Thread: Rotating Ballnut - design ideas
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.
Having said that, I did start making a few some months ago, but got distracted by another project:
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?
Jonathan, i would like to purchase some of the bearings from you. how much are they. 30t 5m bored out to correct size.
[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:
I'm away racing next weekend, but after that I should have time to finish these ... at last.
Last edited by Jonathan; 25-09-2016 at 09:09 PM.
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.
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!
Last edited by richienz; 25-10-2016 at 01:38 AM.
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
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:
Last edited by Boyan Silyavski; 05-11-2016 at 10:06 PM.
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