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Resolution 3d printing


What Does Resolution Mean in 3D Printing?

Looking for a high resolution 3D printer? “Resolution” is an often discussed but seldom understood value in the world of 3D printing and additive manufacturing. How does XY and Z resolution influence on the quality of your 3D prints? What's minimum feature size and what layer thickness should you choose?

In this comprehensive guide, you'll learn how 3D printer resolution affects your 3D prints and how it differs between SLA, FDM, and DLP 3D printers.

Technology has been in a resolution war for decades. Televisions recently quadrupled pixel counts from HD to 4K and are poised to do it again soon to 8K. Cell phones, tablets, and anything with a screen will have its resolution as the lead on the spec sheet, provided that it’s something to boast about. But this is nothing new. Resolution wars have been waged since digital technology became popular, and the printing industry was one of the first battlegrounds.

If you were around in the 80’s and 90’s, you remember Canon, Brother, HP, Epson, and Lexmark (among others) battling it out for print speed and resolution. What started at 100x100 dots per inch (DPI) quickly escalated to 300x300, then 600x600, and finally the current industry standard of 1200x1200 DPI. Back then, the meaning of these values was clearly understandable; even the units made perfect sense. Unfortunately, things get more complicated when you add another dimension to printing.

A print’s level of detail is impacted by the 3D printer's resolution in all three dimensions.

In 3D printing and additive manufacturing, there are three dimensions to consider: the two planar 2D dimensions (X and Y) and the Z dimension that makes it 3D printing. Since the planar and Z dimensions are generally controlled via very different mechanisms, their resolutions are going to be different and need to be treated separately. As a result, there is a lot of confusion about what the term “3D printing resolution” means and what level of print quality to expect.

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Formlabs' high resolution SLA 3D printers have high Z-axis resolution and a low minimum feature size on the XY plane, allowing them to produce fine details

What makes a 3D printer high resolution? There’s not a one-number answer. Since 3D printers produce parts in 3 dimensions, you will have to consider at least two numbers: the minimum feature size of the XY plane and the Z-axis resolution (layer thickness or layer height). The Z-axis resolution is easily determined and therefore widely reported even though it is less related to print quality and surface finish. The more important XY resolution (minimum feature size) is measured via microscopic imaging and is therefore not always found in spec sheets.

Practically, it means that you should pick a 3D printer that performs well in both categories (in all 3 dimensions).

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A lot has changed since the first desktop 3D printers became available to the public. Now stereolithography (SLA) 3D printers, like the Form 3+, are competing for the same desktop spots as fused deposition modeling (FDM) 3D printers. One of the main advantages that resin-based SLA 3D printers hold over their plastic-melting cousins is print quality: SLA 3D printers produce significantly smoother and more detailed prints. While SLA printers can usually also achieve significantly smaller layer thicknesses, the reason for the improved print quality lies in their much higher XY-resolution.

SLA 3D printers (right) offer higher resolution and can produce significantly smoother and more detailed prints than FDM 3D printer (left).

Unlike on FDM 3D printers, minimum feature size in the XY plane on SLA 3D printers is not limited by molten plastic flow dynamics but rather optics and radical polymerization kinetics. While the math is complicated (and outside the scope of this post), it shakes out to this: features on SLA prints can be approximately as small as the diameter of their laser spots. And laser spots can be really small, especially compared to the nozzle size of FDM printers' extruders.

Read our in-depth guide about FDM vs. SLA 3D printers to learn how they compare in terms of print quality, materials, applications, workflow, speed, costs, and more.

Resin 3D printers like SLA, LFS and DLP technologies offer the highest resolutions of all 3D printing processes available on the desktop. The basic units of the these processes are different shapes, making it difficult to compare the different machines by numerical specifications alone.

DLP 3D printers have a fixed matrix of pixels relative to the build area, while laser-based SLA and LFS 3D printers can focus the laser beam on any XY coordinate. This means that laser-based machines, given high-quality optics, can more accurately reproduce the surface of a part even if the laser spot size is larger than the DLP pixel size.

Whichever resin 3D printing process you choose, however, professional resin 3D printers should be able to capture the finest details of your creations, from photorealistic models to intricate jewelry.

