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You would need to have the fixed end machining done at both ends and the fixed end machining is were all the money is so it would be more expensive.
I dont do the machining, this is done at a local engineering company so i would need to get a quote.
Quote:
Originally Posted by tribbles
I have customers who uses this method to get faster motion, but normally would use a servo motor and specific gearing that is only for this type of application.
Unless you get the parts on ebay, it will cost a few hundred just for the gearing.
Also fixing both ends of the ball screw offer similar results (Within about 25%)
Quote:
Originally Posted by Ross77
Waste of time on something like a router. You fit double thrusts on both ends, adjust to get a preload, and all that happens is the end frames deflect inwards so the screw is still whipping even with double bearings.
The design has to take this into account.
Bystronics have realised this on their new range of lasers, they have massive end castings and tension the ball screw to something like 70 tonnes tension [ no typo ] to stop it whipping.
Mind you they are using twin drives with 15 HP servo motors on each drive :whistling:
I feel the OP needs to sit down, count his pennies then come up with something that's workable instead of throwing down pie in the sky figures for his first build.
Why the insane rapids anyway ? The whole idea is to bury the tool and work at feed rate.
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iim not set on the smaller motors but as i have them now i may as well give them ago the machine does not have to work mega fast! its being made out of aluminium. ill give anything ago (within reason) if it works ok and saves abit of money! if not then ill have to go for some " muchas maracas ". that Z axis you got there gary looks a fair bit of kit what OD and pitch is that ball screw?
This version has a 20mm ball screw with a 5MM lead, but can go up to 25mm diameter with any lead.
We are also working on a smaller version that uses a 16mm ball screw, so will be a lot smaller, but i wnat to keed the width to keep the ridgidity.
I only use profiled rail, so no round or supported round rail.
If you have a more details specification, email it over to me and i can work out what you need.
Quote:
Originally Posted by AdCNC
Thanks Gary ill have to go over a few things then once ive got all the axis up and running then ill drop you a mail with some photos and details. see what you think!
If the problem with long ballscrews is whip why not fit traveling intermediate bearings as in travelling steady would only need a bearing in which the ballscrew would slide and then some sliding mechanism to pull the steady back into place when the axis moved to the other end. t least 2 steadies would be needed each side (if double ballscrews) plus space at each end to park the steady.
Just an idea!
Peter
You would still have a bit of chatter and vibration and i think the cost of this would also be more than the cost of a larger ball screw.
Quote:
Originally Posted by ptjw7uk
It's only circumventing a bad design.Quote:
Originally Posted by ptjw7uk
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I want to retrofit a lathe with servo 1.8kw 3000 rpm.
lathe between center is 1.6m and the leadscrew for z axis is 1.8m diameter 30mm 4TPI
i will replace the leadscrew with ballscrew.
What diameter-pitch ballscrew will be optimal for this situation ?
Also what is better to drive the ballscrew with coupler directly from servo or drive it with pulleys & timing belts ?
What pulleys & timing twill be strong enough and without backlash ?
Please don't resurrect ancient threads, start a new one.
Anyway, to answer your question, there is no easy 'optimal' as it all depends. However the easy option is to go near like for like and use 30mm dia 5mm pitch.
However that screw is rarely going to be turning at more than a few rpm (<1 for metric fine threading, <100 for a finishing pass and maybe 1000 for a rapid traverse) and despite it's 11kg weight only needs <1Nm to accelerate it to cutting speed in under 1mm of traverse. So a servo is massive overkill and gearing it down while avoiding backlash is going to be tricky.
Thank you for your answer.
My lathe has prismatic ways not linear ways with bearings.
So you suggest me to go with 3205 ballscrew and direct driving with coupler ?
1000rpm*5mm = 5m/min rapids is 5m/min good linear rapid speed for a lathe ?
Because my servo is 3000rpm with this setup i will get max 15m/min rapids but the question is if the ballscrew can rotate at 3000rpm without problems.
Because of ballscrew inertia higher pitch ballscrew (10mm) at lower rpm and gearing down would be better ?
If i gear down what pulleys-timing belts will eliminate backlash ?