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3D Printing Problems & Diagnoses: FDM Printing

3D Printing Problems & Diagnoses: FDM Printing

You purchase a 3D printer, it’s easy to assemble, and your first prints come out great but then when you go back to do something else a week later, nothing seems to work the way it should. For your mangled, lopsided, and non-printing prints, here is a brief troubleshooting guide for some major problems. 


1) X or Y axis sliding

This problem is most common in 3D printers that have been in action for a while and have seen some good prints. Most 3D printer movement functions are reliant on belts that allow both the printhead and print bed to move in the x and y axes. Over time, the functionality of these belts can deteriorate as the nuts and bolts slowly inch out of place. The more a printer moves/prints, the jerky movements will loosen crucial components that keep your print in place. 

One simple way to test this is by checking the belts on the printer. Belts should be tight and slightly firm when pinched, but should not be taut. Belts should be equally all over, top and bottom. A discrepancy in this can cause some of the symptoms of x and y “sliding”. Belt tensioners are often used to tighten the belts, and if your 3D printer does not already have them, are available as models on many 3D printing sites. Adjust your belts to have uniform tightness all around. 

Another potential issue is a loosened nut or bolt somewhere in the print bed structure. Often, a loose component responds poorly to jerky printing motions and causes a repositioning of the head every time it shifts. One way to cure this is to take apart the print bed and search for any loose parts, tightening as you rebuild them. 

Lastly, any rods or components with debris on them can cause trouble with printhead motion. Check to see if there are any stray pieces of filament or other litter in your printer before trying it out again. Don’t forget to always recalibrate after making adjustments.

First layer not adhering to the print bed:

There are a few causes and remedies to this issue. Most commonly, the problem tends to be in the z-height calibration. The first step for this is to run through whatever z-calibration is specified by the 3D printer, these can be autonomous as the printer calibrates itself, or more commonly they are done by hand and using a standard piece of paper as a reference for height. 

If that doesn’t help, some materials benefit from a higher print bed temperature (if your printer has a heated bed included). Increase heat bed temperature in increments of 10 degrees, and adjust to see what looks best for your print. Your print bed may also have residue or grease from your hands or whatever touched it in previous runs, most print beds can be cleaned with rubbing alcohol and kimwipes. 

Another option is to switch out your print bed. In slightly older 3D printers, many people created print beds using some kind of insulation tape. However, print beds can now be customized and made out of different materials such as steel or glass. Some steel print beds have the added benefit of being removable as well as flexible, making it easier to pop off the harder to remove prints. 

One home-made solution is also to use an adhesive, many 3D print beds can be combined with adhesives such as hair spray. Some 3D printing specific products are also developed for this purpose such as PVA glue sticks and 3D print bed sprays such as 3DLac. 

Print edges are “falling off” or bending out of shape:

If your print edges are falling off the sides as seen in the picture, you most likely should be printing with supports. With this type of 3D printing, the software will direct the printer to print the model layer by layer, even if there is no underlying layer. This means that when printing a model with any potential overhang, the overhanging layer would print onto air without supports.

Most slicing softwares such as Cura can generate extremely capable supports will prevent these slips or stringy areas from happening. If you find that software generated supports can be difficult to achieve, there is also always the option of using your own modeling application to generate your own supports (for the experienced/advanced modeler). 

Prints are warping:

Warping can be the result of several factors, and therefore there are quite a few fixes. One automatic fix is to use a heated bed calibrated to the appropriate temperature for whichever thermoplastic you are using. This will regulate the heat to the bottom layer and retain its properties as layers are built above it. 

If the environment in which you are printing is open and susceptible to drafts, temperature changes, and humidity, the addition of a printing chamber or enclosure may help prevent warping due to atmospheric fluctuations. This can be similarly remedied by preventing the conditions in the room from changing by keeping a regular temperature on the thermostat and sealing any drafts. A humidifier or dehumidifier may also help to maintain balance in the rooms.