In SLA and LFS 3D printing (left), layer lines are close to invisible. As a result, surface roughness is reduced, which ultimately leads to smooth surfaces, and for clear materials, more translucent parts. DLP 3D printers render images using rectangular voxels, which causes an effect of vertical voxel lines (right).

Learn more about the differences between SLA and DLP 3D printers and see how they compare in terms of resolution, accuracy, precision, build volume, surface finish, speed, and workflow.

In the world of 3D printing, no factor influences print quality more than XY resolution. Often discussed but seldom understood, the definition of XY resolution (also called horizontal resolution) varies by 3D printing technology:

  • SLA and LFS 3D printers: a combination of the laser’s spot size and the increments by which the laser beam can be controlled
  • DLP 3D printers: the pixel size, the smallest feature the projector can reproduce within a single layer
  • FDM 3D printers: the smallest movement the extruder can make within a single layer

As a rule of thumb, the lower the number, the better the details. Yet this number is not always included in spec sheets, and when it is, the published value is not always accurate. To truly know a printer’s XY resolution, it’s important to understand the science behind the number.

Practically, how does XY resolution affect your 3D prints? In order to find out, we decided to test the Form 2 SLA 3D printer. The Form 2 has a laser spot size of 140 microns (FWHM), which should allow it to print fine details on the XY plane. We put it to the test to see if this ideal resolution holds true.

To test the Form 2’s minimum feature size on the XY plane, we designed a model (left) with lines ranging from 10 to 200 microns and printed it in Clear Resin (right).

First, we designed and printed a model to test the minimum feature size on the XY plane. The model is a rectangular block with lines of varying widths in horizontal, vertical, and diagonal directions to avoid directional bias. The line widths range from 10 to 200 microns in 10 micron steps and are 200 microns tall, which equates to two layers when printed at 100-micron Z resolution. The model was printed in Clear Resin, washed twice in an IPA bath, and post-cured for 30 minutes.

The model was photographed and tinted green to improve visibility. On the right side of the window, the vertical yellow line with black points measures the width of a photographed line.

After post-curing, we put the model under a microscope and took high-resolution photos for analysis. Using ImageJ, the NIH’s free image analysis software, we first scaled the pixels of the images and then measured the actual widths of the lines printed. We collected over 50 data points per line width to eliminate measuring errors and variability. In total, we printed and analyzed three models on two different printers.

The results indicate that the Form 2 has the same ideal and actual XY resolution for features that are 150 microns and larger.

As the print’s line width decreases from 200 to 150 microns, the ideal values are within the 95% confidence interval of the measured value. As the intended line widths get smaller than 150 microns, the measured interval starts to deviate significantly from the ideal. This means that the printer can reliably produce XY features as small as 150 microns, about the size of a human hair.

The Form 2’s minimum feature size on the XY plane is about 150 microns—only 10 microns larger than its 140-micron laser. The minimum feature size can never be smaller than the laser spot size, and there are many factors that affect this value: laser refraction, microscopic contaminants, resin chemistry, and much more. Considering the printer’s entire ecosystem, a 10-micron difference is nominal. Not every 3D printer’s published resolution holds true, so it’s a good idea to do plenty of research before choosing the one that's right for your project.

If your work calls for prints with intricate details, look for a printer with an XY resolution that’s backed by measurable data, not just a number.

When you read 3D printer spec sheets, you’ll see one value show up more than any else: Z resolution. Also known as layer thickness or layer height, the vertical resolution was the first major numerical differentiation between early 3D printers. Early machines struggled to break the 1 mm barrier, but now layer thicknesses on FDM 3D printers can be sub-0.1 mm thin, while LFS and SLA 3D printers are even more precise.

Formlabs 3D printers support layer thicknesses between 25 to 300 microns, depending on the material. This selection of layer heights gives you the ideal balance of speed and resolution. The main question is: what is the best layer thickness for your print?

High resolution 3D printing comes with a tradeoff. Thinner layers mean more repetitions, which in turn means longer times: printing at 25 microns vs. 100 usually increases the print time four-fold. More repetitions also mean more opportunities for something to go wrong. For example, even at a 99.99% success rate per layer, quadrupling the resolution lowers the chance of print success from 90% to 67% if one assumes that a failed layer causes total print failure.

Lower layer thickness equals more time, artifacts, and errors.

