Solving Software Issues
In the last chapter, I presented a host of potential causes and solutions for hardware-related problems. Software issues, as well as hardware issues, can cause many of those problems. I have split the discussion into two chapters because software causes are quite different than hardware causes. Similarly, solving software issues takes very different forms.
Like the last chapter, I will present discussions on the various aspects of software that can cause print quality issues. And like the last chapter, I will present categories of problems and discuss the possible causes and solutions. These include changes you can make in the slicer, printer controller, and firmware.
Hardware problems can sometimes be easy to detect and even correct. Even the less obvious hardware problems, once correctly diagnosed, typically have a visible and logical solution. For example, a broken part or a loose belt are things you can see and replace or adjust. However, software problems are not always that obvious.
In some cases, the software or its settings are not the actual cause of the problem. Thus, I recommend you explore all hardware causes before jumping directly into changing the software settings. For example, if your print bed is not level (trammed), objects could lift when placed in one corner of the print bed but not others. Changing the temperature via the slicer software is not going to fix this or similar problems.
However, there are situations where software settings can be changed to help correct a printing problem. For example, increasing the temperature of the hot end to ensure better layer adhesion. In other cases, the software can be the cause of the problem. For example, incorrectly specifying the diameter of the filament in the slicer can cause very poor prints, including extrusion failures.
Like the hardware problems discussed in the last chapter, knowing the software settings that can be used to treat and cure print quality issues can help you fine-tune your software so that you can get the most out of your printer.
In the following sections, I present discussions of each of these areas, with examples of how the software can be changed, as well as example screenshots of some of the more obscure settings. Let’s begin with the settings that you can change in the slicer to correct printing problems.
Slicer
The slicer, or CAM software, can be considered the most important step in the 3D printing tool chain. Recall that the slicer is responsible for taking input in the form of printer configuration settings such as filament size, temperature settings, and so forth, and an object file (.stl) to form a file that contains commands to direct the printer. This file is a .gcode file (or .x3g for MakerBot printers) that is either read from an SD card or sent to the printer directly from the computer.
Clearly, if there are any printer settings in the slicer that do not match your printer hardware, the resulting file will also not match your printer. Printing a file with incorrect printer or slicing settings will result in improperly printed objects. In the most extreme case, this means the printing fails. At the least, it means one of several print quality issues.
Even if the settings are valid and match your printer hardware, you can use the slicer to change certain parameters to help combat some of the more common printing problems. That is, objects that print poorly can sometimes be fixed with slicing changes. In similar fashion, you can use the slicer settings to help combat problems such as adhesion, as you will see in the next section.
Adhesion problems most often occur between the first layer and the print surface. When the print pulls away from the print surface, it is called lifting. Adhesion problems can also occur between other layers of the object. Poor layer adhesion at higher layers is sometimes called cracking or warping.
Lifting can be controlled in a number of ways. The last chapter presented several possible causes of lift related to hardware. You also saw how the print surface treatment can affect lifting. However, there is another element to consider: controlling the temperature of the heated print bed.
If your printer has a heated print bed, you should consider using it when printing objects. While a heated print bed is required for ABS, it is often considered optional for PLA and other filaments. The generally accepted heated print temperature for ABS is around 110ºC and PLA is around 60ºC.
Note The combination of printer hardware and filament may vary slightly from these estimates. Experimentation and vendor recommendations should be your guide. For example, you may find you can lower the temperature if your printer has an enclosure.
Remember, the temperature settings are stored in the print file. Setting these values on your printer or through a printer controller application is possible, but most printers will override these settings as soon as the codes are read from the file. The following is a sample command (or code) to set the temperature.
M190 S60 ; wait for bed temperature to be reached
REMEMBER, SLICER FILES ARE PRINTER SPECIFIC
One of the common mistakes for those who print with ABS and PLA is to attempt to print a file that was generated for PLA with ABS. In this case, the heated bed is too cold and lifting is much more likely to occur. The temperature for the hot end is also likely to be wrong, so you can also risk extrusion problems. On the other hand, if you attempt to print a file sliced for ABS with PLA, the print bed will be too high, which can cause the print to sag and print very poorly. Since the hot-end temperature for ABS is normally higher, you could also encounter burning smells from the extruder.
If the print bed is too cold, it can cause the first few layers to cool too quickly, causing the layers to contract and pulling the object away from the print bed, which happens more often with ABS. In this case, it isn’t a matter of having a properly prepared print surface, rather it is a case of not enough heat stored in the layers to ensure a slower and more even cooling of the object layers.
