Thanks for the share JB, ok to put this in the Open Source section?Quote:
Originally Posted by Jonathan
.Me
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Thanks for the share JB, ok to put this in the Open Source section?Quote:
Originally Posted by Jonathan
.Me
Yes if you want I will. I considered posting it there but decided not to as, if I recall correctly, members can't reply to posts in the open source section?Quote:
Originally Posted by Lee Roberts
I considered using threaded nuts, but decided not to risk it in this case as I don't know how accurate the thread is. If the thread is slightly wonky/'drunk' or not concentric then that's clearly going to cause a problem that's hard to fix...Quote:
Originally Posted by silyavski
Hi Jonathan,
While you are contemplating if you would ever find the time to make me two of these beauties, i am trying to make a detailed drawing in Sketchup which i could share here with your permission.
Would you throw some light on few details please:
-distance from motor shaft center to pulley center? nema 23 yes?
-exact belt length for 30:30 ?
-did you make the 2 holding nuts or buy them?
-thickness of inner and outer race ring of the bearing? It is the 7207 2rs bearing from here yes?
Nema 23, 5M HTD belt 340mm long which enables the motor pulley to be anything from 15T to 30T without changing the belt length. Center distance 90-115mm approx.
I bought them - KM5 locknuts:
PACK OF 5 KM Series KM5 Locknut 25mm x 38 mm x 7mm FREE P&P | eBay
That's the correct bearing. You should be able to get the rest from the SKF website. Interestingly the seller specifies that the bearings are 15° or 25° contact angle, but the ones I got have the suffix 'B' which (going by SKF's nomenclature) means they're 40°. Excellent if true...
Jonathan, THANKS!
Great work and info!
As this rotating ball nut idea consumed my weekend and the whole last week, and i am sure much much more of Jonathan's time, here is the Sketchup file for all to use, if this is alright with Jonathan:
Notes:
1. Every part is labeled , so can easily be found in internet
2. The bearings are recessed 0.5mm in the casing
3. The aluminum is 20mm thick and the bar can be 100x100, 100x90 or as originally 5"
4. Everything is tight fit / I still don't get it how the bearing casings are centered from both sides but hey, i am not a machinist yet :-)/
6. The clearing between the 2510/25.. nut and casing is 1mm
7. The clearing between rotating shaft and the ball screw is 1mm
8. The 2 retaining nuts actually are PACK OF 5 KM Series KM7 Locknut 35mm x 52 mm x 8mm FREE P&P | eBay as the thread will be 35mm
9. There could be small corrections of the lips that hold the outer and inner bearing racing rings, will update if necessary.
10. The motor is from Zapautomation 3Nm SY60STH86-3008B NEMA 23 STEPPER MOTOR, which i assume most will use for this job 8mm shaft
Attachment 11011Attachment 11012 Attachment 11013
2) Optional
3) Note that on the drawing I posted the motor mount is 88mm wide, not 90mm which is the height of the main block. I intentionally left a 1mm gap so that when the block is bolted to a flat surface, you wont end up with the assembly partially resting on the motor mount (if the motor mount isn't attached accurately). The gap is on both sides since I put mounting holes on both sides of one block so they can be mirrored.
4) Very carefully. You use a 4-jaw chuck and a dial indicator.
7) Same, that's fine.
10) Or CNC4you if you want a cheaper option.
Minor point - on your drawing the 6 tapped holes that fasten the ballnut to the mount go all the way through the flange on the shaft. I made them blind holes so if you accidently try to use too long a bolt, the bolt doesn't go all the way through and damage the bearing.
I know you had the housing made from several pieces originally but they looked a bit complex so is it feasible to make the rectangular housing from 4 or 5 just rectangular pieces bolted together with the motor mounting plate being one side ?
Damn, the very pages I must has skipped :stupid:
Yes I realise about alignment, it just seemed easier for someone without a decent machine shop.
I see, will correct it.Quote:
Originally Posted by Jonathan
There are 2 minor changes from the original design:
- i made the motor mount from the wider side, as many will like maybe 34 nema and it looks more sturdy. I wanted to make a combined nema 23 and 34 mount, but i feel sleepy now. when ready will see if it will stay like this or follow your original design.
-i believe i shortened the rotating shaft by making its wide part go through the motor mount plate. It is now 2mm to place the ball screw nut in its place,10mm for the ball screw nut holding thread, 2mm ring to push only the small bearing ring and 90mm the rest.