Does higher resolution (thinner layers) result in better prints? Not always—it depends on the model to be printed and the 3D printer’s XY resolution. In general, thinner layers equals more time, artifacts, and errors. In some cases, printing models at lower resolutions (i.e. thicker layers) can actually result in higher-quality prints.

Thinner layers are typically associated with smoother transitions on diagonals, which leads many users to generalize and push Z resolution to the limits. But what if the model consists mostly of vertical and horizontal edges, with 90-degree angles and few diagonals? In those cases, additional layers don’t improve the quality of the model.

The issue is compounded if the XY resolution of the printer in question is not perfect and “colors outside the lines” when drawing the outside edges. More layers means more mismatched ridges on the surface. While the Z resolution is higher, the model will look like it is significantly lower quality in this case.

That being said, there are times when you want higher resolution. Given a printer with good XY resolution and a model with intricate features and many diagonal edges, dialing down the thickness of the layers will yield a much better model. In addition, if that model is short (200 or fewer layers) upping the Z-axis resolution can really improve the quality.

Certain designs benefit from a higher Z resolution: organic forms, rounded arches, small embossings, and intricate engravings.

Intricate models with elaborate details call for a higher Z resolution. SLA 3D printed parts have sharp edges, sleek surfaces, and minimal visible layer lines. This example part was printed on the Formlabs Form 3 desktop SLA 3D printer.

As a general guideline, err on the side of thicker layers and only bump up the Z resolution when completely necessary. With the right printer and a certain type of model, higher Z resolution will capture the intricate details of your design.

Draft Resin, the fastest 3D printing resin available for a Formlabs SLA printers, prints at 200 microns and 100 microns, while retaining the a smooth surface finish.

In PreForm, Formlabs provides users with the choice of different layer thicknesses. Depending on the material and the requirements of the application, parts can be printed in the following layer heights: 200, 160, 100, 50, and 25 microns.

The desktop Form 3+ and the large format Form 3L SLA printers are ideal for high resolution 3D printing.

After learning about 3D printing resolution and sorting out the differences in technology and outcomes, we hope it’s much easier to select 3D printer that best matches your workflow and output needs.

To explore the next generation of SLA 3D printing, learn more about the Form 3 and Form 3L LFS 3D printers. 

Curious to see the what high resolution 3D printing looks like firsthand? Order a sample part shipped to your office.

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3D printer resolution - what does it really mean?

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In the world of 3D printing we often speak of the 3D printer resolution of the machines. Because 3D printing is such an accurate procedure, the accuracy of 3D printers is in the size of microns. A micron is one thousandth of a millimeter, so it is extremely small. By displaying the 3D printer resolution, the buyer has a general idea of what the printer is capable of. There is more to the story, however.

A 3D printer resolution example:

If the 3D printer resolution is set to 200 microns and we want to print 2mm height over a distance of 10 cm, it would mean we need 10 layers in order to achieve the desired height .

However, if printed at 100 microns, it would mean that there would be 20 layers used to create the height of 2mm and that would mean 0.1mm step between each layer and a smoother surface delivering a better-looking acute angle.

3 types of deviation

While the 3D printer resolution is very important, you also need to use the best material for your design. Even when you have the most accurate 3D printer on the market, it’s possible that there’s a slight deviation. It might be too small to spot with the human eye, but it might make the difference between a functional print and one you can’t use. Therefore it’s important to know that there are three types of possible deviations when we speak of the 3D printer resolution: machine-, material- and end result deviation.

Machine deviation

Manufacturers of 3D printers can only promise that their machine resolution is what they claim it is. Therefore they advertise with this factor, as do we. The accuracy of our 3D printers is 10 microns, which we’re very proud of. However, it is normal that there is a possible deviation on the Z axis, as gravity pulls the material down. Therefore, we differentiate the resolutions of the X and Y axes (2D) and the Z axis which makes it 3D.

While the 3D printer resolution of the X and Y axes is easy to pinpoint, the Z axis falls victim to gravity. When printing in height, gravity can cause more material to come out of the printer than is intended. Therefore the 3D printer resolution is often a bit lower than is said on a manufacturer’s website. As stated, the accuracy ofTractus3D printers is 10 microns on the X and Y axes. On the Z axis we recommend not printing below 50 microns to make sure your prints are as you desire.

