us, it still remains in the future. Despite the fact that Adept designs 100’s of parts per month we don’t own a 3D printer and don’t expect to purchase one anytime soon. That’s not to say we don’t utilize rapid manufacturing a great deal. However, by not bringing a single technology in house we are not bound or tempted to fit our process into the single technology we own. Prototyping companies put out a horde of advertising displaying complex assemblies that have been 3D printed in order to entice us towards their machines and services, but beware, (we’ll talk about that a little later). I don’t want to necessarily talk about 3D printers but more about prototyping as a whole. Specifically about when to prototype and when not to prototype, a sort of Shakespearean… “to Prototype or not to Prototype”.

Rotor Pattern
Rotor Pattern

After 30 years in Engineering and having lived the age of computerization within the engineering community, I remain awed by the capabilities and tools at our disposal. But like most facets of today’s technology, just because we can, doesn’t mean we should. What I’m referring to is the onslaught of decision making surrounding when and how to prototype. I’m not only addressing; Poly-jet, Stereo-lithography, ID Light, Laser sintering, Fused Deposition Modeling and Direct metal laser sintering, (I’m sure I may have missed a few), but one method that seems to have taken a back seat when discussing methods of prototyping.  All these processes rely on the primary phase which they depend, 3D modeling. Even this is becoming easier, where there are freeware and online programs that help you create your ideas in 3D compatible formats enabling fabrication by one of these processes. However 3D modeling in of itself is a prototype. Which brings be back to the original question, when to prototype? Well, if you’ve already built a 3d model you already have.

Prototyping is a method of simulating an end result. In some instances these methods of prototyping are becoming methods of manufacture. As I wrote earlier about the GE

Functional Prototype
Functional Prototype

LEAP fuel nozzle being manufactured by Metal Laser Melting. Where a fuel nozzle of 17 parts was manufactured as a single assembled component or perhaps Solid Concepts fully functional 1911 semiautomatic pistol. I expect in our lifetime these methods of manufacture will become mainstream. But, as Solid Concepts points out, the fabrication of the pistol required experts using state-of-the-art equipment to produce it, not to mention countless man hours. So, the methods that are available to you and I will produce similar items, however they are still crude, inaccurate and unreliable. Simulation is a large part of Engineering, as is Prototyping. In essence all computer model simulations are prototypes. Prototypes that we don’t have to fabricate, can be easily modified, are incredibly accurate (often too accurate!) and can be destroyed repeatedly!

Computer models and simulations provide a perspective worth 100’s of prototypes. I remember hearing decades ago how Detroit used to make 100’s of prototypes of an automobile and now (20 years ago) they make 6. I expect that number has actually risen while the methods of engineering and manufacture have evolved and our tools are being used more effectively, efficiently and ingeniously put to use.

Prototype Development
Detailed Assembly

Computer simulations have come as far if not farther than rapid or additive manufacturing. An issue I take notice with, is the fact that rapid manufacturing has stolen the term rapid prototyping, because the fabrication process is only one piece of the puzzle and it happens to be a very costly one! Not to say that engineering hours are cheap, so there lies the quagmire! The cost to engineer and prototype is at the core of engineering decision making process. Assembling the correct engineering plan for the given project needs to be closely monitored and tailored to the projects near and long term objectives . Computer engineering/designing/modeling is at the forefront of the overall process. But the computer modeling element is not a one size fits all objective!? Because the rapid manufacture technologies available to the average machine or product developer are limited, your “prototyping” dollars must be carefully assessed and applied.

Model Analysis Prototype
Model Analysis Prototype

Every simulation or prototype has it’s objective and must be designed for that objective.  Components slated for plastic injection molding are perhaps the simplest because the additive manufacture processes offer components in an array of materials that closely approximate real materials and the process yields similar tolerances. And, if these parts are structural, provided you select the correct material, process and align the grain direction appropriately you can yield a good simulated part. But remember you will have only one configuration to evaluate and to reevaluate you’ll have to purchase another prototype. If you require components of greater strength or tighter tolerances then it often pays to work your computer simulations further because your methods of rapid manufacture get more costly and time consumin
g. Clearly we can’t cover even a small cross section of considerations when it comes to when and how to prototype. But before you prototype be sure to ask your designer or engineer; “what is the objective of this prototype?”, “what will this prototype tell us, that we don’t already know?” and “how will this prototype move us closer and faster to our final objective, that can’t be achieve other ways?”.

Deciding when to prototype and when not, is a complex decision. Like most engineering decisions there are a host of considerations. Sometimes vested interest just have to see and touch what is being done. However first and foremost listen to your engineer, no matter how glassy eyed you may get as you listen to the decision making process, it is a process of trade-offs, filled with reason and rationale. And as you evaluate which simulations to perform and which to forego be sure to ask, what the risk are if we go with intuition, do we perform the analysis and to what level do we need to analyze. But always remember it’s expensive to build and cheap to modify computer models.

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