[kostas1]

Hi,

I need your help about what should be the maximum length for a 1610 ballscrew...
I am thinking to make my x axis 2m long and I am not sure if 2m 1610 ballscrew can handle this length or should I get something bigger in diameter(i.e 2010)?
I have keling 640oz-inch motors, G203V drives, KL-6515 power supply and C11 breakout board...
Have anyohne built such a long machine with single ordinary setup of ballscrew/ballnut/motor?
What are the maximum RPMs that a 2m 1610 ballscrew can sustain?Could it handle 1000, 1500 or even 2000 RPMs?

Note:I calculate my gantry weight will be about 25kg...hiwin linear guides will be used..

Thanks in advance,
Kostas.

[kostas1]

Is there any link that could help me find a solution to this?

Thanks

[CPH-J]

Hi kostas,

I don't know if it helps you, but i'm using 2005's for my x-axis, they're 1400mm. My axis stalls at around 7600mm/min due to whipping. Thats around 1500rpm, so at 2m i would advise you to go larger in diameter.

[kostas1]

Hi CPH-J,
thanks for your answer...another user told me that he uses 1605 in his 1000mm axis and has no problems even at 2000 rpm...he may have ligther ganrty though, ha?
I'll try and phone contact a supplier to find out what paramateres define the maximum length that a ballscrew should have..

Thanks,
Kostas.

[kostas1]

Hi,
I found some links which are helpful in calculating what is the preferred and right ballscrew to select for the machine...

1) Ballscrew Calculators

2) BallCharts

3) Ballscrew Glossary

Do you think that these types can be adapted to any ballscrew measurement?Or it is only about nook industries products?
Can we extract useful conclusions from them?

Thanks...
Kostas.

[posix]

why not use a rotating nut instead of rotating screw? no whip.

[kostas1]

I would use anything would do the job...I don't mind at all...How this can be done?

Also do these formulas in the links work with any ballscrew?

[kostas1]

Having these calculations in mind, I wonder if I could use a 1610 screw over a 2000mm length...
By making some calculations from here we can see that we get 1078 RPMs (431IPM) for ballscrew length = 2m and end fixity D...
Below are some other calculations for 2m length:

2010 screw @ 1348 RPM = 539 IPM
2510 screw @ 1685 RPM = 674 IPM

What do you think?Could we be based on these calculation to put out a valid general conclusion for how balscrews behave...

Thanks....

[posix]

well you just rotate the nut instead of the screw. do a search in linear motion for "rotating nut"

[ger21]

Yes, the Nook info should be good for other manufacturers screws.

[kostas1]

Ok,
which is the less expensive and easier way to do it?Rotating nut or rotating screw?

Where could I buy rotating nuts from?

[marchantdice]

We can supply Rotating Ballnut Nut Assemblies...but I'll be honest a Rotating Ballnut will cost x2 1/2 the price of a 25mm ballscrew Assembly...and the lead time is 12 weeks...

[kostas1]

Hi,
well, I purchased the follwing ballscrews from Chai: one 1800mm 2510, one 1200mm 2510, one 400mm 1605 for 3 axis, one ballscrew in each axis...
Do you think that one ballscrew will can handle the 1800mm length, given that I rotate screw?
Would it be better to also add a second ballnut to the longest ballscrew (x) so as to make it more stable?

What do you think/predict?

Kostas.

[TSJ]

If you rotate the ball nut why can't you just mount the motor to the gantry (using good techniques for cable management), attach a timing pully to the nut and motor and spin the nut with the motor. You have to lock down each end of the ball screw and support the ball screw at the gantry. If you have a problem with the belt you have to disassemble half of the ball screw attachments. I must be missing something, what will take 12 weeks.

[marchantdice]

Your going to have problems rotating a Chinese Ballscrew assembly...
I'll be honest you will have 2 problems....
1. what we call high and low
2. rotating ballnuts are usualy high helix 20x20, 25x25, 32x32 and 40x40

a second ballnut, this will not help you resolve issues with speeds...

Hi,
well, I purchased the follwing ballscrews from Chai: one 1800mm 2510, one 1200mm 2510, one 400mm 1605 for 3 axis, one ballscrew in each axis...
Do you think that one ballscrew will can handle the 1800mm length, given that I rotate screw?
Would it be better to also add a second ballnut to the longest ballscrew (x) so as to make it more stable?

What do you think/predict?

Kostas.

[marchantdice]

The rotating ballnut must be housed, that is to say you must not fix a pulley directly to the ballnut....bearings must be fitted around the ballnut within a housing, the housing can then be assembled with a toothed pulley...the motor is then fixed to the frame / gantry...

If you rotate the ball nut why can't you just mount the motor to the gantry (using good techniques for cable management), attach a timing pully to the nut and motor and spin the nut with the motor. You have to lock down each end of the ball screw and support the ball screw at the gantry. If you have a problem with the belt you have to disassemble half of the ball screw attachments. I must be missing something, what will take 12 weeks.

[kostas1]

Ok guys,
I am a little confused...we also have to have in mind the cost...

1) So if I go to rotating ballnut,how does this cost?

2) Also,what I am going to do with the machined ends of ballscrews in case that I will put rotating nut?Do the machined ends be useless then?

3) An option would be to buy an extra ballscrew,motor,driver to have two screws in the long axis that will move the gantry...is this approach more economic than putting a rotating ballnut and changing the ballscrews I already purchased?

4) Nook industries calculators show that I can have critical speed 2080RPM when using 25mm diameter ballscrew in a length of 1800mm and fixing type=D...So where is the real problem? Will it rack in the edges and don't have clear cuts near them?

Guys, it is really confusing and complex as I have had no experience before...I need a true explanatory guide on this...:tired:
Thanks,
Kostas.

[marchantdice]

Purchase an additional Ballscrew Assembly...you can either link the stepper motors in Mach3 or connect 2 stepper motors to 1 driver (not a reccomended method) but if you want a 4th axis this method will leave a free socket?

[kostas1]

Hi,
no,I will have 3 axis only...
This image you attached is the rotating nut right?
It seems that I cannot use it since:
1) I already purchased machined ballscrews ends
2) I will buy extra set of motor/driver/screw?

Will I have problem with the existing KL-6515 power supply, the C11 break out board and the connections?

Thanks,
Kostas.

[kostas1]

Hi,
I finally decided to go with one ballscrew in the middle of the gantry, but I made a trade off:I widen the gantry upright sides to 25cm and now I am thinking if It is better to make it 30cm...By widen the gantry upright sides, any racking possibility is minimized right?

Kostas.