In last month’s issue, we covered four of our most regularly performed 3D printer maintenance procedures. These tips included replacing the PEI build surface, when to change the nozzle, how to clean and lubricate the bearings and smooth rods, as well as cleaning the extruder fans. In this issue, we will provide another five maintenance procedures that we couldn’t fit into last month’s issue.
We show you more ways to maintain your printer to avoid it malfunctioning or producing poor quality prints.
V-ROLLER & BEARING CLEANING & LUBRICATION
In the previous issue, we discussed how to clean and lubricate the linear bearings and smooth rods on your 3D printer, What we didn’t realise at the time was just how common the V-roller system has become, such as the Ender and Creality range of printers. The V-roller system replaces the more traditional smooth rod and bearing system by using an aluminium V-grooved extrusion as a channel for rollers. The rollers clamp to either side of the V-grooved extrusion, just like you see above with the Creality CR-X dual colour single extruder 3D printer.
The rollers and V-groove in this situation will regularly need to be cleaned because as the rollers wear, they generate significant particulate rubber dust that sticks to the roller and V-groove. Over time, this particulate rubber can create an obstruction in the V-groove which will degrade the print quality by creating an uneven surface. If left unchecked, this will translate to printing artifacts. The good news is, this is a very simple maintenance task, only requiring you to wipe down the rollers and V-groove with a damp sponge. Doing this will ensure that the rollers and V-grooves are clean and giving as low friction a movement as possible.
ROLLER BEARING ASSEMBLY
This is the roller bearing assembly for the Creality CR-10 range of printers. Each of these rollers contains a bearing that is pressed into the rubber roller. Over time, this bearing will require lubricating.
To lubricate the bearing, you need to remove the roller from the unit. You may need to follow the manufacture’s recommendations to do this, as there are significant differences in the process between brands and models of printers. With the roller removed, you will have access to the bearing’s outer race, which you can see in this exploded view of a sealed ball bearing.
With the bearing flat on its side, you can apply a few drops of a fine grade machine oil onto the shield of the bearing. This fine oil will wick between the shield and the races to lubricate the ball bearings and retainer. This system does not require lubricating anywhere near as often as the linear bearing and smooth rod combination, as the bearings are less likely to dry out due to their orientation.
WHEN TO PERFORM THIS MAINTENANCE
Clean the rollers and V-groove every 100 hours or so of operation. A good habit to get into is to clean the rollers and V-groove every time you change filament spools.
We recommend you regularly inspect the bearings at the same time. Gently move the axis and feel for any abnormalities in the travel. Add a few drops of oil into the bearings once every 12 months and by keeping them clean, these bearings should last for many years of hobbyist use.
BELT AND BOLT TIGHTENING
Many 3D printers on the market today rely on a belt system to convert the rotational movement of a stepper motor into the X and Y directional movement.
Over time, your 3D printer’s belts start to stretch and your printer will slowly lose the ability to print dimensionally accurate parts. That is to say, parts that precisely match the component you’re trying to print.
Usually this stretching and print quality degradation is a slow process, and for the most part, it’s not instantly apparent. The belts can, however, become so loose that they can slip on the toothed gears.
When this happens, you will have very obvious stepping on your prints and in extreme cases, an entire layer shift where the next layer being printed is not aligned with the previous. This happens because the 3D printer does not have any feedback mechanisms to validate the position of the extruder. It simply assumes that the tool head will be where it expects for the duration of the print. Any deviation from this, caused by belt slippage, etc. will not be accounted for.
This image shows you a simulated extreme case of belt slippage. In this print, the entire model has been shifted on the X axis by about 1 or 2mm, causing severe overhangs on the tail and right of the print.
Of course, layer shifting is the most extreme result of a loose drive belt on your 3D printer. You’re much more likely to experience significant ghosting or ringing before such drastic print failures. This ringing can be caused by loose belts because a loose belt introduces slop in the axis.
This slop allows the tool head to move in an uncontrolled direction due to its mass. This is because the moving tool head has quite a bit of momentum when moving, and with slop, the tool head can continue moving in the direction of this momentum until it is stopped by the tension on the belt. The looser the belt, the more slop, and thus, the greater the distance the tool head can continue moving in an undesired direction. This shows up on your prints as a ghost image or ringing on sharp edges where the print head needs to change direction quickly but continues to move in the wrong direction until the slop is taken up.
