@@TheExplosiveGuy "I wonder how they compare to a ball screw system..." Under a comment by @Christian Barnay is a reply by @Bala K. Here's what @Bala K wrote: "Believe me, yes. We switched from bulky ball screws to Planetary roller screws with reduced size and dramatic performance. High thrust forces with screw diameters almost half of ball screws" There's some additional information in that comment thread. You might want to find it. As I write this the comment has 8 replies. I'm going to follow the links in that thread myself.
"Sir we've finished the Planetary roller screws, but we're 8 million under budget" "Whelp, if you don't spend it you lose it, give it all to marketing"
UA-cam: It's been a long day, want to unwind by learning about Planetary Roller Screws? Me: I don't know what those are.... UA-cam: they have high axial stiffness Me: say no more...
Hi there , what part of the suit would you use this with ? Are you thinking in regards to extending and retracting limbs ? it would definitely work , however you would need a complicated system of drivers and bearings to allow for the rotating shaft to turn freely. I personally think hydraulics or pneumatics would be a better option because of their relative simplicity. Great idea though ! If you got it to work , it would probably be very strong and reliable , just heavy.
@@BigEvy both of the alternative options you chose would have too large of components to properly place movable parts on a reasonably size humanoid shaped robot.
@@nom6758 really? That's too bad. I have seen some tiny cylinders, but the pumps and power supply would be a challenge I guess. I think there's some footage of a powered suit online , I don't know what it uses .
The problem is they're not back drivable and would require an external torque sensor. A power failure could result in being trapped in the suit, a software or sensor failure could result in severe injury.
I've seen a good number of comments comparing similar systems. Just to clarify a few things on bearings and planetary gears. Ball bearings use spherical spacers (balls) to isolate the internal shaft from the casing. These balls are held in place with a collar to prevent them from moving out of position, usually as a result of side loads. The balls rolling against the internal shaft and outer housing produce very little friction. Most of the resistance and heart generation comes from the collar that surrounds the bearings themselves. Roller bearings are nearly identical in form and function to ball bearings. They use cylindrical rollers instead of balls to isolate the internal shaft from casing. Roller bearings are usually more expensive, but can outperform ball bearings because they are linked together only at the ends instead of being partially encased in a collar. Similar to ball bearings, the rollers produce little friction from rolling compared to the limits holding them together but, unlike ball bearings, you can lengthen a roller without needing to add more sections of rollers. Planetary gears are even more fun. They are much more expensive to produce, but don't necessarily require anything to connect one 'free' gear to the next because they all must rotate with the internal shaft and the casing. Gears under load rolling against each other do create more friction than a ball or cylinder, but they don't require supports with joints under load with pins that slide against each other. There are scenarios where a roller can be more efficient, such as when there is no or little side load, but properly manufactured gears will edge out in terms of friction in most cases. As for transfering load, things get much simpler. A ball bearing can transfer load along a much smaller surface than a gear, and a flat roller (unless angled, but that requires significant sliding motion in addition to rolling) cannot transfer any load. Even giving the ball bearing a Generous 30% effective contact surface per collar housing, you still need to use several of these housings to distribute force along the length of the shaft. If the in line, ball to ball, linear, effective surface contact area along the shaft is also a Generous 30%, you end up with a combined contact area efficiency of 10% compared that which you would get from an equivalently sized, planetary gear system. Ideally, you would be able to make a device 1/9th the size with the planetary roller screws, though imperfections and costs would make smaller systems economically unviable in my opinion. I haven't done the math to give any real approximations, but that smaller size should result in lower inertial resistance to momentary movements, and the higher contact area should allow for higher precision and resistance to backpressure. Planetary gear systems are also excelent force multipliers, so you could design the system such that 10 revolutions of the shaft only result in a single 'step'. You have no idea how badly I want to test a system like this directly against its counterparts. I don't think it will ever replace the more common roller bearings for most tasks where cost is more valuable than space, but I can imagine extremely high precision or high load functions would make these systems worth the increase in price.
To replace a bearing like you said, you would need a zero-lead roller screw. It's possible, incredibly compact and used in some very niche applications. Bearings still have good days ahead of them :-)
Everything seems perfect in CAD animation with bodies that don't care about collisions (see 00:50 rollers teeth and helix passing through the outer ring teeth and helix). I would be much more interested in an actual demonstration of a physical prototype to see if the movement is really as smooth and fast as pretended.
Believe me, yes. We switched from bulky ball screws to Planetary roller screws with reduced size and dramatic performance. High thrust forces with screw diameters almost half of ball screws.
That's it. the whole world can be brought to a stop with nothing more than cartoons as a basis. empirical evidence of the work in actual use, is what's required.
This video is just a demonstration of the working principle behind planetary roller screws. The concept of these devices is nothing new and they have been used for various applications over the past several decades. Although their application has been somewhat limited for various reasons, they have been proven to be great assets. If you want to see a physical demonstration of a planetary roller screw here's a link: ua-cam.com/video/2Mjbkv5pXbU/v-deo.html skip to 00:30 to see it moving.
I now have a positive impression of these devices that I was previously unaware of. Maybe This Old Tony can make a set to drive his mill table and head.
@@akzorz9197 I don't think there is much to be gained on a 3d printer (over ball screws). and the balls screws are gonna be considerably lighter (fewer components). I would like to see if I could print a model of one of these, just to be able to hold it in hand & play with it. If that goes well, I am gonna try to turn one of the lathe. It wont have the precision a commercial one would have, but i think it''ll be a fun project.
That's rather clever. I would imagine that the performance gains relative to conventional mechanisms grows exponentially with size. So long as you have the spare available torque for the beefier mechanism, you could get an absurd output. In fact, with a few adjustments, you could probably rival midrange and up hydraulic presses. Also, it looks absolutely amazing. It would be cool just having a working replica as a display piece.
@Piotr Lenarczyk Hi Piotr, in fact, alternative standard solutions exist. You can either have oversized rollers to have a backlash free mechanism, or split nuts to have preloaded screws for the most demanding applications regarding stiffness and susceptibility to load direction changes!
Тут смысл в уменьшении передаточного числа. Если гайка за один оборот сдвинется на один виток резьбы, то данная муфта при одном обороте внешнего корпуса сдвинется на столько витков резьбы, насколько число зубьев зубчатого венца корпуса(за который цепляются зубья маленьких шестерёнок) больше числа зубьев на этой маленькой шестерёнке. Если допустим число зубьев корпуса муфты в семь раз больше числа зубьев шестерёнки, то за один оборот корпуса муфты она сдвинется сразу на семь витков резьбы.
what's the advantage over a regular nut? On a regular nut surface contact between the screw threads and the nut is larger than in the roller screws case so what's the advantage? It seems to me the regular screws are more rigid/stiff than this. Is the advantage no backlash? If so how is it achieved?
