A lot of people have talked about the impact 3D printers will have on Manufacturing. But what people don't think of is its' impact on the design process itself. I've recently been designing a number of mechanical brackets/components, and having the ability to print out the prototypes as I evolve the designs has made a bigger impact on the functionality of the resulting components than I expected.
For example, I'm working on a modified carriage design to convert the 3D printer to use dual extruders. I'm modeling the design in Solidworks, and I've gone through half a dozen design changes. At each stage I printed it out to "test" the changes. Here's the steps I went through.
Here is the existing printhead carriage with a single extruder:
The new printheads I want to use differ from the current one in that the cooling fans are normally placed directly underneath the motor and blow the air out at the top of the hotend. This makes the mounting considerably more complicated. My first thought was to keep the metal plate base of the carriage and add a bracket between the plate and the motor/printhead itself. I first created a very simple "block" design model with just the basic elements, and immediately printed it out. At that stage I did not have models for some of the existing parts (e.g. the motor brackets, Y-axis carriage, hotend, etc.), so having this physical object in hand I was much better able to visualize how the pieces would fit together. Total CAD design time was less than 15 mintues, and it took a couple of hours to print.
But this model had some fundamental issues: First, it had no way to easily remove the hotend if I needed to clean them. Second, there was no clear way to attach the bracket to the plate with the 6 nuts sticking out on top and still leave room for the fans. Looking at the parts in my hands I decided to make the following changes:
- I cut gaps in the front to allow the hotends to be removed without taking everything else apart. I'd add a separate font plate attached with screws to hold the hotends in.
- I decided to switch to a single-picece design where the carriage bearings and supports were directly attached to the bracket. To do this I had to thicken the bracket to leave room for the nuts on top and add deep countersunk holes. Again I printed it out:
Less than 30 minutes later I had my next design iteration:
With this print I was able to test fit the printheads and determined this general approach would work still with minimal modeling of the existing components. Next I had to fix the precise hole alignment for the base, and attached the fans. Also I decided to increase the gap in the front:
Now I turned my attention to fitting the fans to the base. One thing I quickly discovered is that the screw points are inset in the sides of the fan so that the air doesn't "leak" out of the sides. I had to create a very precise indentation on the surface to fit this correctly (as marked on the previous model). With no thought as to how to fabricate it, I quickly made the modification to the 3D model:
And then I printed it out:
Already I was 90% of the way to a correct fit. After one more round of minor tweaks I got everything to fit precisely. (note in the following picture the right motor should be flipped; I need to fabricate a new attachment bracket to mount it correctly):
At this stage I've expended just a few hours of work and produced a fully functional prototype. Now I can focus on fabrication techniques for the bracket. My original intent was to CNC machine it out of Aluminum, but the prototype is stiff enough that it may be sufficient for the final version. So I've decided to finish assembly of the system as-is, and then judge whether I even need to machine the final component.
Moreover, the process was so easy that I've decided to simultaneously prototype and test a second approach that leaves the fans below the carriage blowing directly on the hotend. This design would be considerably simpler and possibly lighter. But it is difficult to easily quantify whether this will provide a more or less effective cooling of the hotends. By testing them side-by-side I can quantitatively compare the two designs.
Effective product engineering should embrace the goal of testing many different design approaches. Moreover, building rapid prototypes allow you to grow your understanding of the problem with minimal cost. Adding a 3D printer as a fundamental part of the design process significantly enhances that goal and results in a markedly better end-product.
Building upon this, the next area to explore is how you can use the fundamental characteristics of 3D printing to change the designs themselves. I call this the Spiderweb Design Process. I'll go through this in more depth in my next project.