I think that all can be further shortened and lightened :
-2mm protruding thread instead of 5mm , when the nuts are tightened
-6mm /shortening the whole assembly/ eating from the clearance near the shaft pulley
-The area where the ball screw nut fastens could be recessed 8mm with diameter 40mm and some more holes could be done / 45 degree following the pattern/
This could lower considerably rotating mass
Attachment 11014
Actually if Jonathan or sb from the forum doesn't have the time to make the parts for me, i have to go to my local guy, who is way off with the 0.01mm, he works in the 0.5 zone definition :hysterical:Quote:
Originally Posted by EddyCurrent
So i would update the drawings with extra drawing , made from OD100 and OD80 round bar. That way it would be more easy for him not to make a mistake an find the center. Further benefit will be that it could be mounted in cut in 2 pieces 85mm or 100mm spindle mount/not perfect but will work/ . anyway, i will mount it directly on its face, not using the bottom holes.
One grubscrew is enough for clamping the pulley to the motor shaft or should I use two at 90 degrees? Are there other simple methods that I could use to be able to change the pulley (ratio) more easily?
Here are my machined parts, still not assembled and tested:
http://i285.photobucket.com/albums/l...ps771483c3.jpg
http://i285.photobucket.com/albums/l...ps9e5c7455.jpg
Machining looks very nice. G.
For the sake of experiment, found some providers of Servo motors with hollow shaft where a ball nut can be mounted. Usually the 3nm motors accept only16xx sizes, for 25xx sizes a 9Nm servos are offered.
I wanted to make sure Hybrid Closed Loop Stepper driver + motor+shipping + this assembly will not equal a proper servomotor price.
No prices on the sites/ means "in the thousands" to me/ . Well , one called me , wow, i got even more suspicious about the price. Now received the quote.
Wow, again. 1600eur the motor and the driver and cables. driver costs 420, so rest is the motor.
Guys, now the most stupid question: How to order the ball screws machined at both ends? Simple thread, long enough for 3 nuts? One inside, then mount plate then another plus locking one?
Paulus - I like the way you've designed it such that the housing is one part, however I'm slightly concerned by the apparent small spacing of the angular contact bearings. According to NSK, you need to have the angular contact bearings spaced by 1.5 times their external diameter, but it looks like in your design they're almost touching, or a double row bearing which wont qualify? I expect you'll still get a reasonably high critical speed from this setup, but not as high as it could have been. The reason the bearings need to be so rigid is that the ballnut will inevitably not be perfectly concentric to the screw. Ideally the error will be small, but any error will cause energy to be transferred from the ballnut to the screw causing them both to oscillate. Both the nut and screw need to be rigidly held to suppress this.
Quote:
Originally Posted by silyavski
Make your own.
I got mine machined the same as the standard end machining for the angular contact bearings at both ends, in case the rotating nut didn't work. All you really need is a cylindrical portion and a thread on both ends. On one end simply use the thread to clamp the screw, ideally into a hole the same diameter as the cylindrical portion so it's held rigidly. Something similar on the other end, except you can use the thread to tension the screw a bit if your frame is strong enough. Also, design the end mounts in two parts so you can adjust the ends of the screw to be concentric with the bearings.Quote:
Originally Posted by silyavski
If you look earlier in the thread you'll see the end mounts I made are very simple - essentially just a block with a clearance hole. They work, but having a hole the same diameter as the screw instead of using it for adjustment will be better.
Edit: Idea for silvaski - to make the housing easier to machine, instead of boring the bearings from both sides you could bore from one side almost all the way through, then machine a spacer tube the right thickness to go in between the outer rings of the bearings.
I knew this is important. I was sleepy the other night when i made the Sketchup drawing and wondered why you separated them so much, but overlooked it. I even gave ideas how to be made shorter :stupid:Quote:
Originally Posted by Jonathan
Thanks Jonathan for your comments,Quote:
Originally Posted by Jonathan
I needed a simple design as I don't have access to precision machining. I wanted one part housing without the need of bearing pair alignment. So I chose a double row? -or how it's called- bearing. Will see how it will perform.
http://i285.photobucket.com/albums/l...pse4777ca1.jpg
Your last design is great, I will be able to modify mine if necessary :)
http://i285.photobucket.com/albums/l...psc67d5470.jpg
Jonathan, from your experience with rotating ballnut, what is the best way of lubrication? As continuous flow lubrication is excluded is it better to use grease instead of oil to last longer? What type of grease/oil do you recommend?
thanks
Quote:
Originally Posted by Jonathan
Very nice design what size pulleys did you use i'm looking into building this myself but want to be sure to order the right pulleys and belt thanks for your time and engineering.