Material deviation

The material can play a significant role in the resolution and outcome of a print. Every material is different and will shrink in its own way and this occurs when it turns from a fluid to a solid – also known as warping. The contraction process takes place when a synthetic material starts to cool down and this can cause the print to bend from the build plate. Of course, as mentioned, each material is different and some will shrink more than others such as PC, which shrinks more than PLA. Therefore, to avoid this, you should ensure that a heated build plate is used, which ensures that the object does not solidify quickly. At Tractus3D, our printers also come with a heated build plate and closed chamber which ensures prevents temperatures from fluctuating, as the warmth is not released.

End result deviation

Last, but certainly not least, is the end result deviation. Everyone purchases a 3D printer to get the most accurate print possible. Even the tiniest deviation can cause a print to not be implemented at all. The end result deviation weighs the machine- and material deviation against each other. This factor can thus be partially influenced by the manufacturer of the machine. Tractus3D printers know which materials have a certain deviation and automatically adapt the machine deviation so the end result is as desired.

How can you test the 3D printer resolution?

3DBenchy as the model for testing and benchmarking the 3D printer resolution

It is important to test the resolution of the 3D printer, so that you can determine the geometrical features that play a part in the outcome. 3DBenchy is used as a way of testing and benchmarking 3D printers. The 3DBenchy is a little boat that has been designed to print at a scale of 1:1 without support material. This makes it possible to look at the different surfaces of the model in order to determine any issues associated with the finish of the surface, warping and accuracy.

3DBenchy on a Tractus3D printer

In the video above a Tractus3D printer is subjected to the test. The 3DBenchy (from bow to stern measures 60 mm) was printed on our smallest 3D printer, the T650. During printing we did not experience warping or bridging difficulties or any other of the aforementioned possible problems. It took less than 2 hours to complete the 3D print and pass the test!

How the 3D printer resolution can affect the outcome

Just like any other type of printing, the type that you use can affect the final outcome of the print job. This is particularly true for 3D printing and so, you can see just why it is important to consider the 3D printer resolution as part of the decision making process.

Size

When it comes to industrial 3D printers, as they evolve, the desire to printer larger objects will grow, and with this will come an increase in the need for the quality. For large objects, there might not always be a need for that level of resolution but in the case of small or detailed objects such as those that have interlocking or connecting parts, accuracy is vital and so, high resolution is an absolute must.

Curves

For those printers that have a lower 3D printer resolution, they will print thicker and so, in those particular objects that have a curve, they edges will be rougher and will have a stepped appearance to it. As the thickness of each layer increases, the step between them increases. Thinner layers would give a larger number of smaller steps, making the curve appear smoother.

Horizontal angles

In the same way as those objects that have curves, when 3D printing objects that have angles horizontally, the number of steps in the printed object will be determined by the 3D printer resolution. If the 3D printer resolution is set to 200 microns and we want to print 2mm height over a distance of 10 cm, it would mean we need 10 layers in order to achieve the desired height and there will be a layer thickness of 1 cm. However, if printed at 100 microns, it would mean that there would be 20 layers used to create the height of 2mm and that would mean 0.5mm step between each layer and a far smoother surface delivering a better-looking acute angle.

How high resolution is achieved

Filament choice

The first thing about ensuring that high resolution is achieved is down to the ability to take care of the filaments in the correct way. The whole printing process is influenced by the filament and so, it is important that great care is taken over it. The filament has to be correctly wound onto the spool and it is crucial that the temperature is set correct for a heated platform to prevent the objects from sticking to it. An example of this would be ABS which requires a temperature of 100 degree Celsius while PLA only requires a temperature of 60 degrees Celsius.

Temperature regulation

As touched upon already, the quality in 3D printed objects as well as the resolution will often come down to the temperature of the extruder or the heated platform. Of course, every material will come with a desired extrusion temperature such as ABS which has the most successful melting point at around 240 degrees Celsius. This can vary depending on the manufacturer so it worth taking that into consideration.

Support

Where complex and highly detailed objects are being printed with a high 3D printer resolution, it is crucial that rafts and support structures are used. The key to getting this right is to ensure that the correct thickness is set for the raft, the right distance between the object and the support and the density. However, the denser the support is, the more difficult it can be to remove once the print job has been completed.

Software

The software that is used can also play a part on the final outcome and quality of the 3D print. Different programs can cause better or less adjoining structures and that can have a significant impact on the overall quality of the final print.