A great print to test this, is the X, Y, Z calibration dice from user Wulfdesign on Thingiverse (https://www.thingiverse.com/thing:646567). This design shows up ghosting and ringing perfectly as the sharp indentations for the X, Y and Z indications create the ideal worst-case scenario for a printer with loose belts.
As you can see in this side-by-side comparison, the cube on the left has significantly less ringing/ghosting on the surface in comparison to the one on the right. To do this comparison, we simply removed the belt tensioner on our Flashforge Creator Pro, which caused the belt to lose some tension and provided just a small amount of slop.
If your prints are showing ghosting or ringing, it’s a good time to verify that your belts are nice and firm. The question you’re no doubt asking yourself is how tight the belts should be? The answer is not at all straightforward.
A general rule of thumb is that your belts should be as tight as possible to reduce the potential for slop in the axis and make the system as rigid as possible. However, what is possible may not be practical. You do not want to overtighten your belts to the point that other components are stressed to their fracture points. Therefore, you need to take into consideration the construction of your 3D printer and tighten the belts accordingly.
Consider, for example, the mounting hardware that the belt is attached to. In some cases, the belt pulleys are directly attached to 3D printed parts. These systems will likely need the most care when tightening the belts as the 3D printed parts will be fairly weak and easily stressed.
If your pulleys are attached to plastic injected parts, they will be much stronger than a 3D printed component, and thus, can be made much tighter. They will still require care to be sure you’re not going to damage the parts.
The best-case scenario is for pulleys held via metal parts, which is ideal as you can tighten the belts significantly tighter than the plastic versions. The weakest part to consider here is likely the stepper motor itself, so overtightening could result in putting excessive strain on the stepper motors bearings, which may shorten their life significantly.
In either case, you should err on the side of caution when tightening your belts, taking extreme care to avoid creating a bigger issue for yourself. You want to tighten the belt by a small amount and test the results before tightening more. Having the belt too loose will reduce the quality of the prints but having it too tight can seriously damage it. Think “taut, not tight”.
While you’re tightening and / or inspecting the belts, it’s a good chance to go over all of the bolts on the 3D printer. As with a loose belt, loose bolts will also reduce the rigidity of the system and will often produce the same ghosting / ringing effects as a loose belt. The good news is, this process is many times less likely to do any damage to your printer, short of using crazy force, of course. Generally speaking, you should use the tools that came with your printer (usually an Allen key) to go over and tighten all of the bolts every few months. This will ensure that your printer is as rigid as possible and help to eliminate ringing.
Note: Ringing and ghosting can be caused by a huge number of things, both hardware and software. Software settings such as printing speed, jerk and acceleration will have an impact on the presence of ringing. If you have not adjusted such settings, then a hardware fault such as loose belts or bolts should be your next starting point for you to investigate.
WHEN TO PERFORM THIS MAINTENANCE
We recommend that you regularly check the belt tension at least every few months to make sure that they are still taut. You should also use this time to inspect the belts for excessive wear and signs or damage resulting from misalignment.
LEAD SCREW CLEANING AND LUBRICATION
Another often overlooked maintenance task on 3D printers is the lubrication of the lead screws. The lead screw is usually a coarsely threaded rod attached to a stepper motor via a motor coupler. This threaded rod is mostly used for the Z axis but not always. In some cases, such as the Snapmaker, each axis of the printer uses this lead screw system.
During normal use, these lead screws will attract dust that will accumulate inside the machined threads and / or at the receiving nut. This debris can build up in the threads and decrease the life expectancy of the stepper motor and / or coupler by increasing the stress on both parts.
The maintenance procedure is nice and simple. You just need to remove the build-up of dust and debris from the lead screw by using a rigid brush such as a toothbrush. The bristles of the brush get into the thread of the screw and help to remove any debris deep in the thread.
Once the threads are cleaned, we generally give the rod a clean using a lint-free cloth to remove any left-over material.
Once you’re satisfied that the threaded rod is clean, it’s time to lubricate it. This is where things tend to get complex. Many people will insist that you must lubricate the threaded rod with a PTFE impregnated grease, and whilst this is likely the absolute best-case scenario, it isn’t always practical.