No, I think its perfectly engineered. Always used to wonder how is it that they exert tens of tons of force on such a small machine? Turns out the force is divided into all that many screws. Its perfect.
@@TheBigInt A standard ACME nut can hold far more load. The face of the thread profile is supported fully. These are designed to compete with ball screws, and are stronger in those applications where zero backlash is required.
No, not when the friction of nuts is too high. Friction can be a disadvantage if you want smooth control of the position, in part because static and kinetic friction is different, but also if you want to prevent the friction from wearing down materials in high load scenarios. A regular nut is good enough for a lot of cases, but this definitely has a place.
@ I've built plenty of stuff using recirculating ball nuts, no friction issues with those. This seems like another step of gearing more than anything. It could even be shiftable depending on whether the shell or planet carrier is held.
These computerised design videos of engineering products are better than a SC-FI movies. Space 2020 never looked this good. And it's educational to boot..
Got my attention.... I know at least two machines still running elmor drives, replaced last year and already wrecked due to high cycle times/constant running. Travel distance, speed and load constant.
When talking about speed, this is in the speed at which the nut body will translate, when you apply rotation to the shaft by a motor coupled to it. The speed that you can attain with a given resolution per turn is generally much higher than a ball screw, because the ball screw speed is limited generally by the recirculation device, that just cannot hanle toom much high frequency shocks, or the balls that get worn out too quickly hitting against it. The absence of such shocks is one of the beauties of this mechanism!
@@AlexJoneses Whatever the type of ball screws, they do have to make the balls recirculate, so they go from a loaded state to an unloaded state, then back to loaded state while recirculating back to the start of the circuit. That's what I meant by shocks on balls.
This type of linear actuator would outperform just about any other actuator when used to drive YoutTube likes if applied to a video with exciting music and arbitrary CAD.
The strength of this system would be massive. Planetary reduction gearbox systems are high torque output. Anyone know if this method has exploration/ core drilling applications?
Износ резьбы будет просто бешеный из-за значительного уменьшения площади соприкосновения. Пока что лучшим способом после гайки остается только прецизионная шарико-винтовая передача
Interesting design. You get speed reduction and torque increase as a consequence. The increase in the contact area of the worm-shaped planetariums gives the unit great durability, this, together with a well-chosen material, provides perfection in the design. A question. How do you get the motorization of the system? who moves it? Maybe that was missing from the video. Thank you very much and greetings.
The motor can be driving the mechanism in two ways. You can either have a motor coupled on a machined end of the shaft. You make the shaft rotate, making the nut translate (you then have to avoid rotation of the nut by guiding it or the part it is mounted in). The other way is to have the nut driven by the motor, either by gears or pulley-belt system, then the shaft will translate and push/pull what you need it to. The rotation of the shaft or it's linked part will be needed then. Hope it's clearer!
@@yoannmonterymard5766 Excellent. It looks like a very reliable unit. We know that in every epicyclic train, there must be a driving element (which in this case is the center), a driven element, and one that is stopped or braked. In this unit, what is the element that is braked, and how do you stop it? Thanks
@@walteradrianlemus246 Hi, in fact, here two cases are possible. You can drive the shaft and make the nut translate. The nut then has to be integrated (by bolting in this example, or with keyway with another standard design) in a housing that is blocked in rotation. In industrial machines, considering the loads to be applied and countered, ball or roller profile rail guides are generally the right choice. Some examples of such guides here: www.ewellix.com/en/global/products/linear-guides/profile-rail-guides The second case is that you make the nut rotate, with a gear or pulley/belt and then the shaft translates. You then have to avoid rotation of the shaft with a proper machined end or a linked part (splines, keyway...)
So an over engineered nut with less friction on the bolt thread and decreased holding strength, but each of your inner threads have their own friction from each other, so you may have actually created more friction overall. It does look cooler than a regular nut though so I guess that's nice.
Regular nuts won't work well in linear actuators which are constantly moving back and forth. Worse if precision movement is needed. Alternative for roller screw is ball screw which have ball bearings as contact surface between nut and shaft. Roller screw is more expensive but has significant advantages. www.olsenactuation.com/case.html?id=70
Standard wipers can be provided to avoid the ingress of the bigger particles, but overall the system is very tolerant to dust (to some extent of course). Lubrication health will be the most important.
@@douro20 The invention is indeed from the late 40's, and the "start-up" created by its inventor (Carl Bruno Strandgren) was acquired and developped in a branch of SKF group, well known for rolling bearings. This branch was divested by SKF in 2018 and is now Ewellix :-)
These roller screw do perform quite well in almost all applications where ball screws are used. Their price is slighlty higher than ground ball screws though, as those rollers are much more expensive to produce than balls. So they are generally reserved for applications requiring more compactness (like on robot arm end) or speed/lifetime for very high duty applications like plastic injection presses, servo presses, high end hexapods, etc...
A roller screw will have several advantages compared to a ball screw: 1) Much more compact for same load/lifetime (typically a roller screw diameter 21 will achieve similar lifetime and duty as a ball screw diameter 40) 2) Better tolerance to shock load, especially good for servo pressing applications 3) No recirculation, no slippage : way better on highly dynamic applications with high speed and accelerations
Looks like a part made to be encapsulated alongside the drive screw in a chamber that is hermetically sealed and is oil filled as to allow for lubrication that this would need... Its like saying that a planetary gearbox in an automatic car is easily ruined by dust... That is why they are built in such a manner that no dust can go in... Theoretically
@@Scrogan Why aren't we just using ball screws anyway? I guess there's more surface area in contact so theoretically it'll handle a heaver load, but I don't know.
@@matthewvandeventer3632 A ball screw will use far less number of balls than a roller screw has contact points, each contact having the same "local" geometry as a big ball. You can have a picture of the principle page 11 of this: medialibrary.ewellix.com/asset/16174
If you compare to a ball screw, it's very much about the size you consider. You can often get about 2-3 times more peak force on a given screw diameter compared to a standard ball screw!
Hydraulics will still be the way to go for either extremly compact applications like most of electro-hydraulic power tools or for very large pressing applications like more than 1000 tons. For all others, the shift is coming... The main advantages reside in the cleanliness, absence of leakage, energy efficiency, and controllability/precision/repeatability of the systems
How is it being driven? Or let me refrase that: which part of that Is being driven? Is there a motor driving the planetary “bolts” directly or is the inner or outer part driven?