If lifting is severe enough, it can even cause the object to come into contact with the hot end. This can cause the entire object to get knocked off the print bed, ruining the print. However, if it has lifted that much already, it is likely to get worse. Sadly, if you are not watching your printer, this can result in a partially printed object and a nesting of filament as the printer happily continues to extrude filament into the air. If the loose filament comes into contact with the hot end, it can melt and stick to places you don’t want it to. Not only does this result in a big mess, it also wastes a lot of filament.
If you are experiencing lifting, check the temperature of your heated print bed. If it is lower than the preceding estimates, try raising it 5 degrees, and then check the results on your next print. In rare cases, I’ve found that lowering the temperature 5 degrees can help print quality in other ways. For example, having the print bed too hot can cause the object to retain too much heat, making it harder to print extreme overhangs. In this case, the overhang layers will curl at the end, giving the overhand a stair-step look rather than a smooth transition. If you are printing with your print bed in excess of 110 degrees, consider lowering it 5 degrees at a time until you have the lowest setting possible that does not cause (or make worse) lifting.
LIVING WITH LIFT
If you have followed the advice here and elsewhere to combat lifting, you should have reduced your lifting problem significantly. However, it is possible you may not completely eliminate the problem. This is especially true for ABS, which requires more effort to perfect. For example, a small amount of lifting—such as a small corner or other part that lifts slightly off the print bed but does not ruin the part—may be acceptable. If you examine Thingiverse carefully, you may find signs of lifting on many things posted to the site. If you have treated your lifting problem using as many techniques as you can, but you still have an occasional small amount of lifting, you may want to declare success.
So how do you set or change the heated print bed temperature? Recall from earlier chapters that the bed temperature can be set in Slic3r on the Filament Settings tab, as shown in Figure 8-1. Similarly, in MakerWare, you set the bed temperature on the Make dialog Temperature tab, as shown in Figure 8-2. Notice in these figures that you can also set the hot-end (extruder) temperature on these screens.
Figure 8-1. Temperature settings in Slic3r
Figure 8-2. Temperature settings in MakerWare
Once again, if you need to change the temperature settings in a print file, you must rerun the slicer. It is possible to edit the .gcode file directly, but make sure you do not introduce any errors. However, you cannot easily edit other formats, such as .x3g.
Another contributor to lifting is when the object has too small of a surface area that is not enough contact with the print surface. If the object has small protrusions or thin areas, you may not have enough filament that makes up the first layer to make a strong bond with the print surface.
The best way to treat this problem is to enhance the object with a brim. Recall that a brim is additional loops of filament laid down around the perimeter of the object, which increases the surface area. Figure 8-3 shows the brim settings in Slic3r.
Figure 8-3. Setting a brim in Slic3r
Another software-based tool allows you to print your object on a raft. Recall that a raft is several layers of filament laid down on the print surface that forms a platform (raft) for the object to rest on. The raft has a larger surface area and can help prevent lifting for small objects and objects with thin areas. Figure 8-4 shows an excerpt of the 3D print preview for an object sliced by the MakerWare application. Notice that the raft appears as a platform in the preview.
Figure 8-4. Raft printed with object in MakerWare
A less frequently used heated print bed technique to combat first-layer adhesion is to set the first layer temperature higher than upper layers. Notice that in Figure 8-1 you can do that with the Slic3r (but not with MakerWare). This setting allows you to set the first-layer temperature high enough to treat your lifting problem, and to set the other layers lower to retain heat in the object and to control cooling (and prevent warping and cracking).
Aside from heated print bed temperature, you can also treat lifting problems by slowing the print speed for the first layer. You can control this easily in Slic3r (MakerWare does this itself) using the Speed dialog on the Print Settings tab, as shown in Figure 8-5.
Figure 8-5. Setting first-layer speed
Notice that in this case I set the speed of the first layer to 30% of the normal speed. Slowing the print speed can improve first layer adhesion by allowing the filament more time to bond to the print surface. If you notice filament peeling away from the print surface, or small perimeters not sticking well, slowing the print speed of the first layer can help you avoid these problems.
Another way to combat lifting is to use anchors (also called mouse ears or lily pads). These are normally small round discs placed on each corner or protrusion of the object to increase the surface area around the corner without increasing it everywhere like a brim would do. You can create anchors however you like and add them to your slicer platter when slicing. The downside is that these anchors must be cut away from the final part.