If you have the PFTE impregnated grease, by all means, use it. If you don’t, however, you can use any fine grade mineral oil. We tend to use oil in our lab, as we have it on hand to lubricate the bearings and smooth rods and thus, we don’t need to keep separate lubricating materials. Of course, being an oil, you need to lubricate more often as you would with grease because the grease tends to stick to the rod better than the fine oil.
You also want to ensure that you don’t over oil the rod as the excess oil can run down the shaft (of a Z-axis thread) and into the stepper motor below it. This could result in damaging the stepper motor.
WHEN TO PERFORM THIS MAINTENANCE
We recommend you lubricate and clean the lead screw at the same time that you clean and lubricate the smooth rods and bearings. In our case, we inspect and, if necessary, clean the leadscrew every 50 hours or so and lubricate it about once a year.
CLEANING THE EXTRUDER GEAR
Our final maintenance topic is a fairly interesting one and quite possibly one of the most easily overlooked. For the most part, your extruder works by pushing a fine 1.75mm thread of plastic filament into the hot end of your printer head. This is where the filament is heated to its melting point, forced through a tiny ~0.4mm die, then deposited onto your build surface. This entire operation requires a very stable and consistent method of delivering the feedstock (the plastic filament) into the hot end, which is performed by the extruder gear.
The extruder gear is a fine-toothed gear that physically makes contact with the filament with the teeth biting into it and forcing it into the hot end to be melted. If this gear is unable to generate sufficient force to push it into the hot end, the print continues without sufficient plastic. This is known as under-extrusion, which simply means that the printer is extruding less plastic than it is expecting.
The print shown here has severe intermittent under extrusion which was caused by a build-up of plastic caught in the teeth of the extruding gear.
The teeth of the extruder gear can easily become clogged by remnants of the plastic filament its attempting to extrude. Each time the gear bites into the filament, a small amount can become lodged in the teeth of the gear.
Over time, this material can build up, which reduces the force the extruder gear can exert on the filament and even causes the extruder gear to slip. This reduced force and / or slipping means that less plastic is being extruded than the printer is expecting and thus the print quality is significantly reduced.
In some cases where the nozzle has been jammed or even partially clogged, and the extruder gear was left slipping on the filament, this process is rapidly increased.
Cleaning, or at least inspecting, the extruder gear needs to become part of your regular maintenance procedure and at very least something you need to do after a filament jam or partial clog.
The process of cleaning the gear itself is not very involved as it's just a matter of clearing debris from the teeth of the gear. However, to get to the gear requires the removal of the extruder. This will differ depending on your 3D printer’s manufacturer, and as such, you will need to refer to the supplied documentation.
Let’s take, for example, the extruder on our Cocoon Create i3. This is a very popular MK10 extruder design, which is very common and shared among many manufactures. To get to the extruder gear in the MK10 direct drive (i.e. no Bowden tube, the stepper motor is mounted directly to the hotend), we need to remove the filament, and disconnect the extruder fan and stepper motor wiring connectors. We then remove the two bolts that secure the fan and stepper motor to the carriage.
We now have the stepper motor and extruder assembly separated from the main unit. From here, we can clearly see the extruder gear and the tensioner bearing that keeps the filament pressed against the extruder gear teeth.
This is a photo of our extruder shown with the hotend, heatbreak, cooling fan and heatsink all removed. The tensioner bearing (left) pushes the filament against the extruder gear (right) with sufficient pressure for the teeth to bite into the filament and force it into the extruder. As you can see, it is relatively clean and only has a little plastic build-up.
To clean the gear, we use a stiff bristled brush for minor buildup such as this. However, if you’re doing this maintenance after a nozzle jam and the printer was chewing at the filament for a long time, the plastic will have likely melted into the gear. In these cases, we clean each of the teeth very carefully using a hobby knife or similar. This way, you can be sure to remove as much of the plastic as possible.
WHEN TO PERFORM THIS MAINTENANCE
We do this procedure every three months, however, we inspect the gear anytime we have had a filament jam or nozzle clog. This way, we are sure to keep our extruder operating as expected.