Resin vs. FDM Printers: How Accurate Are They?

The advent of 3D printing technology has allowed many users to create trinkets that used to reside only in their minds. However, creating accurate designs also hinges on your 3D printer’s ability to preserve detail, and some types of 3D printers do that better than others. 

Resin 3D printers produce more accurate and detailed products than FDM printers. That is because the laser technology that resin printers use allows for more detail compared to the extrusion method of FDM printers. Furthermore, the type of material can also affect accuracy. 

This article will go into more detail about the resin and FDM printers. I will compare these devices’ accuracy and overall quality and discuss the critical differences between FDM and resin printing. Keep reading to understand the process more. 

Resin vs. FDM Printers: Which Is More Accurate?

Resin 3D printers are more accurate and produce prints of better quality than FDM printers. Resin 3D printers can preserve more detail and achieve thinner layer lines, allowing them to include the most minute details on the print, which FDM cannot. 

Reasons Resin Printers Are More Accurate Than FDM Printers

So, why do Resin printers produce better 3D printed objects? Let’s take a look: 

• A resin printer can create a print with a higher resolution.
• Resin layers can be thinner, creating tighter bonds between each layer.
• Since the layers are denser, there are fewer chances of gaps between components of your print. 
• Resin 3D printers offer better build plate and bed adhesion. 

Reasons FDM Printers Are Less Accurate Than Resin Printers

• Since the nozzle limits the thickness of your 3D printed layers, the print is usually lower resolution.
• The heating and cooling process in FDM printing results in more variables related to layer adhesion, often introducing warping, poor adhesion, and toppling.
• Since the nozzle must travel over your print as it extrudes, irregularities such as stringing, gaps, and other artifacts are more typical with these printers. 

I’ll expound more on these reasons throughout the article. But first, I’ll define what accuracy exactly is. 

What Is Accuracy in 3D Printing? 

Accuracy in 3D printing is the exactness of printed dimensions to the designed ones. For instance, if the design has a height of 12 cm (4.7 in) and the print is 11.99 cm tall, it’s pretty accurate. Many factors, especially XY resolution, affect accuracy. 

Factors Affecting Accuracy

There are many factors affecting accuracy: 

• XY Resolution. XY resolution is also known as horizontal resolution. It refers to the smallest laser dot size, pixel size, nozzle size, or extruder movement. The smaller the value, the better the resolution. It also contributes the most to accuracy. 
• Z Resolution. Z resolution is also known as vertical resolution. It refers to how tall or thick layers can be. The smaller it is, the better it will be for finer details. However, if fine details or curves are not crucial for the design, higher values may be optimal.  
• Bonding. In FDM, the more prominent bonding force lets the layers on the top sink, causing the print to warp or deform. Adhesion between FDM layers is also poorer because FDM tends to leave more gaps due to the lower resolution. Meanwhile, resin prints have tighter bonds and fewer gaps.  
• Materials. Some filaments or resins are better for creating prints with higher levels of accuracy. It is best to choose such products. 
• Calibration. Your calibration settings should also be appropriate for the project to ensure accuracy. For instance, too high or low temperatures can affect how the plastic melts for FDM. The way your printer or computer sliced the 3D design also affects accuracy. 

What Is Resolution in 3D Printing? 

In 3D printing, designs are chopped into layers before your printer creates them. An analogy for this would be a big box divided into smaller containers. 

However, not all 3D designs consist of boxes or simple shapes. Some can have complicated figures and intricate designs. The resolution is crucial to accommodate such intricacies.  

Resolution in 3D printing is the smallest dimension your 3D printer is capable of creating. The resolution represents the smallest square area an FDM printer can extrude or the tiniest laser points an SLA printer can have. There are two kinds of resolution: XY and Z. 

The smaller the layers or laser points are, the higher the resolution and accuracy. That is because there are smaller gaps left, which would ensure a smoother finish. 

You might be able to understand it more clearly if you picture this: imagine that you have divided the inside of a circle into boxes. The smaller the boxes are, the fewer and smaller the gaps will be, especially near the circumference. Thus, printing is a bit like pixel art, and the more squares (resolution) you can fit inside the shape you want to print, the more detailed it will be. 

XY/Horizontal Resolution

There are two resolutions, and the first and most important is the XY resolution. The XY axes are the length and width of the layers. Resin printers have better XY resolution. 

For resin printers, the XY resolution is the laser point or pixel size, and these tiny lasters can science much smaller dimensions than FDM nozzles. 

Meanwhile, for FDM, XY resolution is the slightest movement the extruder can make within a layer. However, such motions can only be as small as the nozzle (200 to 400 microns), and plastic flow dynamics (e.g., thermal expansion) allow it to be. 

Some resin printers can have an XY resolution of 140 microns, as small as a strand of hair. For accuracy, it is better to research printers with good XY resolution as it leads to tighter bonds, fewer gaps, and better accuracy.   

Z/Vertical Resolution

Meanwhile, the Z resolution refers to the height or thickness of layers. It is often included in 3D printer specs but contributes less to accuracy. Still, resin printers have better Z resolution than FDM printers. Some resin 3D printers can have a Z resolution of 25 to 300 microns, while those of filament printers are 100 to 300 microns.

However, lower Z resolution values are not necessary for better accuracy, especially if the design is more on straight edges than diagonals or curves. Higher Z resolution may hamper accuracy, as thinner layers leave more room for error. However, if there are a lot of intricate curves to your design, then a low resolution may be best.    

What Is Precision in 3D Printing? 

Precision is often confused with accuracy. However, precision and accuracy are not the same. 

Precision in 3D printing is consistency or repeatability. If you have the same design and make ten prints using a precise 3D printer, each model would have precisely the same dimensions as all of the others. 

For example, if your printer is precise and accurate, your 12 cm (4.7 in) design on such a printer will make ten 12 cm prints with minimal deviations. Regardless of the number of models, the results are the same because the printer is precise.  

Final Thoughts 

Overall, if you are looking for an efficient and accurate 3D printer, you need one that has all three: accuracy, resolution, and precision. Resin 3D printers are generally better in these areas than FDM 3D printers. They have low XY and Z resolution values, making them best for small, intricate, and curvy designs. The bonds between resin layers are also tighter, leading to a smoother finish. They also have reliable precision.