Creating anchors is easy. Just use OpenSCAD to create a disc about 0.5mm thick (or two layers, depending on your layer thickness). Some prefer to make their anchors three or four layers thick for really strong bonds. However, the thicker the anchor, the harder it is to cut away. The following is the code for creating a disc-shaped anchor.
cylinder(0.5,5,5);
To use the anchors, open your slicer and place the object on the platter. Then add as many anchors as you need and place them on the corners, as shown in Figure 8-6. Notice that I placed the anchors on each corner of the object. Some slicers will allow you to combine the anchors and your object into a single part. This is known as a mashup and it is something I will demonstrate more fully in a later chapter.
Figure 8-6. Use anchors to combat lifting
Print Quality
Closely related to first-layer adhesion are print quality issues that occur at higher layers. These are often layer adhesion problems that are treated in similar fashion as lifting. The layer adhesion problems discussed here include warping, splitting, and sagging.
All of these problems can be treated with changing the temperature of the print bed and hot end. However, they are caused by filament cooling unevenly. Thus, like adhesion, you should fix any hardware problems before experimenting with temperature as a means to fix these print quality issues.
Caution Never set the temperature higher than the maximum safe settings of your hot end. Check your documentation or contact your vendor to find the limits of your hot end heating range.
Examples of where to set the temperature of the hot end in the slicer are shown in Figures 8-1 and 8-2. Recall also that the hot end temperature is another setting that is maintained in the printer file, and not something you can change on the printer itself.
In most cases, you will raise the temperature of the hot end 5 degrees at a time, and then check the results. In rare cases, you could lower the temperature of the hot end 5 degrees at a time. Before changing your hot end temperature, be sure that you are familiar with the hot end features and capabilities. Never set the hot end higher than its maximum setting.
Tip Most firmware incorporates a maximum temperature to keep you from accidentally setting the temperature higher than what the hot end can endure. Check to make sure this value is set to your manufacturer’s maximum recommended temperature.
FILAMENT TEMPERATURE LIMITATIONS
When the temperature is too low, extrusion failure is likely. However, raising the temperature of the hot end can improve adhesion and extrusion. But you can go too far. If the temperature is too high, you will see the filament oozing from the hot end. Some ooze is possible, but the filament should not ooze more than a slight seeping over a few minutes. If it continues to ooze from the nozzle, you may want to lower the temperature. Another possibility is that the filament could burn.1 In some cases you may even seem some steam from the hot end.2 If either of these occurs, stop your printer and reduce the temperature.
Warping is when the higher layers of an object cool more quickly than the lower layers. When this happens, there may be too high a temperature in the object. Lowering the temperature of the print bed can help combat warping. If you are printing with PLA and using a fan, you may want to slow the fan speed to force less air over the object. Too much air can cause the higher layers to cool more quickly than the lower layers.
As I briefly mentioned earlier, warping can also occur on areas with overhang, which is a portion of the object that protrudes from the base at a low angle. Overhangs can be hard to print because they tend to cool much more quickly and can warp at the ends of each layer. When this occurs, you cannot do much about it while the object is printing. Most times the object is still usable because the hot end will tend to push out the thin layers on the next pass. However, the quality of that portion of the object will suffer.
The best way to treat overhangs is to use supports. Supports are thin layers of filament extruded to form a scaffold to support the object during printing. You can turn on supports in Slic3r on the Print Settings page, as shown in Figure 8-7. Supports can be enabled in MakerWare on the Make dialog by checking the Supports checkbox.
Figure 8-7. Enabling rafting and supports in Slic3r
Using supports effectively creates a false portion of the object that allows thin layers to be printed with greatly reduced warping. These supports are very thin and can be easily removed from the printed object by breaking them away, and then trimming with a hobby knife. Figure 8-8 shows an example preview of an object sliced with support turned on. Notice in this case that there appear to be vertical walls that form bridges for the overhangs.
Figure 8-8. Print preview of an object with supports for overhangs
Lastly, you should check that you are not turning off the print bed during printing. Take another look at Figure 8-1. Notice you can set the print bed temperature for lower levels differently than with higher levels. If you neglected to turn on the heated print bed for higher levels, this could cause warping, as described here.
Splitting (sometimes called cracking) is similar to warping; however, splitting occurs when the lower layers of the object cool faster than the upper layers. This can cause one or more layers of the object to lose adhesion and, well, split the object. Figure 8-9 shows an object that has split.
