[handlewanker]

Hi.....there is a very real problem if you work with partial grooves.

For instance, if you had a box and the face in front of you was at an angle of 45 deg, any attempt to push the box forward would also push it sideways with equal force.

Having the balls impinging on a partial groove in the rollers is tantamount to them pushing on the roller grooves at the 45 deg angle not as a direct axial thrusting force to the frame.

The action of the screw when it's rotating forwards (whatever) is to apply force to the back side of the balls as they are deep seated in the screw thread form........ this force on the back side of the balls is applied to the back side of the roller groove, and if it is as full a form as the screw, the force will be converted to axial thrust to the frame, the roller groove acting as a fulcrum.

There will be some backwards reactionary force to the roller but with a full form thread profile not enough to consider important.

HOWEVER..........with a half form to the roller thread profile, the balls will exert the force on them at an angle to the roller of approx. 45 deg (whatever)........putting undue stress on the roller ball races.

True, the 45 deg force that acts on the screw(s) side grooves acts in both directions and the roller fulcrums the partial load in the axial direction, but at the expense of undue stress to the roller bearings.

Having a roller with a partial groove means the second roller, also with a partial groove, is acting in the opposite direction....the front side of the ball...... and so the full force from the screw, via the balls, is applied to just a partial segment of one roller profile.

I agree that it could work, but for how long, and how long would the tiny bearings last.......they are not sealed in that small size, at least the ones I have seen, so inclusions are a very real problem apart from lubrication.

My opinion is that this design is compromised due to the design calling for two grooved rollers, (to maintain ball contact with the screw)...... and as the space for two rollers against one ball limits the roller diam and subsequently the bearings too.....radial support for the rollers will also be in doubt.

BUT........the proof would have to be in the pudding......it would have to be made to this design to prove the validity of the claim.

In the very last design I proposed, the design has one set of rollers or double roller sets, as the case may be, and can be 10mm diam with a full groove profile to ball contact, and the bearings for the roller radial support are not mounted on the rollers but against them......the rollers actually float between the thrust bearings and the radial bearings........bearing sizes are therefore substantial and sealed too.
Ian.

[daniellyall]

you can get sealed tiny bearings down to 0.047'' they use tiny ones in planes. 5/32 OD $15 from mcmaster

you can get them out of big printers

[handlewanker]

Hi.....the mind boggles.....5/32", " .157" or in Metric.....almost 4mm diam.....the bore would make it so small you 'd have to working with watch making equipment.

I think the drive forces on a router using 1605 screws would make any such small bearings history in a very short time.

I came across this problem every time I thought up a design for a ball nut alternative and the people using the early roller nut designs too.

The devil is always in the detail.

A prototype for test and evaluation purposes does not necessarily have to be a long life commodity with ball races and hardened etc, so bearings can just be pierced frame type as long as the aspect ratio of the bearing/spindle diam is at least 2:1......almost all clocks and watches are made with pierced frames like this.

A prototype is merely to test the principle short term and it can be R&D'd to make it as a production item as required.

You'll get bogged down with long term exigencies if you look too far ahead instead of perfecting the immediate design principle......... one reason why I resort to sketching using MS Paint and my Wacom graphics pad to envisage a project buzzing around in my head.......I also have a Wacom touch screen graphics pad where you draw directly on the screen, but I prefer the Wacom Intuos 3 bigger pad and the desk top computer and saving the files in Jpeg format that anyone can read.
Ian.

[daniellyall]

using bearings that will just fit they have a Dynamic Load of 70 lbs just need to find a thrust bearing that will fit.

having a cage and a big roller probley will be better that what i will draw up next

[handlewanker]

Hi, I've been busy......this sketch shows (with lots of circles) how the probable enhanced working model would be.

Although it's still a proposal it's gone past the prototype stage and on to how it would function in the real World as a working model.

I've colour coded the various circles to represent the various entities.

In this view, all of the working parts are now positioned at the bottom beneath the screw with only the tension roller at the top.....this is to enable it to have a pool of oil at the bottom where the bottom rollers dip in and so spread the oil around the whole assembly......there being lubricant retainers on either end of the box to keep the oil in.

