Make a rod or tube that is a bit smaller in diameter than the minor diameter of the ballscrew grooves, and longer than the nut. You can then run the nut off the end and on to the rod.
If the end of the screw is machined, then you need this to be a tube so the tube can go right up to the end of the threads.
The rod/tube will keep the balls where they should be and as long as you don't let that come out, you'll be fine. I usually put a zip tie on each end so bumping it doesn't get you in trouble.
Ok, understood...
So the best way to make it from the beginning is to use this pulley?
What if I firstly connected the motor directly to ballscrew and some other day decided to also put a pulley?Will it be feasible or I had to change the machine's design?
Thanks and sorry but I am a beginner...
Kostas.
Can you take the nut off? Yes Would you want to? Hardly.
The replacement of the balls can be an exercise in futility as it is a PIA to do. Granted, it can be done and once you do it, the next time is easier. BUT the process is time consuming and not one that works well with SWAG or helter skelter processes. There are better and more productive things to do with your time.
The raceways that the balls travel thru are not simply curved radii like a gutter at a bowling alley. Rather they are a form of a gothic arch. This causes the balls to make 4 point contact - 2 points in the nut, two in the screw. Essentially, the balls make contact at points roughtly 45 degs off of vertical up and down on the nut and screw.
To adjust backlash, simply put in larger or smaller balls. BUT you only should change balls in 0.0001" increments. Hence, it is often a hit miss process of fitting severa size balls to get what you want for backlash. SInce you are working in tenths changes in ball diameter, the trick is to find a source of various diameter balls this accurate when/if you sit down to reset backlash in a ball screw/ball nut.
I used to source balls of this accuracy from Winstead Precision ball. Whether or not they have what you need or will still sell in small quantities is the problem. And, you have to buy HUNDREDS if not thousands of balls at a time - the Graingers and M-C's of the world dont' typically specialize in balls of this quantity, size differential and/or accuracy. Regarding accuracy, you want to get Grade 5 balls - there is a noticable difference 'tween 5's and anything less accurate.
Explanation: picture a go cart running on 4 different sized tires. It is easy to see how the tires would be unequally loaded. Same deal when you use Grade 5's versus 10's, 25's or even 100's to try to roll evenly and smoothly thru the ball path where you are essentially operating with metal to metal contact and ZERO radial/axial clearance. All of a sudden if larger or smaller balls come into play, things get noticeably harder or easier to turn.
Resettnig clearance in ball screws is NOT a hit or miss deal. Throwing a half thou SWAG change in ball size could result in locking the nut onto the screw and, worse yet, brinnelling the pall path. Once you brinnel the ball path, the screw is junk as you'll always have brinnell dents at that point and the screw will ALWAYS turn rough and sloppy at the damaged point.
Find a ball screw repair house and have them do it. It is not that expensive. In my case I know how to do it, know where to get EVERYTHING yet I still pay to have it done. That should say something about the process.
(Ballnut, spindle and a few balls on the floor - what can go wrong?)
Ballnuts can be removed by the end use however as a ballscrew manufacturer we would not reccomend this as rebuilding can cause issues......
So remove the ballnut from the spindle and most of the balls will fall out.
Replacing the original balls, this is easily done using a mandrel (a tube machined to the same diameter as the spindle root diameter) insert the tube into the bottom of the ballnut, fill the first circuit advancing the mandrel as you go. 2nd, 3rd circuit etc etc.
Next place the spindle horizontal in a machine vice (use 2 peices of wood to protect the spindle) placing the start of the spindle thread in the 12 o'clock position. Carefully look in side the ballnut for the start of the first circuit and mark the position on the out side of the ballnut.
Slide the mandrel and ballnut over the end machining with the ballnut in the 12 o'clock position rotate the ballnut in a clockwise direction and the nut will advance down the spindle (like a nut and bolt) If the ballnut sticks, lightly tap the nut body.
You only learn by making a mistake......
Preloading, leave this to the manufacturers or a rebuild service.
Offcourse jazek, the manufacturer will use the same g-codes.
Though i'm sure that there will be a difference in the machining proces in regards of how many times the grindingstone will be dressed and how many cycles he will run it.Cycles meaning a tolerance check and regrinding when necessary.
I also can't see what would stop a manufacturer to put the 10 by "accidentally" C1 grade screws on stock and getting to charge some one that orders c1 much more for the same screws whilst just manufacturing you 10 different c5 screws.
I'ld like to hear what nccam has to say about this subject.
Finally CHIPS you can have as much as you can without the doc. complainting about your cholesterol.
Jwezy is right, that ball screw plant is pretty much geared to make one product accuracy grade. Hence, you can PROBABLY get away with the lowest accuracy part although you'll PROBABLY be getting high accuracy. SOMETIMES, the ONLY difference is the certification papers.
I know of an instance where the highpoint of eccentricity markings on a bearing were essendially phony. The bearings had NO perciptible or even measureable eccentricity BUT the market was so accustumed to seeing high point, markings, they put them on even though there was none.