The motor can be driving the mechanism in two ways. You can either have a motor coupled on a machined end of the shaft. You make the shaft rotate, making the nut translate (you then have to avoid rotation of the nut by guiding it or the part it is mounted in). The other way is to have the nut driven by the motor, either by gears or pulley-belt system, then the shaft will translate and push/pull what you need it to. The rotation of the shaft or it's linked part will be needed then. Hope it's clearer!
How do i transmit power to the "nut" instead of a bolt? What if i want to mount a motor on the moving part and not on base screw housing? Not sarcasm, sencire question
Can be either driving the shaft (you need a machined shaft end not shown on the video), or the nut (with a gear or pulley/belt system). The non driven part will then translate. You basically use those to make electromechanical versions of hydrualic jacks.
Yes, if you need higher speed and acceleration, if you need to bear with high peak loads, or if you need to have a more compact system to handle high loads and lifetime
It needs lubrication indeed, similarly to rolling bearing and gearboxes. The lubrication will be closer to those of gears than rolling bearings though!
Actually, you will find them in several high precision or heavy duty machining centers like vertical axis of gantry milling machines, but more on high precision grinding or broaching machines rather than on lathes 🙂 Applications where power density matters (at the end of robotic arms for example) will use them much more, though ;-)
its not a matter if you can afford it or not, its if you need that level of accuracy it will give. would i bother of it was for a desktop 3d printer? no.... if i was building a laser range finder to pinpoint the location of a spaceship going to mars... then yes....
@@martinjones6694 But what about cnc milling machines? There, the accuracy is 0.001 mm. In addition, Linear Bushings allow the use of higher machining conditions, and their rigidity is higher.
@@hibahprice6887 the accuracy of a cnc mill depends on the accuracy of the parts that make up the machine. The 0.001mm is probably true for some machines but it’s not some universal thing. There’s plenty of much higher. Tormach had a 0.0001mm mill as an example. Most home shop cnc machines don’t have more than .1mm accuracy even if the software used often lets you request a higher precision. But you setting a requested dimension doesn’t mean the machine is actually able to produce that. The same is true for 3D printers. Marlin, a common firmware for printers allows for your code to have up to 0.0001mm precision. But no 3D printer can actually produce anything like that. Even the best commercially available printers I’ve seen have at best 0.02mm precision for z and 0.01 for x and y. But even that is in precision for the printing itself. Plastic not being entirely rigid and significant thermal expansion throws that measurement off so you’re more likely looking at a 0.1-0.05mm accuracy for a final product. That being said. For these screws. I doubt that they will replace ball screws in precision machines. The reason ball screws are used is not only because of the precision but also because of their low friction. These have metal rubbing against metal the entire length of the each of those screws. That’s going to be a lot of heat that needs to be cooled away if temperature is to remain constant so that measurements are not thrown off and take accuracy with it. It’s an interesting design could be an alternative in some situations. But it’s not going to be for precision cnc machines.
@@danieljonsson8095 I am following the project of a homemade granite CNC, where a person uses linear bushings, they have all the advantages over other types, and they are not so expensive .. You can forget about 0.0001 accuracy, any machines will bend at least 1 micron from temperature conditions, load , and so on .. It is unrealistic to calculate, if we talk about home-made CNC, then such a solution is the most optimal, we have them available at a price, there are almost no analogues
Износ резьбы будет просто бешеный из-за значительного уменьшения площади соприкосновения. Пока что лучшим способом после гайки остается только прецизионная шарико-винтовая передача
Что это вообще за агрегат? Я не понимаю зачем такое нужно и как работает. Я понимаю когда есть винт и обычная гайка, ими можно организовать поступательное движение по прямой оси.
@@Y3ypn-am0p17 тут дело в уменьшении передаточного числа. Если гайка за один оборот сдвинется на один виток резьбы, то данная муфта при одном обороте внешнего корпуса сдвинется на столько витков резьбы, насколько число зубьев зубчатого венца корпуса(за который цепляются зубья маленьких шестерёнок) больше числа зубьев на маленькой шестерёнке. Если допустим число зубьев корпуса муфты в семь раз больше числа зубьев шестерёнки, то за один оборот корпуса муфты она сдвинется сразу на семь витков резьбы.
@@ЯрославШевченко-х7й но, я так понимаю, что так же пропорционально упадет момент.... в основу любого изобретения удачно вписывается один извечный вопрос: НахренА?... Я, честно говоря, не понимаю где может сильно понадобится такое чудо, тем более, что оно очень сильно ограничено тем, что крутить нужно именно "гайку"...
Не знаю... мне ажется, что это просто демонстрация своих рисовальных возможностей... По сути - этот механизм вообще работать не будет, если его хорошо смазать.
@@ЯрославШевченко-х7й Планетарная передача подобрана так, что ролики катятся по гайке и винту без скольжения. В идеале планетарный редуктор не нужен. ролики итак будут катится если есть достаточный натяг. Редуктор просто увеличивает надёжность. преимущество перед ШВП -- не надо ловит шарики при сходе с канавки гайки и направлять в начало, шарики в ШВП трутся друг о друга, так как нет сепаратора.
Exactly, rollers are rolling inside the nut without friction and around the shaft with very limited friction. All in all, efficiency is very close to ball screws, but with much higher load acceptance than ball screw in most cases!
@@mtraven23 If we are talking about lead accuracy, which means if I make 30 revolutions of a 10mm lead, how far off the 300mm mark am I really when checking with a reference linear rule, then the planetary roller screw is just as much accurate as top grade ground ball screws. Which means about +/-23µm off the mark in standard and +/-6µm upon request with additional controls.
@@yoannmonterymard5766 wow, 6 microns is tight. I didn't think there was anything inherently less accurate about the planetary roller screws, just that we make/ use way more ball screws, hence manufacturing might be better. are they similar in cost? seems like they might be a bit pricer?
@@mtraven23 Generally a bit pricer than ground ball screws, significantly more expensive than rolled ball screws. All depends on the quantities, duty cycle, sizing, etc...
When you reach the end, the nut disengages from the shaft, but nothing falls apart, as opposed to a ball screw. You can just put it back in place with a minimum of care!
The main goal is to convert a rotation from a motor to a translation movement. With high efficiency (those parts are rolling, not sliding) and high power density. Basically, they are used to replace hydraulic jacks by electromechnical ones :-)
I don't get it. The first part of the animation make it look like it acts as a roller bearing, with no movement of the assembly relative to the leadscrew. The rest shows the outer casting spin as well as the leadscrew. Is it meant to be a roller bearing, a positioning screw/nut, both, neither? That animation leaves me with more questions than answers.
