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Discussion in 'MACHINE BUILD LOGS' started by jumps4, Aug 22, 2012.
Thanks. Placing an order today.
Hi Steve, just wondering if your anti backlash ball nuts you got are really no backlash. I seem to have about .010 play in my x-axis. Just wondering if you noticed the same and just use anti backlash in Mach 3 to compensate?
I had a crap ton of play in the ones linearmotionbearing2008 aka Chai sent me. Do not trust the spacers out right. I bet you can get almost a quarter turn more in them if you pull the pins.
I have no idea what your setup looks like but if you have the thrust bearing from china that comes with the ball-screw, then I would look there.
disassemble the bearing and make sure the outer races are facing thin side out away from each other and then put a thin spacer between the outer races of the bearings. the inner races cannot touch each other or the bearing will not have
any preload when you adjust the Locknut on the ball-screw.
but to answer your original question, the screws I have still have .0014 backlash on X & Y and it is in the ballnut.
Thanks Steve, I did do what you said on an earlier post about the bearings. They where in backwards and I did pit a spacer in between to separate the outer races. I will go through that again before a order double ball nuts or 2 more standard ones to make a double nut setup. On my other machine I used Mcmaster carr ball nuts and screws, doubled up the nuts and get about .0005. They are tight but accurate. Back to the drawing board.
Steve, I checked it out again and went another .012 shim so now I'm at .024 shim between the races. I really did not see any difference. How wide of shims did you use as a comparison?
I would remove the motor, lock the table and turn the screw back and forth to locate the play.
if you cannot find play in the ballnut or bearings, then if your gibs are too tight you will see what looks like big backlash
when you check it with an indicator, but what is actually torque in the screw building up before it can break loose the gib to allow motion.
there are two videos about what is going on with ballscrew torque and gib adjustment I did a while back here
Thanks Steve, It's the ball nut. Ordered 2 more nuts to double up to fix this. Anti backlash in a single nut I think is a sales gimmick. Single nuts with no backlash are very expensive compared to the Chinese stuff as we've both discovered.
Glad to see the doublenut resolved your issues.
Yes, it worked great, thanks.
Steve thank you for all your insight, I doubled up on the ball nuts and got awesome results, .0001 on the X after numerous cuts using the Mach 3 wizard and .0000 on the Y after the same cuts. I used a DRO as the comparison, I'm jazzed.
Ya mean I have to double nut to get it tight enough to operate???????????
Oh well back to the drawing board AGAIN!!
you can email Chai directly and he can offer you some options, also if you wanted double nuts with a single flange you have to order it via email because they are not listed on ebay. it's also cheaper if you go this route because it saves him listing fees. here is his email address: firstname.lastname@example.org
that sounds great I'd love to have no backlash.
sorry for the slow replies the site keeps turning off my notifications for some reason.
What's the procedure to put two ball nuts on, I was under the impression once you take it off you can't get it back on. Reason I ask is because I cut my ballscrew to short but I have a piece long enough, just wondering how to reinstall on longer screw
I'm making you a video I'll post it as soon as YouTube is finished
normally before I try to change a ball-nut I insert a grease fitting and lube it to help insure I keep all the balls in.
In the video I did it dry being really careful.
this is a 1605 screw to do another size, measure the inside diameter of the ball-screw thread and make a tube that size.
here is a video I found showing how to repack the balls if everything went wrong
Steve, your awesome, making the video was a great help to a lot of people I'm sure. Quite simple once you do it right once. The first time like so many others, my balls where all over the shop. I actually had to order more from Thompson that time. Now I always use a shallow box top in case of disaster.
That made it look easy, off to savannah for vacation, I'll try it when I get back
Roadster, what did they quote you for the double nuts?
Yes Steve good video thanks. I ran into hiccup on my cnc conversion with my laptop going gunny bag on me and spent the weekend rebuilding my XP system (that M soft wont even talk to yo about) & HP site was hand to hand combat to get the drivers, but back on track now and will try a test drive on the Electronics today
Yes roadster what was the quote on the nuts??
If you need to repack a ball nut and have steady hands you can use bearing grease cake it in with a screwdriver or some sort of thick plastic spatula. then you can place the balls onto the tracks with a screwdriver with a little grease on the end. There is usually a half thread of separation between each track. the balls will stay put in the grease with ease (although I have not attempted anything larger than a 2505 screw). At that point if your hand is steady enough you can screw the nut back on in the orientation desired. don't forget the nylon sweeper.
I found this to be easier instead of trying to align the nut and insert balls while threading the screw simultaneously like seen in some of the videos on youtube.
I tried the grease technique on a 1605 ball screw and it worked great.
Hello Steve: I am working on converting my G0484 Mill/Drill to CNC and your build shows me that it can be done. I am using much smaller steppers but will see what happens. Using three 425oz-in/ 4.2A with two 36v/9.6A power supplies. Products from Wanti. Debating on ballscrews for now. If this setup doesn't work as planned, will make it a CNC Plasma Cutter. Thanks again for all your posts. Take care. Burt
I think the motors will move the mill the problem comes in when more than one axis has to move at the same speed .
the slowest axis sets the max speed for all the axis moving. the weight of the z axis will require a gear reduction and may greatly
reduce the speed of everything else. It will probably require lift cylinders or counter balance.
I'm curious to see how well it works and please post your results.
I'm often accused of great overkill with my choice of motor sizes. but the one thing I can say is
I have never missed a step machining and If I wished I could run rapids of 200 IPM.
A lot of people want to add feedback to their system to catch a missed step at a great cost for extra electronics, that doesn't correct the error in most cases, it stops machining due to an error.
My approach was to have the power to not miss the step in the first place.
Thanks for your kind review
You can always use timing gears and a belt to gear it down for the smaller steppers. It will impact your rapids speed though. I think the best place for ball screws is Chai on ebay. I got 3 screws, double ball nuts and couplers shipped for $186 if memory serves.
Steve and Dave:
Thank you for the replies. I am at the point of wiring the enclosure and the motor cables now. At 71 I don't seem to have the soldering ability I used to have. I am driving the Quill in Z rather than the whole head, that comes later. I forgot to mention I am using a 2:1 reduction on all three axes via 5m htd timing belts. Saving up for ballscrews and nuts as the next level of modification. The mods so far are the minimum I could do to see if I can just get a system to run under Mach3 demo control. I will take a look at Chai on ebay and see what he has available these days. I will post pictures once I get something worthwhile to show. Keep up your good works and take care.
I think you said you used 880 stepper for the 4th axis, do you think I can use a 600 or is it to small
It probably will work if your axis rotates smoothly