Ditto that for this particular plant's ABEC ratings. The bearings were all ABEC 7 (ISO P4) or better, yet the bearings were packaged and priced to the order requirements that were made. Yes, ABEC 7's were packaged as 7's, 5's and even 3's, and priced pursuant to the market price for the corresponding grade of bearing.
Caveat: not all bearing companies do that sort of deal so you you CAN'T take this as a blanket claim.
Regardless of the application, the more accuracy you scrimp and save for and build into your machine, the better it will run/finish. In other words, buy the best you can't afford and you woun't be disappointed. Nobody I know of was ever disappointed from buying something better than they needed.
that being said ,i must have completely misunderstood the manufacturing process of these beautiful tools referred to as ballscrews.I'll study more.
I guess one should keep track of wich manufacturer was the las tto upgrade their production machinery since they'll pro bably have most high-grade overstock.
my earlier response was stooled on the idea that flat and especially form/thread grinding requires frequent tolerance checks and adjustment for the wear of the grindingstone.
So i assumed a manufacturer will put more effort into the checking and adjusting of the higher then the lower grade screws.
'
The last i would like to state is that i think the "lower grade"precision ballscrews are way-deluxe for a hobbyist so you almost can't miss when acquiring screws that are in good condition.
Finally CHIPS you can have as much as you can without the doc. complainting about your cholesterol.
Hi Nice right up on b screws, but i have a question,
How do i calculate what torque i need to lift a given weight over a given distance with a Bscrew ( ground ) 5 tpi.
Any one help?
hello to all
So speaking about starts......
If I have a single start screw, we'll say 1 TPI, rotating at 600rpm ..... it will travel 600ipm.
Now if I have a 4 start, same screw details....1 TPI, same speed, will it travel 2400ipm ?
and slightly off topic:
Will I need a stepper with 4 times the torque to turn it?
1 TPI = 1 Turn Per Inch meaning that for every whole turn nut will be displaced 1inch so ,a 20start 1TPI screw will displace 1inch per turn
Sorry but i can't hel with the torque needs so when i have to pikk i just make sure i overkill.
Finally CHIPS you can have as much as you can without the doc. complainting about your cholesterol.
Need help , I recently read an article on replacing the ball bearings . so I thought I would do it to refresh mine , after a close look found the bearing were out of round , replaced them and now cannot get them to stay in after being replaced , this is a dual barrel ballscrew , am I doing something wrong , I did not loose any parts , any help is appreciated.
Freeflow
Is it normal for preloaded rolled ball screws to feel "gritty" or bumpy as they are turned manually?
I am running Thompson Ball Nut 7820827 and Ball Screw 5707540 (Reid Supply TBS-412TBS-20) with wave washer preload 50-100lb on a RF-30 conversion. The position of the bumps are repeatable to some degree - if the nut is rotated slightly and then returned to the position of the bump. If I give the nut a bit spin and return to the original position of the bump, the size of the bump changes or disappears. Could this have something to do with balls entering or exiting the return tube? or just lining up differently? This is happening on all three axis. Cleaning and lubing each assembly did not help. I am going to try replacing (eBay) the ball bearings next. Any ideas what causes this or fixes?
-Nick
I finally looked real close and found that all the balls are 2 and 1/2 thousanths differant in size , alternate loading untill the canister will not hold any more balls , this took care of the problem for me , I am yet to test for losing steps though , will comment after the test run ,
Regards
freeflow![]()
Hi Swede,
It was nice article..I learned a lot and I have some questions about my machine which I started to build...I already have 3 640 oz-in Keling motors,3 Geckos 203V, 1 KL-6515 power supply and the C11 board...(waiting for the chinese spindle of 2.2kW)
What I would like to know now is what ballscrew to use?My machine will be 1x1.5m and I 'll mostly cut wood and some cuts of aluminium...I want it to be a bit fast and wonder if 5mm pitch is the right one or should I go to 10mm pitch?If my max motor RPM is 1200, then with the 5mm pitch I'll have 236.22 IPM right? Doubling it to 10mm I ll have 472.44IPM...
What would you suggest to do?I am quite confused and don't want to waste money..
Thanks in advance...
Kostas.
It's not that simple. How much torque will you have at 1200rpm? If you want to move at 472ipm, you'll need enough force to accelerate up to that speed. If using Mach3, acceleration is linear, so you'll need the same force at 450ipm as you do at 20ipm, during acceleration. But the torque drops off as rpm's increase.
My guess would be to go for the 10mm lead.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Get the 10mm, gear down for 5mm resolution if needed.
Gerry:thanks for the answer...I don't want to move at 472IPM...I'll be very satisfied with 300IPM also.We talk about rapid speed now and 472IPM is the theoretic speed given the motors' power and ballscrew pitch...
Phungi:thanks...What do you mean by this?
How could I gear down to 5mm if I already bought 10mm?Get the 10mm, gear down for 5mm resolution if needed.
Thanks..
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)