The complexity of the nut and shaft machining is similar to a ground ball screw, but the rollers are much harder to make versus balls. The 10x ratio seems exagerated versus ground ball screws. For small ball screws compared to small roller screws, it can be this magnitude, mainly due to scale of standard production effect, but the performance is on a whole different level!
Note that the planet screws must be "clocked", so the gear teeth must be cut in precise relation to the thread start. Easy enough for a CNC, not so easy for manual machining.
@@UncleKennysPlace Wow yes. Most of the time you don’t think about these things until you had to trying to make them. Does this mean each outer screw is unique due to it only being a small amount further down / up the thread on the bar than its neighbouring ones? Something tells me this needs a little more accuracy than my steel rule and verniers! And just thought, the outer gears that the planetary gears ride on also have to be relatable to it all and each other. 😳
@@grumpyone5963 No, the spacing between each roller is clocked so they can be identical. A slight variation can likely be accepted by having a little bit of longitudinal allowance for the gears since it's the outer/roller/inner thread profile in combination with radial position that gives the positional accuracy for the whole package. (Now is the question, while I'm sure my thoughts are correct can I makes sense of that sentence myself? :-D )
@@UncleKennysPlace if you have a leadscrew clock and can index and lock headstock it wouldn't be to hard on manual. That said I'd rather cnc a part like this.
@@sharg0 you are assuming the engineer isn't a sadist I bet you could mathematically figure out a thead, dia, and clock position for an array of identical worms.
Erm.. so how do you prevent grit dust and dirt grinding away inside there !! This could be useful for joining colonies on other planets 🪐 as you wouldn’t need to be in the outside
I don't need these, but it doesn't stop me from wanting them.
I know I need them, I just haven't figured out why. They're the perfect solution. Now I just have to find the problem.
Me too
I'm doing my best to think something up🤣, these are awesome. I wonder how they compare to a ball screw system...
@@TheExplosiveGuy "I wonder how they compare to a ball screw system..."
Under a comment by @Christian Barnay is a reply by @Bala K. Here's what @Bala K wrote:
"Believe me, yes. We switched from bulky ball screws to Planetary roller screws with reduced size and dramatic performance. High thrust forces with screw diameters almost half of ball screws"
There's some additional information in that comment thread. You might want to find it. As I write this the comment has 8 replies. I'm going to follow the links in that thread myself.
@@ddegn well thank you kind stranger😁, I'll be looking as well.
"Sir we've finished the Planetary roller screws, but we're 8 million under budget"
"Whelp, if you don't spend it you lose it, give it all to marketing"
Exactly
friction will be striking
It wouldn't be the youtube comments section without negativity and morons.
They already have high res cad models from development so why not use it for promotion? It isn't only for YT, this would be show in all kind of expos.
The graphic artist is just as brilliant as the object!
I dunno, the way he put the planet gears in would have sheared the teeth off the ring and planet gears ;)
other than the sequence of installation, everything is brilliant.
Not really. The main lead screw doesn’t move in relation to the collar when the animation rotates.
UA-cam: It's been a long day, want to unwind by learning about Planetary Roller Screws?
Me: I don't know what those are....
UA-cam: they have high axial stiffness
Me: say no more...
Yes yes yes i pissed reading this because you are right
"That's what she said!" meme.
This is exactly what I needed... *Unzips*
I use them 20 years ago on high precision équipments under high loads, very good results!
so, guess what's getting saved to my Powered Exoskeleton playlist
lmao, too good
Hi there , what part of the suit would you use this with ? Are you thinking in regards to extending and retracting limbs ? it would definitely work , however you would need a complicated system of drivers and bearings to allow for the rotating shaft to turn freely. I personally think hydraulics or pneumatics would be a better option because of their relative simplicity.
Great idea though ! If you got it to work , it would probably be very strong and reliable , just heavy.
@@BigEvy both of the alternative options you chose would have too large of components to properly place movable parts on a reasonably size humanoid shaped robot.
@@nom6758 really? That's too bad. I have seen some tiny cylinders, but the pumps and power supply would be a challenge I guess. I think there's some footage of a powered suit online , I don't know what it uses .
The problem is they're not back drivable and would require an external torque sensor. A power failure could result in being trapped in the suit, a software or sensor failure could result in severe injury.
From the engineering point of view, it's just beautiful to watch!
I've seen a good number of comments comparing similar systems. Just to clarify a few things on bearings and planetary gears.
Ball bearings use spherical spacers (balls) to isolate the internal shaft from the casing. These balls are held in place with a collar to prevent them from moving out of position, usually as a result of side loads. The balls rolling against the internal shaft and outer housing produce very little friction. Most of the resistance and heart generation comes from the collar that surrounds the bearings themselves.
Roller bearings are nearly identical in form and function to ball bearings. They use cylindrical rollers instead of balls to isolate the internal shaft from casing. Roller bearings are usually more expensive, but can outperform ball bearings because they are linked together only at the ends instead of being partially encased in a collar. Similar to ball bearings, the rollers produce little friction from rolling compared to the limits holding them together but, unlike ball bearings, you can lengthen a roller without needing to add more sections of rollers.
Planetary gears are even more fun. They are much more expensive to produce, but don't necessarily require anything to connect one 'free' gear to the next because they all must rotate with the internal shaft and the casing. Gears under load rolling against each other do create more friction than a ball or cylinder, but they don't require supports with joints under load with pins that slide against each other. There are scenarios where a roller can be more efficient, such as when there is no or little side load, but properly manufactured gears will edge out in terms of friction in most cases.
As for transfering load, things get much simpler. A ball bearing can transfer load along a much smaller surface than a gear, and a flat roller (unless angled, but that requires significant sliding motion in addition to rolling) cannot transfer any load. Even giving the ball bearing a Generous 30% effective contact surface per collar housing, you still need to use several of these housings to distribute force along the length of the shaft. If the in line, ball to ball, linear, effective surface contact area along the shaft is also a Generous 30%, you end up with a combined contact area efficiency of 10% compared that which you would get from an equivalently sized, planetary gear system. Ideally, you would be able to make a device 1/9th the size with the planetary roller screws, though imperfections and costs would make smaller systems economically unviable in my opinion.
I haven't done the math to give any real approximations, but that smaller size should result in lower inertial resistance to momentary movements, and the higher contact area should allow for higher precision and resistance to backpressure. Planetary gear systems are also excelent force multipliers, so you could design the system such that 10 revolutions of the shaft only result in a single 'step'.
