[NIC 77]

Hi. Nope. Not committed at all. Definitely keen to hear what you have to say though. Sorry, the lead of these screws is not 40mm - you mean the pitch? These are diameter 40mm with a pitch of 5mm. Is lead the same as pitch?

I meant if it was something like a 3240 or 2540 you might be able to make it work with gear reduction from the motor, depending on the motor used and what you wanted to accomplish.

Pitch and lead are often used interchangeably, I have misused the terms myself sometimes. The lead is the linear distance moved per rotation of the ballscrew. The pitch x the number of starts = the lead. Most ballscrews we use only have 1 start, but multi start ballscrews do exist. Multi-start leadscrews are common.

For a single start ballscrew the lead and the pitch equate to the same thing. But the best term to use is "lead" as then there is no confusion about what you're talking about.

Currently I have two SFU1605 at a span of 2m on the Y. They are being driven by a couple of Nema 24 closed loop steppers and tend to whip because of the size. Speed is not a problem because I machine alloy and want to be able to do so well. Max speed I need at most is 2000mmMin I have had this setup for quite a few years and its been really good.

The way to fix the whip is to increase the diameter of the ballscrew or increase the lead of the ballscrew so that it doesn't have to spin as fast.

2000mm / min = 79 IPM. That's really slow for a machine of this size. You don't want to cut wood with it ever? If you're taking the time and money to upgrade the ballscrews you might as well pick ones that will give you the best upgrade performance as far as diameter and lead are concerned.

The amount of torque the motor has to put out to accelerate and decelerate the ballscrew in rotation is usually more dominant than the effect that the mass of your gantry has on the system, even with a fairly heavy gantry. It depends on many factors and the max acceleration used.

I have a document from THK that gives their rolled ballscrew moments of inertia for different sizes. The values will be almost identical for any rolled ballscrew.

A 16mm diameter ballscrew has a moment of inertia of 5.05 x 10^-4 or 0.0005 kg*cm^2 / mm length

A 40mm diameter ballscrew has a moment of inertia of 1.97 x 10^-2 or 0.0197 kg*cm^2 / mm length

0.0197 / 0.0005 = 39.4 meaning that the 40mm diameter ballscrew has 39.4 times more rotary inertia !!

The Nema 24, is slightly larger and better than the Nema 23 I have which is lifting a 12kg 4.5kw spindle on the Z. Also the Nema motors I have are P series. So my thoughts were, the Nema 24s I have will have plenty of torque to drive these 40mm 5mm pitch screws proven by the one Nema 23 lifting the massive spindle I have. The Nema 24s, if they work, I can always upgrade at a later date.

Unless you want to upgrade yourself to servos over 1300 watts (that's just a preliminary guess) it's not something easily fixed at a later date.

Oh - SFU 4005-5 is 5mm pitch there is a SFU 4005-4. I tend to not work out things correctly I just try them out. I did consider a 4mm pitch.

The 40 should be the diameter and the 05 should be the lead for a 4005 ballscrew. At first I was wondering if the -5 and -4 could be referring to the number of starts and if these were multi start screws but a quick online search makes me think that the -5 and -4 are referring to the ballnut style. For example, the -4 might not have a flanged ballnut. That's something to ask the seller.

What do you think?

Off the top of my head, something like a 2525 ballscrew with 2:1 belt driven gear reduction might be your best option.

If you don't want to hassle with the gear reduction then 2510, 2020, and 2525 are options. I don't know at this point which would be best for you.

If you were going to upgrade to 750W servos for a router of super performance then I might even say something like 3220 to 3240 with 3:1 to 5:1 belt driven gear reduction, but I would need to look at the critical speeds and do some math to give a better answer.

The point is that the 4005 is just a really really bad choice.