FDM 3D printing is an exciting technology in which users can easily develop new products and parts based on their 3D designs. It is the most widely used additive manufacturing technology, thanks to the low cost machines and ease of operation. There is a large community of worldwide users and manufactures formed after the RepRap revolution, which helps new users to learn what they have to do to excel in FDM 3D printing. One such important thing to learn is about the common defects and failures that may occur when you print a part in your FDM 3D printer.
FDM printing is relatively an easy process compared to other additive manufacturing technologies. But it is not foul-proof. There are a number of issues and defects that may occur to your print parts which results in loss of material, energy and time. The reasons may wary, such as poorly maintained FDM 3D printers, low quality filaments and manual errors, but every problem have solutions. Let's see about the 5 major failures and defects that occur frequently in FDM 3D printing and easy methods to avoid them.
1. Warping
In FDM 3D printing, extruder deposits molten material layer after layer to form the part. This layer of material eventually cools down and makes the part rigid and form the desired shape. But uncontrolled cooling of layers results in thermal stress in the part which pulls the bottom layers upward and cause a curved bottom section as shown in the image. This deformation is called warping. It is frequent in some FDM materials such as ABS, PC and Nylon due to their high coefficient of thermal expansion. Warping may also occur due to the lack of proper bed adhesion in which the printed part separates from the bed and curve. This results in deformed print parts and your valuable time is wasted. But there are some simple methods to solve this issue.
Use a heated bed: When printing warp prone materials it is always better to use a heated bed. Usually a bed temperature in the range of 90 - 110 is sufficient for materials such as ABS, PC and Nylon. Heated bed helps to prevent the rapid cooling of layers which reduces the warping tendency. But in case of tall objects this will not solve the issue completely as the heat of bed will not reach upper layers. In that case
Use a heated enclosure: As mentioned above, warping is caused by the uncontrolled cooling of layers. So with the use of a heated enclosure you can adjust the surrounding temperature and control the cooling of layers. Hence combined use of heated bed and heated enclosure is the best practice to avoid warping.
Disable fan cooling: For materials like ABS and PC it is better to turn off your part cooling fan so that the layers will cool down slowly.
Use of adhesives: Different materials stick better to different bed adhesives. So when you printing with a particular material, look for the best adhesives or build plate available and use them.
Avoid sharp corners if possible: Warping is severe at sharp corners of your part. So if it possible, round of the outer wall or add chamfer to your design.
Use of brim or rafts: If warping is persistent even after doing everything you can do, then the best solution is to use raft or brim. These are layers printed outside the original part design for better build plate adhesion. So with the use of raft or brim you can improve the bed adhesion and reduce the chance of warping.
2. Nozzle Clogging
When you are 3D printing some part and after a while you notice that the extruder is just moving in thin air and nothing comes out of it and then you realize that the print is beyond saving. You will first look at the filament. Is it over? Or is it broken? No. Then you will look at the feeder drive system, Is it working properly? If there is no problem with it either then you realize that it is nozzle clog, the arch - enemy of every FDM 3D print enthusiasts. There will be no one who uses a FDM 3D printer and didn't face this situation. It is the major reason for most of the print failures and can occur frequently. So proper attention is needed to avoid this issue otherwise a lot of material and time will be wasted. There are a number of possible causes to nozzle clog such as contamination in the filament, dust or degraded material in the nozzle, excessive retractions, feeder system malfunction or poor cooling of the nozzle. So you may have to go through all these reasons before finding the exact problem and solving it. First if your nozzle is clogged follow these steps to remove it.
Manually push the filament and try to extrude
Heat up the nozzle and use a needle to push through the nozzle hole. Be careful when you do this as the nozzle is hot so wear a protection glove.
Heat the nozzle for a while then dismantle it and extract the clogged particle with some pointy tool.
Try 'cold pull' or 'atomic pull'
Use a cleaning filament: There are extruders cleaning material filament available in the market. Use them once in a while.
As told earlier nozzle clog can happen due to various reasons. So it is important to be careful and take these precautions to avoid nozzle clogging.
Clean the nozzle frequently: Regular cleaning is essential for better print quality. Clean inside and outside of nozzle once in a week.
Check your nozzle before you start printing: Extrude some material and check the flow. If there are irregularities in the extruded filament clean the nozzle.
Store your filament in a dust free environment: Any dust or other particles present in the filament will eventually reach the nozzle. So remove the dust and keep the filament in a tightly sealed cover or box and store in a dry cool place.
