Standard Roof Rack Fairing Mount Getting In Your Way?! Engineer it better and 3D Print it!

It is no mystery that I love my Subaru. I bought it with the intention of using it and I have continually made modifications with a focus on functionality.

When I bought my roof crossbars in order to mount ski and/or bike racks, I quickly realized I needed to get a fairing in order to reduce drag and wind noise. The fairing functions as designed, and looks great as well. However, when I went to install my bike rack, I noticed that the fairing mount was in the way of mounting at the tower. As a result, I had to mount the rack inboard of the tower by a few inches. This mounting position had a few negative results:

  • The bike was slightly harder to load/unload
  • The additional distance from the tower resulted in additional crossbar flex and bike movement
  • Additional interference between bikes when two racks are installed

These issues could all be solved if the fairing mount was simply inboard a few more inches. If only I had access to the resources to make such a concept a reality…. oh wait, PADT has all the capabilities needed to take this from concept to reality, what a happy coincidence!

First, we used our in-house ZEISS Comet L3D scanner to get a digital version of the standard left fairing mount bracket. The original bracket is coated with Talcum powder to aid in the scanning process.

The output from the scanning software is a faceted model in *.STL format. I imported this faceted CAD into ANSYS SpaceClaim in order to use it as a template to create editable CAD geometry to use as a basis to create my revised design. The standard mounting bracket is an injection molded part and is hollow with the exception of a couple of ribs. I made sure to capture all this geometry to carry forward into my redesigned parts, which would make the move to scaled manufacturing of this design easy.

Continuing in ANSYS SpaceClaim, as it is a direct modeling software instead of traditional feature-based modeling, I was able to split the bracket’s two function ends, the crossbar end and fairing end, and offset them by 4.5 inches, in order to allow the bike rack to mount right at the crossbar tower. I used the geometry from the center section CAD to create my offset structure. A mirrored version allows both the driver and passenger side fairing mount to be moved inboard to enable mounting of two bike racks in optimal positions. The next step is to turn my CAD geometry back into faceted *.STL format for printing, which can be done directly within ANSYS SpaceClaim.

 

After the design has been completed, I spoke with our 3D printing group to discuss what technology and material would be good for these brackets, as the parts will be installed on the car during the Colorado summer and winter. For this application, we decided on our in-house Selective Laser Sintering (SLS) SINTERSTATION 2500 PLUS and glass filled nylon material. As this process uses a powder bed when building the parts, no support is needed for overhanging geometry, so the part can be built fully featured. Find out more about the 3D printing technologies available at PADT here.

Finally, it was time to see the results. The new fairing mount offset brackets installed just like the factory pieces, but allowed the installation of the bike rack right at the tower, reducing the movement that was present when mounted inboard, as well as making it easier to load and unload bikes!!

I am very happy with the end result. The new parts assembled perfectly, just as the factory pieces did, and I have increased the functionality of my vehicle yet again. Stay tuned for some additional work featuring these brackets, and I’m sure the next thing I find that can be engineered better! You can find the files on GrabCAD here.

 

ANSYS Workbench Polyhedral Meshing

The ANSYS App Store contains all sorts of free and paid apps developed by ANSYS as well as trusted partners. These apps improve workflows and allow users to build in best practices. An app that has been of particular interest to me is Workbench Poly Meshing for Fluent

This app enables the power and capacity of Fluent Meshing, most notably the polyhedral meshing feature, with the ease of use of the ANSYS Workbench Meshing environment. In order to show the functionality of this app, I will demonstrate with the generation of a polyhedral mesh on a sample geometry from the Fluent Meshing tutorials.

To start out, I have imported a .igs file of an exhaust manifold into ANSYS SpaceClaim Direct Modeler, which has powerful repair and prepare tools that will come in handy. I notice that the geometry is comprised of 250 surfaces, which I need to fix in order to create a solid body. By navigating into the ‘Repair’ tab and selecting the ‘Stitch’ operation, SpaceClaim notes there are two stitchable edges in my geometry. I select the green check mark to perform this operation and am greeted with a solid geometry. I complete my tasks in SpaceClaim by extracting the fluid volume using the ‘Volume Extract’ tool in the ‘Prepare’ tab.