Figure 8-9. Splitting example
Splitting is often caused by drafts. Eliminating drafts can help considerably. However, you can also treat splitting by ensuring that your heated print bed is at the proper temperature and that the hot end temperature is set correctly. In some cases, slowing the print speed can also treat splitting. Slower speeds tend to improve the layer bonds. Again, the problem occurs when the object cools much faster than the newest layers. Raising the heated print bed by 5 degrees may help.
When objects split like the one shown in Figure 8-9, chances are the split or crack isn’t isolated to those areas where the split is visible. I have seen objects that have had a small split in one area fail from layer-sheering forces (stress placed on the object parallel to the layers). This revealed that the object had poor layer adhesion throughout. In fact, when I removed the object and applied layer-sheering force, it broke in other places. Thus, when you encounter splitting or cracks in your prints, treat the problem and reprint the object.
Sagging occurs in one of two ways: when bridging large gaps and when the object is too hot. Bridging small gaps is not usually a problem. Indeed, the slicer has accommodations for that. For example, a small hole or nut trap can be covered with a layer of filament without too much of a problem. However, large areas or areas without any form of support can be a problem for some printers.
If the gap is really big—more than a few centimeters—the slicer may not be able to compensate, and the only solutions are to use supports in the form of the slicer option or to use artificial supports (parts designed into the object itself).
Figure 8-10 shows an object with a large gap (bridge) that I decided to experiment with. It is a small air dam to be mounted on a power supply to redirect air away from the print bed. Rather than adding supports, I decided to try to print the object without them to see if the sagging filament could be removed or repaired. Fortunately, that was exactly the case; only the one layer sagged. The other layers were able to bridge the gap and printed reasonably well. Figure 8-10 shows the end result.
Figure 8-10. Bridging a gap
If the sagging is limited to a single layer under the gap or bridge, you can repair the sag. For PLA, simply use a hot air gun to heat the sagging filament and press them into the object. Be careful not to get it too hot because it can warp the object. You will not be able to get the filament hot enough to reform the layer bonds, but at least you won’t have to cut away the filament or toss the object.
For ABS, use a lint-free rag soaked with acetone and rub it on the sagging filaments until they become soft, and then press them into the object. Within a few moments the acetone will evaporate, and the object will be repaired and likely just as strong as if it had not sagged. Figure 8-11 shows the repaired gap for the object in Figure 8-10. In this example, the sag was extreme (and intentional). Some of the filament broke and fell onto the print surface. Hence there are some places where there is no filament. While the surface may not be smooth, it permitted me to use this test object, even though I expected it to fail.3
Figure 8-11. Repaired sagging filaments in gap
Consequently, I reprinted this object with supports turned on in the slicer. The problem was the support option printed supports the entire length of the object making it a pain to clean and wasting a lot of filament.
I then redesigned the object to include supports as part of the object itself. This printed much better, and since the gaps were much smaller, I was able to print without turning supports on in the slicer. Figure 8-12 shows a rendering of the redesign.
Figure 8-12. Designing supports into your models
If your heated print bed is too hot, it can cause the object to remain soft and sag. That is, the filament does not cool enough to become firm enough to support the weight of the layers above. When this occurs, lower the heated print bed temperature by 5 degrees and try the print again.4 If the sagging is severe, you may want to lower the temperature by 10 degrees at a time.
When printing with PLA, sagging can also be treated by increasing the fan speed on higher layers. This will ensure that the filament that is used to bridge the gap is cooled faster, and thus can keep its shape. You can also increase the number of shells, or in some slicing applications, increase the number of top layers. But these techniques only work if the gap is at the top of the object.
It can help to change the print speed for printing gaps (bridges). If the print speed is increased, it will reduce the chances of the bridge drooping, but may increase the likelihood that it will break.
Lastly, printing supports is the best way to avoid sagging in bridges and gaps.
If your object prints well but it isn’t the right size (it’s too big or too small), you may be able to solve the problem by using a slicing feature called scaling. Scaling allows you to shrink or enlarge the object by a certain percentage. Figure 8-13 shows the scaling settings in Slic3r and Figure 8-14 shows the scaling option in MakerWare. In each case, you can scale the object proportionally.
Figure 8-13. Scaling in Slic3r
Figure 8-14. Scaling in MakerWare
As you can see from the MakerWare scaling options, you can scale any axis, and so long as uniformed scaling is checked, it will adapt the other axes settings. However, if you turn off uniformed scaling, you can scale the axes independently. This can be very helpful if the object is just slightly off on one axis or if you want to print interesting distortions of objects. You can also scale the object with the mouse by clicking the object, selecting Scale, and then while holding the mouse button down, move in and out. The object will scale as you move the mouse.