Basically, the 2 grooved rollers are held rotating in space between the balls and the plain back up rollers, coloured in red.

The plain back up rollers are just 2 cam followers against each end of the rollers, non adjustable and attached to the frame ends, forming two points of a triangle with the third point being the ball(s).

I think that having two sets of grooved rollers and 12 balls total at the bottom forming the two points of a triangle and the top adjustable roller as the third point applying the tension gives more load capacity than just a single grooved roller and 6 balls, although only 6 balls work at any one time in either direction the other 6 balls serve to take up the backlash.

End thrust for the grooved rollers is by one set of thrust bearings fixed to one grooved roller and another set on the other grooved roller being adjustable for the backlash component.

The bronze disc ball retainers rotate in bushes in the end faces and do very little work normally, just there to act as a cage function.
Ian.

[louieatienza]

Hi.....there is a very real problem if you work with partial grooves.

For instance, if you had a box and the face in front of you was at an angle of 45 deg, any attempt to push the box forward would also push it sideways with equal force.

Having the balls impinging on a partial groove in the rollers is tantamount to them pushing on the roller grooves at the 45 deg angle not as a direct axial thrusting force to the frame.

The action of the screw when it's rotating forwards (whatever) is to apply force to the back side of the balls as they are deep seated in the screw thread form........ this force on the back side of the balls is applied to the back side of the roller groove, and if it is as full a form as the screw, the force will be converted to axial thrust to the frame, the roller groove acting as a fulcrum.

There will be some backwards reactionary force to the roller but with a full form thread profile not enough to consider important.

HOWEVER..........with a half form to the roller thread profile, the balls will exert the force on them at an angle to the roller of approx. 45 deg (whatever)........putting undue stress on the roller ball races.

True, the 45 deg force that acts on the screw(s) side grooves acts in both directions and the roller fulcrums the partial load in the axial direction, but at the expense of undue stress to the roller bearings.

Having a roller with a partial groove means the second roller, also with a partial groove, is acting in the opposite direction....the front side of the ball...... and so the full force from the screw, via the balls, is applied to just a partial segment of one roller profile.

I agree that it could work, but for how long, and how long would the tiny bearings last.......they are not sealed in that small size, at least the ones I have seen, so inclusions are a very real problem apart from lubrication.

My opinion is that this design is compromised due to the design calling for two grooved rollers, (to maintain ball contact with the screw)...... and as the space for two rollers against one ball limits the roller diam and subsequently the bearings too.....radial support for the rollers will also be in doubt.

BUT........the proof would have to be in the pudding......it would have to be made to this design to prove the validity of the claim.

In the very last design I proposed, the design has one set of rollers or double roller sets, as the case may be, and can be 10mm diam with a full groove profile to ball contact, and the bearings for the roller radial support are not mounted on the rollers but against them......the rollers actually float between the thrust bearings and the radial bearings........bearing sizes are therefore substantial and sealed too.
Ian.

What dp you think happens when the typical ballscrew with .002" backlash changes direction? The balls run on only one side of the screw thread.

As to balls wearing, there will be the requisite lubricant, just with any screw. The key with my idea is that the two rollers give more of a point contact and work independently to reduce friction.

I make no claims. I call things like I see it, and if you envelop the balls like in your design their tendency will be to roll in that direction. But sinvmce that is not in the same path of the screw thread it will just rub and rub. At that point you have a glorified ACME nut. Also my design is far simpler. But simple doesn't always mean easy. And of course sealing is mandatory for any type of ballscrew; just because I didn't mention it means it's not included. I pointed this out to you first in fact, so I'm fully aware.

The latest contraption has so many parts it borders on the insane. I'd feel horrible asking someone to draw it let alone build it.

I should point out too that a true planetary roller screw is less efficient than a ballscrew, and at 4 times the coat. I cannot think one one machining center that uses them despite their supposed benefits.

[handlewanker]

Hi, I know what you mean precisely as to the depth of the ball in the screw.......the more depth the better the load capacity.....balls as they roll freely will find their own sweet spot on their periphery......they roll when they have contact on the periphery no matter where it originates.....balls rolling have to be the least friction creating devices known to Man.....and a little bit of liquid engineering like oil or grease smooths the way.