I setup my workflow in ANSYS workbench with my added ‘Fluent Meshing’ ACT module between the ‘Mesh’ module and ‘Fluent’ module. I can then proceed to create my desired surface mesh in ANSYS meshing and setup a few required inputs for Fluent Meshing.


Once this process has been completed, I can update my ‘Fluent Meshing’ cell and open the ‘Fluent’ setup cell to display my polyhedral mesh!

IMPORTANT NOTE: all named selections must be lowercase with no spaces, and the file path(s) cannot contain any spaces.

 

Metal 3D Printed Shift Knob: Is It Cool(er)?

I had a really great time designing the Metal 3D printed shift knob from my previous blog post. I was curious what the other benefits of the knob may be besides being cool to look at and show off. What better way than to use the simulation software that we use here at PADT every day!

One of the clear differences between my solid spherical knob and the Metal 3D printed version is surface area. Being that PADT is based in Tempe, AZ, some may say that we have “warm” summers down here. Couple the 120F days with a black car, and the interior can get very hot, at some points feeling like the sun itself has taken up residence inside the back seat. With modern A/C, this heat can be mitigated fairly quickly, only to attempt to shift into gear to be scalded by the shift knob!

I wanted to see what the rate of cooling for the two knobs would be in a basic situation with some basic assumptions. Using ANSYS transient thermal, I initialized the knobs to 150F, temperatures that can be quickly reached in parked cars here in AZ. I added a convection heat transfer boundary condition on the outer surface of each shift knob, assuming a film coefficient of 50 W/m^2C, and that the ambient temp in the car is at a cool 70F.

 

I ran the simulations for 5 minutes, and the results were in line with what I expected. As the 3D printed knob has more surface area for cooling, it’s final temperature was ~84F, compared to the solid spherical knob at a final temperature of 115F!

 

Want to learn more, check out the article in “Additive Manufacturing Media.”

Metal 3D Printing a Shift Knob

I have always had an issue with leaving well enough alone since the day I bought my Subaru. I have altered everything from the crank pulley to the exhaust, the wheels and tires to the steering wheel. I’ve even 3D printed parts for my roof rack to increase its functionality. One of the things that I have altered multiple times has been the shift knob. It’s something that I use every time and all the time when I am driving my car, as it is equipped with a good ol’ manual transmission, a feature that is unfortunately lost on most cars in this day and age.

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I have had plastic shift knobs, a solid steel spherical shift knob, a black shift knob, a white shift knob, and of course some weird factory equipment shift knob that came with the car. What I have yet to have is a 3D printed shift knob. For this project, not any old plastic will do, so with the help of Concept Laser, I’m going straight for some glorious Remanium Star CL!

One of the great things about metal 3D printing is that during the design process, I was not bound by the traditional need for a staple of design engineering, Design For Manufacturing (DFM). The metal 3D printer uses a powder bed which is drawn over the build plate and then locally melted using high-energy fiber lasers. The build plate is then lowered, another layer of powder is drawn across the plate, and melted again. This process continues until the part is complete.

The design for the knob was based off my previously owned shift knobs, mainly the 50.8 mm diameter solid steel spherical knob. I then needed to decide how best to include features that would render traditional manufacturing techniques, especially for a one-off part, cost prohibitive, if not impossible.   I used ANSYS Spaceclaim Direct Modeler as my design software, as I have become very familiar with it using it daily for simulation geometry preparation and cleanup, but I digress, my initial concept can be seen below:2016-10-18_16-19-33

I was quickly informed that, while this design was possible, the amount of small features and overhangs would require support structure that would make post-processing the part very tedious. Armed with some additional pointers on creating self supporting parts that are better suited for metal 3D printing, I came up with a new concept.