Recall from the discussion about first-layer adhesion that I mentioned surface area as a potential cause of lifting. If your object has a larger surface area on another plane (side), you can use the slicer feature called orientation (sometimes called rotation) to reorient the object on the print bed.
Tip If you design the object yourself, it is best to set the orientation before you export the file.
For example, suppose you have designed the dollhouse table shown in Figure 8-15. It is a simple design and presented in the orientation that you envisioned it—right-side up.
Figure 8-15. Dollhouse table
Notice the legs of the table. They’re small and only a fraction of the object touches the print surface. Not only that, but there is a large area that will have to be bridged (the table top). You could add supports to ensure that the gap doesn’t sag; however, if you flip the object over, you have a much larger surface area and the small bits (legs) are pointing up. Figure 8-16 shows the reoriented object.
Figure 8-16. Dollhouse table reoriented
Sadly, there is no straightforward way to rotate an object like this in Slic3r. However, you can rotate the object in Repetier-Host and MakerWare. Figure 8-17 shows the rotation settings for Repetier-Host and Figure 8-18 shows the rotation dialog in MakerWare.
Figure 8-17. Rotating objects in Repetier-Host
Notice the two highlighted text boxes in Figure 8-17. These are the settings for rotating and translating objects. Notice I rotated on the Y axis (but could also have done the X axis) and I had to raise the object up 32mm. This is so that the object will position on the print bed correctly. I could also have used the Auto Position button to automatically position the object once I rotated it. You can also use the Center Object and Drop Object to achieve this result. Auto Position will also ensure that multiple objects will not overlap.
Tip If you do not know the size, the Auto Position feature is the best option to reposition a rotated object in Repetier-Host.
Notice in Figure 8-18 that you must select the object and then select Turn to see the rotation settings. Simply click the plus or minus sign for whatever axes you want to change, 90 degrees at a time. Or you can enter the value as I have done. Notice in the background the object is oriented correctly. Like Repetier-Host, the Lay Flat button ensures the object will lay flat on the print bed.
Figure 8-18. Rotating objects in MakerWare
As you can see from this simple example, orientation can also be used to eliminate bridging and to help prevent warping. Figure 8-19 shows an object that can be printed easily and, in most cases, well. However, you may experience some sagging and even warping on the overhang (the rounded portion). If you reorient the object as shown in Figure 8-20, you not only increase the surface area but also eliminate the overhang and its possible issues.
Figure 8-19. Object with overhang
Figure 8-20. Reoriented object reducing overhang
Another example of how orientation can help is with printing supports. Consider the object from Figure 8-19. Sometimes designers want to orient curved sides in the Z axis because they can print slightly better that way.5 In this case, the object would appear as shown in Figure 8-21. In order to print this object in this orientation, you would have to use supports because there is no way to print an overhang that is parallel to the print bed without them.
Figure 8-21. Reoriented object without overhang requiring support
Figure 8-22 shows what this object looks like with supports added. As you can see, there will be a lot of cleanup necessary to remove the supports.
Figure 8-22. Object print preview with supports
However, you should still consider this option if you need to use it. In fact, one reason you might want to reorient an object in this manner is for sheering. The layers in the object in Figure 8-21 will run perpendicular to the layers in the object in Figure 8-20. If you need to consider sheering forces, you may want to reorient your object to ensure that the layers run perpendicular to the sheering force.
For example, if the object in Figure 8-20 is going to be used as an anchor for supporting a pulley or as an idler bearing for a belt-driven mechanism, and thus the forces will be pulling away from the base, this orientation could be slightly stronger than the orientation of the object in Figure 8-20. This is because the layers run perpendicular to the sheering force in Figure 8-21, but parallel in Figure 8-20. Think of it this way: it is easier to break layer bonds than it is to break filament.
When creating your own objects, or printing objects made by others, check the orientation of the object before printing it. Consider not only how much surface area is needed for a strong first layer bond, but also reducing overhangs and gaps (bridges). In some cases, sheering force may determine how you orient the object. Better still, you can avoid using supports—and thereby reduce sagging!