You have no idea how badly I want to test a system like this directly against its counterparts. I don't think it will ever replace the more common roller bearings for most tasks where cost is more valuable than space, but I can imagine extremely high precision or high load functions would make these systems worth the increase in price.
To replace a bearing like you said, you would need a zero-lead roller screw. It's possible, incredibly compact and used in some very niche applications. Bearings still have good days ahead of them :-)
The music implies this is what Ethan Hunt would use in his Bridgeport.
Machine: Impossible.
I was thinking this is some new superhero.
"clap clap"
You should talk to Thompson Couplings, a high torque self aligning CV joint manufacturer in Australia.
Ok, you've got my attention.
The movie trailer music is the mvp here.
Everything seems perfect in CAD animation with bodies that don't care about collisions (see 00:50 rollers teeth and helix passing through the outer ring teeth and helix). I would be much more interested in an actual demonstration of a physical prototype to see if the movement is really as smooth and fast as pretended.
Believe me, yes. We switched from bulky ball screws to Planetary roller screws with reduced size and dramatic performance. High thrust forces with screw diameters almost half of ball screws.
@@balak7161 It does look like there is more contact than the tangent points of ball screws. Would there be a continuous lubrication system needed?
That's it. the whole world can be brought to a stop with nothing more than cartoons as a basis. empirical evidence of the work in actual use, is what's required.
This video is just a demonstration of the working principle behind planetary roller screws. The concept of these devices is nothing new and they have been used for various applications over the past several decades. Although their application has been somewhat limited for various reasons, they have been proven to be great assets. If you want to see a physical demonstration of a planetary roller screw here's a link: ua-cam.com/video/2Mjbkv5pXbU/v-deo.html skip to 00:30 to see it moving.
@@ironfox2778 nice work. I just like how kitchen theorists shut up when see real proofs.
I now have a positive impression of these devices that I was previously unaware of. Maybe This Old Tony can make a set to drive his mill table and head.
underrated comment
We have had gears since Archimedes and now still people find new ways to use them and put them together. It's amazing.
seeing this comment i wonder if you ever heard about Archimedes II, a guy from australia who turned the Tube instead of the Screw
wasnt sure if i were able to find the related video again quickly, but here it is: ua-cam.com/video/-fu03F-Iah8/v-deo.html
I don't know why but I would love to see a scaled down version demonstrated on a super-stable 3d printer.
That would be one incredibly expensive and overpowered 3d printer.
I was just thinking... how does one get this for their Z?
@@akzorz9197 I don't think there is much to be gained on a 3d printer (over ball screws). and the balls screws are gonna be considerably lighter (fewer components).
I would like to see if I could print a model of one of these, just to be able to hold it in hand & play with it. If that goes well, I am gonna try to turn one of the lathe. It wont have the precision a commercial one would have, but i think it''ll be a fun project.
That's rather clever. I would imagine that the performance gains relative to conventional mechanisms grows exponentially with size. So long as you have the spare available torque for the beefier mechanism, you could get an absurd output. In fact, with a few adjustments, you could probably rival midrange and up hydraulic presses.
Also, it looks absolutely amazing. It would be cool just having a working replica as a display piece.
Indeed, it does replace hydraulic cylinders in numerous applications. You can find big roller screws on servopresses up to 1000 tons and more.
I love the T2 Judgement Day-esque music... PLANETARY ROLLER SCREWS DUNN DUNN DUNN
BWAAAAUGH
no idea what these are, but i'll take 4 of 'em
If you want something to accurately go up and be stiff, these are what you need.
@@DisorderedArray I thought viagra is the thing to use in situations like that.
@@yourlocaltoad5102 ba-dum-tssss
@@yourlocaltoad5102 viagra is out, planetary roller screws are the way of the future
Just got one of those for my penis implant.. 100% would recommend
wow, i'm impressed, never thought of it being used like this.
Thank you for video.
Counter roller could ensure positioning accuracy within clearance (free local wear correction and analysis) at cost of speed;)
@Piotr Lenarczyk Hi Piotr, in fact, alternative standard solutions exist. You can either have oversized rollers to have a backlash free mechanism, or split nuts to have preloaded screws for the most demanding applications regarding stiffness and susceptibility to load direction changes!
Тут смысл в уменьшении передаточного числа.
Если гайка за один оборот сдвинется на один виток резьбы, то данная муфта при одном обороте внешнего корпуса сдвинется на столько витков резьбы, насколько число зубьев зубчатого венца корпуса(за который цепляются зубья маленьких шестерёнок) больше числа зубьев на этой маленькой шестерёнке.
Если допустим число зубьев корпуса муфты в семь раз больше числа зубьев шестерёнки, то за один оборот корпуса муфты она сдвинется сразу на семь витков резьбы.
Ну вот , а я сюда из тик-тока и у меня лишь один вопрос был - Что тут происходит?)
Bloody Brilliant!
Good work on the graphics too!
what's the advantage over a regular nut? On a regular nut surface contact between the screw threads and the nut is larger than in the roller screws case so what's the advantage? It seems to me the regular screws are more rigid/stiff than this. Is the advantage no backlash? If so how is it achieved?
Overengineered nut?
No, I think its perfectly engineered. Always used to wonder how is it that they exert tens of tons of force on such a small machine? Turns out the force is divided into all that many screws. Its perfect.
@@TheBigInt A standard ACME nut can hold far more load. The face of the thread profile is supported fully. These are designed to compete with ball screws, and are stronger in those applications where zero backlash is required.
Yes. Undoubtedly
No, not when the friction of nuts is too high. Friction can be a disadvantage if you want smooth control of the position, in part because static and kinetic friction is different, but also if you want to prevent the friction from wearing down materials in high load scenarios. A regular nut is good enough for a lot of cases, but this definitely has a place.
@ I've built plenty of stuff using recirculating ball nuts, no friction issues with those. This seems like another step of gearing more than anything. It could even be shiftable depending on whether the shell or planet carrier is held.
So many interesting specs were absent in this video
but you got dramatic stock soundtrack, that'll have to suffice ;)
What a clever contraption.
please, this factory has manufactured roller screw over 50 years....it was applied in many applicaitons you just don't know
These computerised design videos of engineering products are better than a SC-FI movies. Space 2020 never looked this good. And it's educational to boot..
This could have been a alternate MCU dimension where Thanos was crushed by roller screws
[super hero noises intensify]
Got my attention.... I know at least two machines still running elmor drives, replaced last year and already wrecked due to high cycle times/constant running. Travel distance, speed and load constant.