Nozzle

The layer height is extremely influential on the quality of 3D prints. Often, standard 3D printing heights are set between 0.1 and 0.3 mm but with the correct nozzle and the right filament, it is possible to increase the height range to 0.05 to 0.35mm. It is worth remembering that the layer height should not be more than the diameter of the nozzle and less than that of half the path width. The lower the layer, the easier it is to create a 3D print that is detailed and accurate with fewer visible layers.

In contrast to this, the path width does depend on the size of the nozzle as most nozzles are around 0.3 and 0.4mm. The minimum width can equate to that of the diameter of the nozzle but it can be increase by around 0.1 to 0.2mm. Commonly, the path width should equate to twice that of the layer height and so, a safe path width can be considered to be between 0. 3mm and 0.6mm.

3D printing speed

The speed of the 3D printer and print job can have a significant impact on the quality and resolution of the final object in FDM printing. When the print job is carried out in more time it means better finishes on corners or edges. Most filaments will also adhere better and have more time to cool down.

Whether you are opting to print with one or two material extruders, retraction is a crucial part of the process. This is down to the fact that it is responsible for retracting the filament when it is not in use. If the speed and distance of retraction is increased then this can prevent the filament from blobbing on the object as well as prevent any unintentional mixing. It will also mean that filament does not hang from the nozzle. In this case when the extruder moves over the object, it does not leave behind thin hairs of plastic on the printed object.

When resolution is not important

Obviously, design engineers want to achieve the very best printing results and that means that they should consider everything to achieve this. However, not every situation requires a high resolution finish. This is down to the part geometries, the parts that are being produced and how they will be used. In some cases, a high resolution is great but where there are time constraints and less of a requirement to print in high resolution then less care or concern can be taken to the final product. Of course, cost can also play a part in this, particularly where costs need to be kept to a minimum as this can mean that low quality resolution objects can be created without any concerns.

The 3D printer resolution of Tractus3D industrial printers

When designing exquisite models for FDM 3D printing, you want them to be as detailed as possible so that you can truly see the expertise put into it. With a 3D printer resolution of 0,01 millimeter (10 microns) on the XY-axis and a resolution 0,05 millimeter (50 microns) on the Z-axis, the Tractus3D DESK printers can print even the finest details. When your objects do not require such detail, you can print at a lower resolution up to 1000 micron.

In the end, Tractus3D systems are capable of the 3D printer resolution we say they can. It is up to the user to make sure they choose the right material for the endproduct. We choose to not set you free into the wild when you buy our industrial 3D printers. We will advise you on what is and is not possible before you purchase our product, so you can get the most out of your printer. This is why our industrial 3D printers have profiles of all the materials, so you know which settings are right for each material. With the help of these profiles, the printer automatically chooses the right temperature and accounts for things such as shrinkage. As a wise man once said: with a great 3D printer, comes great responsibility.

What is the resolution of a 3D printer? What does it affect. How to setup!.

In many technical descriptions, one can come across such a characteristic of a 3D printer as resolution. This parameter is changeable and therefore it is also important to understand what it is and what values ​​​​it can take, since this will be reflected in the print results.

An analogy can be made with an ordinary image, that is, a picture. The higher the resolution, the better the picture will be, the higher the detail. However, the size of such an image will be larger. This is natural for any devices (phones, tablets, TV screens, etc.). It's the same with a 3D printer. nine0003

Any 3D model is formed by slicing. This is the process of cutting into separate horizontal layers, from which a physical model is formed.
The 3D printer has two types of resolutions:
• along the X and Y axes;
• Z-axis.

The first will be the resolution in the 3D plane, and the second will be the height of the layer.

In the specifications of a 3D printer, the maximum resolution is the minimum layer height value. The lower the layer height, the better the detail will be. At the same time, the number of layers will also increase, which will affect the printing time - it will increase. nine0003

For comparison, we can take FDM, SLA printers. Printing technologies are different, as are the characteristics. For an FDM printer, the minimum layer height is 0.05mm. An indicator less does not make sense, since these devices are not suitable for printing highly detailed products, as well as small models. And a smaller value of resolution along the Z axis will not affect the print quality. In SLA 3D printers, the layer thickness can be 0.005mm. Therefore, such devices are used to print small parts, such as jewelry, dental products. nine0003

A legitimate question arises: “Is high resolution always required?” If you set the layer thickness to the minimum value, then the print time will always increase. For example, if you print a product not at 100 microns, but at 25 microns of layer height, then the printing time will increase by 4 times, that is, in direct proportion.