Filament and Extrusion
Problems with filament and extrusion, in general, can sometimes be difficult to diagnose. This is because of the slight variations that exist among filament. Recall our discussion about filament and how it can vary in size and temperature settings. PLA does not have the same properties as ABS. In some cases, even the same type filament, but of different colors, can have different heating properties.
The most common problems are poor extrusion, oozing of the filament from the nozzle,6 and layer inconsistencies. All of these can be controlled, or at least reduced, with key settings in the slicer. I discuss each in more detail in the following sections.
If your slicer is set up to match the settings of your printer and the filament you are using, extrusion should occur normally without much issue. Hardware-related issues are still a concern (obstructions, blocked nozzle, etc.), but once those issues are solved or eliminated, you should be fine. However, if your slicer settings do not match your filament, you can encounter poor extrusion.
The most common issue is filament that extrudes too much or too little. This is caused by using the incorrect filament diameter in your slicer. Figure 8-23 shows the filament settings for the Slic3r application.
Figure 8-23. Filament settings in Slic3r
Tip Be sure to measure your filament each time you slice an object.
If you enter a value that is too large, the extruder may not extrude enough filament. In this case, the layer adhesion may suffer and the part may be easier to break with sheering force. In the case where you use a setting that is too low, the filament may clump, or strings (sometimes called threads) may appear as the hot end moves from one place to another. If you see a lot of stringing, check your slicer for the proper setting for the filament diameter.
Another cause of poor extrusion is using the wrong settings for your hot end temperature. Too high a setting can cause the filament to extrude more easily, which also causes clumping and stringing. Too low and the filament may not extrude properly. Signs of the wrong temperature can manifest as the extruder drive pulley slipping or chattering. You may also see cases where the filament comes out in spurts or with short sections of thinner filament. In other cases, you may see the filament appearing as dots. If the filament is not extruding in a clean line, you likely are experiencing problems with hot end temperature.
In the extreme, this problem can cause the filament to strip and extrusion to stop. I upgraded one of my printers recently with a really nice set of milled aluminum extruder hardware, only to discover that the spring I used was just a wee bit too stiff. This caused the stepper motor to strip for only one of several spools of filament. The filament was a bit softer than the other spools. I fixed the problem temporarily by increasing the hot end temperature. The correct resolution was to replace the spring.
If your filament seems to clump or string among the part, reduce the hot end temperature by 5 degrees and try the print again. If it gets better, try another 5 degrees until you find the correct setting for that filament.
Similarly, if your filament does not extrude well and there are no obstructions or blockages in the hot end or nozzle, increase the hot end temperature by 5 degrees at a time until the filament extrudes well.
When I encounter situations like this, where I know it is a slicer setting, especially with hot end temperatures, I use a printer controller application to test extrusion by heating the hot end to the new value and extruding between 30mm and 100mm of filament. You can tell everything is going well by observing the extruder and the filament as it exits the nozzle. If it flows well and the extruder turns without stopping, stuttering, or any noise of stripping, I then retry my print. This saves me a lot of filament and doesn’t ruin as many parts. Fortunately, you only have to do this if you encounter a new filament or filament from a different vendor.
One of the side effects of having the hot end set to the optimal temperature for extrusion is oozing. If the printer sits idle with the hot end heated to temperature, you can observe a small amount of filament oozing from the nozzle. This is normal, so long as it isn’t more than a few millimeters. And depending on how long your printer will be idle, this should not be a problem. The filament that oozed out will be expelled when the printer does its purge around the object or along the front of the print bed, as with a MakerBot.7
However, if you are experiencing a lot of ooze, you may have your hot end set too high. Too much oozing can transfer to the object in the form of extraneous bits of filament, rounded corners that should be sharper, and odd deposits of filament in places where the hot end has moved from one location to another. This is normally not the thin strands, strings, or threads like you see with a hot end that is a little too hot. In this case, the hot end is much hotter than necessary. If this happens, reduce the hot end temperature by 5 degrees at a time until the oozing slows to only a small amount. If your filament is oozing more than 5mm to 10mm in a few seconds, your hot end is too hot.
It should be noted that some hot ends have a larger heat chamber or are designed in such a way that oozing is more prevalent. For hot ends like this, the slicer application can be helpful in controlling the effects of oozing. The Slic3r application has a feature that can help: retraction. Figure 8-24 shows the Extruder settings on the Printer Settings tab. This is the same location that you enter the nozzle size to match your printer.
