Nowadays, in our hackers, it is very common to load stepper motors with the same axis as their axis-especially when we connect them to lead screws or worm gears. Unfortunately, stepper motors are not really used for this kind of load, and doing so with a lot of force will damage the motor. But don’t be afraid. If you find yourself in this situation, [Voind Robot] provides you with a very simple but very effective upgrade solution that allows your stepper motor to handle axial loads without problems.
       In the case of [Voind Robot's], they started with the worm gear drive on the robotic arm. In their case, the moving arm may apply a huge axial load to the stepping shaft through a worm—up to 30 Newtons. Such a load can easily damage the internal bearings of the stepper motor in a short time, so they chose some double-sided reinforcement. To alleviate this problem, two thrust bearings were introduced, one on each side of the shaft. The role of these thrust bearings is to transfer the force from the shaft to the motor housing, which is a stronger place to apply this load.
       This technique is very simple, in fact it has been more than five years. Nevertheless, it is still very important today for any 3D printer manufacturer considering connecting a lead screw to a Z-axis stepper motor. There, a single thrust bearing can eliminate any axial play and result in an overall rigid construction. We like simple machine design wisdom like this. If you are looking for more printer design tips, check out [Moritz's] Workhorse Printer article.
       Yes, a few years ago I made an i3 variant printer called i2 Samuel. It is designed with thrust bearing on z to eliminate pressure on the stepper
       The allowable axial load of most stepper motors does not exceed the mass *g. If it is more, your design is flawed or amateurish, and this is usually the first one.
       good idea. By the way, can anyone tell me where I can buy small bearings? I have quite a few main fans with Doom™ rumble, but they still work.
       ”This trick is so simple, it’s actually been more than five years.” Yes, I agree that the thrust bearing was invented more than five years ago.
       Stepper motors generally seem to have some degree of axial float in the shaft and are fixed with spring washers. This is to keep the axial load on the bearing within the specification when the motor heats up and different thermal expansion occurs. The arrangement shown here does not provide thermal expansion, so there may still be long-term problems with motor bearings. The presence or absence will depend on the location of the shaft on which the thrust bearing is installed. Ideally, the thrust device will all be located at one end, and the other end will float freely as the part expands. In fact, it is best to only install the thrust bearing at the output end, as close as possible to the output bearing, and rely on the original output bearing to control the thrust in the direction outside the motor. Assuming (for demonstration) a 604 bearing with a 4mm shaft (instead of Nema23′s 6mm shaft), then the radial radial load is 360N and the rated axial load is 0.25 times (0.5 times for larger bearings). So the output end The original deep groove ball should work, with an axial load of 90N. In the example given (30N), in terms of bearing life, it actually does not seem to be of concern. However, the axial float in the shaft against the preloaded spring may indeed need to be addressed, and a single thrust bearing on the output end can do this.
       However, it is better to equip the worm with a separate set of thrust bearings and allow the entire motor to float axially with a suitable torque reaction device. This is a common arrangement in which the motor drives a ball screw with its own angular contact bearing set through a Lovejoy or similar coupling. However, this does add a lot of extra length.
       Andy, I’m going to write the same thing: He seems to have added the bearings without any gaps, just hoping that the correct bearings can withstand the load.
       It is the last paragraph. Unless tapered roller bearings or angular contact ball bearings or separate thrust bearings are used, the motor should not bear a large axial load on its shaft.
       The motor should drive the shaft through a belt, gear, elastic coupling or spline coupling. The greater the rigidity of the coupling, the higher the accuracy requirements of the motor for shaft alignment.
       Agree, the arrangement chosen here may even be harmful to the service life of the motor. The ball bearings of the motor itself are likely to still bear a large load. The photo seems to show enough space to support the worm. Choosing to support the worm with 2 angular contact bearings at both ends and driving it through a spline shaft or key shaft is already a better choice, IMHO. The flexible coupling in the middle is a further improvement to it.
       Before you touch the spring washer to the bottom, the ime stepper will not really bear any axial load, the shaft and the bearing are in sliding fit
       Depends on the stepper. I have also seen that if the spring washers are compressed too far, one or even both of their bearings will bear the axial load.