I did mention earlier that I have experience with mills and lathes etc etc so I know what it takes to bore a hole or turn a shaft etc, having made many jigs and fixtures for precise drilling applications in the past.

This device I've proposed is purely an exercise in co-ordinate drilling and boring.......nothing rocket science.....even an apprentice could drill and bore the holes with ease.

Knowing what it takes to machine to tight limits, I can therefore design with the full knowledge that it has to be made with the means available and the experience you have.

Many draftsmen design without having the foggiest clue how it will be made.......subsequently the damm thing is a failure......of that fact I have bitter experience.

The design that I now have finally submitted, is purely an exercise in co-ordinate drilling and boring etc......so anyone who has an ounce of skill can safely turn the handles and watch the digital readout knowing that a hole will be in the exact spot ....even to tenth's of a thou if necessary......but it's not that pedantic in this case.

A bit more trumpet blowing and the house will fall down.......but I'd sincerely say it can be done and easily too.

Perhaps, to put the proverbial money where the proverbial mouth is, if a drawing was made with the position of the holes for the end plates, I'm certain that anyone under contract could produce it, and as the tolerances on those hole positions is not all that tricky....succeed beyond expectations.......it's that simple.

If a scale drawing is produced of just the end plate you can pick off the co-ordinates for the various hole positions without working up a sweat......going to a CNC mode and the machine will do it all for you.

I don't believe in watch making working conditions, not at my age....too much fuss and bother etc, so I make it easy for myself and design accordingly

BTW, the latest design I proposed may appear to have many parts, but that is because it contains two separate but identical sets of parts spaced either side of the centre line at the bottom......in other words mirror imaged.......nothing complicated about that.......I also added two more plain rollers to each set in the form of cam follower type bearings, drawn in red in the last sketch.....this is extremely simple to have and it makes the assembly totally simple to make......IE....the grooved rollers do not have to be eccentrically adjusted or rotate on tiny bearings at all....they rotate in space similar to the balls against the cam follower bearings..
Ian.

[handlewanker]

BTW.......none of the commercially available exotic roller nuts so far shown in the thread past posts have ever been seen or heard of in any router, mill or lathe that you could name.

That is to say, they are an exceptionally rare breed, whereas the designs we are endeavouring to invent are geared to everyday practical use at a fraction of the cost.....and DIY capable.
Ian.

[daniellyall]

your latest drawing will be a pieces of piss to draw up lou`s idea looks easy to do as well as yours already drawn lou`s idea up. the thing that is the killer with this is the bearings cheap ones are all up $30 good guilty one`s over a $00.

the only other types you can get are the multi movement one`s, using steel balls or ceramic and air controlled bull screws that is so if this works how ever its done will save a lot of screws being bined

[louieatienza]

BTW.......none of the commercially available exotic roller nuts so far shown in the thread past posts have ever been seen or heard of in any router, mill or lathe that you could name.

That is to say, they are an exceptionally rare breed, whereas the designs we are endeavouring to invent are geared to everyday practical use at a fraction of the cost.....and DIY capable.
Ian.

There is absolutely nothing practical about your latest design.

As to the lack of use of these "exotic" motion systems in common machinery, that should tell you something of the impracticality of its use in terms of implementing and cost. The manufacturers of roller screws claim the cost is saved through the life of the screw.

I actually own a roller screw, and fascinating as it is you'd probably be surprised how much force it takes to turn the screw. Though admittedly that could be the end seals.

[handlewanker]

Hi Louie, It may seem impractical at first glance, but the real attribute to the design is that you don't have to scratch your head or pull any more hair out trying to work in the support bearings to the grooved roller....BTDT......this latest design I proposed takes care of that problem..........if you look again at the sketch you'll see it is actually 2 sets of roller/ball assemblies situated on either side and at the bottom half of the screw.

Having a single plain roller on top of the screw for adjustment now gives the assembly a 3 point suspension and making adjustment a simple exercise.

I've added two rollers that are actually cam follower type, that is they have a short threaded spindle sticking out of one end and I'm using this to attach the cam follower to the frame to press against the back side of the grooved roller.