Figure 8-24. Treating oozing with Slic3r
Notice the Retraction section. Here you can use settings to retract a certain amount of filament, for lifting of the Z axis, to set speed, and more. The two most common options to set are lift and retraction length. As you can see in the example, I have set retraction to 2mm and a lift of 1mm. This will cause the extruder to turn backward for 2mm, sucking in the filament.
The lift is primarily used to prevent the nozzle from striking areas of the print that may be higher than the current Z position. Lifting also gives the filament a chance to break away from the layer, and thereby reduce stringing from the retraction. Use retraction if your hot end oozes a bit more than you’d like or if there is significant stringing (small threads stretching across movements without extrusion) but your hot end temperature settings are correct.
NOT ALL FILAMENT IS CREATED EQUAL
As I mentioned in earlier discussions about filament types and heat characteristics, filament can vary. In fact, different colors and even different vendors of the same type (PLA, ABS, etc.) can have different heating properties and even vary in diameter. Once you zero in on the heated print bed (if equipped) and hot end settings that work best for the filament, make a note of these settings and the diameter on the spool itself. I like to use a sticky label to write down the optimal values. This can help you remember the finer details if you have more than a couple of spools or you do not use a spool for some time. You really don’t want to go through all of the experimentation again, do you?
Note There is a community project underway called the Unified Filament Identification project (UFID) working on an open standard for filament manufacturers to include data about filament on the spool in a manner that can be machine-read, and therefore automate the process.
One of the hardest things to diagnose are inconsistencies that appear among the layers of the print. These can manifest as missing portions of a layer or filament run, gaps in the print layer, extra filament deposited in holes, and poorly formed objects.
The most common cause for some of these inconsistencies is insufficient cooling on PLA prints. You should always use a cooling fan that directs air onto the top layers of the object. This will ensure that the layer cools fast enough to make a good bond and a firm and consistent layer. Having too much air flowing over the layer can cause the layer to deform, portions of the filament run to come loose, and poor layer adhesion in general. If this occurs, check the speed of your fan in the slicer and use the automatic settings. These are generally acceptable and optimized for properly cooling PLA. Figure 8-25 shows the cooling settings in Slic3r.
Figure 8-25. Cooling settings in Slic3r
Notice that you can choose to keep the fan on at all times. This will keep the fan running at whatever speed you set as the default (see the center of Figure 8-25). So far, I have not found a need to use this setting. The setting you want to use for PLA is the “Enable auto cooling” check box. This will ensure that the fan changes speed as the object is printed (see Figure 8-25 for a description of how this works).
For some objects, the print speed may contribute to inconsistent prints. I have seen this in tall objects with intricate portions at the higher levels (small protrusions, small holes, tall, thin columns, etc.). Slowing the print speed can improve quality for objects with these features.
Another possible cause for inconsistent prints is using a layer height that is too coarse for your hardware. Recall from the calibration chapter that some layer heights can introduce errors in the layer calculations. If you are printing an object with a high layer height, try using a lower value to see if it improves consistency.
Lastly, it is possible that when printing large objects (particularly those printed with PLA) can cool too much before the layer is complete and the next layer is applied. To combat this issue, increase the temperature of the heated print bed, slow the fan, or use an enclosure to ensure that more heat remains in the object at lower levels.
The printer control software can be very useful, and for the most part (and most vendors’ variants), it is very reliable. However, I have found that certain early releases and, in some cases, major releases of printer controller software contain bugs.
Most times, these bugs are nuisances or have no impact on your use of the features. However, in the case of one popular printer controller software, several versions were known to have issues with certain computing hardware. Indeed, when the retina displays came out for the MacBook Pro laptops, there were some issues with using the software on these machines.
I have also encountered problems with communication stability on several different printer controller software. If you feel you have to have the latest version, be advised to test it thoroughly before relying on it to print objects from your computer.
Lastly, it is also very easy to make a mistake and direct your printer to do something it should not. Most common are homing issues, but you can also sometimes incorrectly enter the temperature for the heated print bed or the hot end. Only care and attention to detail can avoid problems such as these.
If you are printing from your computer, you can sometimes encounter problems when your computer goes to sleep.In fact, depending on your computer’s energy settings, your computer could go to sleep and suspend all applications.
When that happens, your print will most likely be ruined. This is because the printer will be waiting for the computer to send more data. If the printer waits too long, the heat built up in the object could dissipate, increasing the risk of warping and splitting. Sometimes awakening your printer will not harm the print. Regardless, if you have a large file to print, you should either transfer it to SD and print it directly from the printer, or turn off your energy-saving settings while you print (screen savers are generally OK).