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This design is much less complex, while still containing features that would be difficult to machine. However, with a material density of 0.0086 g/mm^3, I would be falling just short of total weight of 1 lb, my magic number. But what about really running away from DFM like it was the plague?

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There we go!!! Much better, this design iteration is spec’d to come out at 1.04 lbs, and with that, it was time to let the sparks fly!

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Here it is emerging as the metal powder that has not been melted during the process is brushed away.

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The competed knob then underwent a bit of post processing and the final result is amazing! I haven’t been able to stop sharing images of it with friends and running it around the office to show my co-workers. However, one thing remains to make the knob functional… it must be tapped.

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In order to do this, we need a good way to hold the knob in a vise. Lucky for us here at PADT, we have the ability to quickly design and print these parts. I came up with a design that we made using our PolyJet machine so we could have multiple material durometers in a single part. The part you need below utilizes softer material around the knob to cradle it and distribute the load of the vise onto the spherical lattice surface of the knob.

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We quickly found out that the Remanium material was not able to be simply tapped. We attempted to bore the hole out in order to be able to press in an insert, and also found out the High Speed Steel (HSS) was not capable of machining the hole. Carbide however does the trick, and we bored the hole out in order to press in a brass insert, which was then tapped.

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Finally, the shift knob is completed and installed!

Want to learn more, check out the article in “Additive Manufacturing Media.”

 

Nerdtoberfest: Printing a Beer Stein with Beer Filament

Noticed an interesting email in my inbox the other day with the subject line:

“Oktoberfest Time: 3D Print a Beer Stein in Beer Filament”

Marketing gold, you have my attention!

After reading the reviews from the filament manufacturer, I dove in and got some of the hoppy, malty filament on order from 3D Fuel. I was very excited when it came in and couldn’t wait to print PADT’s own beer stein for our upcoming Nerdtoberfest event. Meanwhile I found a nice starting point with a file from GrabCad and added my own additions and alterations.

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I quickly went to load the beer filament into one of our 3D printers, when I noticed that the roll size was not compatible with the spool holder on the printer. It was this disconnect that would have previously stopped this experiment in it’s track, however, the future is NOW!

I popped onto the Thingiverse, and alas, I was not alone in having this issue and a plethora of solution were populated before me. I was about to 3D print and adapter to allow my 3D printer to accept a new roll size that was found to be incompatible just moments before. Disaster averted, I was now cooking with gas, er, beer.

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The printing process was uneventful and the beer filament printed well. We now have a beer mug printed out of beer filament for PADT’s annual Nerdtoberfest!

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Engineering a Better Pokemon Go Experience

padt-pikachu-1The other day, I saw a post on Engadget about a special case for Pokemon Go users to solve the problem of missing your prized Jigglypuff that you have happened across in the wild (or let’s face it, probably a CP 10 Rattata who is going to break out multiple times before disappearing in a puff of smoke…). The case is designed to give the user access to on screen controls and a nice channel to keep your Pokeball flinging finger straight and true.

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Original Device designed by Jon Clever

As pointed out in the article on Engadget, this case is only useful in the capture screen. This caveat aside, the other issue with the case is that it obscures the screen. Here at PADT, we are fortunate to sell a wide variety of 3D Printing machines, some of which are capable of multiple colors and material durometers. I decided to design my own take on the case from Jon Clever to be prototyped on our Stratasys Connex 3.

Pokemon Go Photo 1

Pokemon Go Photo 2

The case was made with black and clear material. The black material can be combined to produce a custom stiffness, so we made that part soft and rubber like and kept the clear portion rigid. The clear has good optical quality, which could be increased with a layer of “clearcoat.”

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If you have a Stratasys Connex 3 or J750 and an iPhone 6, you can make your own with these STL files, one for the rubber part and one for the clear part.

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Other variations and additional possibilities would be made possible with the new Stratasys J750, the first true full color printer that can also mix clear and solid as well as hard and soft materials.  The J750 was just released and highlighted on our recent road show. Visit our blog article on the Scottsdale show to learn more about this incredible printer.

Additional information about PADT and our wide range of 3D Printing offerings here.