Every manufacturing process is beholden to a triangle of processing tradeoffs and 3D printing is no exception:
We believe the highest value for most manufacturing projects is achieved at the center of this diagram. This is where quality, cost and speed intersect to form a balanced equilibrium. However, in practice this equilibrium is rarely achievable and most projects focus on reaching a solution where at least two of these variables overlap. Therefore, most manufacturing processes can be fit into one of the following categories: fast and cheap (low quality), high quality and fast (expensive) or high quality and cheap (slow). Next, we will show how variable infill settings allows FDM 3D printing to span two of these categories.
The different manufacturing processes can be categorized as such:
- Low resolution FDM: fast and cheap (low quality)
- High resolution FDM: high quality and cheap (slow)
- SLA/SLS/DLP/MJF: high quality and fast (expensive)
At SD3D we focus our efforts on developing state-of-the-art FDM 3D printing technologies and processes. We believe that FDM is the most flexible of the 3D printing technologies since it falls into two of the three focus spots within the processing triangle whereas the other technologies are typically configured to only focus on the high quality and fast focus point. Variable infill is a unique feature associated with FDM printing that is not utilized in the other processing methods. As you will see throughout this article, selection of the infill parameter can have very interesting implications to the strength, quality and processing rate of FDM manufactured parts.
The difference between 3d printed part strength, quality, processing speed and cost are functions of three independent input variables: infill, layer height and the type of material being processed. We will be focusing on PLA throughout this article, which is the most commonly used FDM 3D printing material. In general, the relationships and results we will be discussing in this article apply to all FDM 3D printing materials, but the specific values referenced may be different.
Infill Settings Vs. Strength
The first observation which is important to consider is that the relationship between the infill you select and the strength of the resulting part is non-linear. Specifically, the rate of part strength increase goes up as the infill percentage approaches 100%:
While the strength increase is non-linear across the entire infill range, the relationship between infill % and both part weight and print time is linear across nearly the entire range (with a slight drop off on the part weight between 90-100% as the extruder begins losing traction due to the high packing pressures). The chart below shows the relationship between 3D print processing time, weight and infill %.
Infill Settings Vs. Printing Time and Infill % Vs. Weight
Strength to Weight and Strength to Print Time Ratios
Overlaying the results of the two previous graphs has very interesting implications to the parts strength-to-weight and strength-to-processing time ratios:
An interesting observation from this chart is that the ratios for 10% and 70% infill are the same and every datapoint between those ranges is lower. Specifically, the range between 30% and 50% infill is the least efficient in terms of both strength/weight and strength/cost. Therefore, you will want to ensure the 30%-50% range is avoided for most projects.
Diving deeper into these parameters yields the following chart:
As can be seen in this diagram, quality is always low at settings above 90% infill. It is also important to note that many larger parts simply cannot be printed properly below ~10% infill. Depending on how large the part is, the top layers will not have enough support from the infill at these low percentages. Thus, the part will yield poor quality on those layers or lead to print failures.
Based on this analysis, the most efficient infill settings for most projects are between 10-30% and 70-90%. Our 3D printing auto quoting tool sets this value to 25% by default. This is the infill selection that we consider to be the best “equilibrium” between strength, quality and cost for most projects. However, if you know that your project requires focus on speed or cost, choose a value between 10-30%. If your project requires more of a focus on quality and strength, then choose a value between 70-90%. If you aren’t sure, feel free to contact us. We can provide advanced FEA for 3D printing to make sure your 3D printed parts do not fail on you.
3D Matter – https://my3dmatter.com/
Optimatter – https://optimatter.com