Tip Screen savers should not cause problems. However, if you encounter problems when using a screen saver, try turning it off to see if this solves the problem.
In the rare event your printer controller software freezes or goes wonky,8 you may have little choice but to terminate the application and restart your print. Once again, if you want to print from your computer, be sure you are using the latest and most stable release of your printer controller software.
A very common and accidental problem those new to 3D printing sometimes encounter9 concerns crashing the axis into its mechanical bits. This occurs when you have started your printer for the first time but have not homed the axes, and then use the printer controller software (or the LCD panel) to move the axis.
Failing to home the axes means the printer can consider its current location as (0,0,0). Moving the axes in the positive direction could mean it attempts to travel farther than physically possible, resulting in the mechanical bits coming into contact with the frame or other parts of the printer. This is bad, and you should avoid it by always ensuring that you home all axes before trying to move (jog) any axis.
Also consider that if you reset your printer (for whatever reason) while it is printing, it can also lose its home orientation, and then it must be rehomed before resuming printing or printing another object.
The firmware isn’t normally something that goes wrong. This is most fortunate because you rely on the firmware working correctly. If it were to fail, so too would almost every feature of the printer! However, there are some cases where the firmware can be used to solve problems. First and foremost is upgrades. If you modify your printer with a new LCD panel or change the axis movement, you will need to change the firmware. Sometimes the problem isn’t obvious until you notice print quality issues or odd noises.
I once came across someone who changed the belt type on one of his axes. This user experienced major problems on the axis that was changed. The problem was that he failed to make the changes to his firmware. For example, if you change from a T2.5 belt and pulley to a GT2 belt and pulley, but keep the pulley sizes the same, you may think you do not need to change the firmware. But that isn’t the case—a 16-tooth T2.5 pulley is not the same size as a 16-tooth GT2 pulley. You should always modify the firmware settings to correspond to the exact hardware.
You may not think that changing the LCD panel is a big deal, but it can be. If the new panel is not compatible with the old one, you could encounter a problem where the LCD is unreadable, has garbage characters displayed, or has no display at all. Be sure to check with your vendor for the correct firmware settings.
Another possibility concerns problems encountered after repairs. If you changed the electronics or repaired them in some way, you may inadvertently erase the firmware settings in nonvolatile memory. If you made any changes by way of a G-code, you could lose those settings when the nonvolatile memory is erased. If you repair your printer and it suddenly acts strangely, especially components you did not modify, try reloading the firmware with the correct settings.
Summary
Software changes can help you solve a number of problems—from controlling the temperature of the hot end or print bed to changing the size of the object (scaling). Make sure your printer controller software is stable, or in the case of upgrades, make sure your firmware settings are changed to match the new hardware; this can solve more specific problems.
In this chapter, I presented some of the more common solutions to printing problems that you can implement in software. As you have seen, the slicer is the most commonly used vehicle for correcting problems, followed by things you can fix with the printer controller, and finally, firmware changes are the least common source of problems and solutions.
While knowing what can cause problems and how to fix them will help you keep your printer going when it breaks or when your print quality suffers, you can prevent some problems from occurring by keeping your printer adjusted, cleaned, and lubricated.
In the next chapters, I cover a topic that is rarely covered in books about emerging technologies: maintenance. In fact, maintenance seems to be missing from some 3D printer manuals. I will discuss maintenance tasks that you should do regularly (every time you print) and in the following chapter, I discuss maintenance tasks you should do periodically to keep your printer in top working order.
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1Bad burning smells are always bad. Even ABS should not smell burnt when extruding.
2Steam may be normal for some exotic filaments. Steam can also indicate that the filament has absorbed too much moisture, in which case you should attempt to dry the filament with desiccant in a sealed bag.
3Hey, that’s part of the joy of 3D printing. Sometimes things you think will never work turn out pretty well, all things considered. Don’t be afraid to experiment!
4Actually, this can be one of the side effects of using an ABS print file with PLA. Check the file to make sure that you are using the right filament.
5Actually, this may be compensating for axis issues.
6Yes, just like an infant’s runny nose. Not quite as repulsive, but it still has a certain “ick” element.
7This is one of my favorite features of the MakerBot. Even a longer ooze of 25mm can be purged during that long sweep across the front of the print bed.
8A highly technical term used to explain unexplained behavior. Not to be confused with hinky, which is altogether more serious and sometimes terminal.
9Once is usually enough to train us to avoid this in the future.