3D Printer: Problems and Solutions in the SLA Process

Although SLA printers are relatively simple, there are enough sources of error. The result is broken or ugly print results. We show the typical problems and how to solve them.

Already during the tests of the cheap 3D SLA printers Elegoo Mars (test report) and Anycubic Photon (test report) we had to face different problems and solve them. In this guide, we summarize our experiences and show possible solutions for common mistakes.

If there is no object on the print platform after printing is complete, the printed product has either become detached or not held to the platform. This error can occur at the first printing or even after a while. A lack of adhesion of the first layer can have many and very different reasons.

One possible cause is an inaccurate calibration. In this case, it helps to realign the print platform and bring a correct zero for the z-axis. To do this, the platform is moved up to the print display so that only one sheet of copy paper fits in between. Then the new zero point has to be stored in the printer. The sheet should be pulled out only with a little effort. It should not be possible to push it under the platform.

In addition, the printing platform must be fat-free and level. Anyone who has adhesion problems despite cleaning with isopropanol can alternatively try acetone. In our tests this has noticeably improved the adhesion. In some cases, it is also necessary to lay hands on and lightly roughen the platform. In the test of the Anycubic Photon we used sleep paper with a 1000 grit. We have placed this on a flat surface and let the printing platform circularly circle on it.

We sanded our pressure plate of the Anycubic Photon. Afterwards the adhesion was clearly better.

Another possible cause of the lack of liability is a loose and not sufficiently secure printing platform. First of all, check that it is screwed tight enough to the z-axis and, if necessary, tighten the set screw more tightly.

If it is sufficiently firmly connected to the boom of the z-axis, the ball joint is checked. If it is loose, tighten the grub screw or grub screws more tightly. But beware, if you tighten the screws while the platform is not upright, you risk insufficient leveling or damage to the print screen.

Even a soiled foil of the resin tank ensures poor adhesion. If the FEP film is very cloudy, the resin does not cure properly because the UV light can not get through. In many cases, cleaning with isopropanol, alcohol or warm water and liquid dishwasher will help. After treatment with a soap solution, the film should then be rinsed well and cleaned again with isopropanol. Using rough kitchen paper can cause fine scratches on the film. Then only the replacement of the film helps. From experience, for example, facial tissues are much softer and therefore more suitable.

The resin can also be a reason for bad adhesion. If it is not sufficiently blended, for example, by vigorous shaking the bottle, it will not cure or not completely. In this case, the resin must be returned to the bottle and then remixed. About two minutes of vigorous shaking is sufficient to get a reasonable consistency. Especially in the case of unsuccessful printing, a sieve should always be used when pouring back, as small cured particles can affect FEP film or display.

If the resin is mixed well, but exposed too briefly, this also leads to a lack of adhesion. An adjusted setting in the slicing software helps here. The recommended exposure times vary from manufacturer to manufacturer and from color to color. The first few layers must cure much longer to ensure adequate adhesion to the printing platform. The correct parameters are usually found in the product description. Alternatively, give it for example here a collection of recommended Exposure times for the Anycubic Photon or here for the Elegoo Mars,

Another source of error is too low a room temperature. For the cure to work properly, it should be around 20 degrees. The ideal temperature varies from manufacturer to manufacturer.

Even an unfavorably positioned print object can be the cause of poor grip on the platform. Once a layer is fully exposed, the print platform must release it from the FEP film. If very thin supports are used, they will not withstand the tensile force and will loosen. Only changes in the slicing software help here.

This is what it looks like when the object adheres to the FEP film instead of the printing platform.

In all these scenarios, several cured layers stick to the FEP film. In order to start a new print attempt, the misprint has to be down. Add the remaining liquid resin from the tank back into the bottle. Anyone wishing to reuse the resin must always use a filter to avoid contamination problems. Then the last remnants are wiped off. After a brief cleaning with isopropanol, the solid layers can be detached from the film with little effort. We use a soft plastic spatula for this purpose. For large-scale misprints whose edges are solved circular. Before the next use of the tank, it is always followed by cleaning with isopropanol and a drying phase of several minutes.

If there is no resin on the print platform or resin tank, there may be a problem with the print screen or the underlying UV LED panel. With luck, only one cable inside the printer has come loose. If not, only a replacement of the defective hardware helps.

If such a hardware defect is to be excluded, something seems to be wrong with the resin. If it does not harden at all, this can only be due to a completely soiled film, clearly too short exposure times or contamination of the FEP film. Who can exclude exposure time and dirty foil, should try a different resin.

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FEP film universal

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Anycubic FEP film

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Anycubic Resin Tank incl. Foil

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Isopropanol 6 liters

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Acetone 1 liter

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Sandpaper 1000 grit

If the support structure, but not the print object itself, stays on the print platform, this indicates that the support is too weak or too few. In this case, adjusting the support settings in the slicing software will help. As a test, the diameter of the columns and the points of contact should be increased. An increase in the number of supports can also help.