One method of preventing warping for some 3D prints is to adjust the cooling during the early stages of the print. Of course, this does not allow you to press a button and step away from the print, but if you have the patience, lowering the cooling functions of the printer during the first steps may keep the model in place (by reducing cooling you reduce the risk of rapid cooling and warping of the thin first layers).

Z-Layer Height is not properly calibrated/extruder misses the table:

Calibrating the height of the z-axis is one of the most highly underrated 3D printing fixes out there. Most issues with layers, sliding, and adhesion are due to improper calibration of the nozzle height and z-axis movement. If your 3D printer has a built in z-axis calibration, go through the motions of calibrating it and see if the quality changes. Many printers will allow you to fine-tune the z height during a print. 

One way to assess a good height is by printing large flat areas that easily show at what height the nozzle extrudes best. As shown above, smooth, flat layers that connect to each other on both sides easily are best, whereas separated lines show too high nozzle height (problems with adhesion, warping, cracks and layer separation), and translucent spreads show too low nozzle height (melting, print layers not aligning in space).

Infill looks messy or doesn’t print correctly:

Infill can print badly as a result of a few things. In some cases, it could be a setting issue rooted in the slicing software used. A good infill density should typically be around 20%, however for more complex or large prints, you may want to increase this value. Like most other aspects of 3D printing through extrusion of thermoplastics, a reduction in temperature and/or heat as well as print speed can increase the accuracy at which a printer functions. 

In some cases, the infill pattern may also impact the quality of the print, and trying out some different patterns may result in a better effect. Lastly, a nozzle blockage may also play a role in poorly printed infill. 

Prints that burn, stick to nozzle, or completely malfunction:

In many cases, random printing failures are the result of misconfigured slicing settings. The range of temperatures and speeds at which 3D printers can operate at are not all optimal for every print. It may take some adjustment and know-how to figure out what print settings are best for different types of prints. 

It’s always a safe bet to reduce the speed of movement of the nozzle; in some cases a reduced speed with a higher temperature can create fine prints at the price of a slower job time. 

Make sure to continually check the printer’s calibration routinely, as well as continue to print things regularly to maintain through use. 

Rough areas where supports are generated after printing:

Supports are a crucial part of printing complex structures with overhanging elements. However, some supports leave undesirable marks on the final printed object. This can be addressed through the slicing software or the finished model itself.
Some more complex slicing softwares are able to generate supports that reduce any markings on the printed object. Additionally, some dual extrusion models are able to distinguish between supports and print and can be programmed to print supports in water soluble filaments (more complex and costly).
Print areas can also be refined in post-production processing, using sanding techniques, as well as acetone baths (ABS) and 3D printing lacquer (see previous blog post about 3D printing post-processing for more advice).

“Rippling” or “waves” on the surface of prints:

These are typically caused by any external vibrations acting on the 3D printer, it’s substrate or within the room. One way to address this issue is to look for the underlying cause: check out if the tabletop or surface you are printing on is loose, or susceptible to residual shaking due to the jerky movements of the printer. In some cases, a reduction of speed can also solve this problem by avoiding unnecessary quick movements that cause shaking and disturbances.

A loose print bed can also be the underlying cause to a “rippling” effect, which can be addressed by tightening any loose components. 

Clogged nozzle/nozzle won’t extrude but the filament is attached:

In the simplest scenario, you may have a nozzle clog which can be cleaned with a small piece of wire. For more complicated clogs, you may need to remove the print head entirely in order to clean it. If your printer has specific instructions for disassembling and cleaning, it would be advisable to follow those. Most simple fixes can be achieved by heating the nozzle on the printer and using a needle or wire to pry out any pieces of stuck filament. 

However, more general fix-alls for clogged thermoplastic printers can be done using acetone, some kind of heat gun or torch and a wire that can be fitted through the nozzle diameter. After soaking the nozzle in acetone for about 10+ minutes, heat up the nozzle on a heat resistant surface (make sure to work in a ventilated space) until extremely hot before using the wire to try to push through any clogged filament. 

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