The reason for this extra addition is so that the grooved roller can float free in space suspended between the cam follower bearings at each end and the ball in a triangular configuration.

Now we don't have to have the grooved roller with bearings, only end thrust bearings, and as I have designed the device to have a grooved roller of 8 -10 mm diam, thrust bearings are easy to achieve......they also do not attach to the end plate and are located between the end of the grooved roller and the end plate to ensure the grooved roller stays in place without axial movement as it turns.

Sometimes you have to look at a design with an open mind and ascertain the reason why a direction change has been made.
Ian.

In this case it is to simplify the making and subsequent assembly of the design.

Originally I had just one set of parts with the grooved roller being cam adjusted, shown on a previous sketch in the horizontal plane with two plain rollers on the back side of the screw.

This was a complication mainly due to the small size of the bearings needed to carry the grooved roller and cam arrangement.

To enable the design to have increased load carrying capacity and also because there was plenty of space to achieve it, I added the second set of grooved roller/balls parts and moved them down to the bottom where they would benefit by being in an oil bath.

The whole package is adjustable for tightness by the top roller that is cam adjusted or spring loaded as the case may be........nothing complicated about that if you look closely at how it works.

Making it is also a simple exercise.

BTW........the roller screws posted in the early parts of this thread with their multi threaded spindles and gears and cross over screwed sleeves were not what you'd call DIY achievable even if you had a degree in calisthenics and rocket science.

K.I.S.S. that is something many know of but cannot practice......I am not one of those.
Ian.

[handlewanker]

BTW.....how would you define something as being practical?......simple?......cheap to make?.......no moving parts?.......cost less than a hamburger?...........the list is endless.

A common ball race is practical if you look at it in that light, but is neither easy or cheap to make and has a lot of moving parts........practically everyone has one in some item of equipment.
Ian.

[handlewanker]

Hi, there is an amendment to the last sketch I drew, but more to the point a modification to the working principle of the design.

Briefly it is this........if the ball groove in the grooved roller (and the screw) has a radius .02mm bigger than the ball, this will cause the ball to be slack in the groove, IE it will have clearance on either side of the ball when it is in the roller groove (and the screw groove), even if it is pressed down onto the apex of the grooves by the adjusting roller.

This new aspect has ground shaking probabilities........Earth shattering in fact.

Referring to the last sketch, the balls in the left set will be pressed against one side of the groove when the screw is driving forwards, while the balls in the right set are pressed against the back of the roller groove, (by adjustment of the thrust bearings in the second set) and so you have an anti backlash solution in one package.

The load is at all times carried on only one set of 6 balls, for either a forwards or backwards rotation of the screw.

This is the only compromise to load carrying as I originally envisaged it having two rows of balls sharing the loading, but the anti backlash feature is a bonus of huge proportions.

As far as I can see, this will be the last development to this design as it now appears to meet the need of "different" and possibly "better" depending on your interpretation of better.
Ian.

[louieatienza]

Well Ian, it sure does meet the criteria for "different." I'll concede that.

I don't think the question is whether or not it can be made; it's whether someone wants to actually make it. As you certainly do not or would not, I fail to see how you expect anyone else to. Or maybe this is an early April Fools' Day gag?!:stickpoke

As to thrust bearings in this application, I don't think it's that much necessary. Not for the loads we typically see in a DIY machine. Plus the force is distributed though a few of them, not just one.

I think an important point you fail to realize is that there is no 3-point contact in your design. That's a fantasy. The groove in the screw envelops almost 3/8 the circumference of the ball, as well as the roller.

[louieatienza]

I decided to draw up of quick 2D sketch of my thoughts. Not shown are the casing, any sweeps,

Attachment 274148

Here you can see the opposing rollers that also contain the ball at the same time. This eliminates quite a bit of superfluous parts. The retainers on each side are mounted to the casing; one fixed, and another that can be tightened to adjust preload. The profile of the half-grooves allow for self-alignment. They also overlap thus enveloping the balls without severely restricting their movement.

I think for such a DIY design, regular radial ball bearings would be fine.