Clean your printer once in a while: Dusting important areas of your printer such as feeder system, build plate and extruder is good for overall lifespan of your machine.
Check extruder cooling fan: Extruder cooling is essential for better material flow. If it is not working properly, check the connection and also check the blades. Clean the blades if there are any debris.
Proper retraction: Do not use excessive retraction settings. Lower the speed and distance of retraction so that the material in the nozzle is not subjected to high pressure.
3. Layer Missing
A successful print is a joy to every user. If it is a large part and you spend so much time designing and processing the print, the happiness you feel when the print is finally over is huge. And after this euphoria when you check the part closely you see some irregular lines or holes in the print and you are crestfallen. If you have a FDM 3D printer you may have experienced this, and Layer missing is a thorn in the eye for many users. The main reason for layer missing is the temporary under extrusion caused by various issues. The cause and the remedy are listed below.
Filament diameter variations: If the filament you use is not of given quality and it's diameter varies considerably, the extrusion flow is not proper which results in weak infill and layer missing. So whenever you use a new filament check the diameters at least 10 different spots and calculate the mean. It should be near the standard value with a maximum tolerance of +/- 0.05.
Filament spool problems: If the filament is not properly wound on the spool it may tangle and will not extrude properly. So check before you use.
Nozzle clog: Partial nozzle clog may result in layer missing so clean the nozzle before starting the print as mentioned earlier.
Feeder system malfunction: Whether you are using a direct drive or bowden extruder check the feeder wheel and spring mechanism for any misalignment or wear. Replace the gear wheel or idler tensioner if necessary and tighten the spring mechanism.
Worn bearings and rod misalignment: If the extrusion is missed fully around the part then the issue may be due to the irregular z axis movement. Check the motion system and if needed, replace worn bearings, lubricate lead screws and linear rods.
4. Layer Shifting
Layer shifting is another major cause for print failure. In a print after a while the layers start to print not at the required position but just some steps further in either X or Y direction or in both direction. This result in a condition where entire part printed after that is not aligned with the bottom layers causing deformed part as shown in the picture. The main reasons and solutions are;
Excessive temperature in stepper motors and their drivers: When a part is printing in FDM machine, all the stepper motors and motor drivers are working continuously. This will increase the temperature of the device and at some point it will reach a maximum at which stepper motor will not work properly and they are incapable to position the extruder at the precise point. The best way to solve this issue is to provide cooling fan to motor drivers. If your printer already have a fan but not sufficient for cooling, then add an external fan. Also slower the print speed which reduces the burden on the stepper motor and drivers.
Mechanical failure: For precise movement you need mechanical parts to work properly. If there is any play or backlash in the components then there is a high chance of layer shifting. So tighten the belts and screws regularly and lubricate linear rods, lead screws and bearings. If your printer have V slot movement system tighten the screw to adjust the play of rollers.
You are printing at a higher speed: Every FDM 3D printer has a range of achievable print speed, so when you are printing a part you should be careful to be at a speed within this range. If the movements are fast there is a chance that extruder move further due to inertia. So if required lower the speed for better print quality.
Build plate is not secured: This may be seem funny but if you not properly fastened the build plate to your heat bed there is a high chance that it may dislocated in the middle of the print and the position of extruder change with respect to the build plate resulting in layer shift. So before starting your print check carefully if the build plate is secured.
5. Over heating
In a print if you notice that the layers are not aligned perfectly but curls upward, it may be due to overheating. When you print with a material the nozzle temperature should be optimum. Filament manufactures only mention a range between the minimum and maximum temperature that can be applied to the nozzle. But if the print temperature is high and the layer is not cooled effectively it bends. There are some simple steps to prevent this from happening.
Calibrate the nozzle temperature: If you use different filaments from different manufactures the optimum nozzle temperature may vary. So you have to calibrate the temperature before you try a new filament. Printing a temperature tower is a perfect calibration method that can help you to determine the optimum temperature required.
Check the part cooling fan: The problem may be due to insufficient part cooling, so check whether the cooling fan works properly and at full speed. If it is not working, there may be debris deposited in the fan blades which prevent the rotation or a loose connection.
Reduce the print speed: You may be going too fast, just slow down a bit. The layers deposited needed some time to cool down. And only after it cooled well new layers can be added above it. So if you are printing a small part the lower layers will not get required time gap to cool down which results in curling. So use lower speeds for small parts.
Print failure can occur to any printer or at any time. We cannot completely avoid some issues but with proper precautions we can limit the possibility. So happy printing!
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