If your model is a flat wall at a right angle, the resolution increase will not affect the quality. At least substantially accurate. In the event that your 3D printer is not well calibrated, then the layers may shift relative to each other. And it turns out that the more layers there are, the greater the displacement and, accordingly, the irregularities. And as a result, at high resolution, you can get a detail of worse quality. nine0003

If you need to print miniature products with complex elements: engravings, roundness, arches, a large number of complex shapes, then high resolution will be a must, because otherwise no elements will be clearly printed, and they may simply be invisible.

Z-axis resolution will be limited by the design of the printer. For FDM devices, this will be the nozzle diameter. It is impossible to set the layer thickness greater than the nozzle diameter, since this would be impossible from a physical point of view. For SLA printers, it is also impossible to supply more than 100 microns, since the layer must be well cured by the laser. The higher the layer height, the longer it will take to illuminate the laser. In addition, due to the high layer thickness, various defects and artifacts can occur, that is, the quality of the product will suffer greatly. nine0007
The X and Y resolution will depend on the design of the printer. When viewed from the point of view of prints, then this indicator will affect the last layers of the product. For an FDM printer, it will also depend on the nozzle diameter, and the smaller it is, the higher the resolution will be. In this case, the fills will be less noticeable, and the quality of the product will be higher. For SLA printers, this characteristic will be determined by the diameter of the laser spot. This value will always be constant and does not change. For DLP printers, this characteristic will depend on the pixel size and projector resolution. nine0003

What Does Resolution Mean in 3D Printing?

Looking for a high resolution 3D printer? “Resolution” is a term from the field of 3D printing and additive manufacturing that is often talked about, while rarely understanding its meaning. How does XY and Z resolution affect the quality of 3D printed models? What is the minimum element size and what layer thickness should I choose?

This detailed guide explains how 3D printer resolution affects model printing and how it differs between SLA, FDM and DLP printers. nine0003

For decades, technology manufacturers have been striving for higher resolution than their competitors. TVs have recently quadrupled their pixel count from HD to 4K, but manufacturers are already thinking about pushing the resolution to 8K. Mobile phones, tablets and other devices with screens show resolution as one of the main characteristics, if, of course, they have something to brag about. But this is nothing new. Resolution wars have been fought since digital became popular and the printing industry became one of the first battlegrounds. nine0003

If you lived in the 80s and 90s, you'll remember how Canon, Brother, HP, Epson, and Lexmark (among others) sought to improve print speed and resolution. 100 x 100 dpi quickly grew to 300 x 300, then to 600 x 600. Finally, now the standard resolution is 1200 x 1200 dpi. Then these values ​​were extremely clear, and the use of units of measurement was quite logical. Unfortunately, things get much more complicated when you add another dimension to print. nine0003

The level of detail of the model depends on the resolution of the 3D printer in all three dimensions.

In 3D printing and additive manufacturing, there are three dimensions to consider: two planar 2D dimensions (X and Y) and a third dimension, Z, which is used for 3D printing. Since planar measurements and Z measurements are usually controlled by completely different mechanisms, their resolutions will differ. Therefore, they must be considered separately. As a result, there is a lot of confusion about the interpretation of the term "3D printing resolution" and false expectations for print quality. nine0003

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Formlabs high-resolution stereolithographic 3D printers feature high Z-axis resolution and a low minimum element size on the XY plane, allowing them to capture fine detail.

What affects the high resolution of a 3D printer? It is impossible to name any one isolated factor. Since 3D printers produce models in 3 dimensions, there are at least two factors to consider: the minimum size of the XY plane elements and the resolution of the Z axis (thickness or height of the layer). Z-axis resolution is easy to determine and is therefore more commonly reported, although it is less related to print and surface quality. The more important XY resolution (minimum element size) is measured with a microscope and is therefore not always found in specifications. nine0003

In practice, this means that the 3D printer must perform well in both categories (in all 3 dimensions).