Heavy objects should be printed hollow to save weight and resin. In that case, it is important to set drainage holes. Without them, the adhesion is worse because it comes to a Sogeffekt. In addition, liquid resin remains inside the object.

In addition to lack of adhesion, an insufficiently secured printing platform can also lead to skewed prints. If the platform is properly secured, it can also be caused by an unevenly attached resin tank. Both screws securing the resin container must be tightened evenly.

Even with too fine and too few supports, deformations of the printed object can occur.

Those who work sloppily in the slicing software get problems with the scale at best. It happened to us at the pressure of the small turret.

Here was slapped when resizing the slicing software.

If you have problems with visible layers despite the high resolution of SLA printers, you should first check the exposure settings in the slicing software. A strong overexposure is a possible cause of visible quality degradation; as well as insufficiently mixed resin. Another solution is a realignment of the print object. Even slicing in a slightly different angle can lead to an improved print result.

The layers are visible. Here help finer layers or a realignment of the object

If liquid resin gets on the print screen, it should be exposed and cured manually. Removing the exposed layer works in our experience with a scraper for glass ceramic cooktops. However, this should only be set very flat, to avoid damage. Usually enough for scraping an old credit card or plastic spatula, which belongs to the scope of delivery of the printer.

Resin on the print screen must be hardened and scraped off.

If the bottom layer of the printed product is dirty and pitted, it may be due to dirt particles on the FEP film. These prevent sufficient exposure and lead to visible defects. Even small air bubbles by shaking the liquid resin lead to defects. After filling it should rest for ten to twenty minutes before printing starts.

Even small impurities (such as dust particles) in the resin lead to faulty surfaces. Remedy for this problem is the filtering of the resin. Suitable paper filters are available in the hundreds package from about 10 euros. Environmentally friendlier are reusable filters – however, these must be properly cleaned after each use with isopropanol.

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Reusable filter

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Disposable filter 100 pieces

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Disposable filter 250 pieces

Miele cleaning scraper for glass ceramic hobs

cleaning scraper

For curing it also does a cheap UV drying lamp for nail polish.

If the surface of the finished object is still sticky and soft after treatment with UV light, the resin is not fully cured. For a clean surface, the unexposed and excess resin must first be washed off. For simple objects, a bath of isopropanol lasting several minutes is sufficient. For more complicated surfaces, use a soft toothbrush, magnetic stirrer or ultrasonic bath. A magnetic stirrer ensures movement and helps with rinsing. In the ultrasonic bath (in isopropanol), the unexposed resin is shaken off. When buying, make sure that the containers are big enough to hold your own print objects.

Subsequently, the finished print must be long enough under UV light. In addition to finished curing boxes, self-construction with a suitable UV LED is also ideal here. The light source not only has to have enough power, but also have the correct wavelength of light for the resin used. The curing then takes, depending on the lamp, resin and object size, up to half an hour and longer.

XYZprinting UV Curing Chamber (3UD10XEU01K / 3UD10XEU00B)

UV curing chamber

Wanhao Boxman UV Light Chamber (BOXMAN-1)

UV curing chamber

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UV LED strip

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UV lamp 36W

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UV lamp 60W

When filigree structures – such as a grid – lose details and gaps fill with resin, this suggests too much exposure time, poorly mixed resin, or poor post-printing cleaning. Who prints many fine structures with a small distance, it must be sufficiently free of unexposed resin.

Fine structures, such as this Eiffel Tower, need to be thoroughly cleaned.

The resin in narrow openings also withstands a simple cleaning bath due to the surface tension. From the experience the use of toothbrush, UV bath or magnetic stirrer helps. For extremely fine objects, the ultrasonic bath is the best solution since the magnetic stirrer and brush can damage the still soft resin.

AEG Electrolux ETC USR5659 ultrasonic cleaner

Ultrasonic bath 0.6 liter

Dema 60944 ultrasonic cleaner

Ultrasonic bath 1.4 liters

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Magnetic stirrer up to 3 liters

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Magnetic stirrer 1 liter

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CRC compressed air 67 400ml

Compressed-Air Spray

If white stains or streaks appear on the surface after curing, this indicates too little drying time after the cleaning bath. The isopropanol must be completely volatilized before curing starts under UV light. If things go quickly, compressed air spray or compressor help with drying.

Here, the isopropanol was not completely volatilized during curing.

Although SLA printers have fewer moving parts than FDM printers, the error sources for failed prints are still diverse.

Basically, we always recommend mixing the resin well and only pour it back into the bottle through a filter. Also a sufficiently high room temperature is important. The finished print objects must be thoroughly removed from resin residues and cured long enough.

The printer must be properly calibrated and the resin tank sufficiently clean. Damaged FEP films should be replaced in good time. After using isopropanol, a waiting period of several minutes should always be followed so that the residues can evaporate.

Changing the object orientation and slicing settings results in very different results. Here you have to play in doubt and try different variants.


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