Very nice the idea of rotating nut!
I want to convert a conventional lathe to cnc and Z axis leadscrew has 1900mm length 30mm diameter.
If i use L1900mm 3210 rotating ballscrew with 2 bk25 end supports i will have 1300rpm citical speed & column strength 28477 newton
The critical speed is ok to me because i will get 10m/min rapids with 1000rpm in ballscrew i have concern about column strength because 28477 newton (2900kg / Z axis servo can give 3400kg ) isn't to big force and also i have fear about sag to 3210 ballscrew and runout at rotation that will do a lot of vibration.
In my situation would be better a rotating nut design like this to overcome these 2 problems (column strength & ballscrew sag/buckling) ?
Also with rotating nut design can i use a lower diameter ballscrew without having whipping ?
Jonathan and all of the determined mad scientists and hobbyists of this forum. This is great work. I really appreciate you sharing the setbacks and successes of hard work. Keep up the great efforts...I learn so much from this. Thank you again......Mutzy
Jonathan, how are you?
1. Where did you get the pulley that is associated with post 79? Was it machined out with a larger bore to fit the shaft or store bought? Where can i get one?
2. I see that there are two different shaft configurations with the pics. One the shaft where the ballnut attaches sits kind of deeper in the cupped out area, and the other sits flush with the whole face. what is the reason for this.
Thank you so much for your time.
I used a standard pulley and bored it out to the size of the shaft.Quote:
Originally Posted by mutzy
This shaft where the face is 'cupped out' leaves a surface to locate the ballnut concentric to the shaft. This works well if the ballnut is accurately machined, but I found that you can't necessarily rely on this so sometimes it's better to just go with a face and align the nut with a DTI.Quote:
Originally Posted by mutzy
Thank you Jonathan. What is a DTI?
Mutzy
Dial test indicator https://www.machinemart.co.uk/p/cm22...c4FBoCNljw_wcBQuote:
Originally Posted by mutzy
e.g:
Attachment 19159
Hello Jonathan, Do you not accept PM? I would like to contact you.
Jonathan do you sell these to other people at all or know anyone specifically who can make the from drawings?
cheers
Ash
Hello Jonathan, how are you today? Wow, you certainly created a great thread here. I can't seem to find distributors that have this size bearing to bore out. Do you have any suggestions of who might sell them? USA would be best for shipping. Once again thank you.
I made it a couple of times. If Johnathan could not, i could do it. Plus i have it from my drawing on my machine and is working perfectly fine.
Though last time i did it, i said i would not do this again for the money i charged then. In short only parts are worth ~200euro, as i have to have them at hand as all is not available locally and shipping costs are included that raise the price,
+answering to 50 emails, 3-4h redrawing for different motors and mounting, 8h to make parts and 2h for 2 people to put them together, 2h packaging, 1h sending . Plus while you are making them you learn from small mistakes.
So if you have 500euro prepared for them, then PM me. Thats the reality folks for bespoke parts. Mind that the cheapest servo motor with hole in shaft is 1500euro plus 400euro for drive, and you need 2x.
What i am saying here is i am just trying to help, not sell. So if sb could do it cheaper, go with him. If not- call me, i will do it.
I know the feeling....Quote:
Originally Posted by Boyan Silyavski
Having said that, I did start making a few some months ago, but got distracted by another project:
Attachment 19179
I already have the bearings etc. I'm willing to finish these off and sell them, as I have a bit more time now. Silyavski's price is about right, maybe a little less - fortunately I bought the bearings before the £ crashed!
What exactly would be included in the units you would sell Jonathan?
That's up to you, but in the past:Quote:
Originally Posted by Black Forest
Attachment 19191
So the mount, including pulleys and belt. You just add the motor and ballscrew.
Jonathan, i would like to purchase some of the bearings from you. how much are they. 30t 5m bored out to correct size.