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A lot has changed since the first desktop 3D printers hit the market. Now stereolithographic (SLA) 3D printers such as the Form 3 directly compete for desktop space with Fused Deposition Modeling (FDM) 3D printers. One of the main advantages of 3D printers that use polymers as consumables over their plastic-melting counterparts is print quality: SLA printers produce models with a smoother surface and a higher degree of detail. While stereolithography printers typically achieve significantly thinner layer thicknesses, the reason for the improved print quality is the much higher XY resolution. nine0003

SLA printers (right) have higher resolution and produce models with smoother surfaces and more detail than FDM printers (left).

Unlike 3D printers based on FDM technology, the minimum size of elements in the XY plane in stereolithographic 3D printers is not limited by the dynamics of the flow of molten plastic, but is more determined by the optics and kinetics of radical polymerization. Although the calculations are complex (and beyond the scope of this article), it can be said that the details on models produced by stereolithography printers are about the same size as the diameter of the corresponding laser spots. And laser spots can be very small, especially when compared to nozzles on FDM printers. nine0003

Check out our detailed guide comparing FDM vs. SLA 3D printers to see how they differ in terms of print quality, materials, application, workflow, speed, cost, and more.

Technologies Resin-based 3D printing such as SLA, LFS and DLP provide the highest resolution of all 3D printing processes available for desktop printers. The primary units of measure for SLA and DLP processes are different forms, making it difficult to compare printers based on numbers alone. nine0003

DLP-based 3D printers have a fixed pixel matrix relative to the work area, while SLA- and LFS-printers that use a laser can focus the laser beam on any coordinate of the XY plane. This means that laser 3D printers with high optical quality can accurately reproduce the surface of the model, even if the laser spot size is larger than the pixel size in the DLP printer.

Whichever resin 3D printing technology you choose, professional 3D printers should capture the finest details of your creations, from photorealistic models to fine jewelry. nine0003

When printing on 3D printers based on SLA and LFS technologies (left), layer lines are almost invisible. As a result, surface roughness is reduced, resulting in a smooth surface, and when using transparent materials, models with greater transparency. DLP printers use rectangular voxels to render images, which can result in vertical lines (right).

Learn more about the differences between SLA and DLP technologies in terms of resolution, accuracy, clarity, print volume, surface quality, speed, and how they work. nine0039

In the world of 3D printing, no other factor affects the quality of models more than XY resolution. She is often mentioned, but rarely understood. The definition of XY resolution (or horizontal resolution) differs depending on the 3D printing technology:

  • stereolithographic 3D printers - a combination of laser spot size and the size of the steps with which the beam can be controlled;
  • DLP printers - pixel size, the smallest detail that a projector can reproduce in a single layer; nine0089
  • FDM printers - the smallest distance that the extruder can move within one layer.

In general, the lower this value, the finer the detail. But this number is not always indicated in the technical specifications, and even if indicated, it is not always correct. To get an idea of ​​true XY resolution, it is important to understand how a printer works.

How does XY resolution affect the quality of your models? To find out, we decided to test a Form 2 stereolithographic 3D printer. The size of the laser spot in the Form 2 printer is 140 µm (FWHM), which should allow it to reproduce fine details on the XY plane. We decided to check if this ideal resolution corresponds to the truth. nine0003

To check the minimum feature size on the XY plane for the Form 2 printer, we designed a model (left) with lines from 10 to 200 µm thick and printed it using Clear Resin (right).

We first designed and printed the model to check the minimum element size on the XY plane. The model is a rectangular block with lines of various widths in the horizontal, vertical and diagonal directions, which are applied to prevent displacement. The line thickness is from 10 to 200 µm, the lines are drawn at 10 µm intervals and have a height of 200 µm, which corresponds to two layers when printed at a resolution of 100 µm for the Z axis. Made from Clear Resin, the model was washed twice in isopropyl alcohol and subjected to a within 30 minutes. nine0003

The model was photographed and painted green for better visibility. The vertical yellow line with black dots on the right side of the window is for measuring the width of the photographed line.

After the final polymerization, we placed the model under the microscope and took a high resolution photograph for further analysis. Using ImageJ, a free image analysis program from the National Institutes of Health (NIH), we scaled the image pixels and measured the actual width of the printed lines. We collected over 50 data points per line width to eliminate measurement errors and variability. We analyzed three models made on two printers. nine0003

The results show that the Form 2 has the same ideal and actual XY resolution for model elements as small as 150 µm.

