Depending on the intended use case for your 3D part, structural integrity can be a crucial ingredient. It could be a matter of ensuring that your product doesn’t collapse when used or even a matter of ensuring user safety.

We’re going to look at an adorable Wacom Penholder as an example and point out the different considerations and precautions taken to ensure structural integrity in the 3D print.

If you’re using your own 3D printer, this will help you understand the best settings to use. If you’re ordering 3D prints online, this will give you a better understanding of the different technologies and materials available for strong 3D prints and what to communicate to your vendor.

For this product, an artist’s Wacom pen will be inserted into the pen hole, applying force downwards. What can we do to make sure this penholder lives a long life? Here are 3 considerations:

Step 1: Layer Direction

Something rarely taken into consideration is the layer direction. Since the force will be coming down onto the penholder, it makes sense for your layers to be printed horizontally. But if the force on your print is coming in from the side, underneath, or at any angle other than straight down, we will get an effect called shearing.

Most engineers are already familiar with this term, but for the designers, think of this as a deck of cards; they won’t budge if you press down on them from the top, but if you push them from the side, the deck will fall apart. The same concept can be applied to 3D prints: the cards are like the 3D printed layers that make up a solid object with more force applied to it.

If you’re working with a 3D printing vendor, the main takeaway here is to make sure you explain the intended use case of your part so the operator can choose the best build orientation.

Step 2: Density

Another element that will guarantee better structural integrity is the density of your 3D print. In the software of every FDM printer, there is usually a Fill Density option; the software for these printers automatically knows to print a pattern of filament inside your model.

At the default setting of 20%, your Fill Density will fill up your model with a nice light amount of filament. This is designed to provide stability while also reducing printing time and material costs.

However, if structural integrity is a critical feature of your project, the Fill Density percentage can be increased.

By simply increasing the Fill Density by 10%, you can see the Viking Wacom Penholder will be printed as a much more solid and slightly heavier object.

If we jump over to an SLA printer such as the Form 1 +, these printers automatically fill all geometry with resin. Many people “hollow out” their models before printing to save time and material cost, but since we’re looking to increase structural integrity, filling the entire geometry with resin is a great option.

If you do decide to hollow out your model, 3mm minimum wall thickness in VeroWhite is a good place to start.

Step 3: Material Choice

One of the most important consideration for structurally sound 3D parts is material choice. Here are 3 great options for strong 3D prints:

ABS - great for parts that need to be strong, but won’t receive heavy use.
ABS-Like - more expensive than ABS, but great for prints that will receive heavy use.
Nylon - most expensive material, but works great for prints that will receive heavy use and need to be high-resolution (i.e. visual models).

If you want to use materials other than plastic resins or are looking to product more than 1 or a few products, you can consider other fabrication technologies including:

In the second image above you can see what the final pen holder design looks like molded and cast out of metal.