The only caveat I have for the design is for a single-start screw, each set of rollers would have to be different to follow the helix. With a 2-start screw the rollers you can make 2 different rollers that will work on all 4 sides. The problem with that is those screws usually have a relatively high lead. But I've seen some miniature precision parts made by model engine builders and such, and we do have CAD and CAM available, so I think they won't be too much trouble to make.

[louieatienza]

BTW.....how would you define something as being practical?......simple?......cheap to make?.......no moving parts?.......cost less than a hamburger?...........the list is endless.

A common ball race is practical if you look at it in that light, but is neither easy or cheap to make and has a lot of moving parts........practically everyone has one in some item of equipment.
Ian.

Maybe expensive for us to make, but not for the large manufacturers. I like to let them do what they do best, so I can concentrate on doing my best with my projects, instead of smashing my brain over the minutiae of the stuff I can readily BUY!

[daniellyall]

I see how you will get a bigger roller now if one had a cnc lathe that be a pieces of cake to do, the hard part I see with you idea is making the form tool to cut the groves it wont be to hard juat take some time to do

[handlewanker]

Hi all......had a deep think about your design Louie..........nope, it is watch making at the best.....not in the making, but in the setting up.

First, I quite like the clever profile design of the rollers and how one interacts with the other.......the essence of good design is KISS........a point most designers forget when the bit is firmly between the teeth.

As far as the rollers being simple to make.....they are just profiles and can easily be made with a CNC or manual lathe, even a form tool to make the grooves is not a big deal........BUT.......you would not want to go and plunge a form tool into a spindle of that small diam and expect to have it accurate.

If you managed to produce the rollers to the form you designed, heat treated them and finished etc.....the last point in the saga is.........how do you adjust them for contact, alignment, and the biggest bogey thrust on 6 tiny rollers?

Plain simple radial bearings will soon not be radial any more and exhibit axial play as anyone who has used radial bearings in a thrust configuration finds out pretty quickly........Chinese designers are fond of this "cost saving".

If you use small thrust bearings as well as the radials on each end, the complication now goes deeper.

Having 3 sets of rollers and balls means they all have to be precisely aligned to one another.....a balancing act of gigantic proportions in a tiny envelope.

If just one roller in any one set is slack or too tight, the whole balancing act trembles.

If the rollers are carried on radial bearings.....what provision do you intend..... to adjust for positioning each set to the screw profile .....in two directions....and for thrust too?

The devil is indeed in the detail in this case.

Lastly, how do you intend to assemble the nut to the screw with all those small parts precariously balanced against each other.......a dab of grease would hold the balls in while you screw the screw into the nut, but subsequent servicing would be a nightmare.

BTW, contrary to what you have said in post #1014, the design I proposed is totally about a 3 point contact configuration......there being two sets of rollers and a third plain roller on top for adjustment, all acting together to maintain equilibrium.

There ARE axial forces to contend with on any router. mill or machine that pushes or pulls to achieve position by spiral grooved screws, and pushing or pulling has to be contained or you're back to square one with the bogey of uncontrolled backlash.

It's a nice try Louie, but you have to be able to make it or get it made, even just a mundane prototype, if you want to prove the pudding.....so if that is achievable then maybe NSK will make you an offer for the design.......but as it's public domain now, that won't happen......the Chinese are already streets ahead now they know how it works....LOL.......and they're experts at adopting ideas.

Meanwhile, as I'm satisfied the design I proposed is as far as I can develop it and doable, I'm working on another design, but this time it's a ball race screw.....totally different to the roller ball nut design, and possibly extremely DIY achievable.
Ian..

[handlewanker]

Maybe expensive for us to make, but not for the large manufacturers. I like to let them do what they do best, so I can concentrate on doing my best with my projects, instead of smashing my brain over the minutiae of the stuff I can readily BUY!

Hi, that was just a comparison....no one really makes a ball race when you can buy them so cheaply.
Ian.

[daniellyall]

the ball race idea does look quite easy to as anyone with a lathe could do it, all they are is balls held in a sleeve, balls in race way or balls in a sleeved raceway with ground groves to run a long that could be done in a mill or lathe with a grinding attachment (what ever they are called) you can do them with ball collars as well there is a lot of ways to do it