As the line width decreases from 200 to 150 µm, the ideal values ​​are within the 95% confidence interval of the measured value. As the expected linewidth becomes less than 150 µm, the measured interval starts to deviate significantly from the ideal. This means that the printer can reliably reproduce elements up to 150 microns in size, as thick as a human hair, on the XY plane. nine0003

The Form 2 printer has a minimum XY feature size of about 150 µm, only 10 µm larger than the 140 µm spot size of its laser. The minimum element size cannot be less than the laser spot size. There are many factors that affect this value: laser refraction, microscopic contaminants, polymer chemistry, etc. Considering the entire printer ecosystem, a difference of 10 µm is nominal. Not all 3D printers have the reported resolution as the actual resolution, so it's a good idea to do a lot of research before choosing the right resolution for your project. nine0003

If you want models with fine detail, look for a printer whose XY resolution is not just listed as a number, but supported by measured data.

When looking at the specifications of 3D printers, you will find that one parameter appears more often than any other. This is the z-axis resolution. Also known as layer thickness or layer height, vertical resolution was the first major numerical parameter by which early 3D printers were differentiated. The first such devices struggled to overcome the 1 mm barrier, but now the layer thickness in FDM-based 3D printers can be less than 0.1 mm, and even less in LFS and SLA printers. nine0003

Formlabs 3D printers support layer thicknesses from 25 to 300 microns, depending on the material. This range of values ​​allows you to find the perfect balance between speed and print quality. But the main question is what layer thickness will be ideal for your model.

The high resolution of 3D printing affects other parameters. The thinner the layer, the more layers need to be printed, resulting in increased model production time: typically, printing at a resolution of 25 µm takes four times longer than printing at a resolution of 100 µm. In addition, the more layers, the higher the probability of errors. For example, even with a layer success rate of 9A 9.99% fourfold increase in resolution reduces the chances of a successful print of the model from 90% to 67%, provided that the layer with the error leads to rejects.

The thinner the layer, the longer it takes to print and the more likely it is to cause errors and distortion.

Is it true that the higher the resolution (the thinner the layers), the higher the quality of the finished models? Not always. It depends on the model and resolution of the XY 3D printer. As a general rule, the thinner the layer, the longer it takes to print and the greater the chance of distortion and errors. In some cases, printing models at a lower resolution (i.e., with thicker layers) may even result in better quality. nine0003

Thinner layers are usually associated with smoother diagonal transitions, causing many users to push Z resolution to the limit. But what if the model consists mostly of vertical and horizontal faces, with right angles and a small amount of diagonal surfaces? In such cases, increasing the number of layers will not improve print quality.

The problem is exacerbated if the printer's XY resolution is not ideal and it "goes out of bounds" when forming the outer edges. The more layers, the more mismatched protrusions will be on the surface. In this case, the finished model will look much worse, even if the Z resolution is higher. nine0003

There are times when you need to increase the resolution. If you have a printer with good XY resolution and a model with complex features and many diagonal edges, reducing the thickness of the layers will allow you to get a much better quality physical model. Also, if this model is small (no more than 200 layers), then increasing the resolution of the Z axis will lead to a real improvement in quality.

Some designs benefit from higher Z resolution: organic shapes, rounded arches, fine embossing and intricate engraving. nine0119

A tiny model with lots of detail and arches needs a higher Z resolution. This cathedral was printed on a Form 2 printer at 25µm resolution.

Try to stick to this general rule: print thicker layers and increase the Z resolution only when it is really necessary. With the right combination of printer and model type, the higher Z resolution will capture the intricate details of your design. nine0003

Gray Resin allows printing at a resolution of 160 microns. Check out the difference in speed for yourself.

Formlabs PreForm software allows you to choose the layer thickness. Starting with version PreForm 3.0.3 , Gray Resin can be printed in 160, 100, 50 and 25 µm layer heights. Printing at a resolution of 160 microns will speed up the iteration process and allow engineers to move from design to finished model even faster. And dentists can produce more aligners per day without sacrificing quality. nine0003

We hope that once you are familiar with the concept of resolution and understand the differences in 3D printing technologies and results, it will be much easier for you to choose a 3D printer that best suits your needs and workflow.

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