Can't wait to see them hold planets in orbit.
How does it compare to the ball screw coupling.
how is this even remotely high speed or acceleration when compared to ball screws?
right this would be a speed reduction
When talking about speed, this is in the speed at which the nut body will translate, when you apply rotation to the shaft by a motor coupled to it.
The speed that you can attain with a given resolution per turn is generally much higher than a ball screw, because the ball screw speed is limited generally by the recirculation device, that just cannot hanle toom much high frequency shocks, or the balls that get worn out too quickly hitting against it. The absence of such shocks is one of the beauties of this mechanism!
@@yoannmonterymard5766 by shock do you just mean backlash, because ball screws that are preloaded to handle backlash do exist and can do exactly that
@@dancearoundtheworld5360 yes but they advertise high speeds (and didn't mention if they meant that linearly or angularly)
@@AlexJoneses Whatever the type of ball screws, they do have to make the balls recirculate, so they go from a loaded state to an unloaded state, then back to loaded state while recirculating back to the start of the circuit. That's what I meant by shocks on balls.
This type of linear actuator would outperform just about any other actuator when used to drive YoutTube likes if applied to a video with exciting music and arbitrary CAD.
I’m upgrading all my screws to these.
whats providing the power to turn the planetary scews?
I can just about operate a tin-opener, but I love shit like this.
So what is this, some kind of heavy-duty linear actuator?
The strength of this system would be massive. Planetary reduction gearbox systems are high torque output. Anyone know if this method has exploration/ core drilling applications?
Идея интересная. Очень. Для прецизионных приборов и лабораторных условий.
Износ резьбы будет просто бешеный из-за значительного уменьшения площади соприкосновения. Пока что лучшим способом после гайки остается только прецизионная шарико-винтовая передача
@@witaliy1980 В обычной гайке трение скольжения, а тут трение качения. И в этой гайке суммарная площадь витков сильно больше.
Цементировка убирает все ети проблемы:)
I wounder how they'll rack up against acme tread for cnc work
Interesting design. You get speed reduction and torque increase as a consequence. The increase in the contact area of the worm-shaped planetariums gives the unit great durability, this, together with a well-chosen material, provides perfection in the design.
A question.
How do you get the motorization of the system? who moves it? Maybe that was missing from the video.
Thank you very much and greetings.
The motor can be driving the mechanism in two ways. You can either have a motor coupled on a machined end of the shaft. You make the shaft rotate, making the nut translate (you then have to avoid rotation of the nut by guiding it or the part it is mounted in).
The other way is to have the nut driven by the motor, either by gears or pulley-belt system, then the shaft will translate and push/pull what you need it to. The rotation of the shaft or it's linked part will be needed then. Hope it's clearer!
@@yoannmonterymard5766 Excellent. It looks like a very reliable unit.
We know that in every epicyclic train, there must be a driving element (which in this case is the center), a driven element, and one that is stopped or braked.
In this unit, what is the element that is braked, and how do you stop it?
Thanks
@@walteradrianlemus246 Hi, in fact, here two cases are possible. You can drive the shaft and make the nut translate. The nut then has to be integrated (by bolting in this example, or with keyway with another standard design) in a housing that is blocked in rotation. In industrial machines, considering the loads to be applied and countered, ball or roller profile rail guides are generally the right choice. Some examples of such guides here: www.ewellix.com/en/global/products/linear-guides/profile-rail-guides
The second case is that you make the nut rotate, with a gear or pulley/belt and then the shaft translates. You then have to avoid rotation of the shaft with a proper machined end or a linked part (splines, keyway...)
So an over engineered nut with less friction on the bolt thread and decreased holding strength, but each of your inner threads have their own friction from each other, so you may have actually created more friction overall.
It does look cooler than a regular nut though so I guess that's nice.
I must admit to thinking something similar. Exactly what's the point of this? A lot more engineering, so why is it better?
Regular nuts won't work well in linear actuators which are constantly moving back and forth. Worse if precision movement is needed. Alternative for roller screw is ball screw which have ball bearings as contact surface between nut and shaft. Roller screw is more expensive but has significant advantages.
www.olsenactuation.com/case.html?id=70
@@kognak6640 Thanks. I get it now.
Is this better than ball screw nut?? I would like to try one for my application. But I will need left and right threaded leadscrews.
I think that's the objective of making them.
@ThisOldTony - I miss your content - how about one of these
Interesting mechanism, great animation< what's it for again??? Oh yeah did you know looped music was invented to drive us all insane???????????
How you deal with the debris?
Standard wipers can be provided to avoid the ingress of the bigger particles, but overall the system is very tolerant to dust (to some extent of course). Lubrication health will be the most important.
The animation should have included barber stripes on the lead screw and the planets so that it was more obvious what was going on here.
Ive got to take a closer look but I believe something like this is used in our big mixers at work that were made by AMF and are pretty old.
Yes. Planetary roller screws were first developed back in the late 1940s.
@@douro20 The invention is indeed from the late 40's, and the "start-up" created by its inventor (Carl Bruno Strandgren) was acquired and developped in a branch of SKF group, well known for rolling bearings. This branch was divested by SKF in 2018 and is now Ewellix :-)
Wonder how these would perform on a CNC mill running at 500+ ipm? Would be a good replacement for ball screws on a large waterjet though.
These roller screw do perform quite well in almost all applications where ball screws are used. Their price is slighlty higher than ground ball screws though, as those rollers are much more expensive to produce than balls. So they are generally reserved for applications requiring more compactness (like on robot arm end) or speed/lifetime for very high duty applications like plastic injection presses, servo presses, high end hexapods, etc...
So this replaces a hydraulic ram and cylinder? Or rather a pair of rams in opposition. Nice idea.
How does this compare to a ball screw? Advantages vs disadvantages.
A roller screw will have several advantages compared to a ball screw:
1) Much more compact for same load/lifetime (typically a roller screw diameter 21 will achieve similar lifetime and duty as a ball screw diameter 40)
2) Better tolerance to shock load, especially good for servo pressing applications
3) No recirculation, no slippage : way better on highly dynamic applications with high speed and accelerations
@@yoannmonterymard5766 Thanks, I wonder why they are not more commonly used, I'd guess because they are more complex and expensive to manufacturer.
@@phillhuddleston9445 You got probably the right point there, plus a part of awareness!
WHAT A BEAUTIFUL MOMENT... And I'm here - you come in too
Looks like dust ingress would be a huge issue long term.