Thank you
Mutzy
Is that just the pulleys you're after, or bearings and pulleys? For the bearings, I got the last lot from here:Quote:
Originally Posted by mutzy
https://www.aliexpress.com/store/pro...053270817.html
[It may help to order 2 at a time to avoid customs charges. Not sure how it works in the USA, but I ordered two with no charges, then got taxed a lot when I bought 10 :(]
Regarding the pulleys, I can get 30t 5m HTD for about £6.30 each. Boring them accurately then drilling/tapping the setscrew holes takes maybe half an hour, so I'd be happy to sell them for £10 each plus postage.
This weekend, I made some progress on the six mounts I'm making:
Attachment 19311Attachment 19312Attachment 19312
I'm away racing next weekend, but after that I should have time to finish these ... at last.
Impressive nuts! I just took a look at your e-moto webpage quickly too , wicked. Great project and racing at Isle of Man wow respect that place is nuts.
Hey I have a large router that is running well but I want to upgrade the main screw to a fixed screw rotating nut design. The screw is 40mm dia 10mm pitch and 3m long so its heavy. Running a 940W AC servo and a Grantite Devices VSD-XE servo drive, and 80VDC supply, I'm getting good response now with 8m/min velocity and about 400mm/s/s acceleration. This took a long time for me to work out the servo tuning but I got there in the end. I'd like to remove the rotating mass to improve my accelerations. The gantry it moves weighs around 150KG I estimate.
So I am wondering are you interested in building me a ball nut for this? Happy to pay market rates of course and if it helps fund any of your emoto projects then all the better. Please contact me if this is interest to you.
Below is my final servo response I got recently which I am really stoked about it, but to speed up my jobs I really want to up the accelerations.
cheers
Richard
Attachment 19421
Quote:
Originally Posted by Jonathan
You can certainly say that of the riders!Quote:
Originally Posted by richienz
With that size ballscrew then you do have a problem with the rotating inertia, not so much the 150kg gantry. Can you measure the ballnut - approximate it as cylinders, then we can work out the inertia of the ballnut compared to the ballscrew to see what you could gain by rotating the nut.Quote:
Originally Posted by richienz
My PhD studies are taking up a lot of time at the moment (need to catch up after all the racing!), but I do intend to have time to finish some rotating nut assemblies soon.Quote:
Originally Posted by richienz
What else can you plot from your system - can you plot the motor torque in addition to the speed response? If so, that's another way to work out the inertia and get better insight into how the system will behave.Quote:
Originally Posted by richienz
I am too scared to watch the racing almost, its impressive riding nothing else is close really is it, but scary when a rider is badly hurt or killed, seems to be all too common.Quote:
Originally Posted by Jonathan
I'll measure up the ball nut and screw and also try find the original part numbers and specs weights etc.
The PID loop tuning I struggle with, yes I can measure the currents I think , my Granite Devices VSD-XE servo drives have an inbuilt virtual oscilloscope that I use to measure the response with, to be honest the PID tuning I am very hit and miss with I can;t quite qork out what low pass filters I should use and why.......
I retuned the PID loops on both x and y on the weekend and its better but still I am sure there is room for significant improvement. whip of the screw is a problem too when I get over 600RPM approx. Thats a 10mm pitch per revolution screw (isthatthe correct terminology?) so thats a speed 6000mm/min , any faster and sometimes it whips and that really gives me the shits. I'm finding that small circle cuts say a 6mm end mill cutting a small 10mm dia helix has some error in the hole and I have to crank the speed back to around 1500mm/min for cutting (the timber) rather than running at higher speeds that I'd like to.
Anyway if you have time I would appreciate your guidance, keep on top of your studies thats top priority! Even if I can plagiarise your design and try build locally with some of your engineering input that would be greatly appreciated but if I can commission you to build one at the right price that works for us both then that's even better!!!
Funny I was a bit ambitious the last figures I quoted in my earlier post looked good on the scope but in real life cutting it was terrible!
Cheers
Rich
This cheap tool looks good for the KM03 locknut used if you have 20xx screws and using KM03 locknuts both sides
Still looking for an inexpensive tool for the KM04 nuts / 25xx screw and KM05/30xx screws. If sb knows , just post it here. Otherwise most probably you have to make yourself one so you could tighten and adjust tension of your ball screws
Attachment 19566Attachment 19567
table of locknuts for reference below, i use 2 each side so total of 4 per screw , locktite on thread, red paint to mark any movement, did not know at the time about washers:
Attachment 19564Attachment 19565