       So like I said, as long as you don’t bottom the spring washer, there will be no excessive axial load on the bearing.
       Yes, but these spring washers are usually very fragile, so in such applications, you can easily bottom them out.
       @ThisGuy This is the key to thrust bearings, they lock the rotor in the center, so the spring washers will never work
       I know everything is relative, but I can’t help but find the exaggeration here a bit interesting-in a more traditional unit, “a huge axial load of more than six pounds”
       This is a bad choice. Roller bearings work well because they reduce friction by rolling instead of dragging-the inherent problem with needle roller thrust bearings is that the end of the needle on o/d moves faster than i/d (unless the needle element is tapered) Yes, for most applications, no one considers). Of course there are tapered needle roller thrust bearings, but this guy is better to use spherical thrust bearings instead-he basically has no limit on the axial load until the bearing breaks or the gasket is indented, or this will pass 6 pounds.
       In addition, after setting a proper preload on the spherical thrust bearing, he has almost no radial resistance. Good idea, some expert opinions could have been used.
       My nonsense, my impression is that he used straight needle roller bearings, but those center races do not look like parts
       I like to discuss all the different bearing configurations and settings, and I like the series of articles covering tapered rollers and tapered thrust bearings in actual design examples. Reminds me of the lathe I am designing.
       Just from the picture, if possible, I would place a support at the end of the shaft of the stepper. Most of the wear and side load forces can be better handled by the support at the position of maximum lateral deflection.
       Agreeing with the comments about tapered roller bearings, the lathe spindle uses them in pairs preloaded at the front because they are designed to withstand both axial and lateral loads, just like the worm gear here produces.
       Can they use a servo flexible coupling, spider coupling, or plum coupling to separate the shaft of the stepper motor from the shaft that drives the worm gear? Not sure about the torsional load they are dealing with. Or maybe a 1:1 gear?
       Then they can direct the force into the motor mounting frame with almost no force to the stepper shaft.
       You should use bearings that can accept the expected thrust loads (angular contact, taper, thrust, etc.), with balls or trapezoidal screws in any case. Motor bearings usually cannot withstand such loads, and failure to properly support the screw will have a negative impact on accuracy. Ideally, the screw positioning assembly is 100% self-supporting, no need to connect to the motor, the motor only provides torque. That’s Machine Design 101. If the load is within the specification, you can abandon the thrust bearing, but it is usually a bad practice to do so, because the thrust load may cause the internal components of the motor to be misaligned, thereby affecting performance. Just look at any ordinary ball bearing and check the acceptable thrust load, you may actually be surprised how small the rated thrust load is in most cases.
       Since there is no edit button, I also added that in most cases, depending on the level of accuracy you require, worm gears used for all intents and purposes can be considered as balls or conical screws, because the forces are almost in the same direction.
       The load on the worm gear is significantly different from the load on the Acme or ball screw. Since Acme and ball screws are used with full nuts, the load is almost purely axial. The worm only acts on the gear on one side, so there is a radial load.
       I will go the other way, and many people will be surprised to find how large the axial load capacity of the ball bearing is. At least 25% radial load, 50% heavier section/larger bearing.
       In any case, if you don’t mind severely shortening bearing life and possible catastrophic failures, please continue to use standard ball bearings to handle thrust loads! FWIW, when the standard ball bearing bears the thrust load, the contact area is reduced significantly. If the size of the bearing is large enough, you may not see anything serious or dangerous, but this is not typical, especially when your parts are “cheap”.
       Now you are just the opposite. If the bearing manufacturer says it is suitable for a radial load of x Newton, that is the specification.
       My figures are based on the SKF online guide. They may know their location better than you. If you prefer random anecdotal arguments: motorcycle wheel bearings are a pair of deep groove balls, they see forces in all directions almost randomly, and can be used for a long time. I drove at least 120,000 miles in my test.
       The default “ball bearing” is a deep groove ball. If it’s nothing else, it’s a deep groove ball. See the categories here. https://simplybearings.co.uk/shop/Products-All-Bearings/c4747_4514/index.html
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