Looks like a part made to be encapsulated alongside the drive screw in a chamber that is hermetically sealed and is oil filled as to allow for lubrication that this would need... Its like saying that a planetary gearbox in an automatic car is easily ruined by dust... That is why they are built in such a manner that no dust can go in... Theoretically
Could say the same thing about a ballscrew
@@Scrogan Why aren't we just using ball screws anyway? I guess there's more surface area in contact so theoretically it'll handle a heaver load, but I don't know.
@@matthewvandeventer3632 A ball screw will use far less number of balls than a roller screw has contact points, each contact having the same "local" geometry as a big ball. You can have a picture of the principle page 11 of this: medialibrary.ewellix.com/asset/16174
Everything works great in a computer simulation! How much thrust force can it handle compared to a ball screw????
If you compare to a ball screw, it's very much about the size you consider. You can often get about 2-3 times more peak force on a given screw diameter compared to a standard ball screw!
أَوَلَيْسَ ٱلَّذِى خَلَقَ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضَ بِقَٰدِرٍ عَلَىٰٓ أَن يَخْلُقَ مِثْلَهُم ۚ بَلَىٰ وَهُوَ ٱلْخَلَّٰقُ ٱلْعَلِيمُ
إِنَّمَآ أَمْرُهُۥٓ إِذَآ أَرَادَ شَيْـًٔا أَن يَقُولَ لَهُۥ كُن فَيَكُونُ
فَسُبْحَٰنَ ٱلَّذِى بِيَدِهِۦ مَلَكُوتُ كُلِّ شَىْءٍ وَإِلَيْهِ تُرْجَعُونَ
What benifits do these have over hydraulics and what advantages do hydraulics have over these
Hydraulics will still be the way to go for either extremly compact applications like most of electro-hydraulic power tools or for very large pressing applications like more than 1000 tons. For all others, the shift is coming... The main advantages reside in the cleanliness, absence of leakage, energy efficiency, and controllability/precision/repeatability of the systems
Holy crap, this is exactly what I was building as the extruder for my 3d printer.
How is it being driven? Or let me refrase that: which part of that Is being driven? Is there a motor driving the planetary “bolts” directly or is the inner or outer part driven?
The motor can be driving the mechanism in two ways. You can either have a motor coupled on a machined end of the shaft. You make the shaft rotate, making the nut translate (you then have to avoid rotation of the nut by guiding it or the part it is mounted in).
The other way is to have the nut driven by the motor, either by gears or pulley-belt system, then the shaft will translate and push/pull what you need it to. The rotation of the shaft or it's linked part will be needed then. Hope it's clearer!
I learned this concept chasing submarines. Ring, Sun, Planet gears?
How do i transmit power to the "nut" instead of a bolt? What if i want to mount a motor on the moving part and not on base screw housing? Not sarcasm, sencire question
mount the nut on a gear to anorther gear connect that to a motor?
Imagine getting a corner of your shirt stuck in one.
And must stay super clean screws collect dust like lots of it.
seems interesting but where is the motor?
Can be either driving the shaft (you need a machined shaft end not shown on the video), or the nut (with a gear or pulley/belt system). The non driven part will then translate. You basically use those to make electromechanical versions of hydrualic jacks.
I wonder how effective they are in a press operation compared to hydraulics.
Not good for super high pressure.
where the music from, reminds me of hawken
So how'd you bypass the 3-gear rule?
nothings meshing except the planet gear and each individual cog, each of which is just out of reach of the next
To understand that concept correctly: it is performing like a ballscrew, but better suited for higher loads or if a greater stiffness is necessary?
Yes. And it can even be used for speed multiplication or reduction.
Yes, if you need higher speed and acceleration, if you need to bear with high peak loads, or if you need to have a more compact system to handle high loads and lifetime
this feels more like a rick & morty interdimensional cable clip
Yes I have to go back and watch
Music name, please?
I don't know why I'm watching this but at least I know about planetary roller screws now
Fantastic video
seems to possibly be a high wear item based on the surface speed of the mating surfaces
the wear is very minimal in fact, as the rollers are "rolling" on the thread rather than gliding!
dose it fix back lash ?
Lubrication of any kind? Looks awesome otherwise. What kind of a bearing do our Pilots have?
It needs lubrication indeed, similarly to rolling bearing and gearboxes. The lubrication will be closer to those of gears than rolling bearings though!
What is causing the rotation?
A motor, that isn't shown in the video.
I guess this can be used for manufacturing lathes that need 1/5000” in of precision
Actually, you will find them in several high precision or heavy duty machining centers like vertical axis of gantry milling machines, but more on high precision grinding or broaching machines rather than on lathes 🙂 Applications where power density matters (at the end of robotic arms for example) will use them much more, though ;-)
RIP those who can't afford normal ball screws
Yeah I am one of them, way to expensive in my country.
its not a matter if you can afford it or not, its if you need that level of accuracy it will give. would i bother of it was for a desktop 3d printer? no.... if i was building a laser range finder to pinpoint the location of a spaceship going to mars... then yes....
@@martinjones6694 But what about cnc milling machines? There, the accuracy is 0.001 mm.
In addition, Linear Bushings allow the use of higher machining conditions, and their rigidity is higher.
@@hibahprice6887 the accuracy of a cnc mill depends on the accuracy of the parts that make up the machine. The 0.001mm is probably true for some machines but it’s not some universal thing. There’s plenty of much higher. Tormach had a 0.0001mm mill as an example. Most home shop cnc machines don’t have more than .1mm accuracy even if the software used often lets you request a higher precision. But you setting a requested dimension doesn’t mean the machine is actually able to produce that.
The same is true for 3D printers. Marlin, a common firmware for printers allows for your code to have up to 0.0001mm precision. But no 3D printer can actually produce anything like that. Even the best commercially available printers I’ve seen have at best 0.02mm precision for z and 0.01 for x and y. But even that is in precision for the printing itself. Plastic not being entirely rigid and significant thermal expansion throws that measurement off so you’re more likely looking at a 0.1-0.05mm accuracy for a final product.
That being said. For these screws. I doubt that they will replace ball screws in precision machines. The reason ball screws are used is not only because of the precision but also because of their low friction. These have metal rubbing against metal the entire length of the each of those screws. That’s going to be a lot of heat that needs to be cooled away if temperature is to remain constant so that measurements are not thrown off and take accuracy with it. It’s an interesting design could be an alternative in some situations. But it’s not going to be for precision cnc machines.
