HARDWARECON Helps Hardware Startups Grow w/ CAD and 3D Printing
Matt Shelton and I decided to make a 3D print of the tradeshow logo for HARDWARECON, which we attended (and displayed) at a recent show. A surprising amount of engineering went into this project, all the way down to the pins holding the gears to the baseplate.
Designing the Part with Jamie Kalb
When Matt and I first discussed the design, he had the great idea of using snap pins to connect the gears and base piece. This way the gears could be easily detached and the pins replaced if they ever broke. Matt knew the perfect piece to use: a snap pin from a heart gear design from Thingiverse. He sent me an STL file of the pin, and I reverse-engineered it in SOLIDWORKS, using lofted sections to match all the dimensions. I set the model up so I could easily modify dimensions to test different designs.
The baseplate itself was a simple design, but the mounting holes for the pins took some thought. The holes were simple to design by hand, but I inserted the pin part and subtracted it out of the model instead. This made it possible to employ the power of SOLIDWORKS’ parametric modeling to automatically update the holes when making a change to the shape of the pin itself.
Pins Printing Orientation
Surprisingly, even the printing orientation of the pins had engineering considerations!
I tried printing them standing up as well as laying down flat. Even though there was no difference in the design, the ones printed standing up snapped easily when the pins were squeezed. The ones laying down flat had much more strength in that direction, due to their layers being oriented to resist the bending. Using the picture of the logo as a template, I created the gears, tracing over it to recreate it in a SOLIDWORKS sketch.
However, there were a couple problems with the gears.
The big one was the number of teeth. A gear’s diameter should be directly related to its number of teeth, so a bigger gear should have more teeth, and a smaller gear should have fewer teeth. In the logo, however, the brown gear and the blue gear are both 12-tooth gears, even though they are very different sizes.
You can see that the gaps between teeth are not the same size on these gears, which causes them to mesh poorly at best. I solved that by bringing the blue gear down to 10 teeth, which matches the teeth-to-diameter ratio of the brown gear. This means that gaps between teeth are the same size for each, and the mesh is much better. I also made the red gear 8 teeth for the same reason.
Next up was the shape of the teeth.
The square profiles you see in the logo would work very poorly, if at all, because the square corners would “bottom out” against the opposing gear when you try to spin them. Actual gears use a surprisingly complex shape called an “involute profile” that allows the contact point to stay a constant distance from each gear center instead of traveling back and forth throughout contact (constant torques), but I didn’t go that far because it looks so different from what the logo shows, and I don’t expect these gears to see any significant loading.
But by simply rounding out the corners of the teeth, they can pass each other without bottoming out. Building an assembly and using SOLIDWORKS’ Physical Dynamics option inside Move Component to test the motion of the gears helped me verify that they turned correctly without having to set up a complex simulation.
We used the Stratasys Fortus FDM printer to create the baseplate.
This allowed us to insert pauses and swap materials at given heights, enabling the color changes for the text. Then we made use of a Connex Polyjet printer to create the gears in 3 different colors, as well as the white color for the rings. All in all, it turned out to be a pretty deep project that took advantage of many different SOLIDWORKS features, as well as both printing technologies (FDM and PolyJet).
Printing the Part with Matt Shelton
Just looking at the picture of the logo, Jamie, who is an applications engineer, noticed there would be an issue with the gears actually operating correctly. Just looking at the logo can hurt an engineer’s eyes because the number of teeth on each gear would not mesh properly as is.
Jamie and I got together before the design process and talked about what materials and colors we wanted to print.
Printing the Plate
We decided to print the plate that the gears would sit on in ABS Ivory plastic on our Stratasys Fortus 250 at a .010” slice height. To create contrast between the text and plate, we extruded the word “HARDWARE” at about .070” and then extruded the word “CON” a few layers further out, and then created a pause after the last layer of the plate was so we could change to Gray for “HARDWARE.” After “HARDWARE” was done printing, we inserted yet another pause to change to a red color for the higher text “CON.” The pins that would hold the gears in place were also printed in an ABS plastic at .007” for the flexibility of ABS.
Printing the Gears & Rings
In order to get multiple colors in a single print, we printed the gears in our PolyJet Vero materials on our Stratasys Connex3. With Vero Magenta, Vero Cyan, and Vero Yellow loaded, I was able to print the 3 gears in colors that were pretty close matches to the logo all in one print.
The inner white rings were printed on another Connex3 in Digital ABS to give the rings some flex so they were more durable when inserting them into the slots on the gear.
All in all, this “simple” project required a decent amount of engineering. We hope you enjoyed learning about how we did it.