A Case Study in Additive Manufacturing, Design, Construction, and Implementation
The Honda TRX450ER is one of the most popular high-performance ATVs ever made. In stock form, it tends to be a reliable and tractable recreational vehicle, recommended for use by those 16 and over:
However, when it’s time to race, the 450 can be transformed into a potent track weapon capable of traveling over 85mph and jumping spans of more than 60 feet at a time:
For racing, the first modifications are generally made to the suspension. High-performance shocks, springs, and a-arms are added to help smooth bumps and absorb impacts from hard landings.
The second set of modifications usually relates to increasing horsepower and torque. The more air an engine moves, the more power it can produce. To increase horsepower, we add less restrictive exhausts along with uprated cams and intake systems. On the intake side, removing the airbox lid is a quick and easy way to increase airflow. When accompanied by a jetting change, this modification helps the engine make more power by ingesting more air:
However, after a day at the track, where dust and dirt tend to cover everything (rider included), the air filter can become caked with debris, detrimentally impacting performance and reliability:
One way to increase airflow while minimizing dirt and debris is to drill holes in the airbox lid. The downside is that airflow may be limited by hole size and dirt and dust lodged above the airbox lid will tend to fall down onto the air filter. Using screens in place, or in connection with a drilled or opened lid also tends to improve performance. However, screens can be expensive ($100+) and may be subject to clogging, particularly with mud. Similar to an air filter, screens will also need to be cleaned.
What is needed is a rugged, low maintenance, performance-enhancing airbox lid. If we couple Computer Aided Design (CAD) with 3D printing, the possibilities are nearly endless. We have the freedom to design the optimal configuration for our airbox lid and use most any available plastic to create the final part. Warning, however, 3D designs are rarely ever finished, they’re just iterated until a momentary period of perfection!
To start, we will select Airwolf’s EVO 3D printer.
The EVO is perfect for the job because it has a large 12″ x 12″ build platform and is capable of working with most commonly available thermoplastics.
Build size is important because the standard Honda airbox lid is approximately 10 3/4” x 7” and our modified part will need to cover a similar footprint.
Build material may be equally important as we need to use a durable material that can withstand the heat and impacts that go along with racing. We want this new airbox lid to be a permanent replacement part, one that can even be sold through the aftermarket.
To enhance airflow while also reasonably protecting the air filter, we will construct a custom vented airbox lid. Rather than venting the top of the lid, we’ll create alternative vents to minimize exposure to dirt and dust that can fall into the airbox. Clearly, this is experimental as we do not affirmatively know that less dirt and dust will enter into the airbox from a different location. That is one of the beautiful aspects of 3D printing, we can let out creative freedom run wild and test different ideas to arrive at the best solution without the expense of special tooling.
The first step is measuring the airbox lid to determine approximate dimensions.
Rather than design and print the entire lid (only to find out that one of our measurements may have been off), let’s start by designing a test “ring” first. This will be quick to design, quick to print, and small in cost (< 50 cents). We will use SolidWorks to design the part as it is one of the best parametric modeling packages available.
After several iterations (approximately 1hour of print time each), we arrive at a properly fitting ring:
Now it’s time to design the first prototype. Lets factor in a couple of design considerations. First, we want this part to be rugged and durable, for off-road racing use. Two things come to mind: MG94 ABS filament and thick perimeters and solid layers.
Let’s start with MG94 as it is a premium variant of ABS that we extrude in house here at Airwolf 3D. It tends to be stronger than conventional ABS and print smoother. We use this ABS for nearly all structural parts as it is a strong and reliable engineering-grade material. When used in connection with the EVO’s heated chamber, MG94 is perfect for highly functional prototypes as well as end-use products.
As hinted above, we’ll definitely need to use the EVO’s chamber heaters on larger parts, and even on smaller height parts like this airbox lid. The heated chamber will make sure the part is free from defects, such as layer-layer delamination. Additionally, we’ll want to use our optional 1mm nozzle. This larger nozzle (compared with conventional .4 and .5mm nozzles) prints significantly faster (up to 3x the flow rate) and tends to produce stronger parts. The large bead line with the 1mm nozzle can print a 1mm perimeter wall with only 1 pass. That wall tends to be stronger than two smaller (.4mm or .5mm) walls printed out with a conventional nozzle.
With printer, filament, and nozzle selected, let’s move on to the fun part-designing the airbox lid cover. As our 3D-printed trim rings confirm our base dimensions, we will now create the top shape of the lid and insert several holes along the sides to increase airflow into the airbox:
Notice the large fillet on the front of the lid-this is to make room for the seat as it is inserted over the airbox. We want to make sure there is ample space as the seat can flex down in a harsh landing.
Now let’s go ahead and personalize the airbox lid. We’ll add a recess into the top portion and add the Airwolf logo:
Finally, we’ll need to create openings for the airbox lid clips to grasp onto the lid. It is necessary for the clips to firmly grasp the lid, so we’ll measure carefully and model the recesses with the same geometry as the factory lid.
Let’s also put a nice draft angle on the bottom of the lid so that it inserts quickly into the airbox:
We are now ready to set the part up for printing. We’ll select ABS, draft print quality (for quicker printing), chamber heat, and full support. As we want to preserve the surface finish of the top of the lid, we’ll orient the part so support is generated automatically underneath the lid. With our 1mm nozzle, the process should take approximately 13 hours (a great overnight print!):
After 13 hours, the part is ready to be removed from the EVO and cleaned up a bit:
Now we would usually spend a good bit of time removing the support from the underside of the part. However, with the new “Lines+” support generated starting with Airwolf’s Apex 1.59, support removal is easy. We can simply remove the part with a judicious application of pressure. The solid support interface layer provides a clean underside:
With the lid printed and support removed, we are all set to go to the races!
See how the final version of the performance-increasing airbox lid is installed and tested in the Honda Trx 450er by watching the video below.