@@danieljonsson8095 I am following the project of a homemade granite CNC, where a person uses linear bushings, they have all the advantages over other types, and they are not so expensive .. You can forget about 0.0001 accuracy, any machines will bend at least 1 micron from temperature conditions, load , and so on .. It is unrealistic to calculate, if we talk about home-made CNC, then such a solution is the most optimal, we have them available at a price, there are almost no analogues
Износ резьбы будет просто бешеный из-за значительного уменьшения площади соприкосновения. Пока что лучшим способом после гайки остается только прецизионная шарико-винтовая передача
Что это вообще за агрегат? Я не понимаю зачем такое нужно и как работает. Я понимаю когда есть винт и обычная гайка, ими можно организовать поступательное движение по прямой оси.
@@Y3ypn-am0p17 тут дело в уменьшении передаточного числа.
Если гайка за один оборот сдвинется на один виток резьбы, то данная муфта при одном обороте внешнего корпуса сдвинется на столько витков резьбы, насколько число зубьев зубчатого венца корпуса(за который цепляются зубья маленьких шестерёнок) больше числа зубьев на маленькой шестерёнке.
Если допустим число зубьев корпуса муфты в семь раз больше числа зубьев шестерёнки, то за один оборот корпуса муфты она сдвинется сразу на семь витков резьбы.
@@ЯрославШевченко-х7й но, я так понимаю, что так же пропорционально упадет момент....
в основу любого изобретения удачно вписывается один извечный вопрос:
НахренА?...
Я, честно говоря, не понимаю где может сильно понадобится такое чудо, тем более, что оно очень сильно ограничено тем, что крутить нужно именно "гайку"...
Не знаю... мне ажется, что это просто демонстрация своих рисовальных возможностей... По сути - этот механизм вообще работать не будет, если его хорошо смазать.
@@ЯрославШевченко-х7й Планетарная передача подобрана так, что ролики катятся по гайке и винту без скольжения. В идеале планетарный редуктор не нужен. ролики итак будут катится если есть достаточный натяг. Редуктор просто увеличивает надёжность. преимущество перед ШВП -- не надо ловит шарики при сходе с канавки гайки и направлять в начало, шарики в ШВП трутся друг о друга, так как нет сепаратора.
This seems much better than linear bearing sleeves on rods for 3D printer z axis screw.
so these are rolling interfaces, like ball screws, right?
Exactly, rollers are rolling inside the nut without friction and around the shaft with very limited friction. All in all, efficiency is very close to ball screws, but with much higher load acceptance than ball screw in most cases!
@@yoannmonterymard5766 my first thought was, "man, I bet those can take a load"
you think ball screws are still marginally more accurate?
@@mtraven23 If we are talking about lead accuracy, which means if I make 30 revolutions of a 10mm lead, how far off the 300mm mark am I really when checking with a reference linear rule, then the planetary roller screw is just as much accurate as top grade ground ball screws. Which means about +/-23µm off the mark in standard and +/-6µm upon request with additional controls.
@@yoannmonterymard5766 wow, 6 microns is tight. I didn't think there was anything inherently less accurate about the planetary roller screws, just that we make/ use way more ball screws, hence manufacturing might be better.
are they similar in cost? seems like they might be a bit pricer?
@@mtraven23 Generally a bit pricer than ground ball screws, significantly more expensive than rolled ball screws. All depends on the quantities, duty cycle, sizing, etc...
I don't know why, but I like this
Power source?
Man that really looks impressive! What happens when you reach the end?
When you reach the end, the nut disengages from the shaft, but nothing falls apart, as opposed to a ball screw. You can just put it back in place with a minimum of care!
Is it backdrivable?
Engineering at his best
This is good work in space only!
great improvement
Glad you think so!
Is this better than worm gear?
What am I missing?
Is it just that it reduces/changes the torque?
The main goal is to convert a rotation from a motor to a translation movement. With high efficiency (those parts are rolling, not sliding) and high power density. Basically, they are used to replace hydraulic jacks by electromechnical ones :-)
@@yoannmonterymard5766 Ok, thanks.
I don't get it. The first part of the animation make it look like it acts as a roller bearing, with no movement of the assembly relative to the leadscrew. The rest shows the outer casting spin as well as the leadscrew. Is it meant to be a roller bearing, a positioning screw/nut, both, neither? That animation leaves me with more questions than answers.
I need some of these for my 3D printer.
Just how many paychecks to get one of them, then how many more paychecks to get the parts needed to use the darn thing.
But will harbor freight carry the? :)
These actually seem less complex to me than ball screws, yet they're 10x more expensive. Is that because of real cost/difficulty or scarcity?
There's so much machining time wrapped up in them that the cost isn't surprising.
The complexity of the nut and shaft machining is similar to a ground ball screw, but the rollers are much harder to make versus balls. The 10x ratio seems exagerated versus ground ball screws. For small ball screws compared to small roller screws, it can be this magnitude, mainly due to scale of standard production effect, but the performance is on a whole different level!
Прикольная штучка. Прецизионное силовое скоростное надежное позиционирование?
ага, особенно производство данного планетарного механизма - филиал ада на Земле.....
@@РусланТаран-м1р ЧПУ станки и производят.
cool any backlash, i think this is the same as a linear bearing, except with teeth yes???? no cheers
Music?
if you are a machinist you can make your own,it didn't look complicated to me. ah yes" left or right"
Note that the planet screws must be "clocked", so the gear teeth must be cut in precise relation to the thread start. Easy enough for a CNC, not so easy for manual machining.
@@UncleKennysPlace Wow yes. Most of the time you don’t think about these things until you had to trying to make them. Does this mean each outer screw is unique due to it only being a small amount further down / up the thread on the bar than its neighbouring ones? Something tells me this needs a little more accuracy than my steel rule and verniers! And just thought, the outer gears that the planetary gears ride on also have to be relatable to it all and each other. 😳
@@grumpyone5963 No, the spacing between each roller is clocked so they can be identical. A slight variation can likely be accepted by having a little bit of longitudinal allowance for the gears since it's the outer/roller/inner thread profile in combination with radial position that gives the positional accuracy for the whole package. (Now is the question, while I'm sure my thoughts are correct can I makes sense of that sentence myself? :-D )
@@UncleKennysPlace if you have a leadscrew clock and can index and lock headstock it wouldn't be to hard on manual. That said I'd rather cnc a part like this.
@@sharg0 you are assuming the engineer isn't a sadist
I bet you could mathematically figure out a thead, dia, and clock position for an array of identical worms.
Erm.. so how do you prevent grit dust and dirt grinding away inside there !!
This could be useful for joining colonies on other planets 🪐 as you wouldn’t need to be in the outside
Video liked for no reason!